Age differences in proactive interference in verbal and visuospatial working memory

Abstract

In a free recall situation, subjects can predict, with some degree of accuracy, which words they will subsequently recall. This study focused on the question of why subjects often recall words to which they assign low prediction ratings. This problem was approached by comparing the properties of recall-not-predicted (RNP) and recall-predicted (RP) words which appeared in subjects' recall protocols. No differences were found between the two types of items (RNP and RP) in retrieval monitoring. The two types of items were differentiated by whether subjects could recollect the actual occurrence of the recalled items in the study list (“remember” responses) or not (“know” responses). Furthermore, the recall of RNP items, but not RP items, was improved by retrieval prompts. These results were taken to support the position that weakly encoded items may be recalled if they encounter a highly favourable retrieval environment, not anticipated by subjects during study.     

REMEDIATION OF ALEXIA: A CASE STUDY

This article describes the results of a remedial program provided to a subject who had incurred aphasia and alexia as a result of a series of strokes. The subject was pretested individually on a battery of tests and provided a specific type of remediation by a trained tutor. Posttests were administered to determine the effects of the instructional methods. Substantial gains were noted in language and auditory comprehension with a lesser gain in word recognition. Scores on other tests remained unchanged and the subject continued to make errors indicative of alexia. The results suggest that further research of the remedial methods over a longer period of time is needed.     

Direction information in multiple object tracking is limited by a graded resource

Is multiple object tracking (MOT) limited by a fixed set of structures (slots), a limited but divisible resource, or both? Here, we answer this question by measuring the precision of the direction representation for tracked targets. The signature of a limited resource is a decrease in precision as the square root of the tracking load. The signature of fixed slots is a fixed precision. Hybrid models predict a rapid decrease to asymptotic precision. In two experiments, observers tracked moving disks and reported target motion direction by adjusting a probe arrow. We derived the precision of representation of correctly tracked targets using a mixture distribution analysis. Precision declined with target load according to the square-root law up to six targets. This finding is inconsistent with both pure and hybrid slot models. Instead, directional information in MOT appears to be limited by a continuously divisible resource.     

Sources of Intertrial Proactive Interference in Rats’ Short-Term Memory in a Delayed Successive Matching-to-Sample Modality Discrimination

Rats were trained on a delayed successive matching-to-stimulus modality task consisting of onset of chamber lights or a tone for the sample stimulus, S1, and a comparison stimulus, S2. Lever pressing to S1 was reinforced as was lever pressing to its matching S2 (light–light or tone–tone pairs) but not to its mismatching S2 (light–tone, tone–light pairs). The interval between S1 and S2 within a trial, the retention interval (RI), was varied between 1 and 6 s within sessions while the interval between S2 and the next S1, the intertrial interval (ITI), was reduced from 24 to 12 s and finally to 6 s over blocks of sessions. In Experiment 1, where S1 was kept at 2 s and S2 at 10 s, rats’ matching accuracy declined over the longer RI, was slightly disrupted as ITIs were reduced to 6 s only over 1-s RIs, and was generally poorer to the tone than light S1. In Experiment 2, where both stimuli were 10 s increasing RIs caused steeper declines in matching accuracy to the tone S1 than light S1 and decreasing ITIs to 6 s disrupted rats performance over both RIs. Matching accuracy to the tone but not to the light S1 was also poorer when a preceding trial's S2 was a light S2 than when it was a tone S2 only during Experiment 2. Thisintertrial stimulus disagreementeffect was not influenced by ITI duration. These results suggest that intertrial proactive interference in delayed matching tasks consists of two separate and independent processes in rats similar to those found in pigeons (Edhouse & White, 1988).