Prevalence-Induced Concept Change in Older Adults

Prevalence-induced concept change describes a cognitive mechanism by which someone's definition of a concept shifts as the prevalence of exemplars of that concept changes. For instance, in a task where people have to judge whether the colour of an ambiguously-coloured dot is blue or purple, if the frequency of objectively blue dots in the environment decreases, people expand their concept of blueness and judge more dots to be blue than they did initially. In a series of experiments, Levari et al. (2018) demonstrated that this phenomenon extends to higher-order decision-making, such as ethical judgments as well. What these findings suggest is that conceptual spaces (whether it's about colours or ethical statements) in humans are not fixed, but are sensitive to change. While Levari et al. (2018) established this phenomenon in young adults, it is unclear how it affects older adults: do they outsource control and become more susceptible to concept change or are they rigid enough in their beliefs to be resistant to it? In the current study, we explore how prevalence-induced concept change affects older adults' lower-level, perceptual, and higher- order, ethical, decision-making. We find that older adults are less sensitive to prevalence-induced concept change than younger adults across both domains. A computational model reveals that these differences might in part be explained by older adults' tendency to perseverate (repeat responses). Our results suggest that older adults' concept space may be less flexible than younger adults' when faced with a changing world.