How normal and retarded individuals monitor and regulate speed and accuracy of responding in serial choice tasks

These experiments investigate whether or not differences in the way that retarded and nonretarded individuals monitor and regulate speed and accuracy of responding contribute to the slower and more variable performance of retarded subjects on choice reaction time (RT) tasks. Rabbitt (1979, 1981) suggested that efficient choice RT performance is mediated by subjects tracking increasingly faster RT bands on successive trials until, by making and recognizing errors, they discover those very fast RT levels that should be avoided and those safe bands, just above typical error levels, that should be tracked. Experiments 1A and 1B established that most retarded subjects detect their errors as efficiently as nonretarded controls, a finding that excludes the possibility that retarded subjects do not monitor accuracy efficiently but achieve comparable levels of accuracy by consistently responding within very slow RT bands that minimize likelihood of errors. Experiment 2 showed that while a qualitatively similar trial-by-trial tracking mechanism mediates the performance of both groups, retarded subjects are less efficient at constraining RTs within very fast, but safe, bands. Increasing error probabilities at longer RTs suggest that momentary fluctuations in stimulus discriminability and/or attention are factors affecting RT variability in retarded subjects. The RT patterns for various sequences of correct responses initiated and terminated by errors suggest that the effective past experience (EPEX) guiding trial-by-trial RT adjustments of retarded subjects is short and inadequate, and it was argued that this can account for much of the remaining RT variability contributing to retarded-nonretarded differences. Not only does a short EPEX increase variability by giving rise to long error-free sequences of slower than average RT but also, when combined with occasional specified random fluctuations, it suggests why retarded subjects can achieve, but not sustain, RT levels maintained by nonretarded subjects.     

Memory for Objects and Faces by the Mentally Retarded and Nonretarded

Visual recognition skills of 26 mentally retarded high school students were compared with the skills of two groups of nonretarded students. All groups were taught to recognize 32 target faces and objects and were retested 1 week, 1 month, and 2 months later. The counterintuitive findings were that there were no significant differences between the retarded and nonretarded groups in memory for faces on any of the retest trials. All groups remembered faces significantly better than they did objects and remembered more of the pictures at 1 week than they did at 1 month or at 2 months. There was no significant loss over time in memory for faces. Relative to nonretarded subjects, the retarded subjects exhibited deficits in encoding and remembering objects but showed no such deficits in encoding and remembering faces. The results suggest that different configurational features may be used to encode objects as opposed to faces.     

Memory in educable mentally retarded adults: Deficit in subject or experimenter?

Educable mentally retarded (EMR) and nonretarded adults free recalled lists of (a) words, (b) minitasks performed by the subjects (SPTs), (c) minitasks performed by the experimenter (EPTs), or (d) task instructions. The EMR subjects were significantly inferior to the nonretarded subjects in the immediate recall of words, EPTs and instructions, but not in the immediate recall of SPTs. This proficiency of the EMR subjects in SPT recall was attributed to the nonstrategic nature of this test. The EMR subjects were, however, inferior to the nonretarded subjects in a final free recall (recall of all lists) of all four types of item.     

GENERALIZATION AND TRANSFER BETWEEN COMPREHENSION AND PRODUCTION: A COMPARISON OF RETARDED AND NONRETARDED PERSONS

The study compared the acquisition, generalization, transfer, and maintenance of language comprehension and production responses by persons at two IQ levels: mentally retarded (N = 10) and nonretarded (N = 10). The two levels of the IQ Level factor were combined factorially with two levels of a Training Condition factor: Comprehension-Production and Production Only. Participants in the former groups were trained sequentially to (a) comprehend coin labels by pointing, and then (b) produce verbally the correct coin label. Participants in the Production Only groups were trained on the latter response only. A three-factor mixed design with one repeated measure plus a multiple baseline across coin responses was employed. Results indicated that both mentally retarded and nonretarded subjects attained a high level of acquisition and maintained their performance on 1- and 4-week follow-up tests. No difference occurred between mentally retarded and nonretarded participants in magnitude of acquisition, but the mentally retarded groups took approximately three times as many trials to complete training. Data also suggested, contrary to past research, that generalization from comprehension to production was bidirectional, with no difference in magnitude between mentally retarded and nonretarded subjects. Transfer from comprehension to production occurred in both nonretarded and retarded subjects; comprehension training facilitated a savings of trials in production training. These results show that language differences between retarded and nonretarded persons are quantitative rather than qualitative as some past research may have suggested.     

Influence of item identification on the memory performance of mentally retarded and nonretarded adults

The role of item identification in the memory performance of mentally retarded and nonretarded adults was examined by varying the identification and memory parameters of a sequential same-different task. In Study 1, retarded subjects' identification ability was demonstrated to be less efficient than nonretarded subjects' ability. In Study 2, target duration and interstimulus interval were varied. Memory performance differed between groups, and the memory deficit for retarded subjects was demonstrated to be independent of their identification deficit. The target durations in Study 2 were relatively brief, and in Study 3, the target duration was increased to insure that all subjects could identify the target. Mentally retarded subjects were demonstrated to have a memory deficit. The results were discussed in terms of possible sources of the memory deficit.     

Automatic and conscious processing in retarded and nonretarded adolescents

Educable mentally retarded and nonretarded adolescents participated in incidental learning tasks that emphasized the utilization of processes that were consciously controlled but not deliberately aimed at memory (Experiment 1). Retarded individuals' performance on a standard recognition test was equivalent to that of nonretarded subjects following phonetic encoding and nonstrategic encoding, but was deficient following semantic encoding. Retarded subjects also demonstrated a lower level of performance on a rhyme recognition task. In Experiment 2, retarded subjects provided a pattern of responding identical to that of nonretarded subjects on a picture-word interference task designed to assess automatic processing. The two groups produced equivalent levels of semantic activation. It was argued that the results of the two experiments indicate deficient semantic processing on the part of retarded individuals relative to that of nonretarded individuals that cannot be accommodated by a structural-deficiency model, a developmental-lag model, or a hypothesis that predicts intelligence-related differences only when the task involves the use of deliberate mnemonic strategies.     

Conceptual organization and memory in nonretarded, mildly retarded, and moderately retarded adults

Moderately retarded, mildly retarded, and nonretarded adults learned a list of 12 items from three categories to a criterion of 75% correct recall in a free-recall learning paradigm. Retention was measured 1 week later. The moderately retarded took more trials and had lower retention and clustering scores than the others. The mildly retarded took more trials and had lower retention than the nonretarded. The results violate Murdock's total time hypothesis (Cooper & Pantle, 1967) but support Mandler's (1967) contention that learning is enhanced by the mental capacity for organization.     

Measures of timed performance and intelligence

The question of an association between IQ and measures of timed performance derived from inspection time and reaction time was examined in a sample of 182 adults and by reanalyzing data involving 48 adults from a previously published study. Multiple regression analysis found that measures of timed performance accounted for as much as 25% of IQ variance in the normal population, but that the inclusion of borderline and mildly retarded subjects resulted in much higher correlation coefficients because of the markedly less efficient performance of these persons in tasks of this kind. This outcome raised doubts about the validity of combining data from retarded and nonretarded subjects. Results ran counter to claims that tasks of the kind used are largely uninfluenced by cognitive variables, so that findings are not necessarily explained satisfactorily in terms of a mental speed factor. It was concluded that these measures of timed performance do not, at this time, provide a basis from which a reliable culture-fair measure of intelligence might be devised.     

Forgetting in retarded and nonretarded persons under conditions of minimal strategy use

Short-term memory processes of mentally retarded (mild, moderate, and severe) and nonretarded persons were compared in a delayed matching-to-sample task that minimized the use of verbal rehearsal. In addition to trials with delays up to 20 s, the inclusion of trials on which the sample and comparison stimuli occurred simultaneously made it possible to isolate memory and discriminability. Forgetting was most pronounced between the simultaneous and 0-s conditions, and nonretarded subjects forgot less than retarded subjects between these conditions. There were no group differences beyond the 0-s delay. Ease of strategy use failed to account for individual differences, and reported strategy use was not related systematically to performance. These findings are incompatible with the hypothesis that normal-retarded differences occur only on tasks involving effortful cognitive strategies. Differences between nonretarded and retarded groups in this study may be due to a failure in automatic encoding processes in retarded persons.     

Inspection time: An index for intelligence?

Recent publicity has been given to reports of high correlations between IQ and “inspection time”, a measure derived from simple discrimination which is assumed to provide an estimate of the time taken by a basic component of the decision process. However, this publicity has not recognised that the inclusion of mentally retarded participants in the experiments concerned may have led to inflated correlations, because of the marked extent to which the performance of retarded subjects is inferior to that of nonretarded subjects. Evidence from the performance of nonretarded subjects in three studies suggests that although speed of decision is related to IQ, the degree of association is smaller than recent publicity has suggested. Inspection time does not appear at present to hold promise as an index from which a “culture-fair” measure of intelligence might be derived.     

Conceptual Organization and Memory in Nonretarded,Mildly Retarded,and Moderately Retarded Adults

Moderately retarded, mildly retarded, and nonretarded adults learned a list of 12 items from three categories to a criterion of 75% correct recall in a freerecall learning paradigm. Retention was measured 1 week later. The moderately retarded took more trials and had lower retention and clustering scores than the others. The mildly retarded took more trials and had lower retention than the nonretarded. The results violate Murdock's total time hypothesis (Cooper & Pantle, 1967) but support Mandler's (1967) contention that learning is enhanced by the mental capacity for organization.     

Tic-Tac-Toe performance as a function of maturational level of retarded adolescents and nonretarded children

Two groups of retarded adolescents, differing from each other primarily in IQ (and mental age), were compared with two groups of nonretarded children, differing from each other in chronological age (and mental age), on a modified tic-tac-toe game. The mental ages of the retarded and nonretarded groups were approximately the same. It was found that the slope of performance improvement with increasing maturational level was the same for both subject groups, but the performance of the retarded adolescents was approximately 1.5 years behind mental age expectations, as derived from the performance levels of the normal children. These findings support previous suggestions of a major retardate deficit in tasks requiring logical foresight.     

Differences in intelligence and automatic memory processes

Intelligence-related differences in memory have been viewed as dependent upon control rather than structural memory processes. A test of this notion was made by comparing retarded and nonretarded persons on a subject-paced continuous recognition memory task which was judged to be nonstrategic. The stimuli were computer-generated faces and words. Analyses of pacing rates and posttest interviews provided no consistent evidence for strategy use. Differences in memory between the retarded and nonretarded subjects were attributed to differences in automatic aspects of encoding.     

Mnemonic strategy instruction in coding, processing, and recall of movement-related cues by mentally retarded children

The purpose of study was to examine the differential coding and processing characteristics of two movement cue types in the investigation of the short-term memory of mentally retarded and nonretarded children. The central focus of the study was to determine the effects of formal instruction in the use of a mnemonic versus no instruction with both types of cues in a memory for movement paradigm. The investigation was conducted across two experiments. The main conclusion drawn from Exp. 1 was that movement 'location' cues were coded, processed, and retained by both the mentally retarded and the nonretarded children, but only the former required instruction in the use of a mnemonic to achieve accurate recall. Exp. 2 was fundamentally a replication of Exp. 1 with the exception that movement 'extent' cues were maintained reliable. The results were similar but not exactly the same as those of Exp. 1. Only the mentally retarded children given mnemonic instruction appeared to code, process, and retain movement 'extent' cues over time. The net result of the two experiments was that formal instruction in the use of a mnemonic was of benefit to the mentally retarded subjects and was not necessary for nonretarded subjects to achieve the same level of movement accuracy.     

Hypnotic susceptibility and verbal automaticity: automatic and strategic processing differences in the Stroop color-naming task.

The original hypothesis of Dixon, Brunet, and Laurence (1990) that highly hypnotizable (HH) subjects process words more automatically than do low hypnotizable (LH) subjects was retested in a paradigm that separated strategic from automatic processes in the Stroop color-naming task. The words red and blue preceded a color patch that was red or blue. Subjects were told that the word predicted the opposite color 75% of the time. Automatic and strategic processes were assessed by varying the interstimulus interval (ISI) between the word and the color patch. Both HH and LH subjects showed significant strategic effects (faster incongruent-trial, color-naming reaction times than congruent-trial reaction times at ISIs over 400 ms), but only HH subjects showed significant automaticity (significantly faster congruent-trial reaction times than incongruent-trial reaction times at 16.7 ms, the lowest ISI).     

Tower of Hanoi performance of retarded young adults and nonretarded children as a function of solution length and goal state

Three experiments were conducted with the Tower of Hanoi task to assess problem solving ability in 6-, 7-, 8-, and 10-year-old nonretarded children and mentally retarded young adults of varying maturational ages. In Experiment 1 we gradually reduced the number of moves required for solution until subjects could solve the 3-disk tower-ending problem. Although all groups experienced difficulty with the standard 7-move problem, all but the trainable retarded group readily solved the 6-move problem. The trainable group did not reach a comparable level of success until the 4-move problem. On the 7-move problem the retarded groups performed at the level of nonretarded groups that were maturationally $\text{1}\text{1}\text{2}$ to 3 years younger. An analysis of first moves indicated that subject groups differed in the strategies they used to solve the problems. In Experiment 2, practice effects were ruled out as a source of the superior performance on the 6- than on the 7-move problem. In Experiment 3, 7- and 10-year-old nonretarded children and mentally retarded young adults did not differ on 5-move problems in which configuration of the goal states was varied. A comparison of all 5-move problems judged to have the same depth of search requirements indicated that the tower-ending problems were significantly easier to solve than the partial-tower-ending problems, which in turn were easier than the flat-ending problems. A limited depth of search capacity sets boundaries on the use of sophisticated strategies and, to a large extent, accounts for the retarded groups' maturational lag.     

Control in memory for movement cues by mentally retarded children

The study was designed to determine the desirability of providing external prompts (1) to use a mnemonic to enhance accuracy of recall and (2) to use response 'priming' in memory for spatial location by mentally retarded persons. Two groups of 40 mentally retarded boys and girls and two groups of 40 MA-matched nonretarded children were compared for accuracy in the recall of movement on an arm-positioning task. No differences were found between mentally retarded subjects and MA-matched subjects treated under the same conditions. However, all groups were unable to make spontaneous control adjustments to accommodate the covert manipulations made just prior to recall. By providing response primes, appropriate performance adjustments were made by all groups, resulting in a significant improvement in accuracy of recall. These findings serve to reaffirm earlier reports showing remarkable similarity between the mentally retarded and MA-matched nonretarded subjects.     

Group Skills Training to Increase the Conversational Repertoire of Retarded Adolescents

Ten retarded adolescents in a short-term residential center lacked appropriate social itneraction skills and were referred for group conversational skills training. Group treatment consisted of an instruction-modeling-rehearsal procedure sequentially targeting three classes of converstaional skills:(1) eliciting information from others;(2) appropriate self-disclosing of interests and personal information; and (3) using reinforcing-complimentary conversational behaviors. During baseline and following each training group, social behavior was assessed by recording unstructured 8-minute dyadic conversations between randomly-paired subjects. Weekly generalization probes consisted of unstructured 8-minute conversations between each subject and a different nonretarded, unfamiliar partner. Results indicated that contingent upon group targeting of a specific conversational skill, the frequency of that skill increased in both (1) the unstructured dyadic interactions between pairs of retarded subjects, and (2)the generalization interactions between retarded subjects and novel nonretarded persons. Follow-up mainenance of skill increases was obtained. The utility of a "single group" multiple baseline design in applied social skills research is discussed.     

Levels of processing and memory in mentally retarded and nonretarded persons

Individual differences in memory were examined from the levels of processing perspective. Mentally retarded persons were expected to be more superficial processors. The recall of nonretarded and two IQ levels of retarded young adults was compared following the presentation of pictorial stimuli with either a shallow processing, deep processing, or control orienting task. Shallow processing was induced by directing subjects to name the colors of the pictures. In the deep processing condition, subjects were told to say what the pictured object was used for. In the control condition, they were directed to look at the pictures. The stimuli were presented as an incidental learning task. Encoding condition was a between-subjects variable. Nonretarded subjects remembered more overall than did the two retarded groups, which did not differ. At each intelligence level, more stimuli were remembered in the deep processing condition than in the shallow condition. There was no interaction of intelligence level with encoding condition. The hypothesis that retarded persons process at a more superficial level was not supported. A “spread of encoding” deficit in retarded persons is favored to explain the recall differences obtained in this experiment.