Biomedical subjects

Anjali Thapar

Publications and source records attributed to Anjali Thapar.

5 recordsLinked to original sources

PubMed2006

Aging, practice, and perceptual tasks: a diffusion model analysis.

Practice effects were examined in a masked letter discrimination task and a masked brightness discrimination task for college-age and 60- to 75-year-old subjects. The diffusion model (Ratcliff, 1978) was fit to the response time and accuracy data and used to extract estimates of components of processing from the data. Relative to young subjects, the older subjects began the experiments with slower and less accurate performance; however, across sessions their accuracy improved because the quality of the information on which their decisions were based improved, and this, along with reduced decision criteria, led to shorter response times. For the brightness, but not the letter, discrimination task, the older subjects' performance matched that of the younger group by the end of 4 sessions, except that their nondecision components of processing were slightly slower. These analyses illustrate how a well-specified model can provide a unified view of multiple aspects of data that are often interpreted separately.

Adult↗

PubMed2006

Aging and individual differences in rapid two-choice decisions.

The effects of aging on performance were examined in signal detection, letter discrimination, brightness discrimination, and recognition memory, with each subject tested on all four tasks. Ratcliff's (1978) diffusion model was fit to the data for each subject for each task, and it provided a good account of accuracy and the distributions of correct and error response times. The model's analysis of the components of processing showed that aging had three main effects: The nondecision components of processing were slower and the decision criteria were more conservative for 60- to 74-year-old and 75- to 85-year-old subjects than for college students, but the quality of the evidence on which decisions were based was as good for the older subjects as for college students on some of the tasks. Individual differences among subjects in components of processing tended to be preserved across the tasks, as was shown by strong correlations across the tasks in the parameters of the model that represent the components of processing. For example, if the evidence on which a subject's decisions were based was good in one task, it tended to be good in all four tasks.

Aged↗

PubMed2004

A diffusion model analysis of the effects of aging in the lexical-decision task.

The effects of aging on response time (RT) are examined in 2 lexical-decision experiments with young and older subjects (age 60-75). The results show that the older subjects were slower than the young subjects, but more accurate. R. Ratcliff s (1978) diffusion model provided a good account of RTs, their distributions, and response accuracy. The fits show an 80-100-ms slowing of the nondecision components of RT for older subjects relative to young subjects and more conservative decision criterion settings for older subjects than for young subjects. The rates of accumulation of evidence were not significantly different for older compared with young subjects (less than 2% and 5% higher for older subjects relative to young subjects in the 2 experiments).

Adult↗

PubMed2003

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

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.

Aged↗

PubMed2003

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

The effects of aging on decision time were examined in a brightness discrimination experiment with young and older subjects (ages, 60-75 years). Results showed that older subjects were slightly slower than young subjects but just as accurate. Ratcliff's (1978) diffusion model was fit to the data, and it provided a good account of response times, their distributions, and response accuracy. There was a 50-msec slowing of the nondecision components of response time for older subjects relative to young subjects, but response criteria settings and rates of accumulation of evidence from stimuli were roughly equal for the two groups. These results are contrasted with those obtained from letter discrimination and signal-detection-like tasks.

Aged↗