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Biomedical subjects

T Nettelbeck

Publications and source records attributed to T Nettelbeck.

At least 37 records · Page 2Linked to original sources

Medication and reinforcement within a token programme for disturbed mentally retarded residents.

The interaction between psychotrophic medication and a token programme as treatment modalities for mentally retarded individuals with behavioural problems was investigated in two studies. In the first, involving four residents, the dependent variables were credits earned and lost each day for performing specified behaviours within the token programme. Each subject was given a major tranquillizer in alternate months over a four month period. There was a noncontingent token phase prior to, and after completion of, the experimental phases. All subjects showed an immediate increase in the level of appropriate behaviour with the introduction of the token economy, and continuing improvements thereafter. Medication did not have a significant effect on the rate of appropriate or inappropriate behaviour. The second study assessed the relative efficacy of token reinforcement and medication in controlling behaviour symptomatic of psychosis in a resident at school and during meal-times in the ward. Five behaviours recorded were swearing, inappropriate laughter, facial grimaces, fighting, and out-of-seat. Following baseline measures, the absence of facial grimaces was reinforced in the school but not in the word. The contingencies were then reversed. A major tranquillizer was then administered, together with a replication of the first two conditions. The use of tokens to control facial grimaces resulted in the concurrent suppression of the four other symptoms. There weas no remission of any symptom as a consequence of medication alone.

Activities of Daily Living↗

Effects of practice on inspection time for mildly mentally retarded and nonretarded adults.

Successive estimates of inspection time (lambda) interspersed with practice were made for 10 mildly retarded adults (mean IQ = 60) and 10 nonretarded adults. Each subject completed approximately 800 trials overall. A significant practice effect was found for both groups, but with average measures of lambda from the retarded group remaining more than twice as long as those from the nonretarded group. Intercorrelations within both groups between measures confirmed that lambda provides a reliable index of discriminative performance. A response requirement involving a keypress was compared with a simplified pointing response, but results indicated that these alternatives did not influence estimates of lambda on the effects of practice.

Adolescent↗

Locating information-processing deficits of mildly mentally retarded young adults.

When 2 nonoperative lights were added to each of the ends of a stimulus display in a 4-choice reaction time (RT) task, the RTs of mentally retarded and nonretarded subjects were slowed to about the same extent. When 2 nonoperative keys were added to each of the ends of the response display, retarded subjects' RTs were slowed more than those of the nonretarded subjects. The combined effects of the conditions involving nonoperative lights and keys were not found to be additive for either group of subjects, suggesting that, separately, each condition resulted in an increase in stimulus-response incompatibility in addition to an increase in the difficulty of stimulus identification or response selection.

Adolescent↗

Influence of procedural variables on estimates of inspection time for mildly mentally retarded adults.

Two groups of 8 young adults (mean IQ = 68), matched on the basis of age and initial estimates of inspection time (lambda), were compared under conditions in which subjects were instructed either to respond as quickly and accurately as possible or to respond accurately and were praised each time that a response was slower than their mean reaction time (RT) during the initial session. Praise slower RT appreciably but did not affect accuracy, so that second measures of lambda were similar to initial estimates. In a second experiment lambda was measured for 8 retarded (mean IQ = 69) and 8 nonretarded adults under conditions in which stimulus-exposure durations either varied randomly or were arranged in regular blocks from long to short durations. Estimates were significantly longer among retarded subjects and were not influenced by procedure. Reaction times were not affected by procedure, being faster on the average for retarded subjects and relatively constant irrespective of exposure duration, whereas for nonretarded subjects RT increased as exposure duration decreased. Despite the resilience of lambda to procedural variation, differences in RT among retarded and nonretarded samples raise questions about which processes lambda is measuring.

Adolescent↗

Age, intelligence, and inspection time.

Ten young males whose IQ scores ranged from 51 to 71 were compared on a simple discrimination task with 10 male university students of the same CA and 28 nonrelated male children. Estimates of inspection time (lambda) were obtained from the pattern of errors made by each subject; lambda is assumed to reflect the rate at which sensory input is accumulated and processed. Average estimates of lambda from four groups of children (7, 8, 9, and 10 years) were 147, 142, 137, and 139 msec, respectively. The mean for university students was 130 msec, whereas that for retarded adults was 256 msec. Mean reaction time (RT) of all nonretarded groups increased as stimulus-exposure duration decreased, children being slower than adults. Retarded subjects' RT was less influenced by stimulus-exposure duration and was faster than that of nonretarded groups at the shortest exposure. These results suggest that slower perceptual speed among retarded persons is a consequence of a permanent deficiency; differences in response strategy may explain the differences in RT.

Adolescent↗

Speed and accuracy in the choice reaction time of mildly retarded adults.

Reaction times (RTs) to inside stimuli in an 8-choice task decreased for some retarded subjects when the response ensemble was concealed. Corresponding increases in errors suggested that these subjects made separate visual checks of the response keys in order to respond accurately. Other retarded subjects maintained accurate performance by taking longer to respond. An examination of error data from a number of RT experiments indicated that retarded subjects made more errors than did nonretarded subjects when stimuli and responses were less descriminable. A comparison of RTs for correct and incorrect responses reflected intermittent rather than general tendencies to sacrifice accuracy for speed, a result consistent with the possibility of occasional attentional lapses.

Adolescent↗

Vigilance of performance of mildly mentally retarded children.

The contribution of developmental factors to the vigilance performance of mildly mentally retarded children was investigated by comparing their vigilance performance with that of nonretarded children of the same CA and with younger nonretarded children of about the same MA. The retarded children showed an earlier and faster decline in vigilance performance than did the CA control group. This result was similar to that of Semmel (1965), but contrasted with that of Kirby, Nettlebeck, and Bullock (1978), who found no such difference in vigilance performance when comparing mildly mentally retarded and nonretarded adults. The MA control group performed in a similar way to the retarded children, suggesting that the more rapid decline in vigilance performance was largely a developmental phenomenon.

Adolescent↗

Discrimination, translation, or response organization: a clarification of factors underlying slower responding among mentally retarded persons.

Apparently contradictory findings regarding the locus of information-processing differences between retarded and nonretarded persons were discussed. We suggested that these apparent contradictions may be due to differences in the relative involvement of central processes associated with perception, stimulus--response translation, and response programming in the experimental tasks that have been used in this type of research.

Auditory Perception↗

Vigilance performance of mildly mentally retarded adults.

Mildly mentally retarded adults were compared on both an auditory and a visual vigilance task with subjects having greater than average intelligence. Contrary to results reported by Semmel (1965) using a visual task, no difference was found in the rate of decline of performance between the two groups in either of the two tasks, although overall performance of the above-average group was superior to that of the retarded group. The results offered no support for the hypothesis that mentally retarded persons suffer from a more rapid decay in arousal under conditions of reduced sensory variation. Nor did they support a suggestion that in this particular situation retarded subjects would demonstrate more inattention than would nonretarded subjects.

Adolescent↗

Reaction time in retarded and nonretarded young adults: sequential effects and response organization.

Two types of sequential effects can occur in 2-choice reaction-time (RT) tasks. In an alternation effect, the RT for a response that differs from the previous response is faster than that for a response that is the same. In a repetition effect, the opposite is the case; i.e., the RT for a response that is the same as the previous response is faster than that for a different response. These effects were investigated in a comparison of retarded and nonretarded subjects in a 2-choice RT task. There were three conditions that differed in the degree of response organization required. For the retarded subjects, both a significant increase in the overall mean RT and a change from alternation to repetition effects were found with increasing degree of response organization. Neither result was found for the nonretarded subjects. For both groups there was a tendency for alternation effects to decrease and repetition effects to increase witwh decreasing intelligence. Overall, sequential effects were found to correlate more consistently than mean RT with both degree of response organization and intelligence.

Adolescent↗

Influence of contextual cues on the choice reaction time of mildly retarded adults.

Nonretarded and mildly retarded subjects were compared on an 8-choice reaction-time (RT) task. Removing a midline that divided the stimulus display in halves slowed RTs of retarded subjects to stimuli adjacent to the line. In the absence of this line, retarded subjects were also much more dependent upon the position of the preceding stimulus and response.

Adolescent↗

Intelligence, reaction time, and inspection time.

Forty-eight subjects with IQ scores ranging from 57 to 138 discriminated between two lines of markedly different length, exposed for varying periods of time. Estimates of inspection time, lambda, a measure assumed to reflect the rate at which sensory input is processed, were obtained from the pattern of errors made by each subject and, therefore, independently from the reaction time (RT) required to respond. lambda correlated negatively with IQ scores. RTs of nonretarded subjects increased as stimulus-exposure duration decreased, whereas for retarded subjects RTs remained constant. This is interpreted as indicating differences between the groups in response strategy under conditions of difficult discrimination. The rate of information processing was also estimated in a different choice RT situation, using as an index the reciprocal of the slope of the function relating RT to degree of stimulus choice. Retarded subjects had slower rates and longer RTs than nonretarded subjects. A second experiment controlling for response-selection factors confirmed that this slowness could not be attributed to gross-movement difficulties and that a slower rate of information transmission seemed to be involved.

Adolescent↗

Inspection time and measured intelligence.

Ten subjects with WAIS Full Scale IQ scores ranging from 119 to 47 were required to discriminate between two lines of markedly different length, exposed in random order for ten different durations, by pressing one of two keys. Estimates of inspection time gamma, the rate at which sensory input is accumulated and passed to subsequent decision processes, were calculated directly from the psychometric functions obtained gamma was found to correlate negatively with subtests contributing to Performance IQ. There was a substantial degree of consistency between estimates of gamma on two different occasions and training did not appear to affect the index, although differences between the two estimates increased as the value of the first estimate increased. Mean overall response latency did not correlate significantly with intelligence and measures obtained from retarded subjects were very like those reported in similar experimental situations utilizing normal subjects. This unexpected finding is interpreted as suggesting that, in this situation, retarded subjects have been prepared to respond on the basis of less evidence than is usually required by intellectually normal subjects.

Adolescent↗

Effects of stimulus-response variables on the choice reaction time of mildly retarded adults.

Nonretarded and mildly retarded adults were compared in two experiments on an 8-choice reaction time (RT) task. Stimulus lights were either distant or close. Both groups responded more slowly when stimuli were distant, this effect being more marked for retarded subjects. Patterns of latencies suggested that, compared with nonretarded subjects, retarded subjects inspected information input for longer periods of time and made more inspections before responding. Faster RTs to stimuli nearest the ends and midline of the display and to stimulus repetitions indicated that retarded subjects were more reliant upon more discriminable cues in the stimulus display.

Adolescent↗