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Biomedical subjects

T Nettelbeck

Publications and source records attributed to T Nettelbeck.

At least 19 recordsLinked to original sources
PubMed1997

The string measure of the ERP: what does it measure?

The event-related brain potential (ERP) has been investigated extensively inan effort to understand the neurophysiological bases of intelligence. Measures derived from the ERP have been used as indices of intelligence, particularly the string measure of the complexity of the ERP. However, the string measure has been criticised for being non-specific and for being dependent on ERP amplitude. These criticisms were tested by investigating relationships between ERP string measure, ERP amplitude measures, and the ERP power spectrum. It was found that the string measure was non-specific in that it indexes both low and high frequency event-related activity; the string measure is also dependent on ERP amplitude. The string measure is therefore not a valid measure of the ERP. It was concluded that the string measure should be abandoned; human intelligence cannot map in a simple way onto gross measures of scalp-recorded electrocortical activity.

Adult↗
PubMed1996

Vulnerability to criminal exploitation: influence of interpersonal competence differences among people with mental retardation.

A study by Wilson & Brewer (1992) has indicated that people with mental retardation are at greater risk of having a crime committed against them than age-matched cohorts from the general population. The present study was designed to test the hypothesis that this heightened vulnerability is partially explained in terms of behavioural shortcomings reflecting interpersonal competence. Twenty victims of crime and 20 nonvictims, all with mental retardation, were recruited so that means for age, adaptive behaviour and IQ were similar. Groups were compared on the Test of Interpersonal Competence and Personal Vulnerability (TICPV) developed for the present study. Results showed poorer interpersonal competence among the victims, indicating that victims had difficulty in deciding on the appropriate behaviour in some interactions. Performance on the test was shown to be internally consistent, stable over time and a valid measure of vulnerability. The study concluded with recommendations for more detailed investigation of the precise behaviours which influence risk as a first step in an attempt at remediation.

Adult↗
PubMed1996

Uncoupling learning from initial recall: the relationship between speed and memory deficits in old age.

Nettelbeck & Rabbitt (1992) found that measures of speed of performance with low knowledge requirements (four-choice reaction time, inspection time and coding-substitution) accounted substantially for age-related changes among 104 persons aged from 54 to 85 years in a number of more complex cognitive measures reflecting general fluid ability. However, the numbers of words recalled from a list after either a single brief viewing of each word, or following a cumulative learning procedure across four trials, provided an exception to this general trend, leading to the conclusion that some aspects of memory may be independent of mental speed. A follow-up of 82 of the same people 18-20 months later was designed to partition performance in a similar cumulative learning procedure into an initial first recall component and a subsequent learning component. This was accomplished by fitting individual cumulative learning data with a hyperbolic power function which met the theoretical requirement of defining separate initial recall and learning parameters. These parameters were found to be independent and it was concluded that learning involved rehearsal, whereas first recall did not. The hyperbolic power function provided a good account for 92 per cent of individual cases. Analyses which combined Nettelbeck & Rabbitt's (1992) data with new measures confirmed the reliability of these authors' results. Furthermore, it was found that first recall, but not learning, was mediated by processing speed. Learning was relatively unaffected by age-related slowing in mental speed, suggesting that Nettelbeck & Rabbitt's results were the consequence of a strong rehearsal component in their memory tasks. Thus, while mental slowing is clearly one important aspect of cognitive decline during old age, it does not constitute a sufficient explanation for changes in all areas of cognitive functioning. Specifically, age-decline in rate of learning with rehearsal appeared to be independent of slowing in speed of information processing.

Aged↗
PubMed1995

The abilities of a musical savant and his family.

The ability of a male autistic savant (TR) to play two unfamiliar piano pieces after listening to a tape-recording was tested, closely following the procedures of Sloboda, Hermelin, and O'Connor (1985). Other components of TR's musical ability--pitch recognition, improvisation, and ability to provide harmonic accompaniment--were also examined. TR's musical precocity was examined in relation to his general level of intellectual functioning as indexed by a battery of standardized psychological tests of intelligence, memory, reading, visual organization, and creativity. His parents and two male siblings also completed tests of intelligence. Results from psychometric testing indicated that TR has idiosyncratic levels of cognitive functioning with difficulties in verbal reasoning but high levels of concentration and memory. His speed of information processing, as indicated by Inspection Time, and was better than average. TR demonstrated perfect pitch recognition and other family members also demonstrated excellent relative pitch. TR's ability to recall and perform structured music within both the diatonic and whole-tone systems was exceptional but dependent upon his familiarity with musical structure and was therefore organized and rule-driven. Furthermore, TR demonstrated competence in improvisation and composition, albeit restricted by his adherence to structural representations of familiar musical rules.

Aptitude↗
PubMed1995

Psychological outcome of ECMO-eligible neonates with severe respiratory failure treated using conventional medical therapy.

OBJECTIVE: The present study addressed a National Health and Medical Research Council (NHMRC) recommendation that the outcome of neonates who are treated conventionally for respiratory problems be further investigated before setting up additional extracorporeal membrane oxygenation (ECMO) centres in Australia. METHODOLOGY: The cognitive and behavioural outcome of ECMO eligible infants who received conventional treatment for respiratory problems at birth was assessed in 18 infants aged 1.5-3 years (index group). ECMO was not available at either of the treating hospitals. Index children were compared to a matched control group of children who did not experience any major complications at birth. Children were assessed using either the Bayley or McCarthy scales of infant development and the Child Behavior Checklist. RESULTS: Overall, a mortality rate of 19% and a psychological morbidity rate of 18% suggest that children born with severe respiratory failure, who meet existing ECMO eligibility criteria, have a good prognosis when treated using conventional medical therapy. CONCLUSIONS: Improvements to conventional treatments indicate that ECMO eligibility criteria may need to be revised to identify accurately those infants who are at extreme risk of mortality if treated conventionally.

Adaptation, Psychological↗
PubMed1994

The "intelligence" of calendrical calculators.

Strategies of 4 men (WAIS-R range 65 to 76) when making calendar calculations were investigated. Each subject completed a battery of standardized psychological tests. Results suggested that subjects were aware of rules and regularities associated with the calendar, including knowledge of the 14 different calendar templates, one of which describes any calendar year. Their strategies were rigidly applied and could not be modified easily, even when doing so would have facilitated performance. The involvement of practice, memory, anchor dates, eidetic imagery, and mathematical algorithms were discussed. We concluded that these savants relied heavily on memory, with little manipulation of cognitive input, as opposed to transforming stimuli.

Adult↗
PubMed1992

Validity of Greenspan's models of adaptive and social intelligence.

Study 1 assessed the construct validity of Greenspan's 1979 and 1981 models of adaptive and social intelligence. Seventy-five adolescents with mental retardation completed four measures of conceptual intelligence, a general measure of adaptive behavior (practical intelligence), and seven measures of social intelligence. A factor analysis of all measures yielded three factors that were obliquely rotated and labelled Practical-Interpersonal Competence (defined by a subset of social intelligence and adaptive behavior measures). Verbal Intelligence, and Accuracy of Inference. An analysis of the seven measures of social intelligence found no evidence to support the hierarchical organization of variables that is proposed in Greenspan's model of social intelligence. The criterion validity of the Practical-Interpersonal Competence construct identified in this study was then assessed in Study 2 (N = 20). Factor scores were calculated from nine measures that were selected to represent the Practical-Interpersonal Competence, Verbal Intelligence, and Accuracy of Inference factors, and correlated with three criterion measures of practical and interpersonal competence. Two of the three criterion measures validated both the Practical-Interpersonal Competence and Verbal Intelligence Factor scores but did not discriminate between the two. The criterion validity of the Practical-Interpersonal Competence construct, therefore, has yet to be established.

Activities of Daily Living↗
PubMed1992

Reliability of seven measures of social intelligence in a sample of adolescents with mental retardation.

This study evaluates the reliability of seven measures, selected to assess the social-cognitive variables hypothesized by Greenspan to define social intelligence. Responses from 75, 30 and 20 adolescents with mental retardation were used to assess each test's internal, interrater, and test-retest reliabilities, respectively. Interrater reliability coefficients were high to very high (.76 to .98), internal reliabilities were moderate to very high (.66 to .90), and test-retest reliabilities were moderate to high (.54 to .74). Internal and test-retest reliability coefficients compared favourably with those reported for the subtests of the Revised Wechsler Intelligence Scale for Children.

Activities of Daily Living↗
PubMed1986

Inspection time as mental speed in mildly mentally retarded adults: analysis of eye gaze, eye movement, and orientation.

The effect of eye movements away from a target on accuracy of visual discrimination was examined. In Experiment I inspection time was measured for 10 mildly mentally retarded and 10 nonretarded adults under two conditions, with each trial initiated by the subject or under experimental control. Retarded subjects did not gain any advantage from controlling trial onset. Video records of eye movements revealed that retarded subjects glanced off-target more than did nonretarded controls, but this was not sufficient to explain appreciably slower inspection time of the retarded group. Experiment 2 supported this conclusion; the same subjects completed a letter-discrimination task with direction of gaze monitored automatically. Although retarded subjects' eye gaze was more scattered early during a trial, gaze was appropriately directed by the time that the target appeared. Results from both experiments supported the hypothesis that speed of central, perceptual processing is slower among retarded persons, over and above the influence of distractibility. Results from three experiments in Part II were consistent with this interpretation. Experiment 3 was designed to eradicate trials among retarded subjects in which gaze was not properly directed, but results showed that too few such events occurred to influence accuracy. Experiment 4 demonstrated that the preparatory procedure in the previous studies resulted in efficient eye gaze among retarded subjects. Experiment 5 confirmed that lower discriminative accuracy among 10 retarded adults (compared with 10 nonretarded controls) was not due to less-efficient orientation prior to discrimination.

Adolescent↗
PubMed1985

A cross-sequential analysis of developmental differences in speed of visual information processing.

Development of processing speed was examined in three backward masking studies. The first verified the central nature of backward masking for children aged 8 and 11 years and for adults. The second suggested that task requirements were equivalent for children similar to those in Study 1, and that age differences in performance were not attributable to nonprocessing variables. The main cross-sequential study estimated speed of processing in 80 children (approximately 6 years to 13 years) and young adults using an inspection time task. Target exposure duration was varied to establish the time required to achieve a high level of discriminative accuracy. Estimates of processing speed increased until about 11-13 years of age; beyond this, the trend was less obvious, and it is possible that inspection time asymptotes at around the onset of adolescence. Performance improvement after 1 year could not be explained as resulting from practice since improvement among controls over a period of 2 weeks was significantly less. Correlations between estimates of inspection time made up to 2 years apart found the measure to be reliable.

Adolescent↗
PubMed1984

Mental retardation and inspection time: a two-stage model for sensory registration and central processing.

Mildly mentally retarded and nonretarded young adults were compared in simple visual discrimination tasks from which can be derived an estimate of inspection time (lambda), assumed to reflect the time taken by some basic component in the decision process. In the first experiment retarded and nonretarded subjects' performance showed improvement in a condition employing a backward mask to limit the duration of sensory information available to subsequent central processes, but substantial group differences in lambda remain unchanged. When target stimuli were presented for short durations, but without interruption by masking, retarded subjects performed less effectively than did nonretarded subjects and, despite extensive practice, did not achieve nonretarded subjects' levels. These results suggested a two-stage serial model of discrimination that was tested in the second experiment. Concurrent manipulation of two factors confirmed that (a) lambda involves initial sensory registration followed by central processing, (b) for both groups these stages are independent, and (c) poorer performance among retarded subjects is the consequence of deficiencies at both stages.

Adolescent↗
PubMed1984

Mental retardation, inspection time, and central attentional impairment.

Performance of mentally retarded and nonretarded adults on simple visual discrimination tasks was compared. Experiment 1 involved a lines-discrimination task used in previous research to measure inspection time. A dichoptic stimulus presentation procedure was employed, with target and masking stimuli presented to different eyes so that only central masking could occur. Experiment 2 involved a discrimination between two lights in different positions, demonstrating that masking was characterized by constant stimulus-onset-asynchrony, because the relationship between target duration and the interval between target offset and mask onset was additive. Results from both experiments confirmed that for both retarded and nonretarded subjects, the backward masking procedures used interfered with visual processing at a central level. In Experiment 3 markedly deviant smooth pursuit eye movements in a pendulum tracking task occurred among retarded subjects but not among nonretarded subjects. This deviancy was additional to other indications of poor attention. In the retarded group the correlation between estimates of inspection time and deviant eye tracking was .64, but other instances of inattentiveness were not related to either of these two measures. This finding was interpreted in terms of an involuntary dysfunction within some central attentional system that involves at least three qualitatively different levels.

Adolescent↗
PubMed1984

Adaptive behavior of mentally retarded adults in work-preparation settings.

Mentally retarded adult trainees (N = 370) at work preparation centers were rated by their supervisors on the AAMD Adaptive Behavior Scale (ABS). Results confirmed the reliability and criterion validity of the ABS, demonstrating its sensitivity to differences in adaptive and maladaptive behavior between subgroups representing variation in seven personal variables: age, sex, estimated intellectual ability, etiology, place of living, the presence or absence of any mobility handicap, and use of medications. Results were compared with those from a study of retarded adolescents attending school (Salagaras & Nettelbeck, 1983). On the average, trainees had a higher adaptive behavior profile than did students, but no significant differences were found in maladaptive behavior. The ABS measures indicated that about 75% of students were behaviorally prepared to make the transition to work preparation centers.

Adaptation, Psychological↗
PubMed1984

Effects of procedure on memory scanning of mildly mentally retarded adults.

The performance of mildly mentally retarded adults on recognition memory tasks was compared with that of nonretarded control subjects. Following Sternberg's (1969) procedure, material to be remembered was presented in a fixed-set procedure, during which subjects were tested repeatedly on the same well-learned set of material, and a varied-set procedure, during which they were only tested on a memory set once before having to learn a new set. Mean reaction times (RTs) in all groups increased linearly as the number of items in the fixed memorized set increased; but "no" RTs of retarded adults tested under the varied-set procedure did not show this pattern. There was a gradation of slopes for the linear regression functions of RT on memory set size in both procedures, from less steep for nonretarded adults to increasingly steep values for nonretarded children and retarded adults. These results suggest that retarded adults use different processing strategies in the two procedures and that rate of processing increases with increasing mental age.

Adolescent↗
PubMed1984

Effects of practice on recognition memory of mildly mentally retarded adults.

The effect of practice on recognition memory of mildly mentally retarded adults was investigated in two experiments using the Sternberg (1969) memory scanning paradigm. In Experiment 1, the slope and zero intercept for item-recognition functions under both fixed- and varied-set procedures decreased over seven sessions of practice among retarded adults and nonretarded children, remaining relatively constant among nonretarded adults. Because performance of only retarded subjects had not yet reached asymptote, Experiment 2 provided these subjects with additional practice at the same task (varied-set procedure only). After extended practice, slopes in the retarded group were near those for both nonretarded groups; therefore, although the generally poorer performance of retarded adults in this task may reflect some structural impairment, the initial level of deficiency is reduced by practice.

Adult↗
PubMed1983

Adaptive behavior of mentally retarded adolescents attending school.

Teachers rated 550 mentally retarded adolescents attending special schools on the AAMD Adaptive Behavior Scale (ABS). Results established the reliability and criterion validity of the ABS for use among school-age students and demonstrated the sensitivity of the scale to variation in adaptive and maladaptive behavior between subgroups of mentally retarded students representing differences in seven personal variables: age, sex, estimated intellectual ability, etiology, place of living, the presence or absence of any mobility handicap, and use of medications.

Adolescent↗