Equally flexible and optimal response bias in older compared to younger adults.

Base-rate neglect is a failure to sufficiently bias decisions toward a priori more likely options. Given cognitive and neurocognitive model-based evidence indicating that, in speeded choice tasks, (a) age-related slowing is associated with higher and less flexible overall evidence thresholds (response caution) and (b) gains in speed and accuracy in relation to base-rate bias require flexible control of choice-specific evidence thresholds (response bias), it was hypothesized that base-rate neglect might increase with age due to compromised flexibility, and so optimality, of response bias. We administered a computer-based perceptual discrimination task to 20 healthy older (63-78 years) and 20 younger (18-28 years) adults where base-rate direction was either variable or constant over trials and so required more or less flexible bias control. Using an evidence accumulation model of response times and accuracy (specifically, the Linear Ballistic Accumulator model; Brown & Heathcote, 2008), age-related slowing was attributable to higher response caution, and gains in speed and accuracy per base-rate bias were attributable to response bias. Both age groups were less biased than required to achieve optimal accuracy, and more so when base-rate direction changed frequently. However, bias was closer to optimal among older than younger participants, especially when base-rate direction was constant. We conclude that older participants performed better than younger participants because of their greater emphasis on accuracy, and that, by making greater absolute and equivalent relative adjustments of evidence thresholds in relation to base-rate bias, flexibility of bias control is at most only slightly compromised with age. (PsycINFO Database Record (c) 2019 APA, all rights reserved).