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

Both Multiple Identity Tracking (MIT) and Multiple Object Awareness (MOA) capacities significantly declined in older observers compared to younger observers.

• Experiment 1 compared younger observers (18-44 years) with older observers (65-80 years).
• Both MIT capacity (precise knowledge of tracked objects) and MOA capacity (imprecise awareness of tracked objects) showed significant age-related decline.
• This decline was observed in a multiple object tracking task paradigm.

Age-related declines in MIT and MOA were linear across the adult lifespan from 18 to 76 years.

• Experiment 2 examined observers spanning 18-76 years of age.
• The decline in both MIT and MOA capacities followed a linear trajectory across this age range.
• This finding extends the age comparison from Experiment 1 to a continuous lifespan perspective.

A single signal-strength parameter (d') best explained tracking behavior for most observers and significantly declined with age.

• Computational models tested whether age effects were explained by one common signal-strength factor (d') or by a dual-process model with an additional recollection parameter (R).
• For most observers, a single signal-strength parameter (d') explained behavior best.
• The signal-strength parameter d' significantly declined with observers' age.
• Reduced sensitivity was identified as the likely mechanism impairing older adults' ability to discriminate and clearly represent visual objects.

A detailed, recollection-based object-location representation (R) plays only a small role in tracking multiple objects and does not vary with observers' age.

• The dual-process model included an additional recollection parameter (R) representing detailed, recollection-based object-location representations.
• The recollection parameter (R) accounted for only a small portion of tracking behavior.
• This recollection factor did not significantly vary as a function of observers' age.
• This result held across both experiments examining younger vs. older adults and the continuous adult lifespan.

MIT and MOA capacities are proposed to share a common signal-strength factor (d') that underlies both precise and imprecise knowledge of moving objects.

• MIT measures precise knowledge of tracked objects while MOA measures imprecise awareness (coarser representation) of tracked objects.
• Both capacities were accounted for by the same signal-strength parameter d' in the computational modeling framework.
• The common factor suggests that a single underlying sensitivity mechanism governs both levels of object representation during tracking.
• This common signal-strength factor declines with age, providing a unified explanation for age-related deficits in both MIT and MOA.