Temporary Self-Deprivation Can Impair Cognitive Control: Evidence From the Ramadan Fast

Abstract

During Ramadan, people of Muslim faith fast by not eating or drinking between sunrise and sunset. This is likely to have physiological and psychological consequences for fasters, and societal and economic impacts on the wider population. We investigate whether, during this voluntary and temporally limited fast, reminders of food can impair the fasters’ reaction time and accuracy on a non-food-related test of cognitive control. Using a repeated measures design in a sample of Ramadan fasters (N = 190), we find that when food is made salient, fasters are slower and less accurate during Ramadan compared with after Ramadan. Control participants perform similarly across time. Furthermore, during Ramadan performances vary by how recently people had their last meal. Potential mechanisms are suggested, grounded in research on resource scarcity, commitment, and thought suppression, as well as the psychology of rituals and self-regulation, and implications for people who fast for religious or health reasons are discussed.

Keywords

cognitive control self-deprivation fasting religion Ramadan ritual resource scarcity commitment thought suppression self-regulation

We went several days on dry bread, and then I was two and a half days with nothing to eat whatever. This was an ugly experience. There are people who do fasting cures of three weeks or more, and they say that fasting is quite pleasant after the fourth day; I do not know, never having gone beyond the third day. Probably it seems different when one is doing it voluntarily and is not underfed at the start.

—Down and Out in Paris and London (Orwell, 1933/1961)

Introduction

Fasting, the practice of abstaining from all or some types of food or drink for a specific period, is prevalent in many cultures and religions around the world (Michalsen & Boschmann, 2014; Mattson, 2022). In Islam, the Ramadan fast is an annual ritual that lasts for a month, with likely influences on the biology and psychology of approximately 20% of the global population. In a survey conducted in 39 countries, over 80% of respondents were reported to fast in Ramadan, making it one of the most common rituals among Muslims (Bell & Lugo, 2012; Ghani, 2013). Ramadan fasts usually last from 10 to 20 hr depending on the time of year and location; this is a severe self-deprivation exercise. So all this begs the question, how does the Ramadan fast in particular, and temporary self-deprivation in general, affect people?

One view is that fasting should have similar effects to hunger. Indeed, prior research has shown fasting to alter body mass, increase dehydration, and trigger headaches in Muslim fasters in Ramadan or Jewish fasters on Yom Kippur (Awada & Jumah, 1999; Mosek & Korczyn, 1995; Rouhani & Azadbakht, 2014). Overall, however, there is little consensus over outcomes of fasting (Benau et al., 2014; Di Francesco et al., 2018; Green et al., 1994; Horne et al., 2015; Mattson et al., 2017; Trepanowski & Bloomer, 2010). Studies looking at mood and psychomotor performance also provide mixed evidence of fast-induced changes in alertness and vigilance (BaHammam et al., 2013; Roky et al., 2000), fatigue, drowsiness, and irritability (Fond et al., 2013; Qasrawi et al., 2017), as well as reaction time and memory (Farooq et al., 2015; H.-H. Tian et al., 2011). Variability in procedures, fasting times, samples, as well as local customs and diets may underlie the heterogeneity of these results (Patterson & Sears, 2017; Teo et al., 2017).

Nonetheless, fasting differs from hunger in important ways, and not all of the effects of fasting may be caused by hunger or physiological states; the psychological experience of daylong restricted access to food could also play a role. A key difference between fasting and hunger is that people are not underfed at the onset of a (daily) fast and know that it will end shortly. When fasting for Ramadan, people prepare for the anticipated limited intake of food and water by eating and hydrating before sunrise, and by managing their caloric expenditure and body water throughout the day. If serious health risks occur, they are free to break the fast. Thus, although fasters’ experience might eventually resemble that of (involuntarily) hungry people in some ways, it also differs markedly because it is planned, voluntary, temporally limited, and can be ended at will.

Ramadan fasters, specifically, may not necessarily feel hungry or thirsty within the first hour of their fast, but they know that food and water cannot be accessed until they break their fast. As a result, if they are committed to keeping their fast, thoughts about food are likely to occupy a special place in their minds, presumably because they are actively suppressed or monitored and resisted. These are cognitively demanding processes and their disruption could subsequently influence cognitive function in other domains. Evidence suggests that people who are hungry or thirsty focus more on food cues and this increased sensitivity affects their cognitive functioning (Dijksterhuis & Aarts, 2010; Keys, 1950; Piech et al., 2010; Radel & Clément-Guillotin, 2012); such cues might influence cognition in fasters as well, even when they are not hungry.

This reasoning is corroborated by several psychological theories and empirical findings, still, others might predict another pattern of results. We discuss a number of these different perspectives below and list several possible mechanisms that may be at play but we do not attempt to test them. The primary goal of this research is to establish the basic effect—how cognitive control may be impacted during a period of voluntary and temporary self-deprivation, such as the Ramadan fast. Heeding Rozin (2001), we see value in a disciplined description of a real-world phenomenon before attempting to discover universal laws and contingent invariances. Curiosity-driven exploration of phenomena, a common first step in the natural and biological sciences, is often obscured in social psychology by a quest to uncover processes and identify mechanisms. As Rozin (2001) notes, discoveries such as Boyle’s gas law or the Mendelian laws of genetics were motivated to give precise accounts of regularities in the world, rather than directly testing or building models using experiments and sophisticated statistical methods. In the case of the Ramadan fast, the lack of social psychological research is particularly intriguing, given the wealth of research on self-control, commitment, willpower, impulsivity, delayed gratification, rituals, and scarcity among others. Of course, systems of non-diversity and narrow sampling are well documented in the field (Medin et al., 2017; Rad et al., 2018). By demonstrating the effect, we think this research could spark interest in this large-scale, high-stakes, and cross-cultural practice, and provide practical implications for nearly a quarter of the world. It also sets the stage for a closer examination of underlying processes, and may further encourage inquiries of this kind (D. M. Wegner, 1992). The following discussion of mechanisms and predictions highlights several areas of research where the current study is likely to contribute.

One prediction for how fasting might affect cognition comes from research that shows experiencing resource scarcity may put people at risk for impaired cognitive performance (Goldsmith et al., 2020; Mullainathan & Shafir, 2013). For example, elevated concern with financial challenges has been shown to diminish poor but not rich people’s performance on tests of cognitive control and fluid intelligence (Mani et al., 2013), with cognitive performance among some groups diminishing as the number of days since last payday increases (Mani et al., 2020). Resource scarcity is conceived in several ways, and perspectives vary regarding its functions, mechanisms, and the reactions it elicits (Griskevicius et al., 2013; Walasek & Brown, 2015). In addition to cognitive and attentional processes, it has been shown to influence consumer decisions and social cognition. For example, under scarcity, people process minority faces with delay, consume more beauty products, and prefer material over experience goods (Krosch & Amodio, 2014; Nelson & Morrison, 2005; Netchaeva & Rees, 2016; Shah et al., 2015; Sharma & Alter, 2012; Tully et al., 2015). Scarcity effects are not limited to money; they have been observed in domains of time, food, mates, and with artificial resources such as the number of shots or guesses in a video game (see Cannon et al., 2019, for a review). Fasting can be construed as a state of resource scarcity concerning food, albeit one that is self-imposed and temporary. If so, then making thoughts of food more salient to fasters might capture their attention and distract them from other tasks, particularly ones requiring cognitive capacity. Specifically, food cues may reduce cognitive performance in fasters during Ramadan compared with after Ramadan. This study may thus contribute to the literature on resource scarcity by focusing on a novel context, one where scarcity is self-induced, religiously motivated, and intermittent, rather than externally imposed, out of one’s control, and indefinite.

While the resource scarcity account makes a clear prediction about the consequences of fasting, similar arguments can be made using models that draw on different sets of processes and mechanisms. Research into thought suppression, for example, finds that attempts to avoid certain thoughts can ironically make them more accessible and recurring (D. M. Wegner, 1994). To prevent attentional lapses, the responsible intentional system needs mental bandwidth to generate unrelated thoughts and engage in self-distraction (Wang et al., 2020). However, this function can be impaired under cognitive load posed by stress, time pressure, and external distractions (Slepian et al., 2014; D. M. Wegner, 2009). People who fast may be trying to suppress food-related thoughts; hence, when they encounter food-related cues, they may need more cognitive resources to suppress those thoughts. This could result in poorer performance on unrelated tasks requiring cognitive processing.

A third perspective comes from research on commitment and self-control. Fasters may adopt situational strategies to maintain their commitment to fasting, such as staying away from food-filled environments, spending time with other fasters, adjusting their sleeping schedule, and refraining from calorie-consuming activities, among others (Bryan et al., 2010; T. Rogers et al., 2014; Schelling, 1984). These strategies could help them resist the lure of immediate gratification as they aim to keep their fast until the very end. But reminders of food run counter to these measures and require conscious effort to fend off. Regardless of how this effort is channeled, be it through reinforcing motivation, re-appraising the situation, overcoming anxiety and stress, or other routes (Duckworth et al., 2018; Fujita, 2011; Hall et al., 1990; Rachlin, 2009; Ward & Mann, 2000), the process is mentally taxing and may well result in impaired cognitive performance.

The three accounts described above make converging predictions but offer somewhat different explanations for how fasting might affect cognition: declined performance caused by food cues. However, the voluntary, temporary and preparatory nature of fasting warrants an alternative view, one where fasting might not have detrimental effects on cognitive processes, or it might actually enhance them. For example, fasting is essentially a ritual: A repeated set of activities that adhere to rigid rules and are embedded in a system of meaning and may not have a direct instrumental purpose (Durkheim, 2008; Hobson et al., 2018; Rappaport, 1999). Rituals have regulatory functions in contexts where uncertainty, stress, or anxiety are high (Boyer & Liénard, 2008; Brooks et al., 2016; Dulaney & Fiske, 1994; Keinan, 1994; Lang et al., 2015), could enhance goal-driven performance and pursuit of self-control goals (Damisch et al., 2010; Laurin et al., 2012; A. D. Tian et al., 2018), and are associated with increased cooperation, perceived social support, and transmission of social norms (Fischer et al., 2013; Norenzayan, 2013; Rossano, 2012; Wen et al., 2016). Fasting could evoke similar processes that constrain thinking, block intrusive thoughts, heighten feelings of self-discipline, and thereby improve cognitive functioning.

Fasting is also an active self-inhibition exercise, which could promote feelings of personal efficacy and confidence, and self-signal a belief that one is capable of achieving goals (Bandura, 1997; Bodner & Prelec, 2003; Loewenstein, 1999). It may further improve self-regulatory performance if people perceive a task as diagnostic of their willpower (Magen & Gross, 2007). Moreover, Ramadan fasters have autonomy over their state and are arguably pursuing a goal that they consider to be of high subjective value and identity relevance (e.g., being an observant Muslim)—such goals are perceived as easier to achieve and are more likely to be pursued (Berkman et al., 2017; Werner et al., 2016). There is also evidence that exerting inhibitory control in one domain can spillover and simultaneously facilitate impulse control in unrelated domains (Dewitte et al., 2009; Tuk et al., 2011). Insofar as these processes can spill over and influence performance in other domains, we can expect fasters’ performance on cognitive control tasks to be unaffected by distracters.

The above discussion illustrates two broad categories of predictions about the impact of fasting on cognitive performance. This is not an exhaustive review and other theories and mechanisms could be discussed. We also do not disentangle these accounts nor do we examine the underlying mechanisms—Our goal is to demonstrate whether and how Ramadan fasting, or more generally, temporary self-deprivation, may affect performance on cognitively demanding tasks. To answer this question, we measure Ramadan fasters’ performance on a non-food-related test of cognitive control during and after Ramadan. A random subset of our respondents answered a few questions about food before performing the cognitive task of interest; they were expected to perform less well during Ramadan (while fasting) compared with after Ramadan (when no longer fasting). Participants in the control condition answered questions unrelated to food and were predicted to perform similarly over time—during and after Ramadan. Moreover, performance during Ramadan is likely to vary depending on how recently people ate: We expect Food-reminded people to perform worse than controls in the first few hours of the fast but not in the later hours. Early in the fast, people are likely satiated and do not spontaneously think of food, but reminders can distract them, raising the specter of the fast and affecting their performance. A few hours into the fast, however, people are hungry; their minds are already preoccupied with food. Food reminders could then have less of an effect, and both Food-reminded and Control participants would be expected to underperform. Note that our cognitive control task is unrelated to food.

Methods

Overview

We adopted a 2 between (Condition: Food-reminder vs. Control) × 2 within (Time: During Ramadan vs. After Ramadan) mixed study design. That is, we measured cognitive control in people who fasted in Ramadan both during and after Ramadan. We also randomly assigned participants to either a “Food-Reminder” condition or a control condition. In the Food-reminder condition, just before the cognitive control task was administered, participants responded to questions about whether they had consumed certain food items in the past 24 hr. In the control condition, participants were asked if they owned certain everyday items. We expect questions about food to distract people and thereby interfere with their cognitive function. Thus, participants in the Food-reminder condition should be significantly less accurate and slower during Ramadan than after Ramadan. Participants in the control condition, however, are not predicted to exhibit differences in performance during and after Ramadan. During Ramadan performances are also likely to vary by time since their last meal. Thus, we are looking for differences within groups across time, as well as between groups and depending on when people last ate.

Procedure and Instrument

Participants were invited to participate in a study on Decision Making in exchange for a participation fee, plus bonus points that depended on the quality of their responses and would be converted to monetary values. All participants signed the consent form approved by Princeton University’s Institutional Review Board (#10649). They then responded to demographic questions about age, gender, income (parents and self), education, employment, and country of residence. Random assignment determined their next set of questions. We asked those in the Food-reminder condition if they had consumed any of the following food items in the past 24 hr: pizza, chocolate, French fries, meat, ice-cream, Coke, cookies, pastries, fruits, coffee. We asked those in the control if they owned any of the following items: bike, diary notebook, hand sanitizer, personal mug, backpack, wristwatch, sunglasses, flashlight, headphones, raincoat.¹ The last question on the survey was, “Were you fasting while participating in this study?,” to which participants responded with Yes or No.

We developed our experiments on Cut (https://cut.social), a web-based platform designed to run interactive tasks on a responsive interface. To measure cognitive control, we used multiple rounds of the two-alternative-forced-choice task (2AFC), a primary instrument for examining performance in tasks that measure reaction time (Gomez et al., 2007). As shown in Figure 1, on each trial of our implementation of the task, participants see either a blue star or a yellow star on the screen’s left or right side, separated by a line in the middle. In the blue star trials, participants must click/tap on the blue star (i.e., Select trials); in the yellow star trials, they must tap on the opposite side (i.e., Avoid trials). The dependent variables are response accuracy, and reaction times in the correctly responded trials.

Figure 1.

Smartphone screenshots of the two-alternative-forced-choice task we used.

The 2AFC requires participants to monitor and discriminate between different stimuli and select/inhibit responses repeatedly. These processes correspond to core components of cognitive control (Miyake & Friedman, 2012). In the current study, participants must first distinguish between blue and yellow stars, determine the correct response, and execute it, knowing that responding quickly and accurately will earn them bonus points (and higher pay). Diminished cognitive control would be evident in a greater number of errors and longer reaction times. Two types of reaction time measures are relevant. The first is raw reaction times for different trial types and conditions over time, which should be generally smaller for Select trials than Avoid trials. The other is the inhibition delay computed as the difference between reaction time of Select trials and Avoid trials for different conditions and over time. A delay is expected because Avoid trials are less common than Select trials and require inhibiting the dominant response. When cognitive control is disrupted, both raw reaction times and inhibition delays are expected to increase. The simplicity and symmetrical response format of the 2AFC make it more appropriate for an online unsupervised study than similar tasks such as the Go-NoGo and Stroop tasks. The classic Stroop task requires participants to pay attention to some features and ignore others. In the Go/NoGo task, the NoGo rounds have wait time and demand patience (Littman & Takács, 2017; Shenoy & Yu, 2012).

Pilot Study

We conducted a pilot study to test our instrument and evaluate the feasibility of our participant recruitment approach. We recruited participants from Muslim Students Associations of several universities in the United States during the Ramadan of 2018 and presented them with a 50-trial two-alternative-forced-choice task. A sample of N = 38 fasting participants completed the study both during and after Ramadan. Twenty-one participants were randomly assigned to the Food-reminder condition, and 17 to the control condition. The sample was predominantly female, educated, and residing in large cities. Food reminded participants exhibited marginally lower accuracy than those in the control condition (96.9% vs. 97.8%, p = .08). However, a 2 between (Condition: Food-reminder vs. control) × 2 within (Time: during Ramadan vs. post-Ramadan) mixed analysis of variance (ANOVA) predicting response accuracy, F(1,36) = 2.375, p = .132, and the inhibition delay (i.e., difference between mean reaction times of the Select vs. Avoid trials) failed to show significant main or interaction effects (Fs < 1.01, p = .3208, $η_{p}^{2}$ = 0.027). A similar model with an additional Trial type factor (Select vs. Avoid) showed raw reaction times in Avoid trials to be larger than in Select trials, F(1,36) = 16.905, p = .0002, $η_{p}^{2}$ = 0.0119. Food reminded participants were generally slower than controls but not significantly, M_diff = −79.8, SE = 43.7, t(36) = −1.825, p = .0764.

The pilot study, with its very small sample, provided no reliable evidence that making food salient affects cognitive performance in Ramadan fasters. It did, however, confirm the feasibility of participant recruitment, and it provided some further lessons. Whereas the pilot included an equal and relatively small number of Select and Avoid trials, it has been shown that to test inhibitory control effectively more trials are needed, with Avoid trials being rarer (Menon et al., 2001; Wessel, 2018)—thereby encouraging a response tendency in the dominant trials, and the need to exercise conscious inhibition in the non-dominant trials. We incorporated these lessons in our main study.

Main Study

Based on our pilot study, we made several adjustments to the main study. First, we changed the ratio of the Avoid to Select trials to 1:3 and increased the number of trials to 120 (i.e., 90 Select and 30 Avoid trials). We also asked all of our participants, “When did you have your last meal?,” and collected responses using a 1 to 8 scale: less than 2 hr ago (1), 2–4 hr ago (2), 4–6 hr ago (3), 6–8 hr ago (4), 8–10 hr ago (5), 6: 10–12 hr ago (6), 12–14 hr ago (7), and over 14 hr ago (8). Participants in the Food-reminder condition responded to this question after the manipulation questions that asked if they had consumed the list of 10 food items mentioned above in the past 24 hr. In the control condition, we asked participants how long had passed since they had their last phone call and obtained data on the time of their last meal at the end of the study. This question enabled us to examine whether participation time affects susceptibility to cognitive underperformance during Ramadan. Early in a fast, people are likely to have just had a sizable breakfast and might be less focused on food. However, questions about food could remind them of their lack of access to food that day, thereby creating a distraction and interfering with cognitive function. Conversely, as the fast nears its end, fasters are likely anticipating their Iftar (final meal of the fast), and they are generally hungry and depleted. Food may be top of mind, whether or not we ask them about it (Ståhle et al., 2011; Teo et al., 2017). Thus, both Control and Food-reminder fasters are likely to display similar declines in cognitive function after several hours of fasting.

In addition to the demographic questions listed above, we asked participants how patient and how religious they view themselves on an 11-point scale ranging from 1 (not at all) to 11 (a lot). Neither self-reported religiosity nor patience differed significantly across time or between conditions (ts < 1.7, ps > 0.2). We also checked whether these correlated with accuracy or reaction times. We find a small positive correlation between self-reported patience and accuracy during Ramadan, r = 0.224, t(188) = 3.155, p = .0018, 95% confidence interval (CI) [0.084, 0.35], but no other significant association with any of our dependent variables. We will not discuss these further.

Sample

We first conducted a prescreen survey several weeks before the beginning of Ramadan 2020 on the crowdsourcing platform, Prolific.co. Using the available filters offered by Prolific, we targeted only people who identified as Muslim, were fluent in English, and had been active subjects in the past 90 days, and invited them to participate in a short demographics survey in exchange for a small fee (see the Supplemental File for detailed demographic data). The prescreen survey included several questions about religiosity and religious practices, including fasting and Ramadan. Specifically, we asked people if they planned on fasting in the upcoming Ramadan, and only those who said they were probably or definitely going to fast were contacted to participate in the main study. Ramadan data collection began on May 10, 2020, and ended on May 22, 2020 (In 2020, Ramadan was between April 23 and May 23). People were invited to participate in a study on Decision Making in exchange for a flat fee plus a bonus, calculated based on their performance and the quality of their responses. We contacted them again about 3 weeks after the end of Ramadan for the follow-up study. The final sample consisted of N = 190 participants who completed both surveys (M_Age= 26.99, SD = 7.65) and responded positively to the last question on the during-Ramadan survey (“Were you fasting while participating in this study?”). This sample size gives us 80% power to detect an effect size of $η_{p}^{2}$ = 0.04 at α = 0.05.

Results

We hypothesized that reminding fasters about food might affect their accuracy and speed during Ramadan compared with after Ramadan. The performance of participants in the control condition, in contrast, was not predicted to differ between the two times. Our cognitive control measures were accuracy and reaction times in two 120-trial two-choice-forced-choice tasks completed during and after Ramadan. We also looked at whether performance during Ramadan depended on time elapsed since a participant’s last meal. In our analyses of during versus post-Ramadan data, we look for within-subject differences in each condition. For the recency of the last meal variable, we rely on a median split (during Ramadan data only), although the same pattern holds when we use a continuous variable. Note that our statistical power differs between the two sets of analyses. See the Supplemental File for details of results and all analyses, and the statistical packages we used. Raw results are in the appendix.

Accuracy

Participants in the Food-reminder condition had lower accuracy during Ramadan compared with after Ramadan (Ramadan = 0.864 vs. post-Ramadan = 0.908), but in the control condition, accuracy was relatively similar across time (Ramadan = 0.885 vs. post-Ramadan = 0.895). A mixed 2 between (Condition: Food-reminder vs. Control) × 2 within (Time: during Ramadan vs. post-Ramadan) × within (Trial type: Select vs. Avoid) ANOVA predicting response accuracy showed significant main effects of Time, F(1,188) = 13.28, p < .0001, $η_{p}^{2}$ = 0.07, and Trial type, F(1,188) = 242.10, p < .0001, $η_{p}^{2}$ = 0.56, as well as significant Condition × Time, F(1,188) = 5.14, p = .025, $η_{p}^{2}$ = 0.03, and Condition × Trial type interactions, F(1,188) = 5.41, p = .021, $η_{p}^{2}$ = 0.03. Response accuracy was higher after Ramadan compared with during Ramadan (M_diff = 0.023 [95% CI 0.0921, 0.354], 5000 bootstrap resamples, bias-corrected and accelerated confidence intervals) and in Select trials than in Avoid trials (M_diff = −0.082 [95% CI −0.694, −0.507]). Examining the Condition × Time interaction, we find that in the Food-reminder condition, participants were significantly less accurate during Ramadan than after Ramadan (Cohen’s d = 0.369 [95% CI 0.184, 0.528]) but not in the control condition (Cohen’s d = 0.0895 [95% CI −0.111, 0.273]). Figure 2A shows this result.

Figure 2.

In Panel A, participants reminded of food were significantly less accurate during Ramadan than after Ramadan. Control condition participants performed similarly over time. Panel B: Food reminders led to longer delays in differentiating avoid and select trials during Ramadan compared with after Ramadan. The control condition participants showed no reaction delay differences across time. Panel C: During Ramadan and within 8 hr since their last meal, control participants were significantly quicker at differentiating avoid and select trials compared with food-reminded participants. Beyond 8 hr, the two groups similarly slowed down. Cohen’s ds calculated using 5000 bootstrap resamples. All confidence intervals are bias-corrected and accelerated.

Reaction time

For each participant, we calculated two inhibition delays (during and after Ramadan) by subtracting the mean reaction times in Select trials from Avoid trials. Responses were in milliseconds; only correct responses greater than 200 (MS) were used. The distribution was relatively symmetrical (G₁ < 0.5) and not transformed. See the Supplemental File for details. Entering this value in a 2 between (Condition: Food-reminder vs. Control) × 2 within (Time: during Ramadan vs. post-Ramadan) mixed ANOVA, we find a significant main effect of Time, F(1,188) = 6.53, p = .010, $η_{p}^{2}$ = 0.032, and no significant interaction (p > .3). Planned contrasts showed that Food-reminded participants were slower during Ramadan than after Ramadan (Cohen’s d = 0.284 [95% CI 0.0254, 0.561], bias-corrected and accelerated confidence intervals from 5000 bootstrap resamples) but not the participants in the control condition (Cohen’s d = 0.118 [95% CI −0.176, 0.414]).² Panel B in Figure 2 shows this result.

We also conducted a second analysis using the raw reaction time data to help ensure nothing unusual was driving outcomes from the above analysis. A 2 between (Condition: Food-reminder vs. Control) × 2 within (Time: during Ramadan vs. post-Ramadan) × 2 within (Trial type: Select vs. Avoid) mixed ANOVA predicting raw reaction times showed a significant Time × Trial type interaction, F(1,187) = 6.54, p = .011, $η_{p}^{2}$ = 0.03. Follow-up analyses showed this interaction to be significant only in the Food-reminder condition, F(1,95) = 6.79, p = .011, $η_{p}^{2}$ = 0.067, and only significant in Avoid trial (M_{Ramadan - post-Ramadan} = 24.14 [95% CI 7.99, 40.29]) but not the Select trials (M_{Ramadan - post-Ramadan} = 14.3 [95% CI −1.89, 30.41]). In the control condition, we only find a main effect of Trial type, F(1,92) = 538, p < .0001, $η_{p}^{2}$ = 0.854.

Time since last meal

Responses to the question of “When was your last meal?” were coded as follows: less than 2 hr ago (1), 2–4 hr ago (2), 4–6 hr ago (3), 6–8 hr ago (4), 8–10 hr ago (5), 10–12 hr ago (6), 12–14 hr ago (7), and over 14 hr ago (8). We entered this score as the response value in a 2 between (Condition: Food-reminder vs. Control) × 2 within (Time: during Ramadan vs. post-Ramadan) mixed ANOVA. Results showed a significant main effect of Time, F(1,188) = 216.560, p < .0001, $η_{p}^{2}$ = 0.535, and no interaction (F < 1, p > .5). In Ramadan, the average number of hours since participants’ last meal was around 9 hr; after Ramadan, it was close to 3 hr. Based on the sample median and the distribution of participants, we split the data into those who participated in the study within 8 hr or less and over 8 hr since their last meal (N_{≤8 hr} = 85, N_{8 hr<} = 105). Eight hours is also roughly the standard duration that people go without eating (e.g., between dinner and breakfast), before their cognitive performance is affected (Adolphus et al., 2016; Pollitt & Mathews, 1998). We find similar results when we use time-since-last meal as a continuous variable. See the Supplemental File for details.

A 2 between (Last-meal: less than 8 hr vs. over 8 hr) × 2 between (Condition: Food-reminder vs. control) × 2 within (Trial type: Select vs. Avoid) mixed ANOVA predicting response accuracy during Ramadan showed significant effects of Last-meal, F(1,180) = 4.822, p = .0293, $η_{p}^{2}$ = 0.020, and Trial-type, F(1,186) = 182.38, p < .0001, $η_{p}^{2}$ = 0.503. People who had eaten their last meal over 8 hr ago were slightly more accurate than those who had eaten within the past 8 hr (M _{≤8 hr - 8 hr<} = −0.0299 [95% CI −0.0544, −0.00617]), and responses in the Avoid trials were significantly less accurate than in Select trials (M_diff = 0.0816 [95% CI 0.0641, 0.1]). A separate linear model using the continuous time-since-last meal variable found similar results—Accuracy was significantly and positively associated with time since last meal (r =.15, [95% CI 0.05, 0.25]). See the Supplemental File for the details.

Looking at reaction times, a 2 (Last-meal: less than 8 hr vs. over 8 hr) × 2 (Condition: Food-reminder vs. control) between-subject ANOVA with inhibition delay as response value showed a significant Last-meal × Condition interaction, F(1,186) = 3.994, p = .0471, $η_{p}^{2}$ = 0.021. Within 8 hr since their last meal, participants had significantly larger inhibition delays when they were reminded of food than when they were not (Cohen’s d = 0.561 [95% CI −0.0343, 1.11]). Beyond 8 hr, the two groups had nearly identical inhibition delays (Cohen’s d = 0.034 [95% CI −0.302, 0.378]). A linear model found an interaction between the continuous time since last meal variable and condition, F(1,186) = 3.84, p = .051, $η_{p}^{2}$ = 0.02. In the control condition, time-since-last meal variable was significantly and positively associated with delay inhibition (r = 0.20 [95% CI 0.001, 0.39]), but not in the Food-reminder condition (r = −0.06 [95% CI −0.25, 0.13]). Entering raw reaction times as response value in a 2 between (Last-meal: less than 8 hr vs. over 8 hr) × 2 between (Condition: Food-reminder vs. Control) × 2 within (Trial type: Select vs. Avoid) mixed ANOVA only showed a significant main effect of Trial type, F(1,185) = 816.730, p < .0001, $η_{p}^{2}$ = 0.815. Select responses were quicker than Avoid responses (M_diff = 76.8 [95% CI 62.8, 91.2]). See the Supplemental File for the details of this analysis.

Finally, across analyses, entering income, age, and sex did not significantly improve model fits. See the details in the Supplemental File.

General Discussion

Fasting in Ramadan is a month-long transformation in the daily lives of a large part of the world’s population. Perhaps no other ritual or practice matches it in intensity and global scale (Patterson & Sears, 2017). The scientific study of this ritual has practical applications and can contribute to multiple research areas in psychology and behavioral science (Campante & Yanagizawa-Drott, 2015; A. D. Tian et al., 2018; Wang et al., 2020; Xu et al., 2015).

We hypothesized that while fasting, food-related probes might interfere with the fasters’ cognitive function, specifically, their attempts to exercise cognitive control. We find that fasters who respond to a few questions about food take longer to differentiate between response types and perform less accurately on a two-alternative-forced-choice task during Ramadan compared with after Ramadan. In contrast, fasters who respond to non-food-related questions do not differ significantly in accuracy or speed across time. We also find evidence that the impact on cognitive control depends, in part, on how long fasters have not eaten. Within 8 hr of their last meals, the Food-reminded fasters showed significantly longer inhibition delays compared with Control participants. After 8 hr, the two groups exhibited similarly long inhibition delays.

One perspective to explain these results is resource scarcity. During a fast, food becomes a scarce resource that when made salient “triggers intrusive thoughts, and reduces cognitive resources” (Mani et al., 2013). Another explanation comes from research on thought suppression. Fasters could be suppressing thoughts about food by means of self-distraction, and reminders of food can impose a cognitive load that undermines this effort (Slepian et al., 2014; Wang et al., 2020; D. M. Wegner, 1994). Likewise, a commitment to fast requires adoption of certain conscious strategies to avoid relapse, and cueing food can thwart these efforts and tax one’s cognitive resources (Duckworth et al., 2018; Hall et al., 1990; Ward & Mann, 2000). In the two latter accounts, stress of failing to fast might exacerbate cognitive load. Regardless of their respective mechanisms, however, all three accounts predict that raising the salience of food-related thoughts could significantly undermine cognitive performance during fasting.

Note that food reminders impair accuracy and speed in avoidance rounds but not in select rounds, suggesting that avoidance and approach processes are affected differently by fasting. The three accounts discussed above can predict this result, although they require a different set of assumptions. Thought suppression and commitment both imply that fasters are avoiding thoughts of food, and reminders of food can disrupt this process, making avoidance more difficult. Some accounts of resource scarcity suggest avoidant behavior is an adaptive response to high scarcity, while others argue that responses might vary by life-history and socioeconomic background (Cannon et al., 2019; Griskevicius et al., 2013; Pepper & Nettle, 2017). Another explanation comes from research by Xu et al. (2015) who show that hunger promotes a general need to acquire food and nonfood objects, and activates acquisition-related concepts and behaviors (see also Briers et al., 2006). Assuming a similar phenomenon occurs in fasters, we would expect delay inhibition to be particularly impaired because in addition to overcoming the dominant response tendency formed by the Select:Avoid trials ratio (1:3), people need to suppress acquisition-related concepts and activate avoidant ones. This is plausible considering that the Ramadan fast requires not only abstinence from drinking or eating but also smoking and sexual relations. Thus, while food is the primary focus of all fasters, a broader inhibition process is at work. A design that tests performance throughout a fast day, or multiple times during the course of Ramadan might be more suitable to investigate this possibility. The latter design could also explore how the body adapts during the month to fasting, with potential effects on cognition.

Time since the last meal affects performance in a mixed way. For example, we find response accuracy during Ramadan to be lower for participants within 8 hr of their last meal compared with those whose last meal was over 8 hr ago. This is a very small difference [95% CI −0.0544, −0.00617] and requires replication. However, this result is consistent with the self-regulatory function of rituals, as well as fasting as a self-inhibition exercise, both of which would predict performances to improve by fasting (Dewitte et al., 2009; Hobson et al., 2018; Witte et al., 2009). And while the overall trend suggests that people respond slightly quicker as the time passes, albeit not significantly, these accounts cannot anticipate the inhibition delay results (i.e., it was significantly smaller in the Control than in the Food-reminder condition within 8 hr of the last meal; after 8 hr the two groups performed similarly). This finding is somewhat consistent with evidence for improved cognitive function induced by fasting or dietary restriction over longer periods of time or in other species (Fontana et al., 2010; Mattson, 2015; Witte et al., 2009), although they too cannot explain why delay inhibition specifically might be impaired.

These findings have implications for understanding hunger and fasting-induced shifts in cognitive function. Evidence for the direct impact of hunger on cognition is equivocal, at least for mild levels of hunger (Adolphus et al., 2016; Benau et al., 2014; Green et al., 1994; Lieberman et al., 2008). But hungry and thirsty people are evidently more sensitive to food-related cues (Aarts et al., 2001; Parmentier et al., 2018; Radel & Clément-Guillotin, 2012; Skrynka & Vincent, 2019) and report mental preoccupation with food (Keys, 1950). Our results suggest that just as the body’s reaction to hunger changes over time (McCue, 2012), so too might the mind’s reaction to fasting. In the early hours of fasting, even though fasters are likely not hungry because they prepared for the fast, subtle probes around food seem to capture their attention, distracting them from related tasks. But when hunger levels are higher, food probes have limited impact on what may already be persistent thoughts of food, and possibly some cognitive decline (Ståhle et al., 2011; Teo et al., 2017). While we did not measure hunger directly and feelings of hunger may fluctuate as time passes, it is reasonable to assume that the fasters are increasingly thinking about food, as they intend to break their fast at a preset time. In line with these findings, other research finds that distraction, not hunger, predicts perceived work performance in intermittent fasters (Appleton & Baker, 2015). Distractibility is higher in dieting individuals in part because of the stress and anxiety induced by dietary restraint (Herman et al., 1978; P. J. Rogers & Green, 1993).

The present study adds to the body of knowledge on cognition under conditions of resource scarcity. Experiencing resource scarcity can distract, impose a load on our cognitive resources and leave less for other tasks. The present research shows, in a novel context, that scarcity can be self-inflicted or limited in time and still cause people to underperform cognitively demanding tasks. This condition does not have to be urgent or prolonged; temporary scarcity experiences can be enough to distract. More research is required to identify the specific mechanisms and processes involved, and to characterize the fasting experience, whether as a form of self-induced resource scarcity or as a self-deprivation religious ritual.

It is noteworthy that the two-choice-forced-choice task and its variants are commonly employed in research on cognitive control. A recent meta-analysis of self-regulation measures showed this task to have high reliability relative to other tasks (Enkavi et al., 2019). However, the single 120-trial task we used in this study may not capture the complex multidimensional construct of cognitive control. Future work might use other measures including self-report items to test the reliability of estimated shifts in cognitive control. Another limitation of this study pertains to the experimental manipulation. Looking to create a list of well-recognized food items, we inadvertently populated the list with indulgent foods (e.g., fries, cookies, pizza, etc.). Perhaps healthier foods would have had a more moderate impact on cognition. Alternatively, we could have listed comparably hedonic items and activities in the control condition (e.g., spa, video games, perfume/cologne). This would clarify whether food, in general, has a particular influence during fasting, or anything hedonic made salient could result in impaired cognitive performance (Special thanks to an anonymous reviewer who brought this to our attention).

Our results also have a number of practical implications. Employers may benefit from adapting the type and duration of work they assign to their fasting employees, and more broadly, to others during religious ritual periods that require abstinence. It is already a legal requirement in some countries to adjust work schedules (Shas, n.d.). Our findings further suggest that the workplace environments can accommodate situational strategies and commitment devices to alleviate some of the cognitive consequences of fasting (Bryan et al., 2010; Duckworth et al., 2016). A more general implication of this research is for consumer well-being. Given its subtlety, the effectiveness of our manipulation is remarkable. But the average consumer is subjected to thousands of ads a day, some directly targeting things that people are actively avoiding (Story, 2007). This continual exposure may have far greater cognitive costs.

Research on deprivation generally focuses on externally induced conditions, and fasting research often examines physiological outcomes. To our knowledge, this is the first study to examine psychological processes evoked by self-deprivation in an ecologically grounded setting. Simply put, we did not pay people to fast; they self-deprived on their own volition and had little reason to believe our study concerned fasting. Ramadan offers an opportunity to investigate interesting research questions and policy concerns. For example, governments around the world adopt different stances toward Ramadan; some merely recognize it, others regulate work or restaurant hours, and some punish public non-compliance. A systematic comparison of countries with differing Ramadan policies and religious diversity could provide valuable insights into the interaction of legal and political institutions with cultural beliefs and practices on social, political, and economic behavior. A limitation of our study is that over 80% of our sample reside in North America or Europe, Muslim-minority countries which are hardly representative of Ramadan fasters. In these populations, fasting is likely motivated by a sense of personal commitment and community involvement rather than by the nationwide routines common to Muslim-majority countries. In sum, the current study does not address the cultural and structural diversity associated with fasting. A cross-cultural study of that type could be particularly valuable when conducted in tandem with studies on health-related outcomes of diets and caloric restrictions in other cultural groups and regions (Mattson et al., 2017; Willcox et al., 2009).

A potential application of this research could be in the development of exercises and rituals that might promote psychological well-being and enhance goal pursuit (Milyavskaya et al., 2015; A. D. Tian et al., 2018). Even if people’s self-regulation is consistently undermined throughout a fast, it is unclear how it is affected over the course of a month. People may emerge from Ramadan better able to resist temptations. Whether “saying no” or restraining oneself in one domain can extend and promote flourishing in other domains is an important empirical question, with ramifications for research on dieting, substance abuse, and other forms of addiction.

Future research could also investigate how and why communal self-deprivation became a religious and cultural practice. In lay view, fasting is commonly regarded as a spiritual and therapeutic exercise, or a penitential soul-cleansing ritual (Lambert, 2003; Shatenstein & Ghadirian, 1998). Others see fasting as an example of dietary restrictions and food taboos that symbolize identity and foster solidarity within groups (Meyer-Rochow, 2009; Rozin, 1996). From a functionalist perspective, communal abstinence could have also evolved as a sociocultural response in times of privation and scarcity (Dirks et al., 1980). Humans have long adopted various risk mitigation and reduction strategies to cope with fluctuating food supplies (Winterhalder et al., 1999). A collective commitment to restrict food consumption could be one such response that could reduce the strain on shared resources. There is also evidence suggesting that fasting is associated with decreased risk-taking (Rad & Ginges, 2017), which in turn, is associated with higher cooperation in social dilemmas (Budescu et al., 1990). Future research could investigate how individual and communal deprivation of food and other resources might affect decision behavior (Briers et al., 2006; Strang et al., 2017; Xu et al., 2015).

As stated in the introduction, this research is primarily interested in the description of an effect from the real world. Descriptive studies are uncommon in psychology, and so are single study papers (Rozin, 2001; D. M. Wegner, 1992). Our decision was in part dictated by the circumstance, since Ramadan lasts just a month each year, thus limiting the window of opportunity and requiring extensive planning beforehand. We hope the current article demonstrates the value of psychological research outside of the commonly studied samples.

Supplemental Material

sj-docx-1-psp-10.1177_01461672211070385 – Supplemental material for Temporary Self-Deprivation Can Impair Cognitive Control: Evidence From the Ramadan Fast

Supplemental material, sj-docx-1-psp-10.1177_01461672211070385 for Temporary Self-Deprivation Can Impair Cognitive Control: Evidence From the Ramadan Fast by Mostafa Salari Rad, Morteza Ansarinia and Eldar Shafir in Personality and Social Psychology Bulletin

Footnotes

Appendix

Between-Subject Means and (Standard Deviations) in Time1 (Ramadan) Split by Time Since the Last Meal (Reaction Times [RTs] in Milliseconds [MS]).

	Food reminder		Control
Variable	<8 hr	8 hr <	<8 hr	8 hr <
Accuracy (Max = 1)	0.8431 (0.141)	0.8739 (0.135)	0.8412 (0.192)	0.8990 (0.094)
RTs (Avoid—Select)	85.84 (33.30)	81.42 (37.70)	61.71 (53.58)	82.43 (36.66)
Raw RTs (Total)	590.4 (141.1)	574.9 (149.0)	578.1 (168.7)	557.9 (137.8)
Raw RTs (Select)	571.3 (139.3)	556.7 (145.9)	562.2 (170.5)	539.0 (135.2)
Raw RTs (Avoid)	656.9 (126.6)	635.0 (142.9)	633.8 (149.7)	620.0 (127.6)

Author Note

Eldar Shafir, is now affiliated to Departement of Psychology, Princeton University, NJ, USA.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: Alfred P. Sloan Foundation grant to Eldar Shafir SES - 1949467 grant to Jeremy Ginges.

ORCID iDs

Mostafa Salari Rad

Morteza Ansarinia

Supplemental Material

Supplemental material is available online with this article. Data & code are available at

Notes

References

Aarts

Dijksterhuis

Vries

(2001). On the psychology of drinking: Being thirsty and perceptually ready. British Journal of Psychology, 92(4), 631–642. https://doi.org/10.1348/000712601162383

Adolphus

Lawton

C. L.

Champ

C. L.

Dye

(2016). The effects of breakfast and breakfast composition on cognition in children and adolescents: A systematic review. Advances in Nutrition, 7(3), 590S–612S.

Appleton

K. M.

Baker

(2015). Distraction, not hunger, is associated with lower mood and lower perceived work performance on fast compared to non-fast days during intermittent fasting. Journal of Health Psychology, 20(6), 702–711.

Awada

Jumah

M. A.

(1999). The first-of-Ramadan headache. Headache, 39(7), 490–493.

BaHammam

A. S.

Nashwan

Hammad

Sharif

M. M.

Pandi-Perumal

S. R.

(2013). Objective assessment of drowsiness and reaction time during intermittent Ramadan fasting in young men: A case-crossover study. Behavioral and Brain Functions, 9(1), Article 32.

Bandura

(1997). Self-efficacy: The exercise of control. Macmillan.

Bell

Lugo

(2012). The world’s Muslims: Unity and diversity. Pew Forum.

Benau

E. M.

Orloff

N. C.

Janke

E. A.

Serpell

Timko

C. A.

(2014). A systematic review of the effects of experimental fasting on cognition. Appetite, 77, 52–61.

Berkman

E. T.

Livingston

J. L.

Kahn

L. E.

(2017). Finding the “self” in self-regulation: The identity-value model. Psychological Inquiry, 28(2–3), 77–98.

10.

Bodner

Prelec

(2003). Self-signaling and diagnostic utility in everyday decision making. The Psychology of Economic Decisions, 1(105), Article 26.

11.

Boyer

Liénard

(2008). Ritual behavior in obsessive and normal individuals: Moderating anxiety and reorganizing the flow of action. Current Directions in Psychological Science, 17(4), 291–294.

12.

Briers

Pandelaere

Dewitte

Warlop

(2006). Hungry for money: The desire for caloric resources increases the desire for financial resources and vice versa. Psychological Science, 17(11), 939–943.

13.

Brooks

A. W.

Schroeder

Risen

J. L.

Gino

Galinsky

A. D.

Norton

M. I.

Schweitzer

M. E.

(2016). Don’t stop believing: Rituals improve performance by decreasing anxiety. Organizational Behavior and Human Decision Processes, 137, 71–85.

14.

Bryan

Karlan

Nelson

(2010). Commitment devices. Annual Review of Economics, 2(1), 671–698.

15.

Budescu

D. V.

Rapoport

Suleiman

(1990). Resource dilemmas with environmental uncertainty and asymmetric players. European Journal of Social Psychology, 20(6), 475–487.

16.

Campante

Yanagizawa-Drott

(2015). Does religion affect economic growth and happiness? Evidence from Ramadan. The Quarterly Journal of Economics, 130(2), 615–658.

17.

Cannon

Goldsmith

Roux

(2019). A self-regulatory model of resource scarcity. Journal of Consumer Psychology, 29(1), 104–127.

18.

Damisch

Stoberock

Mussweiler

(2010). Keep your fingers crossed! How superstition improves performance. Psychological Science, 21(7), 1014–1020.

19.

Dewitte

Bruyneel

Geyskens

(2009). Self-regulating enhances self-regulation in subsequent consumer decisions involving similar response conflicts. The Journal of Consumer Research, 36(3), 394–405.

20.

Di Francesco

Di Germanio

Bernier

de Cabo

. (2018). A time to fast. Science, 362(6416), 770–775.

21.

Dijksterhuis

Aarts

(2010). Goals, attention, and (un)consciousness. Annual Review of Psychology, 61, 467–490.

22.

Dirks

Armelagos

G. J.

Bishop

C. A.

Brady

I. A.

Brun

Copans

Doherty

V. S.

Fraňková

Greene

L. S.

Jelliffe

D. B.

Kayongo-Male

Paque

Schusky

E. L.

Thomas

R. B.

Turton

(1980). Social responses during severe food shortages and famine [and comments and reply]. Current Anthropology, 21(1), 21–44.

23.

Duckworth

A. L.

Gendler

T. S.

Gross

J. J.

(2016). Situational strategies for self-control. Perspectives on Psychological Science, 11(1), 35–55.

24.

Duckworth

A. L.

Milkman

K. L.

Laibson

(2018). Beyond willpower: Strategies for reducing failures of self-control. Psychological Science in the Public Interest, 19(3), 102–129.

25.

Dulaney

Fiske

A. P.

(1994). Cultural rituals and obsessive-compulsive disorder: Is there a common psychological mechanism? Ethos, 22(3), 243–283.

26.

Durkheim

. (2008). The elementary forms of religious life. Oxford University Press.

27.

Enkavi

A. Z.

Eisenberg

I. W.

Bissett

P. G.

Mazza

G. L.

MacKinnon

D. P.

Marsch

L. A.

Poldrack

R. A.

(2019). Large-scale analysis of test–retest reliabilities of self-regulation measures. Proceedings of the National Academy of Sciences, 116(12), 5472–5477.

28.

Farooq

Herrera

C. P.

Almudahka

Mansour

(2015). A prospective study of the physiological and neurobehavioral effects of Ramadan fasting in preteen and teenage boys. Journal of the Academy of Nutrition and Dietetics, 115(6), 889–897.

29.

Fischer

Callander

Reddish

Bulbulia

(2013). How do rituals affect cooperation? An experimental field study comparing nine ritual types. Human Nature, 24(2), 115–125.

30.

Fond

Macgregor

Leboyer

Michalsen

(2013). Fasting in mood disorders: Neurobiology and effectiveness. A review of the literature. Psychiatry Research, 209(3), 253–258.

31.

Fontana

Partridge

Longo

V. D.

(2010). Extending healthy life span—From yeast to humans. Science, 328(5976), 321–326. https://science.sciencemag.org/content/328/5976/321.abstract

32.

Fujita

(2011). On conceptualizing self-control as more than the effortful inhibition of impulses. Personality and Social Psychology Review, 15(4), 352–366.

33.

Ghani

(2013). Most Muslims say they fast during Ramadan. http://www.pewresearch.org/fact-tank/2013/07/09/global-median-of-93-of-muslims-say-they-fast-during-ramadan/

34.

Goldsmith

Griskevicius

Hamilton

(2020). Scarcity and consumer decision making: Is scarcity a mindset, a threat, a reference point, or a journey? Journal of the Association for Consumer Research, 5(4), 358–364. https://doi.org/10.1086/710531

35.

Gomez

Ratcliff

Perea

(2007). A model of the go/no-go task. Journal of Experimental Psychology, 136(3), 389–413.

36.

Green

M. W.

Rogers

P. J.

Elliman

N. A.

Gatenby

S. J.

(1994). Impairment of cognitive performance associated with dieting and high levels of dietary restraint. Physiology & Behavior, 55(3), 447–452.

37.

Griskevicius

Ackerman

J. M.

Cantú

S. M.

Delton

A. W.

Robertson

T. E.

Simpson

J. A.

Thompson

M. E.

Tybur

J. M.

(2013). When the economy falters, do people spend or save? Responses to resource scarcity depend on childhood environments. Psychological Science, 24(2), 197–205.

38.

Hall

S. M.

Havassy

B. E.

Wasserman

D. A.

(1990). Commitment to abstinence and acute stress in relapse to alcohol, opiates, and nicotine. Journal of Consulting and Clinical Psychology, 58(2), 175–181.

39.

Herman

C. P.

Peter Herman

Janet

Patricia

Joyce

Donna

(1978). Distractibility in dieters and nondieters: An alternative view of “externality. Journal of Personality and Social Psychology, 36(5), 536–548. https://doi.org/10.1037/0022-3514.36.5.536

40.

Hobson

N. M.

Schroeder

Risen

J. L.

Xygalatas

Inzlicht

(2018). The psychology of rituals: An integrative review and process-based framework. Personality and Social Psychology Review, 22(3), 260–284.

41.

Horne

B. D.

Muhlestein

J. B.

Anderson

J. L.

(2015). Health effects of intermittent fasting: Hormesis or harm? A systematic review. The American Journal of Clinical Nutrition, 102(2), 464–470.

42.

Keinan

(1994). Effects of stress and tolerance of ambiguity on magical thinking. Journal of Personality and Social Psychology, 67(1), 48–55.

43.

Keys

(1950). University of Minnesota Laboratory of Physiological Hygiene. The biology of human starvation. University of Minnesota Press.

44.

Krosch

A. R.

Amodio

D. M.

(2014). Economic scarcity alters the perception of race. Proceedings of the National Academy of Sciences of the United States of America, 111(25), 9079–9084.

45.

Lambert

(2003). Fasting as a penitential rite: A biblical phenomenon? The Harvard Theological Review, 96(4), 477–512.

46.

Lang

Krátký

Shaver

J. H.

Jerotijević

Xygalatas

(2015). Effects of anxiety on spontaneous ritualized behavior. Current Biology, 25(14), 1892–1897.

47.

Laurin

Kay

A. C.

Fitzsimons

G. M.

(2012). Divergent effects of activating thoughts of God on self-regulation. Journal of Personality and Social Psychology, 102(1), 4–21.

48.

Lieberman

H. R.

Caruso

C. M.

Niro

P. J.

Adam

G. E.

Kellogg

M. D.

Nindl

B. C.

Kramer

F. M.

(2008). A double-blind, placebo-controlled test of 2 d of calorie deprivation: Effects on cognition, activity, sleep, and interstitial glucose concentrations. The American Journal of Clinical Nutrition, 88(3), 667–676.

49.

Littman

Takács

. (2017). Do all inhibitions act alike? A study of go/no-go and stop-signal paradigms. PLOS ONE, 12(10), Article e0186774.

50.

Loewenstein

(1999). Because it is there: The challenge of mountaineering . . . for utility theory. Kyklos, 52(3), 315–343.

51.

Magen

Gross

J. J.

(2007). Harnessing the need for immediate gratification: Cognitive reconstrual modulates the reward value of temptations. Emotion, 7(2), 415–428.

52.

Mani

Mullainathan

Shafir

Zhao

(2013). Poverty impedes cognitive function. Science, 341(6149), 976–980.

53.

Mani

Mullainathan

Shafir

Zhao

(2020). Scarcity and cognitive function around payday: A conceptual and empirical analysis. Journal of the Association for Consumer Research, 5(4), 365–376.

54.

Mattson

M. P.

(2015). Lifelong brain health is a lifelong challenge: From evolutionary principles to empirical evidence. Ageing Research Reviews, 20, 37–45.

55.

Mattson

M. P

. (2022). The intermittent fasting revolution: The science of optimizing health and enhancing performance. MIT Press.

56.

Mattson

M. P.

Longo

V. D.

Harvie

(2017). Impact of intermittent fasting on health and disease processes. Ageing Research Reviews, 39, 46–58.

57.

McCue

M. D.

(Ed.). (2012). Comparative physiology of fasting, starvation, and food limitation. Springer.

58.

Medin

Ojalehto

Marin

Bang

(2017). Systems of (non-)diversity. Nature Human Behaviour, 1(5), 1–5.

59.

Menon

Adleman

N. E.

White

C. D.

Glover

G. H.

Reiss

A. L.

(2001). Error-related brain activation during a Go/NoGo response inhibition task. Human Brain Mapping, 12(3), 131–143. https://doi.org/10.1002/1097-0193(200103)12:3<131::aid-hbm1010>3.0.co;2-c

60.

Meyer-Rochow

V. B.

(2009). Food taboos: Their origins and purposes. Journal of Ethnobiology and Ethnomedicine, 5(1), 18–27.

61.

Michalsen

Boschmann

(2014). Fasting therapy—Old and new perspectives: Themenheft: Forschende Komplementärmedizin / Research in Complementary Medicine 2013, Vol. 20, No. 6. S. Karger AG.

62.

Milyavskaya

Inzlicht

Hope

Koestner

(2015). Saying “no” to temptation: Want-to motivation improves self-regulation by reducing temptation rather than by increasing self-control. Journal of Personality and Social Psychology, 109(4), 677–693.

63.

Miyake

Friedman

N. P.

(2012). The nature and organization of individual differences in executive functions: Four general conclusions. Current Directions in Psychological Science, 21(1), 8–14.

64.

Mosek

Korczyn

A. D.

(1995). Yom Kippur headache. Neurology, 45(11), 1953–1955.

65.

Mullainathan

Shafir

(2013). Scarcity: Why having too little means so much. Macmillan.

66.

Nelson

L. D.

Morrison

E. L.

(2005). The symptoms of resource scarcity: Judgments of food and finances influence preferences for potential partners. Psychological Science, 16(2), 167–173.

67.

Netchaeva

Rees

(2016). Strategically stunning: The professional motivations behind the lipstick effect. Psychological Science, 27(8), 1157–1168.

68.

Norenzayan

(2013). Big Gods: How religion transformed cooperation and conflict. Princeton University Press.

69.

Orwell

(1933/1961). Down and out in Paris and London (vol. 61). Harcourt Brace Jovanovich.

70.

Parmentier

F. B. R.

Pacheco-Unguetti

A. P.

Valero

(2018). Food words distract the hungry: Evidence of involuntary semantic processing of task-irrelevant but biologically-relevant unexpected auditory words. PLOS ONE, 13(1), Article e0190644.

71.

Patterson

R. E.

Sears

D. D.

(2017). Metabolic effects of intermittent fasting. Annual Review of Nutrition, 37, 371–393.

72.

Pepper

G. V.

Nettle

(2017). The behavioural constellation of deprivation: Causes and consequences. The Behavioral and Brain Sciences, 40, Article e314.

73.

Piech

R. M.

Pastorino

M. T.

Zald

D. H.

(2010). All I saw was the cake. Hunger effects on attentional capture by visual food cues. Appetite, 54(3), 579–582.

74.

Pollitt

Mathews

(1998). Breakfast and cognition: An integrative summary. The American Journal of Clinical Nutrition, 67(4), 804S–813S.

75.

Qasrawi

S. O.

Pandi-Perumal

S. R.

BaHammam

A. S.

(2017). The effect of intermittent fasting during Ramadan on sleep, sleepiness, cognitive function, and circadian rhythm. Sleep & Breathing = Schlaf & Atmung, 21(3), 577–586.

76.

Rachlin

(2009). The science of self-control. https://doi.org/10.2307/j.ctv1kwxfs2

77.

Rad

M. S.

Ginges

(2017). Loss of control is not necessary to induce behavioral consequences of deprivation: The case of religious fasting during Ramadan. The Behavioral and Brain Sciences, 40, Article e338.

78.

Rad

M. S.

Martingano

A. J.

Ginges

(2018). Toward a psychology of Homo sapiens: Making psychological science more representative of the human population. Proceedings of the National Academy of Sciences, 115(45), 11401–11405.

79.

Radel

Clément-Guillotin

(2012). Evidence of motivational influences in early visual perception: Hunger modulates conscious access. Psychological Science, 23(3), 232–234.

80.

Rappaport

R. A.

(1999). Ritual and religion in the making of humanity. Cambridge University Press.

81.

Rogers

P. J.

Green

M. W.

(1993). Dieting, dietary restraint and cognitive performance. The British Journal of Clinical Psychology / The British Psychological Society, 32(1), 113–116.

82.

Rogers

Milkman

K. L.

Volpp

K. G.

(2014). Commitment devices: Using initiatives to change behavior. The Journal of the American Medical Association, 311(20), 2065–2066.

83.

Roky

Iraki

HajKhlifa

Ghazal

N. L.

Hakkou

(2000). Daytime alertness, mood, psychomotor performances, and oral temperature during Ramadan intermittent fasting. Annals of Nutrition and Metabolism, 44(3), 101–107. https://doi.org/10.1159/000012830

84.

Rossano

M. J.

(2012). The essential role of ritual in the transmission and reinforcement of social norms. Psychological Bulletin, 138(3), 529–549.

85.

Rouhani

M. H.

Azadbakht

(2014). Is Ramadan fasting related to health outcomes? A review on the related evidence. Journal of Research in Medical Sciences, 19(10), 987–992.

86.

Rozin

(1996). Towards a psychology of food and eating: From motivation to module to model to marker, morality, meaning, and metaphor. Current Directions in Psychological Science, 5(1), 18–24.

87.

Rozin

(2001). Social psychology and science: Some lessons from Solomon Asch. Personality and Social Psychology Review, 5(1), 2–14.

88.

Schelling

T. C.

(1984). Self-command in practice, in policy, and in a theory of rational choice. The American Economic Review, 74(2), 1–11.

89.

Shah

A. K.

Shafir

Mullainathan

(2015). Scarcity frames value. Psychological Science, 26(4), 402–412.

90.

Sharma

Alter

A. L.

(2012). Financial deprivation prompts consumers to seek scarce goods. The Journal of Consumer Research, 39(3), 545–560.

91.

Shas. (n.d.). Oman labour law. https://directory-oman.com/labourlaw.htm

92.

Shatenstein

Ghadirian

(1998). Influences on diet, health behaviours and their outcome in select ethnocultural and religious groups. Nutrition, 14(2), 223–230.

93.

Shenoy

A. J.

(2012). Strategic impatience in Go/NoGo versus forced-choice decision-making. Advances in Neural Information Processing Systems, 25, 2123–2131.

94.

Skrynka

Vincent

B. T.

(2019). Hunger increases delay discounting of food and non-food rewards. Psychonomic Bulletin & Review, 26(5), 1729–1737.

95.

Slepian

M. L.

Oikawa

Smyth

J. M.

(2014). Suppressing thoughts of evaluation while being evaluated. Journal of Applied Social Psychology, 44(1), 31–39.

96.

Ståhle

E. L.

Granström

Isaksson

Annas

Sepp

(2011). Effects of sleep or food deprivation during civilian survival training on cognition, blood glucose and 3-OH-butyrate. Wilderness & Environmental Medicine, 22(3), 202–210. https://doi.org/10.1016/j.wem.2011.02.018

97.

Story

(2007, January 15). Anywhere the eye can see, it’s likely to see an ad. The New York Times.

98.

Strang

Hoeber

Uhl

Koletzko

Münte

T. F.

Lehnert

Dolan

R. J.

Schmid

S. M.

Park

S. Q.

(2017). Impact of nutrition on social decision making. Proceedings of the National Academy of Sciences of the United States of America, 114(25), 6510–6514.

99.

Teo

Crawford

Yehuda

Jaghab

Bingham

J. J.

Gallon

M. D.

O’Connell

M. L.

Chittum

H. K.

Arzola

S. M.

Berry

(2017). Whole dietary patterns to optimize cognitive function for military mission-readiness: A systematic review and recommendations for the field. Nutrition Reviews, 75(suppl_2), 73–88. https://doi.org/10.1093/nutrit/nux009

100.

Tian

A. D.

Schroeder

Häubl

Risen

J. L.

Norton

M. I.

Gino

(2018). Enacting rituals to improve self-control. Journal of Personality and Social Psychology, 114(6), 851–876.

101.

Tian

H.-H.

Aziz

A.-R.

Png

Wahid

M. F.

Yeo

Constance Png

A.-L.

(2011). Effects of fasting during ramadan month on cognitive function in muslim athletes. Asian Journal of Sports Medicine, 2(3), 145–153.

102.

Trepanowski

J. F.

Bloomer

R. J.

(2010). The impact of religious fasting on human health. Nutrition Journal, 9, Article 57.

103.

Tuk

M. A.

Trampe

Warlop

(2011). Inhibitory spillover: Increased urination urgency facilitates impulse control in unrelated domains. Psychological Science, 22(5), 627–633.

104.

Tully

S. M.

Hershfield

H. E.

Meyvis

(2015). Seeking lasting enjoyment with limited money: Financial constraints increase preference for material goods over experiences. The Journal of Consumer Research, 42(1), 59–75.

105.

Walasek

Brown

G. D. A.

(2015). Income inequality and status seeking: Searching for positional goods in unequal U.S. States. Psychological Science, 26(4), 527–533.

106.

Wang

D. A.

Hagger

M. S.

Chatzisarantis

N. L. D.

(2020). Ironic effects of thought suppression: A meta-analysis. Perspectives on Psychological Science, 15(3), 778–793.

107.

Ward

Mann

(2000). Don’t mind if I do: Disinhibited eating under cognitive load. Journal of Personality and Social Psychology, 78(4), 753–763.

108.

Wegner

D. M.

(1992). The premature demise of the Solo experiment. Personality and Social Psychology Bulletin, 18(4), 504–508.

109.

Wegner

D. M.

(1994). Ironic processes of mental control. Psychological Review, 101(1), 34–52.

110.

Wegner

D. M.

(2009). How to think, say, or do precisely the worst thing for any occasion. Science, 325(5936), 48–50. https://science.sciencemag.org/content/325/5936/48.abstract?casa_token=fkT1BKb6PX4AAAAA:3w6CiSn3z3A4PZD62vq-ZKbyIZ-mmL24kzcIPexFC6nRa_IVOd36rKoj66ZAOWre1pw0JzqejSBSQ

111.

Wen

N. J.

Herrmann

P. A.

Legare

C. H.

(2016). Ritual increases children’s affiliation with in-group members. Evolution and Human Behavior, 37(1), 54–60.

112.

Werner

K. M.

Milyavskaya

Foxen-Craft

Koestner

(2016). Some goals just feel easier: Self-concordance leads to goal progress through subjective ease, not effort. Personality and Individual Differences, 96, 237–242.

113.

Wessel

J. R.

(2018). Prepotent motor activity and inhibitory control demands in different variants of the go/no-go paradigm. Psychophysiology, 55(3), Article e12871.

114.

Willcox

D. C.

Willcox

B. J.

Todoriki

Suzuki

(2009). The Okinawan diet: Health implications of a low-calorie, nutrient-dense, antioxidant-rich dietary pattern low in glycemic load. Journal of the American College of Nutrition, 28 (Suppl), 500S–516S.

115.

Winterhalder

Tucker

(1999). Risk-senstive adaptive tactics: Models and evidence from subsistence studies in biology and anthropology. Journal of Archaeological Research, 7(4), 301–348.

116.

Witte

A. V.

Fobker

Gellner

Knecht

Flöel

(2009). Caloric restriction improves memory in elderly humans. Proceedings of the National Academy of Sciences of the United States of America, 106(4), 1255–1260.

117.

A. J.

Schwarz

Wyer

R. S.

(2015). Hunger promotes acquisition of nonfood objects. Proceedings of the National Academy of Sciences, 112(9), 2688–2692. https://doi.org/10.1073/pnas.1417712112

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