A diffusion model analysis of the effects of aging on letter discrimination.

Abstract

The effects of aging on accuracy and response time were examined in a letter discrimination experiment with young and older subjects. Results showed that older subjects (ages 60-75) were generally slower and less accurate than young subjects. R. Ratcliff's (1978) diffusion model was fit to the data, and it provided a good account of response times, their distributions, and response accuracy. The results produce similar age effects on the nondecision components of response time (about 50 ms slowing) and the response criteria (more conservative settings) to those from R. Ratcliff, A. Thapar, and G. McKoon (2001), but also show a reduced rate of accumulation of evidence for older subjects. The model-based approach has the advantage of allowing the separation of aging effects on different components of processing.Investigations of age-related differences in cognitive tasks have often revealed a pattern of declining performance with advancing age. The most dominant hypothesis has been the generalized slowing hypothesis, which states that all information processing is similarly affected by age (e.g., Birren, 1965;Brinley, 1965;Cerella, 1985Cerella, , 1990Cerella, , 1991Cerella, , 1994Fisk & Warr, 1996;Salthouse, 1985Salthouse, , 1996Salthouse, Kausler, & Saults, 1988). For some researchers, the general slowing hypothesis has been replaced by one that argues that different task domains show different degrees of slowing, for example, verbal versus spatial domains (see Allen, Ashcraft, & Weber, 1992;Allen, Madden, Weber, & Groth, 1993;Cerella, 1985Cerella, , 1994Hartley, 1992;Hertzog, 1992;Lima, Hale, & Myerson, 1991;Madden, 1989;Madden, Pierce, & Allen, 1992;Myerson, Ferraro, Hale, & Lima, 1992;Myerson, Wagstaff, & Hale, 1994;Perfect, 1994;Sliwinski & Hall, 1998). Whether general or domain specific, the slowing hypothesis has been favored by many cognitive aging researchers because it provides a relatively simple and intuitively appealing explanation of age-related decrements across a variety of laboratory tasks and everyday behaviors.A major source of support for the slowing hypothesis is the empirical regularity observed in Brinley functions. In a Brinley function, older subjects' response times are plotted against young subjects' response times and the result is almost always a straight line with a slope in the range of about 1.5 to 2.5 (

A diffusion model account of criterion shifts in the lexical decision task

“…Recently, several aging studies have also included a speed-accuracy manipulation (i.e., Ratcliff, Thapar, & McKoon, 2001;Ratcliff, Thapar, & McKoon, 2004;Thapar, Ratcliff, & McKoon, 2003). These studies used tasks in which error RTs were always longer than correct RTs; apart from the errors being slower than correct responses, the pattern of results was similar to the one reported here.…”

Age-related differences in diffusion model boundary optimality with both trial-limited and time-limited tasks

“…First, the older participants did respond substantially more quickly with fixed-time blocks than with fixed-trial blocks, demonstrating that they made some attempt to follow instructions. Many previous studies show that older participants also change boundaries in response to speed versus accuracy emphasis instructions, providing more evidence that older adults are willing to comply with experimenter-defined goals (Ratcliff, et al, 2001Thapar et al, 2003). Second, even the young participants showed limitations in their ability to optimize reward rate across the difficulty conditions with fixed-time blocks, and it is reasonable to think that these limitations would be more severe for the older population.…”

Comparing perceptual and preferential decision making

“…The range of tasks that have been modeled with the diffusion model include lexical decision (Wagenmakers, Ratcliff, Gomez & McKoon, 2008;Dutilh, Krypotos & Wagenmakers, 2011), letter discrimination (Thapar, Ratcliff & McKoon, 2003), brightness discrimination (Ratcliff andRouder, 1998, 2000), the random dot motion task (van Ravenzwaaij, Dutilh & Wagenmakers, 2012), and the implicit association test (Van Ravenzwaaij, Van der Maas & Wagenmakers, 2011).…”