Abstract
Scholars from different disciplines have investigated the nature of love for centuries. It has been only in the past century that social psychologists have begun to scientifically investigate the complexity of love in comparison with other emotions (Hatfield & Rapson, 2009, for review). We laud Lamy (2016) for his thoughtful intentions to pursue this long-lasting tradition and extend his goal to better understand the definition and neural bases of love by focusing on recent scientific evidence from social psychology and neuroscience. The better is our understanding of love, the greater is our respect for its significant role in mental and physical health.
From a lay viewpoint the subjective feeling of love can be subject to a broad range of personal definitions. From a scientific viewpoint, however, love is defined as a complex mental state involving basic and complex emotions as well as cognitive, rewarding, and goal-directed behavioral components (Hatfield & Rapson, 2009). Each subtype of love also has its own definition. Passionate love, for instance, is defined as “a state of intense longing for union” that is characterized by one’s motivated and goal-directed mental state to grow together with a significant other (Hatfield & Rapson, 2009). In line with the fact that love includes some characteristics specific to basic emotions, love is classified in several cross-cultural studies as an emotion, among other basic emotions such as joy, independently of the languages in which it is expressed (Hatfield & Rapson, 2009). Moreover, love is measurable and has a unique behavioral signature, as demonstrated in a recent eye-tracking study (Bolmont, Cacioppo, & Cacioppo, 2014). Furthermore, like complex emotions, love implies a long-lasting temporal dimension, which differentiates it from basic emotions or biological drives like lust.
In the last decade, neuroscientists have contributed greatly to a better understanding of the complexity of love by demonstrating that: (a) each subtype of love has specific neural correlates (Ortigue et al., 2010), and (b) passionate love has different neural correlates than lust (Cacioppo, Bianchi-Demicheli, Frum, Pfaus, & Lewis, 2012; Cacioppo & Cacioppo, 2013). Because the low statistical power characteristic of contemporary neuroimaging studies not only reduces the chance of detecting true effect but reduces the likelihood that a statistically significant result reflects a true effect (Cacioppo, Frum, et al., 2013), we recently performed quantitative meta-analyses (Caciopppo, Bianchi-Demicheli, Frum, et al., 2012; Ortigue, Bianchi-Demicheli, Patel, Frum, & Lewis, 2010) to obtain a better indication of the brain regions activated by love than those provided in any single empirical investigation.
Overall, our fMRI meta-analyses revealed that passionate love sparked increased activity in the subcortical brain areas sustaining basic emotions, euphoria, reward, and motivation, and in cortical brain areas involved in more complex emotional and cognitive processing (e.g., embodied cognition, body image, and attention). By demonstrating such a specific subcortico-cortical network, these results provide further evidence towards love as a complex emotion rather than a basic emotion only.
Interestingly, when comparing passionate love with lust (Cacioppo, Bianchi-Demicheli, Frum, et al., 2012; Cacioppo, Bianchi-Demicheli, Hatfield, & Rapson, 2012), our results revealed not only an overlapping brain network within subcortical emotion-related areas and higher order cortical areas, but also neural differences. For instance, the posterior insula was significantly more activated by feelings of lust (than passionate love), whereas the anterior insula was significantly more activated by feelings of passionate love (than lust). A result that was recently reinforced by a case study of a patient with a lesion in the anterior insula who showed a selective decision-making deficit for love, but not for lust (Cacioppo, Couto, et al., 2013). This posterior-to-anterior insular distinction between lust and love reinforces the neuro-functional characteristic of a posterior-to-anterior progression from interoception to an ultimate representation of all feelings. This is in line with the view that love is an abstract construct, which is partly based on the mental representation of repeated past emotional moments with another. This specific pattern of activation suggests that love builds upon a neural circuit for emotions and pleasure, adding regions associated with reward expectancy, and habit formation.
These behavioral and neuroimaging results clarify how a rigorous neuroscientific approach integrated with other disciplines such as social psychology has the potential to answer age-old questions as to the mechanism underlying and function of love. Love, termed pair-bonding in nonhuman mammalian species, has an evolutionary base; has a distinctive neurobiological substrate; and in humans manifests as a combination of physical sensations and feelings that is in response to certain stimuli or events. However, whether or not this research means love is a basic emotion depends on one’s definition of a basic emotion.