Encoding and retrieval processes in the memory for conceptually distinctive events

Memory for conceptually isolated (distinctive) words was investigated in two experiments. In Experiment 1, recognition of distinctive targets was compared with recognition of targets from homogeneous lists and with recognition of background information. Distinctive targets were better recognized than the same words presented in homogeneous lists. No effects of distinctiveness on the recognition accuracy of background items were observed. These results fail to support the hypothesis that distinctive information receives extra resources during encoding at the expense of surrounding background information. In Experiment 2 the effects of distinctiveness on recall were evaluated. Distinctive targets were more likely to be recalled than targets from homogeneous lists. However, unlike the effects found in recognition, background items were more poorly recalled from lists containing distinctive targets than from homogeneous lists. Organizational processes in recall were also evaluated. There was greater subjective organization for target and background items from lists containing distinctive targets than from lists containing nondistinctive targets. These results were discussed in terms of encoding and retrieval explanations of the effects of distinctiveness.     

Visual perseveration in normal and mentally retarded children

Visual perseveration was investigated within mentally retarded and second, fifth, and eighth grade normal children (Ns = 12 each group). Subjects matched an auditorially presented click to the onset and offset of visually presented stimuli. Time differences between visual stimulus offset and the point at which subjects reported simultaneity of the click and visual stimulus offset was assumed to reflect visual perseveration. Results showed: (a) no differences between the normal children as a function of age; (b) no difference between groups for stimuli of 100 msec. or longer duration; and (c) retarded subjects judged stimuli of 20 and 50 msec. to be of shorter duration than did normal subjects. This highly specific distinction between retarded and normal subjects suggests a difference in an early stage of perceptual processing.     

Toilet training of normal and retarded children

Early elements in an operant chain of toilet behaviors were trained in three normal infants and five retarded children. Following that, eliminative behaviors were conditioned by operant procedures. Each child was equipped with an auditory signalling device that gave cues to the learner. Baseline behavior was recorded for a period of five days. The procedure for training consisted of two steps. First, a response was obtained through physical, verbal, and auditory prompts. Second, prompts were faded until the child responded in the presence of the auditory signal. When the device was removed the child performed without the auditory prompt. Parents were instructed in a similar procedure to enhance generalization in the home. Seven of the eight subjects reached a criterion and maintained that behavior during three criterion sessions.     

Encoding and retrieval processes in learning-disabled, head-injured, and nondisabled young adults

Using a multi-trial, free-recall paradigm (Rey Auditory-Verbal Learning Test; Lezak, 1983), the acquisition and retention by learning disabled (LD) young adults with a Halstead Impairment Index less than or equal to 0.3 (low LD) or greater than or equal to 0.4 (high LD) was compared with that of nondisabled and head-injured (HI) young adults. Significant group differences, particularly during the last three acquisition trials, confirmed the effectiveness of this method in revealing subtle learning and retention deficits. Analyses of Trial 1 recall showed group differences in the prerecency but not the recency portion of the serial position curve, thus implicating long-term but not short-term memory differences between the groups. Analyses of pair frequency (Sternberg & Tulving, 1977) data showed that the three clinical groups had difficulty organizing the to-be-learned material for effective retrieval. Following an interpolated task, retention was poorer for the clinical groups than for the nondisabled and varied inversely with the degree of neuropsychological impairment. Finally, during retention, the nondisabled and low LD groups retained and used the list organization established during acquisition whereas the high LD and HI groups did not.     

Information producing responses in normal and retarded children.

Normal and retarded children were given trials on several discriminations which varied in difficulty. On standard discrimination trials the retarded subjects did not differ from the MA control subjects in the number of errors made but both groups made more errors than the CA control group. On other trials if subjects were not sure which stimulus was correct they were allowed to press an information key which made the discrimination easier. The retarded subjects made significantly more informational key responses than either of the control groups. These results confirmed the findings of prior investigations dealing with outerdirectedness in an experimental situation which did not allow distractibility to be a significant factor.     

Nonselective read-out from iconic memory in normal, borderline and retarded adolescents

The hypothesis that retarded individuals read-out information from iconic memory at a slower rate, relative to their CA matched peers, was tested. Three IQ groups (normal, borderline and retarded) were selected with 10 subjects in each group. A tachistoscope presented a stimulus array and a post-stimulus cue for 100 msec. each, separated by a variable interstimulus interval (ISI). This stimulus array consisted of 10 letters arranged on two horizontal rows. The post-stimulus cue was a circle which surrounded the position of the correct letter. Nine ISIs were used and ranged from −100 (cue before array) to 500 msec. A 3 × 9 repeated-measures analysis of variance revealed non-significant effects for IQ and the IQ × ISI interaction. A significant effect was found for ISIs (p < .01) which reflected reduced performance at the intermediate ISIs for all intelligence groups. The hypothesis of a read-out deficit in the retarded was not supported. The present findings were discussed in relation to previous research which supported a read-out deficit in the retarded.     

The sufficient conditions for directed forgetting in normal and educable mentally retarded adolescents

A series of studies investigated the conditions under which normal and educable mentally retarded adolescents (13 to 15 years old) would or would not disregard irrelevant information in memory. A directed forgetting task was used in which the person was required to recall short sequences of picture names. In some sequences there was a cue to forget the first few pictures (irrelevant information) and to remember only the subsequent pictures (relevant information). When normal adolescents were given no explanation of the forget cue, there was interference from the irrelevant information. A minimum explanation of the cue, however, was sufficient to eliminate interference for the normal adolescents. The same minimal explanation was not sufficient for mentally retarded adolescents. It was clear that irrelevant information in memory interfered with the performance of retarded adolescents given only a minimal explanation of the forget cue. These results are important since most naturalistic situations do not involve an elaborate explanation of the importance of disregarding irrelevant information previously stored in memory.