Recognition memory in healthy aging: The role of expected and unexpected semantically complex visual stimuli

This study investigates recognition memory in healthy older individuals, emphasizing the impact of expected (familiar) and unexpected (novel) semantically complex visual stimulus on recognition performance. A digital recognition task was created using monochromatic illustrations representing either expected (e.g., a person cooking in a kitchen) or unexpected (e.g., a person cooking in a bedroom) action-location relationships. A total of 103 participants (aged 60–75) underwent an encoding phase, followed by a 30-minute interval before a recognition test that included both previously viewed and novel pictures. Recognition performance was analyzed using signal detection theory metrics, including d-prime (sensitivity) and response criterion (c). Our results indicate that sensitivity (d' values) was significantly higher for unexpected items compared to expected ones, suggesting that novel stimuli enhanced recognition. However, response bias (c values) did not significantly differ between conditions, indicating a conservative recognition strategy for both stimulus types. Subsequent analyses revealed that the enhanced recognition of unexpected items was attributable to an increased ability to accurately reject new items rather than improved encoding of old items during the initial exposure. These findings suggest that older individuals perceive unexpected stimuli differently from known (expected) stimuli, with their memory advantage for unexpected pictures stemming from superior discriminating of new (lure) items rather than improved encoding. This study highlights the importance of using semantically meaningful and complex visual stimuli in cognitive assessments of older populations, enhancing the ecological validity of memory assessments.