Aging, memory and visual search

Potential age-related differences in the memory processes that underlie visual search are examined in the present study. Using a dynamic, gaze-contingent search paradigm developed to assess memory for previously examined distractors, older adults demonstrated no memory deficit. Surprisingly, older adults made fewer refixations compared to their younger counterparts, indicating better memory for previously inspected objects. This improved memory was not the result of a speed-accuracy trade-off or larger Inhibition-of-Return effects for older than for younger adults. Additional analyses suggested that older adults may derive their benefit from finer spatial encoding of search items. These findings suggest that some of the memory processes that support visual search are relatively age invariant.     

Testing the limits of cognitive plasticity in older adults: application to attentional control

Laboratory based training studies suggest that older adults can benefit from training in tasks that tap control aspects of attention. This was further explored in the present study in which older and younger adults completed an adaptive and individualized dual-task training program. The testing-the-limits approach was used [Lindenberger, U., & Baltes, P. B. (1995). Testing-the-limits and experimental simulation: Two methods to explicate the role of learning in development. Human Development, 38, 349-360.] in order to gain insight into how attentional control can be improved in older adults. Results indicated substantial improvement in overlapping task performance in both younger and older participants suggesting the availability of cognitive plasticity in both age groups. Improvement was equivalent among age groups in response speed and performance variability but larger in response accuracy for older adults. The results suggest that time-sharing skills can be substantially improved in older adults.     

Let's pretend: The role of motoric imagery in memory for sentences and words

A number of theories suggest that for young children, concepts should have an important motoric (or sensory-motor) component. A levels-of-processing theory is proposed which predicts that processing on motoric imagery should facilitate memory for both isolated words and for sentences. Experiment 1 examined the effects of motoric enactment (viz., pretend play) of sentences on memory for the sentences. Motoric imagery facilitated memory for both children (5 to 7 years of age) and adults, though, contrary to expectations, the effects were weaker for the children than for the adults. Further, it was found that motoric imagery affected the initial acquisition, but was not important as a retreival cue. Experiment 2 examined the effects of motoric imagery on free recall of lists of unrelated words. Under these conditions, motoric imagery facilitated memory for both children (7 to 9 years of age) and adults equally; in contrast, visual imagery instructions had no effect on memory. These results indicate that motoric imagery may facilitate memory under conditions in which visual imagery has no effect. Theoretical implications are explored for previous experiments on pretend play which suggest that training for pretent enactment can facilitate cognitive development.     

Age differences in the control of looking behavior: do you know where your eyes have been?

Previous research has shown that during visual search young and old adults' eye movements are equivalently influenced by the appearance of task-irrelevant abrupt onsets. The finding of age-equivalent oculomotor capture is quite surprising in light of the abundant research suggesting that older adults exhibit poorer inhibitory control than young adults on a variety of different tasks. In the present study, we examined the hypothesis that oculomotor capture is age invariant when subjects' awareness of the appearance of task-irrelevant onsets is low, but that older adults will have more difficulty than young adults in inhibiting reflexive eye movements to task-irrelevant onsets when awareness of these objects is high. Our results were consistent with the level-of-awareness hypothesis. Young and old adults showed equivalent patterns of oculomotor capture with equiluminant onsets, but older adults misdirected their eyes to bright onsets more often than young adults did.     

Psychometric functions and a correlation model of binaural detection

Sets of psychometric functions for the detection of tone in noise are reexamined for several interaural listening conditions. Best-fit sets of functions are determined for a “correlation” model of binaural masking level differences (MLDs). Based on only three parameters, this model predicts both the forms and relative positions of all such functions. The finding that MLDs are relatively independent of the detection level chosen for their determination is predicted by the model, and the sets of theoretical functions describe the data nearly as well as a previously determined empirical relation which requires M + 1 parameters for M curves.     

Aversive properties of the negative stimulus in a successive discrimination

Experiment I sought to determine if the stimulus correlated with extinction in a successive discrimination was an aversive stimulus. An escape response provided an index of aversive control. Two groups of pigeons were exposed to a multiple variable-interval 30-sec extinction schedule. For the experimental group, a single peck on a second key produced a timeout during which all lights in the chamber were dark. For the control group, pecks on the second key had no contingency. The rate of responding on the timeout key during extinction for the experimental group was higher than that of the control group during all sessions of discrimination training except the first. In Exp. II, green was correlated with variable interval 30-sec and red was correlated with variable-interval 5-min. Timeouts were obtained from variable-interval 5-min. There were more timeouts from extinction in Exp. I than from variable-interval 5-min in Exp. II. Experiment III showed that not presenting the positive stimulus reduced the number of timeouts from the negative stimulus for the two birds from Exp. I that had the highest rate of timeouts from extinction, but had little effect on the two birds that had the lowest rate of timeouts. These results suggest that in a multiple schedule, the stimulus correlated with extinction, or the lower response rate, functions as a conditioned aversive stimulus. Explanations of the timeout response in terms of extinction produced variability, displaced aggression, and stimulus change, were considered but found inadequate.