Understanding the behavioural, neural, and attentional mechanisms of prosociality : multimodal comparisons between younger and older adults

Abstract

Prosociality, the voluntary behaviour intended to benefit others, is fundamental to human interaction. According to a comprehensive model of prosociality (Dunfield, 2014), it can be subdivided into helping, sharing, and comforting, based on the different needs of others. Results of previous research indicated that older adults act more prosocially than younger adults. However, most of these studies operationalised prosociality as monetary sharing. Therefore, whether older adults are more prosocial in helping and comforting than younger adults is unclear. In this PhD project, four studies were conducted to clarify whether older adults are more prosocial in helping, sharing, and comforting than younger adults and to examine the underlying behavioural, neural, and attentional mechanisms. Study 1 is a systematic review and meta-analysis that aimed to quantify age differences in different types of prosociality and identify potential moderators of these age effects. By synthesizing 51 studies, the results indicated that older adults were more prosocial than younger adults in general. The results of moderator analyses indicated that the age effect was only significant in sharing, but not in helping or comforting. It should be noted that not many studies were conducted for helping and comforting, probably due to the lack of a comprehensive measure of prosociality. Therefore, a comprehensive measure of prosociality, the Picture-based Measure of Prosociality (PB-Prosocial) was developed and validated in Study 2. This measure uses naturalistic pictures to enhance ecological validity. Study 2a established its content validity using the Delphi procedure in a panel of 26 experts. Study 2b validated this measure in 457 younger adults and it demonstrated good psychometric properties. Study 3 adopted the PB-Prosocial to investigate age differences in prosociality. A survey including 238 younger and 266 older adults was conducted in Hong Kong. The results indicated that older adults were more prosocial in sharing but not in helping or comforting. The behavioural mechanisms suggested that older adults were more familiar with situations when sharing was needed and perceived a lower cost associated with sharing. Using this picture-based approach, Study 4 integrated fMRI and eye-tracking to clarify the neural and attentional mechanisms of prosociality in 30 younger and 33 older adults. Neuroimaging results showed that older adults showed similar brain activation to younger adults during helping, but decreased activation in regions associated with decision-making and empathy during sharing and comforting. Eye-tracking results indicated that older adults spent more time looking at recipients’ faces during helping but not during sharing or comforting. Moreover, significant correlations between eye-tracking and brain activation, as well as between brain activation and self-reported prosocial intentions, suggested that prosocial intentions were supported by attentional and neural bases. To summarise, this PhD project developed a new measure of prosociality and shed light on the behavioural, neural, and attentional mechanisms underlying prosociality in older and younger adults using multimodal methods. Theoretically, this research extends the existing theories about the developmental trajectory of prosociality by highlighting the importance to include different types of prosociality. Practically, suggestions were provided to promote prosociality across the lifespan.