Earthquakes on the Mind

Abstract

Objective: The present study explored the impact a natural disaster has on human performance.

Background: Previous research indicates that traffic accidents increase after disasters. A plausible explanation for this finding is that disasters induce cognitive disruption and this disruption negatively affects performance (e.g., driving quality).

Method: A total of 16 participants (7 men and 9 women) performed a sustained-attention-to-response task before and after a 7.1-magnitude earthquake. Performance (errors of omission, errors of commission, and reaction time) was compared before and after the earthquake.

Results: Errors of omission increased after the earthquake. Changes in errors of commission and reaction times were, however, dependent on individual differences in stress response to the earthquake.

Conclusion: The results indicate that natural disasters may have a negative impact on performance.

Application: Communities need to be aware of the increased risk of accidents following disasters and develop countermeasures, including individualized assessment tools.

Keywords

attention disaster earthquake response inhibition stress sustained attention vigilance

Introduction

Previous research has indicated an increase in self-reported stress and cognitive intrusions following natural disasters (Cardena & Spiegel, 1993; Neria, Nandi, & Galea, 2008). The impact of disasters on subsequent accident rates has also been noted (Gigerenzer, 2004; Stecklov & Goldstein, 2004; Su, Tran, Wirtz, Langteau, & Rothman, 2009). After the 9/11 terror attacks, Gigerenzer (2004) noted an increase in traffic fatalities. Gigerenzer argued that this rise was attributable to an increased preference to travel by ground versus by air. Gigerenzer’s original analysis was, however, subject to the ecological fallacy (e.g., using aggregate data to infer individual behavior).

A more recent study indicates that the rise in traffic fatalities was not attributable to an increase in miles driven and indeed was regional in scope (Su et al., 2009). In the last 3 months of 2001, there was a significant increase in traffic fatalities in the northeastern United States, and this increase was not attributable to increased road mileage. Instead, Su et al. (2009) attributed the rise to a decrease in driving quality caused by a regional increase in stress levels. Similarly, Stecklov and Goldstein (2004) noted a 35% spike in road fatalities 3 days after terror attacks in Israel; this spike occurred despite a notable overall reduction in traffic density and mileage after the terror attacks.

A plausible explanation for the increased risk of accidents after disasters is disaster-induced cognitive disruption (Cardena & Spiegel, 1993). Smallwood, Fitzgerald, Miles, and Phillps (2009) reported elevated levels of intrusive thoughts after negative mood inductions. Disasters are negative mood inducers. Nolen-Hoeskema and Marrow (1991) noted that those who have a ruminative style of responding were more likely to report stress and depression symptoms as a result of an earthquake event. Those who ruminate about the earthquake event may be those most likely to show task disruption, as the disruption is attributable to intrusive thoughts that siphon cognitive resources. Intrusive thoughts may compete with tasks for processing resources, and thus, disasters may indirectly disrupt performance via their impact on mood and thought occurrence (see McVay & Kane, 2010; Smallwood, 2010).

Indeed, Helton and Warm (2008) reported a negative correlation between the amount of self-reported task-unrelated thoughts and overall target detections in a vigilance task. In more recent studies, Helton and colleagues (Helton & Russell, 2011; Ossowski, Malinen, & Helton, 2011) reported decreased target detections when individuals are exposed to negative emotional stimuli. The threatening nature of negative emotional stimuli may alter the subjective state of the participant and encourage more elaborate thought processing. This thought processing may drain cognitive resources necessary for task performance (Ossowski et al., 2011).

No previous study has, however, examined the objective performance effects of a natural disaster. We were conducting a study on human performance employing a sustained-attention-to-response task (SART; Robertson, Manly, Andrade, Baddeley, & Yiend, 1997) that required two sessions, and between these two sessions, a significant unforeseen earthquake event occurred. On September 4, 2010, Christchurch, New Zealand, experienced a 10-km deep 7.1-magnitude earthquake with an epicenter 40 km from the city center. Unlike the comparable-magnitude Port au Prince, Haiti, 2010 earthquake, no deaths occurred in the Canterbury-Christchurch earthquake on September 4 (although subsequent aftershock events have resulted in deaths). This initial result was attributed to the combination of timing of the event, occurring at 4:35 a.m. local time, and the stringent building codes of New Zealand.

The Christchurch quake did, however, induce massive property damage in Christchurch, estimated at more than NZD $4 billion, and created hardships for the populace. This hardship included evacuation of many from their homes and the disruption of power and water supplies to much of the city. In the following month, Christchurch experienced hundreds of aftershocks with magnitudes greater than Magnitude 3. Given the unprecedented opportunity to investigate the impact of a large-scale natural disaster on performance, this study was quickly modified to focus on the effects of the earthquake.

The SART is a go/no-go target detection task with a high go, low no-go rate and was developed to measure lapses of performance in short durations (less than 6 min). People make frequent errors of commission, for example, inappropriate responses to the no-go signals, in the SART (Chan, 2001, 2002; Dockree et al., 2004, 2006; Johnson et al., 2007; Smallwood et al., 2004; Smallwood, Baracaia, Lowe, & Obonsawin, 2003; Smilek, Carrier, & Cheyne, 2010). The SART is, moreover, sensitive to speed-accuracy trade-offs in regard to both commission errors and go-signal response rates, thereby providing a measure of inhibitory control (Helton, 2009; Helton, Head, & Russell, 2011; Helton, Kern, & Walker, 2009; Helton, Weil, Middlemiss, & Sawers, 2010; Peebles & Bothell, 2004).

Errors of omission, for example, failures to respond to the go signals, also occur in the SART. Cheyne and colleagues (2009) argue the errors of omission in the SART are attributable to complete perceptual task disengagements and may be indicators of distracting intrusive thoughts. An alternative perspective suggested by Helton and colleagues (2010, 2011) is that the errors of omission are tactical forced rest stops enabling enhanced inhibitory control—in lay terms, taking a breather. Regardless of interpretation of omission errors, the SART is a sensitive measure of executive control.

Previous research indicates an increase in general stress levels after natural disasters and, more specifically, in the case of an earthquake event, increased reports of dissociative experiences, such as cognitive intrusions and more depersonalization (Bergiannaki, Psarros, Varsou, Paparrigopoulos, & Soldatos, 2003; Cardena & Spiegel, 1993; Neria et al., 2008). We, therefore, expected changes in SART performance postearthquake indicative of cognitive disruption and degraded executive control. We also examined stress responses to the earthquake by employing the short form of the Depression Anxiety Stress Survey (DASS-21; Henry & Crawford, 2005). People respond to stressors differently. Those who experience depression are more likely to become conservative, whereas those who experience greater anxiety are more likely to become impulsive (Eysenk, Derakshan, Santos, & Clavo, 2007). Therefore, in addition to general cognitive disruption, we expected individual differences in stress responses to be important in predicting postearthquake performance changes on the SART.

Method

Participants

Participants were 7 male and 9 female graduate students. They all had normal or corrected-to-normal vision according to self-report responses to sensory interview questions given prior to the experimental session.

Procedure

Participants were tested individually in laboratory cubicles, which were quiet with no external windows. Both sessions, preearthquake (July 30, 2010) and postearthquake (September 24, 2010), were conducted at 2:00 p.m. on a Friday to reduce potential circadian effects. Participants were seated 40 cm in front of a 24-cm × 32-cm computer screen set at approximately eye level. Participants in both sessions performed a SART. In the SART, participants viewed the presentation of black number stimuli presented in 94-point Arial font on a white background in a three-item array (see Figure 1). Participants were to press a computer key to any number 1 through 9 except the target number, 8, which required them to withhold a response. Target and nontarget number presentation was random. Target numbers occurred with p = .11 and nontargets with p = .89.

Figure 1.

Example of the sustained-attention-to-response task display.

The numbers were presented for 250 ms followed by interstimulus intervals (ISIs) of 1,000 ms, in which responses were recorded. During the ISIs, black plus-sign masks were employed to eliminate afterimages. The total onset-to-onset interval was 1,250 ms, with 48 stimuli events per minute. The entire SART was 6.75 min long. The stimuli were presented randomly in the center of the screen or 40 mm to the left or to the right of center with equal probability.

After the postearthquake session, the participants also filled out the short form of the DASS-21 (Henry & Crawford, 2005), a self-report measure of their average hours of sleep a night, and a two-item measure of trait emotional stability (Gosling, Rentfrow, & Swann, 2003). The later two-item measure of trait emotional stability correlates r = .81 with the longer Big 5 personality measure of neuroticism (see Gosling et al., 2003). In the present study, the DASS-21 was anchored to how the participant felt since the September 4 earthquake event. The DASS-21 items are scored with a rating from 0 (did not apply to me) to 3 (applied to me very much or most of the time), and in the present case, we simply averaged the items for the Anxiety factor and for the Depression factor.

The DASS-21 was employed in another study (Kemp, Helton, Richardson, Blampied, & Grimshaw, in press) 4 weeks after the September 4 Christchurch earthquake in which we surveyed 240 people who experienced the earthquake. From this larger sample, the DASS-21 had reasonable internal consistency with the DASS-21 Anxiety, α = .89, and the DASS-21 Depression subscales, α = .91. Additionally, those people who reported some or severe damage to their homes (n = 104) had significantly greater anxiety and depression than did those with no damage (n = 132) to their homes caused by the September 4 earthquake or aftershocks. The DASS-21 does appear to be sensitive to the specific impact of the earthquake and not just generalized anxiety and depression.

Results

Performance

The performance measures from the SART are errors of commission (inappropriate button responses), errors of omission (inappropriate response withholds), and reaction time for appropriate presses. For the SART, an error of commission involved pressing to a number 8, and an error of omission was withholding a response to any other number 1 through 9. These performance metrics were compared across the two sessions. The participants made significantly more errors of omission after the earthquake (M = 2.63, SE = 0.94) than prior to the earthquake (M = 0.63, SE = 0.18), t(15) = 2.18, p = .046, d = .74. There was, however, no statistically significant difference in errors of commission, t(15) = 0.17, p = .868, or appropriate response times, t(15) = 1.56, p = .140, respectively.

Performance and Stress Response

Despite the small sample size, to better describe the relationships between the variables, we examined differences in performance during the postearthquake session with the use of regression analyses. In these models, we examined the impact of earthquake-induced anxiety and depression on the performance of the second session, controlling for the participant’s preearthquake performance, emotional stability, average hours of sleep a night, and gender. These results are presented in Table 1. For errors of omission, the total regression model was statistically insignificant, F(6, 9) = 0.81, p = .59, R² = .35. For both errors of commission, F(6, 9) = 4.17, p = .028, R² = .74, and response time, F(6, 9) = 9.60, p = .002, R² = .87, the total models were statistically significant.

Table 1:

Regression Analyses for the Postearthquake Session for the Three Performance Metrics (N = 16, df = 9)

	Errors of Omission			Errors of Commission			Response Time
Variable	β	t	p	β	t	p	β	t	p
Prequake performance	.47	1.56	.15	.73	2.98	.02	.90	6.58	.00
Emotional stability	−.60	−1.74	.12	.04	0.17	.87	−.12	−0.76	.47
Sleep hours	.31	1.01	.34	−.14	−0.70	.50	.23	1.72	.12
Gender	−.27	−0.81	.44	−.28	−1.07	.31	.01	0.06	.96
Anxiety	−.09	−0.30	.77	.77	3.32	.01	−.54	−3.59	.01
Depression	−.24	−0.81	.44	−.52	−2.74	.02	.44	3.26	.01

Discussion

Errors of omission in the SART may be indicators of the effects of disruptive cognitive intrusion on human performance caused by either zoning-out episodes (Smallwood & Schooler, 2006) or forced rest stops attributable to increased cognitive demand (Helton et al., 2011). Although this study was not a true experiment with random assignment to conditions given the nature of the event (unforeseen disaster), vigilance performance typically improves with task experience (Colquhoun & Edwards, 1970; Parasuraman & Giambra, 1991). Indeed, this effect is specifically the case with the SART, in which performance improves with more task experience (Whyte, Grieb-Neff, Grantz, & Polansky, 2006). If anything, therefore, performance should have improved with the second postearthquake session. The increase of errors of omission postearthquake suggests the occurrence of earthquake-induced cognitive intrusion and disruption. This finding may have significant implications for postdisaster work performance and the increased risk of accidents following disasters (Su et al., 2009). Failing to perform a required action in some settings could have grave implications.

The SART, demanding both sustained attention and response inhibition, is also sensitive to individual differences in sacrificing the speed of a response for the likelihood of making a commission error (Helton, 2009, 2010). Essentially, the faster an individual responds, the more likely the person is to make an error of commission. Depressed people are more likely to become conservative, whereas anxious people are more likely to become impulsive (Eysenk et al., 2007). Although this study involved a small sample, and replication with a larger sample would be beneficial, participants who experienced greater earthquake-induced anxiety had more errors of commission and responded more quickly postearthquake in comparison to their preearthquake performance. Those who experienced greater earthquake-induced depression, however, had fewer errors of commission and responded more slowly postearthquake in comparison to their preearthquake performance. Anxious individuals postdisaster may be more likely to make hasty actions. Those experiencing depression postdisaster may take longer than normal to take action.

Smilek et al. (2010) have suggested that the length of reaction time in the SART may be indicative of the extent to which the participant is occupied with intrusive thoughts. Longer reaction times during the SART may be indicative of greater perceptual decoupling, and this may be more likely to occur in those reporting greater postdisaster depression. Indeed, Smallwood et al. (2009) found greater propensity to lapse in those reporting negative moods. Of critical importance is that individuals will respond differently to disasters. This finding may be important in assessing relative risk of accidents postdisaster (Su et al., 2009). In addition, the present findings further highlight the close relationship between response speed and commission errors in the SART (Helton, 2010).

In conclusion, with early individual assessment, improved and individualized interventions may be developed to mitigate the cognitive impact of disasters. Although the results of the present study are based on a relatively small sample, the results confirm psychological theories regarding the impact of disasters on performance, and these theories may help explain the increase in traffic fatalities and accidents after disasters (Su et al., 2009). Human factors professionals may need to help mitigate disaster-induced cognitive disruption in the nonclinical population. The present results may also have general implications for human performance in other high-stress environments.

Key Points

A disaster increases stress and thoughts about the event.

Intrusive thoughts about the disaster may cause an increase in accident risk by disrupting ongoing performance.

In the present study, performance after an earthquake was worse than performance prior to an earthquake.

References

Bergiannaki

J. D.

Psarros

Varsou

Paparrigopoulos

Soldatos

C. R.

(2003). Protracted acute stress reaction following an earthquake. Acta Psychiatric Scandinavia, 107, 18–24.

Cardena

Spiegel

(1993). Dissociative reactions to the San Francisco Bay Area earthquake of 1989. American Journal of Psychiatry, 150, 474–478.

Chan

R. C. K.

(2001). A further study on the sustained attention response to task (SART): The effect of age, gender and education. Brain Injury, 15, 819–829.

Cheyne

J.A.

Solman

G.J.F.

Carriere

J.S.A.

Smilek

(2009). Anatomy of an error: a biderectional state model of task engagement/disengagement and attention-related errors. Cognition, 111, 98–113.

Cheyne

J. A.

Carriere

J. S. A.

Smilek

(2006). Absent-mindedness: Lapses of conscious awareness and everyday cognitive failures. Consciousness and Cognition, 15, 578–592.

Colquhoun

W. P.

Edwards

R. S.

(1970). Practice effects on a visual vigilance task with and without search. Human Factors, 12, 537–545.

Dockree

P. M.

Bellgrove

M. A.

O’Keefe

F. M.

Moloney

Aimola

Cartoon

Robertson

I. H.

(2006). Sustained attention in traumatic brain injury (TBI) and healthy controls: Enhanced sensitivity with dual-task load. Experimental Brain Research, 168, 218–229.

Dockree

P. M.

Kelly

S. P.

Roche

R. A.

Hogan

M. J.

Reilly

R. B.

Robertson

I. H.

(2004). Behavioural and physiological impairments of sustained attention after traumatic brain injury. Cognitive Brain Research, 20, 403–414.

Eysenk

M. W.

Derakshan

Santos

Clavo

M. G.

(2007). Anxiety and cognitive performance: Attentional control theory. Emotion, 7, 409–434.

10.

Gigerenzer

(2004). Dread risk, September 11, and fatal traffic accidents. Psychological Science, 15, 286–287.

11.

Gosling

S. D.

Rentfrow

P. J.

Swann

W. B.

(2003). A very brief measure of the Big-Five personality domains. Journal of Research in Personality, 37, 504–528.

12.

Helton

W. S.

(2009) Impulsive responding and the sustained attention to response task. Journal of Clinical and Experimental Neuropsychology, 31, 39–47.

13.

Helton

W. S.

(2010). The relationship between lateral differences in tympanic membrane temperature and behavioral impulsivity. Brain and Cognition, 74, 75–78.

14.

Helton

W. S.

Head

Russell

P. N.

(2011). Reliable and unreliable warning cues in the sustained attention to response task. Experimental Brain Research, 209, 401–407.

15.

Helton

W. S.

Kern

R. P.

Walker

D. R.

(2009). Conscious thought and the sustained attention to response task. Consciousness and Cognition, 18, 600–607.

16.

Helton

W. S.

Russell

P. N.

(2011). The effects of arousing negative and neutral picture stimuli on target detection in a vigilance task. Human Factors, 53, 132–141.

17.

Helton

W. S.

Warm

J. S.

(2008). Signal salience and the mindlessness theory of vigilance. Acta Psychologica, 129, 18–25.

18.

Helton

W. S.

Weil

Middlemiss

Sawers

(2010). Global interference and spatial uncertainty in the sustained attention to response task (SART). Consciousness and Cognition, 19, 77–85.

19.

Henry

J. D.

Crawford

J. R.

(2005). The short-form version of the Depression Anxiety Stress Scales (DASS-21): Construct validity and normative data in a large non-clinical sample. British Journal of Clinical Psychology, 44, 227–239.

20.

Johnson

K. A.

Kelly

S. P.

Bellgrove

M. A.

Barry

Cox

Gill

Robertson

I. H.

(2007). Response variability in attention deficit hyperactivity disorder: Evidence for neuropsychological heterogeneity. Neuropsychologia, 45, 630–638.

21.

Kemp

Helton

W. S.

Richardson

J. J.

Blampied

N. M.

Grimshaw

(in press). Sleeplessness, stress, cognitive disruption and academic performance following the September 4, 2010, Christchurch earthquake. Australasian Journal of Disaster and Trauma Studies.

22.

McVay

J. C.

Kane

M. J.

(2010). Does mind wandering reflect executive function or executive failure? Comment on Smallwood and Schooler (2006) and Watkins (2008). Psychological Bulletin, 136, 188–197.

23.

Neria

Nandi

Galea

(2008). Post-traumatic stress disorder following disasters: A systematic review. Psychological Medicine, 38, 467–480.

24.

Nolen-Hoeksema

Morrow

(1991). A prospective study of depression and posttraumatic stress symptoms after a natural disaster: The 1989 Loma Prieta earthquake. Journal of Personality and Social Psychology, 61, 115–121.

25.

Ossowski

Malinen

Helton

W. S.

(2011). The effects of emotional stimuli on target detection: Indirect and direct resource costs. Consciousness and Cognition, 20, 1649–1658.

26.

Parasuraman

Giambra

(1991). Skill development in vigilance: Effects of event rate and age. Psychology and Aging, 6, 155–169.

27.

Peebles

Bothell

(2004). Modelling performance in the sustained attention to response task. In Proceedings of the Sixth International Conference on Cognitive Modeling (pp. 231–236). Pittsburgh, PA: Carnegie Mellon University/University of Pittsburgh.

28.

Robertson

I. H.

Manly

Andrade

Baddeley

B. T.

Yiend

(1997). “Oops!” Performance correlates of everyday attentional failures in traumatic brain injured and normal subjects. Neuropsychologia, 35, 747–758.

29.

Smallwood

(2010). Why the global availability of mind wandering necessitates resource competition: Reply to McVay and Kane (2010). Psychological Bulletin, 136, 202–207.

30.

Smallwood

Baracaia

S. F.

Lowe

Obonsawin

M. C.

(2003). Task-unrelated-thought whilst encoding information. Consciousness and Cognition, 12, 452–484.

31.

Smallwood

Davies

J. B.

Heim

Finnigan

Sudberry

O’Conner

Obonsawin

(2004). Subjective experience and the attentional lapse: Task engagement and disengagement during sustained attention. Consciousness and Cognition, 13, 657–690.

32.

Smallwood

Fitzgerald

Miles

L. K.

Phillps

L. H.

(2009). Shifting moods, wandering minds: Negative moods lead the mind to wander. Emotion, 9, 271–276.

33.

Smallwood

Schooler

J. W.

(2006). The restless mind. Psychological Bulletin, 132, 946–958.

34.

Smilek

Carrier

J. S. A.

Cheyne

(2010). Failures of sustained attention in life, lab, and brain: ecological validity of the SART. Neuropsychologia, 48, 2564–2570.

35.

Stecklov

Goldstein

J. R.

(2004). Terror attacks influence driving behavior in Israel. Proceedings of the National Academy of Sciences USA, 101, 14551–14556.

36.

J. C.

Tran

A. G. T. T.

Wirtz

J. G.

Langteau

R. A.

Rothman

A. J.

(2009). Driving under the influence (of stress): Evidence of a regional increase in impaired driving and traffic fatalities after the September 11 terrorist attacks. Psychological Science, 20, 59–65.

37.

Whyte

Grieb-Neff

Gantz

Polansky

(2006). Measuring sustained attention after traumatic brain injury: Differences in key findings from the sustained attention to response task (SART). Neuropsychologia, 44, 2007–2014.