The effect of base-rate priors on decision-making and confidence in healthy aging.

When explicit knowledge of the prior was given, younger adults performed more accurately than older adults, with both groups showing more accuracy for items in the color with an unequal base rate.

• Participants (younger n=78, older n=56) performed a two-alternative-forced-choice task judging orientation of dots in dynamic Glass pattern stimuli
• Stimuli varied in coherence and were presented in two colors, one with an unequal base rate and one with equal base rates
• In the explicit condition, participants were told about the base-rate difference prior to the task
• Both age groups showed an accuracy benefit for items in the unequal base-rate color in the explicit condition
• Younger adults outperformed older adults overall in the explicit condition

When the prior was implicitly learned, there was no overall age difference in accuracy, and older adults showed a greater benefit of the unequal prior in accuracy than younger adults.

• In the implicit condition, participants learned the base-rate prior through experience with the task rather than being told explicitly
• No significant overall age difference in accuracy was found in the implicit condition
• Older adults demonstrated a larger accuracy benefit from the unequal base-rate prior compared to younger adults in the implicit condition
• These results suggest older adults may particularly benefit from implicit learning of base-rate priors

In both explicit and implicit conditions, participants were more confident in decisions about stimuli that were consistent with the prior.

• This confidence boost for prior-consistent judgements occurred in both age groups and both conditions
• Judgements consistent with the prior were more confident than judgements inconsistent with the prior even when no diagnostic sensory information was present
• This finding suggests that a base-rate prior can influence confidence even in the absence of evidence

Older adults were generally less confident in their decisions in the implicit condition despite their performance not being significantly different from younger adults.

• The dissociation between confidence and accuracy in older adults was specific to the implicit condition
• Older adults' accuracy was not significantly different from younger adults in the implicit condition, yet they reported lower confidence
• This pattern suggests older adults may underestimate their own performance when the prior is implicitly rather than explicitly provided

Linear Ballistic Accumulator (LBA) model parameter estimates indicated that older adults have a slower information processing rate, greater response caution, and require more evidence before making a decision.

• LBA model parameters were estimated for both age groups
• Older adults showed slower information processing rates compared to younger adults
• Older adults exhibited greater response caution than younger adults
• Older adults required more evidence before making a decision
• These results largely align with past research on aging and decision-making

The results suggest that older adults may be negatively impacted by explicit presentation of multiple sources of information during decision-making.

• Older adults underperformed relative to younger adults specifically in the explicit condition where base-rate information was provided alongside sensory evidence
• In the implicit condition, where information was integrated through experience rather than explicit instruction, older adults showed comparable or greater benefit than younger adults
• This pattern implies that managing multiple explicit information sources simultaneously is particularly challenging for older adults