Anjali Thapar

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).

False recall and false recognition induced by presentation of associated words: Effects of retention interval and level of processing

The effects of retention interval and level of processing on false recall and false recognition of associates were examined. False recall and false recognition were induced by presenting subjects with words closely associated with a nonstudied word. Both level of processing and retention interval affected false recall (Experiment 1) and false recognition (Experiment 2) in the same direction with which they affected accurate recall and accurate recognition. That is, semantically processed lists exhibited higher levels of later false recall and false recognition than did superficially processed lists. Furthermore, a decline in false recall and false recognition occurred across retention intervals of 0, 2, and 7 days. However, the decline in false recall and false recognition was less pronounced than the decline in accurate recall and accurate recognition. Results are consistent with source monitoring and fuzzy trace explanations of false recall and false recognition.

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. Ratcliffs (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.

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.

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.

Effects of aging and IQ on item and associative memory.

The effects of aging and IQ on performance were examined in 4 memory tasks: item recognition, associative recognition, cued recall, and free recall. For item and associative recognition, accuracy and the response time (RT) distributions for correct and error responses were explained by Ratcliffs (1978) diffusion model at the level of individual participants. The values of the components of processing identified by the model for the recognition tasks, as well as accuracy for cued and free recall, were compared across levels of IQ (ranging from 85 to 140) and age (college age, 60-74 years old, and 75-90 years old). IQ had large effects on drift rate in recognition and recall performance, except for the oldest participants with some measures near floor. Drift rates in the recognition tasks, accuracy in recall, and IQ all correlated strongly. However, there was a small decline in drift rates for item recognition and a large decline for associative recognition and cued recall accuracy (70%). In contrast, there were large effects of age on boundary separation and nondecision time (which correlated across tasks) but small effects of IQ. The implications of these results for single- and dual-process models of item recognition are discussed, and it is concluded that models that deal with both RTs and accuracy are subject to many more constraints than are models that deal with only one of these measures. Overall, the results of the study show a complicated but interpretable pattern of interactions that present important targets for modeling.

Effects of level of processing on implicit and explicit tasks.

The series of experiments presented in this article replicate the interaction that B. H. Challis and D. R. Brodbeck (1992) reported between list design (blocked or mixed) and level of processing for word fragment completion: The advantage for semantically processed words over shallowly processed words was greater when the conditions were blocked than when they were mixed on the study list. A similar interaction was found for perceptual identification (a data-driven implicit task) and priming in general knowledge questions (a conceptually driven implicit task). However, both data-driven and conceptually driven explicit tasks failed to reveal such a pattern.

The Heritability of Memory in the Western Reserve Twin Project

The heritability of memory ability was examined using 137 monozygotic and 127 samesex dizygotic twin pairs from the Western Reserve Twin Project. Memory was assessed by eight measures drawn from the following batteries: the Wechsler Intelligence Scale for Children-Revised, the Colorado Test of Specific Cognitive Abilities, and the Cognitive Abilities Test. The results indicate that phenotypic correlations are generally low across these memory measures and heritability varies as a function of memory measure. These findings suggest that the heritability of memory varies as a function of the memory measure employed. Therefore, future studies investigating heritability estimates of memory should use a multimeasure battery to study this construct.

Mirror effect in frequency discrimination

In recognition, types of stimuli that are relatively easy to classify as old when old are also relatively easy to classify as new when new. The experiments reported here extend this mirror effect to discriminations among above-zero situational frequencies. Frequency discrimination exhibits a mirror effect when words are compared with nonwords or when low-linguistic-frequency words are compared with high-linguistic-frequency words. Accurate knowledge concerning the relative memorability of test items is neither necessary nor sufficient for the presence of a mirror effect.

Aging and recognition memory for emotional words: a bias account.

The present study investigated age-related differences in the locus of the emotional enhancement effect in recognition memory. Younger and older adults studied an emotion-heterogeneous list followed by a forced choice recognition memory test. Luce’s (1963) similarity choice model was used to assess whether emotional valence impacts memory sensitivity or response bias. Results revealed that the emotional enhancement effect in both age groups was due to a more liberal response bias for emotional words. However, the pattern of bias differed, with younger adults more willing to classify negative words as old and older adults more willing to classify positive words as old. The results challenge the conclusion that emotional words are more memorable than neutral words.