This study investigated how age affects the recruitment of the neural correlates of impression formation and social evaluation, and how the engagement of regions within this network might vary based on age-related changes in socioemotional goals. Much research has identified decreases in prefrontal function in aging (Nyberg et al., 2010
; West, 1996
), with supplementary neural regions compensating for this deficit (Park & Reuter-Lorenz, 2009
). However, the majority of the previous work did not use social tasks, and it is unclear whether the functional impairments extend to regions underlying social cognition, and specifically, the engagement of medial prefrontal cortex and connected regions. Importantly, the current data extends literature involving self referencing (Gutchess, et al., 2007
) and theory of mind (Castelli, et al., 2010
), indicating that a broad mentalizing network, including medial prefrontal regions, is involved in impression formation (Ma, et al., 2011
) and functionally, is relatively spared in healthy aging. The current work demonstrates that brain regions implicated in impression formation and mentalizing, including dmPFC, vmPFC, and TPJ (anatomically corresponding to angular gyrus in , but functionally defined in social neuroscience literature as TPJ (Saxe & Kanwisher, 2003
)), are similarly recruited among young and older adults when forming impressions and socially evaluating others.
Moreover, the current work demonstrates how the social nature of the material itself may not be enough to engage this social processing system. Previous memory research has demonstrated that successfully encoding impressions correlates with increased activity in dmPFC, whereas hippocampal engagement corresponds to trying to memorize a sequence of statements, orienting to the material in a non-social way (J. Mitchell, et al., 2004
). We found that making social evaluations (interpersonally meaningful and interpersonally irrelevant) relative to orienting to person information in a non-social manner increased activation in a broad network of regions implicated in social cognition, including left dmPFC, right vmPFC, bilateral PrC, left TPJ, left TP, and bilateral fusiform gyrus. Although mPFC is implicated in responding to self-referential thought (Kelley, et al., 2002
), we did not find differential medial prefrontal activity when contrasting the social-meaningful with the social-irrelevant conditions across conditions or across age groups. This suggests that regardless of age, participants recruited a number of regions involved in the processing of person information to evaluate others, which differs from self-reference tasks primarily mediated by mPFC engagement.
Although dmPFC and other regions in the current work were similarly recruited with age, suggesting the functional preservation of a social evaluation network, this research also supports the idea that age-related changes in socioemotional goals and social expertise may moderate the engagement of neural regions. Behavioral work indicates that older adults can perform at the level of young when given a purposeful goal (Hess, et al., 1998
; Hess & Tate, 1991
). Other research evidences that older adults show expertise in social situations compared to a younger cohort (Hess & Auman, 2001
; Hess, et al., 2005
). Surprisingly, the rTP exhibited heightened activity in older relative to young adults when contrasting the social and non-social conditions. The rTP, a region implicated in mentalizing (Ma, et al., 2011
) and social cognition (Olson, Plotzker, & Ezzyat, 2007
), has been identified as a region involved in storing information regarding social behaviors (Zahn, et al., 2007
). Although not predicted a priori, enhanced activation in rTP among older adults relative to young seems consistent with the growing literature on this region (Beadle, Yoon, & Gutchess, in press
), potentially indicating that older adults rely on stored social experiences to evaluate others, based on their greater accumulated life experiences relative to young. This speculatively provides potential neural evidence supporting behavioral findings of enhanced social mastery in older adults relative to young. Older adults showed deactivation in rTP while making non-social evaluations, while young adults engaged this region during these decisions, although to a lesser extent then when making the two social evaluations. This may demonstrate that young adults can more successfully access social resources in the presence of a distracting and irrelevant task. Notably, when comparing activity related to the social-meaningful and social-irrelevant evaluations (See ), older adults did not show differential activity within rTP. This suggests that older adults recruit rTP to evaluate different kinds of social questions, and do not solely focus on interpersonally meaningful incoming information.
When comparing the social-meaningful and social-irrelevant evaluations, activity between young and older adults differed in bilateral PCC. This may reflect age-related changes in the prioritization of incoming information. Socioemotional Selectivity Theory posits that while young adults focus on novelty and information acquisition, older adults concentrate on information with heightened socioemotional meaning (Carstensen, et al., 1999
; Fung & Carstensen, 2003
). Interestingly, a recent fMRI study of impression formation noted that while dmPFC is recruited to process person information, PCC engagement may reflect the valuation of this incoming person information, such that PCC activity during impression formation corresponds with the subsequent strength of evaluations (Schiller, et al., 2009
). In the current study, older adults had increased PCC activity over young in the social-meaningful versus social-irrelevant contrast. This difference was largely driven by young adults’ increased activity during the social-irrelevant evaluations. This potentially reflects young adults’ focus on knowledge related goals, in that given an ambiguous question (e.g., pet ownership), young adults may have taken the time to consider the possibilities when evaluating others, whereas older adults may have chosen to reserve cognitive effort for a more personally engaging task.
Other work, however, suggests that PCC activity may be related to appearance-based over character-related judgments (Moran, Lee, & Gabrieli, 2011
), and highlights PCC’s role in attentional processes (Pessoa & Padmala, 2005
). In this light, the increased activity in PCC for young over older adults for the social-irrelevant condition might not be related to value assignment per se, but actually representing attention required to extrapolate knowledge from ambiguous information. Regardless, an attention-based framing may still support young adults’ overall emphasis on information acquisition over older adults, given that older adults might be less likely to concentrate and exert cognitive effort on judgments lacking social meaning.
Unexpectedly, older adults showed increased activity for the social-meaningful evaluations in left IFG, when compared to young adults. Although not as widely cited in impression formation literature, IFG has been implicated in processing intentions of observed actions (deLange, Spronk, Willems, Toni, & Bekkering, 2008
), and as indicating the degree of self-relevance (Kelley, et al., 2002
). Older adults showed greater activation in this region for making socially meaningful over social, but interpersonally irrelevant, judgments while young adults did not. Heightened activity in this region in older over young adults for the social-meaningful evaluations may illustrate that these evaluations held greater semantic meaning for older adults, given that left IFG has been implicated in semantic processing (Fiez, 1997
), and in retention of semantic meaning (Hamilton, Martin, & Burton, 2010
). We speculate that this may reflect older adults’ prioritization of processing information with emotionally and socially meaningful content (Carstensen, et al., 1999
; Fung & Carstensen, 2003
; Hess, et al., 1998
). Consistent activation in this region for older adults during the two social evaluations could also possibly indicate the labeling of incoming social information as salient, influencing recruitment of the neural mechanism underlying social evaluation, given a recent study suggesting that attenuation in left IFG activity represents the filtering out of irrelevant information in order to highlight the salience of human, but not non-biological action (Chong, Williams, Cunnington, & Mattingley, 2008
Given that our sample consisted of well-educated and active older adults, these results may not generalize to the entire older adult population. Because the older adults who volunteered for this study had relatively active lifestyles, this may have buffered cognitive decline that may have been more apparent in a more sedentary cohort. The “use it or lose it” approach to cognitive decline (Hultsch, Hertzog, Small, & Dixon, 1999
) would suggest that the regions involved in social evaluation remained well preserved with age, although recruitment of some of these regions may be modulated due an increased focus on socioemotional information relative to young, because forming impressions and evaluating others is such an important part of an active lifestyle. Furthermore, even though our sample of older adults engage these processes much like young adults, it is difficult to know the extent to which forming impressions of others in the scanning environment captures everyday interactions with others in a natural environment. Although the age groups display similar recruitment of regions involved in social evaluation, suggesting that our older adults may be immune from age-related decline, it is important to note that they performed worse than young on tasks of processing speed and executive function. This suggests that our sample of older adults is similar to those in fMRI studies showing age-related decrements in functionality (Gazzaley, Cooney, Rissman, & D'Esposito, 2005
; Hedden & Gabrieli, 2004
). To address whether the preserved activation of brain regions underlying social evaluation resulted from our active and well-educated sample of older adults, a potential follow-up study could include a task where older adults would be expected to show decreased performance or neural activation.
Additionally, differences in pet ownership experience between the age groups could have contributed to differential activation to the social-irrelevant evaluation, which was framed as a question of pet ownership. However, an assessment of pet ownership characteristics between the age groups1
revealed that more older participants currently owned pets than young, and that older adults reported more years living with and percentage of time per day with pets than young, although all young participants had lived with pets in the past. Additionally, young and older adults did not differ in the degree of personal connection to their pets. Thus, differential neural activity to the socially irrelevant evaluation involving pet ownership cannot be solely due to age differences in the self-relevance of the question itself. Rather, the ambiguity of determining pet ownership question may have caused increased activation among young relative to old in the social-irrelevant condition if young adults took time to consider the possibilities of pet ownership in an unconscious effort to acquire knowledge, whereas older adults did not.
Notably, although both young and older adults exhibited neural recruitment of dmPFC during social evaluation, we cannot establish whether both groups similarly generated impressions without corresponding behavioral data from the present study. However, previous behavioral findings support the idea that the generated impressions may indeed be similar and that if anything, older adults may show more consistent use of behavioral information than young. For instance, older adults assess diagnostic behavioral material to a greater extent than young in some circumstances (Hess & Auman, 2001
; Hess, et al., 2005
). Furthermore, recent work has also found that older adults infer target traits more accurately than young (Cassidy & Gutchess, in press
It is important to note that the potential age-related preservation of the neural correlates of social evaluation may not extend to all aspects of social cognition. Although our study extends research on self-referencing (Gutchess, et al., 2007
) and theory of mind (Castelli, et al., 2010
), supporting age-invariance in brain function during these social tasks, functional impairments may not become apparent until these social processes are studied under different task conditions. Future work must not only test the reliability of this finding using different contexts (e.g., cognitive load), to assess the extent of preserved functionality within these brain regions, but also test the extent to which older adults can remember these impressions. While findings showing that the recruitment of neural regions underlying impression formation is relatively stable with age are important, this information cannot be used to anticipate the future behaviors of others unless the impressions are successfully encoded into memory. Although some work (Todorov & Olson, 2008
) suggest that the ability to remember impressions is age-invariant, other research has demonstrated that older adults receive disproportionate benefits in memory when evaluating relationship-based questions after forming impressions (Cassidy & Gutchess, in press
). This suggests that the regions underlying the successful retrieval of impressions might depend on how individuals orient to information at encoding. The hypothesis that memory for impressions is preserved with age, however, needs to be tested using fMRI in a subsequent memory paradigm to extend the current work and clarify how the engagement of the neural correlates of social evaluation may change with healthy aging.
These findings add to a burgeoning literature on the social neuroscience of aging, and provide the first evidence that with advancing age, the neural underpinnings of social evaluation may remain functionally intact. These findings show that functionality in brain regions underlying social cognition may be preserved with age, in contrast to influential work showing age-related functional decline and compensatory mechanisms (Cabeza, et al., 2002
; Hedden & Gabrieli, 2004
). Importantly, we also show that age-related changes to socioemotional goals may modulate the recruitment of regions within this social processing network. Future work can clarify how aging impacts how the impressions underlying these social judgments are transferred into memory, and how aging may affect the neural substrates of other social decisions.