Abstract:

The positivity effect in facial trustworthiness evaluation refers to the phenomenon that older adults (OA) tend to evaluate unfamiliar faces as more trustworthy than younger adults (YA). Numerous previous studies have reported the presence of the positivity effect in judgments of trustworthy, neutral, and untrustworthy unfamiliar faces. Socioemotional selectivity theory (SST) and the dynamic integration theory (DIT) explain the underlying mechanisms of the positivity effect from the perspective of cognitive control and cognitive decline respectively, but a unified model has yet been established. According to the SST, OA with adequate cognitive resources can actively improve their evaluation of facial trustworthiness by selectively paying more attention to trustworthy faces or/and less attention to untrustworthy faces. In contrast, according to the DIT, cognitive decline in OA can lead to a passive increase in attention towards trustworthy faces or/and a decrease in attention towards untrustworthy faces, which can also improve the evaluation. There are discrepancies in the results of previous empirical studies as well. Some studies have supported the motivation explanation of the SST by demonstrating that OA may require sufficient cognitive resources to better process trustworthy faces than YA and thereby improve the evaluation of these faces. However, other studies have supported the cognitive explanation of DIT by showing that OA may “passively” improve their trust evaluations by reducing their processing of untrustworthy faces due to cognitive decline. Neuroimaging studies have found that the functions of the amygdala and anterior insula, which are sensitive to untrustworthy faces, decline with age. This could lead to a decrease in the ability of OA to recognize untrustworthy faces, resulting in reduced processing of such faces and a perception of higher trustworthiness evaluation. On the other hand, the function of the caudate nucleus, which is sensitive to trustworthy faces, enhances with age. This may enhance the rewarding significance of trustworthy faces for OA, resulting in increased processing of such faces and a perception of higher trustworthiness. Based on the theoretical mechanisms and empirical researches mentioned above, a dual-process model of the positivity effect in facial trustworthiness evaluation is proposed. Specifically, for trustworthy faces, OA may tend to “actively” increase their attention to it and show higher trust evaluations through cognitive control. For untrustworthy faces, OA may “passively” decrease their attention to it due to cognitive decline and show higher trust evaluations. Future research should take into account the physiological, psychological, and social changes that come with aging to construct a more comprehensive theoretical framework for explaining the OA positivity effect in facial trustworthiness evaluation. Secondly, by quantifying the age-related differences in facial trustworthiness at different stages using eye-tracking and event-related potentials (ERPs), we might be able to better understand the cognitive mechanisms underlying the positivity effect. In addition, using multiple analytical methods and combining them with behavioral data can further clarify the neural mechanisms. Finally, mindfulness practices as well as transcranial magnetic stimulation can be also introduced to help reduce older adults' vulnerability to fraud in the initial interpersonal interactions.

Key words: facial trustworthiness, positivity effect, older adults, interpersonal trust