The role of image realism and expectation in illusory self-motion (vection) perception in younger and older adults

Research on the illusion of self-motion (vection) has primarily focused on younger adults, with few studies including older adults. In light of documented age differences in bottom-up and top-down perception and attention, the current study examined the impact of stimulus properties (speed), cognitive factors (expectancy), and a combination of both (stimulus realism) on vection in younger (18-35 years) and older (65+ years) adults. Participants were led to believe through manipulation of the study instructions that they were either likely or unlikely to experience vection before they were exposed to a rotating visual stimulus aimed to induce circular vection. Realism was manipulated by disrupting the global consistency of the visual stimulus comprised of an intact 360 degrees panoramic photograph, resulting in two images (intact, scrambled). The speed of the stimulus was varied (faster, slower). Vection was measured using self-ratings of onset latency, duration, and intensity. Results showed that intact images produced more vection than scrambled images, especially at faster speeds. In contrast, expectation did not significantly impact vection. Overall, these patterns were similar across both age groups, although younger adults reported earlier vection onsets than older adults at faster speeds. These findings suggest that vection results from an interplay of stimulus-driven and cognitive factors in both younger and older adults.