A common signal-strength factor limits awareness and precise knowledge of multiple moving objects across the adult...

This study investigated age differences in the precise knowledge and imprecise knowledge, or awareness, of multiple moving visual objects, measured by Multiple Identity Tracking (MIT) and Multiple Object Awareness (MOA) capacities, respectively, in a multiple object tracking task. Experiment 1 demonstrated significant decline of both capacities in older observers (65-80 years) compared to younger observers (18-44 years). Experiment 2 showed that age-related declines in MIT and MOA were linear across the adult lifespan (18-76 years). Additionally, we used computational models to test whether age effects could be explained by one common signal-strength factor (d') or by a dual-process model with an additional recollection parameter (R). Our results indicate that a detailed, recollection-based object-location representation (R) only plays a small role in tracking many objects and this factor does not vary with observers' age. For most observers, a single signal-strength parameter (d) explained behaviour best, and this parameter significantly declined with observers' age. This suggests that reduced sensitivity likely impairs older adults' ability to discriminate and clearly represent visual objects, resulting in both lower MIT and MOA capacities.