Bridging social psychology of cognition and behavior genetics: A new look at twin studies. – TWINS

A prominent finding in twin research is the very high degree of intellectual resemblance among monozygotic (MZ) twins, relative to dizygotic (DZ) twins and nontwin siblings, a phenomenon reflecting the action of genetic as well as environmental factors (e.g., socio-economic status, parenting, education). Here, we assume that twins’ intellectual resemblance may also vary as a function of twins’ inclination to compare with their co-twin in daily life (hereafter referred to as ‘social comparison orientation’ or ‘SCO’) and related susceptibility to the classic test situation in twin research (a coactive setting associated with the opportunity to obtain social comparison information). Consistent with this completely new hypothesis, a pilot study performed for the present ANR proposal revealed that even MZ twins vary in their inclination to compare with their co-twin. Above all, making twins high in SCO simply believe that their co-twin was working on a different—rather than identical—task, thereby removing the social comparison opportunity with the co-twin on the task at hand (the same task measuring fluid intelligence in both conditions), resulted in reduced within-pair behavioural similarity. Thus, it seems that twins’ inclination to compare with their co-twin may actually contribute to their intellectual resemblance, which is a completely new and important finding in twin research. This experimentally induced change in intellectual resemblance of MZ twins suggests to pay special attention to factors that were intensively investigated in experimental social psychology and largely overlooked in twin research. The present project relies on these highly provocative data with the ambition to offer a new—experimental and psychosocial—look at twin studies that were so far with no exception observational and blinded to the action of social comparison in test situations. It is assumed here that the lack of social comparison opportunity may actually conflict with the twins’ motivation to compare with their co-twin, a conflict that may be associated with altered behavioral similarity, increased stress (assessed via heart rate variability), and decreased response monitoring (assessed via error negativity/an evoked-related potential generated by the rostral cingulate zone), all these phenomena being indicative of a behavioral regulation breakdown. At the interface of social psychology of cognition and behavior genetics, and also relying on cognitive neuroscience concepts and methods, this ambitious project implies a specific ANR funding that will help improve our understanding of social comparison dynamics among MZ as well as DZ twins and nontwin siblings, specify their neurophysiological correlates, and perhaps more importantly, evaluate their impact on heritability estimates of cognitive abilities. This project might also open new avenues of research in the exploration of gene-brain-behavior relationships, with consequences for the long-debated notions of heritability and psychological assessment. It has therefore the potential to connect independent research traditions in the perspective of a cross-fertilization.