Aging Slows Access to Temporal Information From Working Memory.

OBJECTIVES: To evaluate the impact of aging on controlled memory search operations, we investigated the retrieval of temporal order information from working memory (WM). METHOD: Young and older adults completed a relative judgments-of-recency (JOR) task. In each trial, participants studied 5-item lists and were presented with two probes from the study list. Participants indicated the probe that had appeared more recently in the study list. RESULTS: Analyses of accuracy data showed that young adults were more successful in correctly detecting the more recent probe compared with older adults. To evaluate the retrieval dynamics, we applied Hacker's (1980) serial scanning model on reaction time data. Results from the model fits revealed that older adults were slower in engaging in the serial memory search operations required to access temporal order information from WM. DISCUSSION: These findings suggest that this age-related impairment in a JOR task might arise from a slower deployment of controlled memory operations, such as serial search.

Optimal time discrimination.

In the temporal bisection task, participants categorize experienced stimulus durations as short or long based on their similarity to previously acquired reference durations. Reward maximization in this task requires integrating endogenous timing uncertainty as well as exogenous probabilities of the reference durations into temporal judgements. We tested human participants on the temporal bisection task with different short and long reference duration probabilities (exogenous probability) in two separate test sessions. Incorrect categorizations were not penalized in Experiment 1 but were penalized in Experiment 2, leading to different levels of stringency in the reward functions that participants tried to maximize. We evaluated the judgements within the framework of optimality. Our participants adapted their choice behaviour in a nearly optimal fashion and earned nearly the maximum possible expected gain they could attain given their level of endogenous timing uncertainty and exogenous probabilities in both experiments. These results point to the optimality of human temporal risk assessment in the temporal bisection task. The long categorization response times (RTs) were overall faster than short categorization RTs, and short but not long categorization RTs were modulated by reference duration probability manipulations. These observations suggested an asymmetry between short and long categorizations in the temporal bisection task.