Inhibition of return and negative priming by persons with and without mental retardation

Persons with and without mental retardation who were matched on CA took part in three tasks: an inhibition of return task, a location negative-priming task, and an identity negative-priming task. Having participants perform all three tasks allowed us to correlate performance among the tasks and assess the various relationships among performance measures on negative priming and inhibition of return. The participants with mental retardation did not exhibit negative priming of identity. However, they did exhibit negative priming of location and inhibition of return. The participants without mental retardation exhibited all three effects. A different pattern of correlations was observed for the participants with and those without mental retardation. Possible reasons for this difference are discussed.     

Neuropsychological profiles of persons with mental retardation and dementia

This study examined the use of neuropsychological tests to assist in the differential diagnosis of dementia among persons with mental retardation. The author compared performances of persons with mental retardation and dementia (n = 10) to persons with mental retardation without dementia (n = 12). Participants were matched by IQ (mild or moderate mental retardation), age, presence of Down syndrome, and gender. In addition, all participants in the dementia group had corroborative medical tests (i.e., imaging, EEG, or high tau low AB42 protein testing) consistent with diagnosis of dementia. Test performance was compared on measures of attention and executive functions, language, memory and learning, and a dementia screening. Results from MANOVAs and nonparametric tests revealed significantly lower performance for persons with mental retardation and dementia in all areas assessed. Cut-off scores were also developed for the sample in order to maximize sensitivity and specificity for the test battery. Despite the small sample size, these findings suggest that there are significant measurable differences in several neurocognitive domains between the two groups.     

Mental rotation of unfamiliar stimuli by teenagers with mental retardation: role of feature salience

Teenagers with mental retardation and two groups of children without mental retardation matched on MA or CA carried out mental rotation tasks of unfamiliar stimuli. Three shapes composed of four arms were used. For each shape, there was a version with a salient feature (F+), and a version with no salient feature (F-). Results showed that teenagers with mental retardation could perform mental rotation tasks with unfamiliar stimuli. However, they had a steeper increase in error rate for F- stimuli than did the MA and CA groups. Individuals with mental retardation may have difficulties in performing mental rotation tasks when stimuli have no feature with a salient axis of elongation.     

Preattentive orienting in adolescents with mental retardation

Visual attention is preattentively drawn to abrupt onsets of stimuli appearing in a visual array. In this experiment, I examined the speed of attentional capture for persons with and without mental retardation. Participants identified target stimuli that were signaled by a valid location cue (20% of the time), an invalid location cue (60% of the time), or no cue (20% of the time). Participants without mental retardation exhibited maximum influence of the cue at cue/target separations that were 100 msec shorter than did participants with mental retardation. These results indicate that processing-speed differences between persons with and those without mental retardation can be observed even when processing resources not involved in the information processing.     

Simulated and community-based instruction involving persons with mild and moderate mental retardation

In this study of simulated instruction and/or community training of four functional living tasks was compared across groups of adolescents and young adults with mild and moderate retardation. Forty individuals participated in the assessment and training activities of this study, including 20 participants with mild retardation and 20 individuals with moderate retardation. A mixed factorial design was used to evaluate differences associated with level of mental retardation, simulated versus community-based instruction, and assessments in school and community settings. Participants with mild retardation performed better than their counterparts with moderate retardation on the simulated tasks and in the community settings. Participants with mild retardation were more successful in generalizing from the simulated instructional experiences to the community settings than were their counterparts with moderate retardation. However, in many of the situations, community training was sufficiently powerful to eliminate any advantage associated with some of the participants having experienced prior simulated instruction. Results are discussed in relation to the need to more closely examine the design and delivery of functional living skills instruction involving individuals with different levels of mental retardation. Specifically, the effectiveness of instructional simulations for teaching functional living skills does not appear to be uniform across level of retardation and targeted tasks. The highest priority question no longer appears to be whether or not simulated versus community-based instruction is more efficacious. Future research might more productively focus on the quality of different instructional simulations in combination with community assessment and/or training opportunities for teaching functional living skills to persons who experience different levels of mental retardation.     

Motor task persistence of children with and without mental retardation

Task persistence by 31 children with and without mental retardation during two challenging motor tasks was investigated. We used a 2 (group) x 2 (gender) MANOVA to analyze trials and seconds per trial. A main effect was found for group affiliation: Children without mental retardation attempted more trials over three sessions. No significant differences were found for seconds per trial, which indicated that all study participants experienced a comparable level of failure in regard to seconds completed before failure. Findings support the hypothesis that children with mental retardation are less persistent at challenging motor tasks than are peers without disabilities. These findings have both theoretical and practical implications.     

Mental retardation and memory for spatial locations

Although memory for spatial location has been frequently investigated with mentally retarded populations, it is not clear that these individuals possess the same spatial memory skills as do their peers without mental retardation. We compared 30 persons with and 30 persons without mental retardation. Following either intentional or incidental learning, participants recalled and then relocated 16 objects on a matrix. The control group recalled more intentionally learned than incidentally learned material. The experimental group performed both tasks better after incidental learning than after intentional learning and scored as highly as the controls on incidental spatial memory. Results suggest that memory for spatial location is an automatic process and, to some extent at least, is not directly affected by the individual's level of intelligence.     

Capacity of persons with mental retardation to consent to participate in randomized clinical trials

OBJECTIVE: Adults with mental retardation have histories of cognitive and adaptive deficits posing unique ethical challenges for research consent assessment. This study examined the capacity of persons with mental retardation to consent to participate in randomized clinical trials. METHOD: A total of 150 adults (50 each with mild and moderate mental retardation and 50 comparison subjects without mental retardation) responded to a set of consent questions for a hypothetical randomized clinical trial testing a medication for aggressive disorders. Intelligence, adaptive behavior, medical treatment history, and consent history were evaluated. Univariate and multivariate methods were used to compare performance across and within groups. RESULTS: Comparison subjects scored significantly higher on measures of consent capacity than participants with mild mental retardation, who scored higher than those with moderate mental retardation. Most subjects with mental retardation were able to make a participation choice, and many understood research methods and appreciated the protagonist's disorder and the consequences of participation. Almost half of those with mild mental retardation understood human subject protections. Performance was weakest on understanding the purpose of research and reasoning about whether to participate, suggesting vulnerability to the therapeutic misconception. Psychiatric and experiential factors did not predict consent capacity. CONCLUSIONS: While adults with mental retardation as a group showed consent deficits, many attained consent capacity scores comparable to those of comparison subjects. Investigators should consider individual differences and a consent format suited to deficits in language, memory, and attention before restricting consent opportunities for persons with mental retardation.     

Allocation of attention and effect of practice on persons with and without mental retardation

Persons with mild and moderate mental retardation and CA-matched persons without mental retardation performed a dual-task, "pencil-and-paper task" (Baddeley, Della Sala, Gray, Papagno, & Spinnler (1997). Testing central executive functioning with a pencil-and-paper test. In Rabbit (Ed.), Methodology of Frontal and Executive Function (pp. 61-80). Hove, East Sussex, UK: Psychology Press), which includes a memory span task and a tracking task. The memory span task loads onto phonological working memory and the tracking task loads onto visuo-spatial working memory. By comparing performance between single and dual-task, we assessed the characteristics of executive function, which allocates attentional resources between two tasks. Results indicate that there was no difference in the characteristics between the two groups, and there was no improvement in the characteristics with practice. Thus, we suggest that when persons with mental retardation perform a dual-task that have no interference in the sub-storage of working memory, their function of attentional allocation can work without impairment.     

Mental health problems in elderly people with and without Down's syndrome

ABSTRACT. This article reports on age-specific findings of mental health problems among residents with Down's syndrome (DS) (n=307) and without (non-DS) (n=1274 in dutch group homes and institutes for people with mental retardation. Whereas a proportional increase of psychological problems was found for elderly DS persons with severe mental retardation, non-DS residents did not show such age-specific differences. High ratings of psychological problems for the elderly DS residents corresponded very well with the diagnosis of 'dementia' made by the physicians. Only for non-DS persons with severe mental retardation was a proportional decrease of challenging behaviour found with advanced age. Whereas psychological problems in elderly DS persons could be explained for the greater part of the diagnosis 'dementia', challenging behaviour-although also common in elderly DS-was shown to be a more independent phenomenon. With regard to psychiatric diagnosis, non-DS residents with mild retardation had six times as much a mental disorder, and non-DS residents with severe or profound mental retardation had up to 15 times as much, compared with their DS peers.     

Vision and touch in ageing: crossmodal selective attention and visuotactile spatial interactions

We investigated whether ageing affects crossmodal selective attention (the ability to focus on a relevant sensory modality and ignore an irrelevant modality) and the spatial constraints on such selective processing. Three groups of 24 participants were tested: Young (19-25 years), Young-Old (65-72 years) and Old-Old (76-92 years). The participants had to judge the elevation of vibrotactile targets (upper/index finger and lower/thumb), presented randomly to either hand while ignoring concurrent visual distractors. In a second task, the role of the target and distractor modalities was reversed. Crossmodal selective attention was assessed by comparing performance in the presence versus absence of distractors. Spatial constraints on selective attention were also investigated by comparing the effect of distractors presented on the same versus opposite side as the target. When attending to touch, the addition of visual distractors had a significantly larger effect on error rates in both of the older groups as compared to the Young group. This indicates that ageing has a detrimental effect on crossmodal selective attention. In all three age groups, performance was impaired when the target and distractor were presented at incongruent as compared to congruent elevations in both tasks. This congruency effect was modulated by the relative spatial location of the target and distractor in certain conditions for the Young and the Young-Old group. That is, participants in the two younger age groups found it harder to attend selectively to targets in one modality, when distractor stimuli came from the same side rather than from the opposite side. However, no significant spatial modulation was found in the Old-Old group. This suggests that ageing may also compromise spatial aspects of crossmodal selective attention.     

Similarities in negative priming between persons with and those without mental retardation of equal chronological age

Adolescents with and those without mental retardation participated in a negative priming procedure in two experiments. They identified letters to stimulus displays presented in pairs. Negative priming was observed as the slowing of response times when the distractor in the first display (prime) became the target in the second display (probe). In the standard procedure, all displays include one target and one distractor. In our modification, prime displays occasionally included a distractor without a target. Although adolescents with mental retardation typically do not exhibit negative priming when responding on the basis of stimulus identity, they did so with single letter primes in these experiments.     

Strengths and weaknesses in executive functioning in children with intellectual disability

Children with intellectual disability (ID) were given a comprehensive range of executive functioning measures, which systematically varied in terms of verbal and non-verbal demands. Their performance was compared to the performance of groups matched on mental age (MA) and chronological age (CA), respectively. Twenty-two children were included in each group. Children with ID performed on par with the MA group on switching, verbal executive-loaded working memory and most fluency tasks, but below the MA group on inhibition, planning, and non-verbal executive-loaded working memory. Children with ID performed below CA comparisons on all the executive tasks. We suggest that children with ID have a specific profile of executive functioning, with MA appropriate abilities to generate new exemplars (fluency) and to switch attention between tasks, but difficulties with respect to inhibiting pre-potent responses, planning, and non-verbal executive-loaded working memory The development of different types of executive functioning skills may, to different degrees, be related to mental age and experience.     

Veridical and false pictorial memory in individuals with and without mental retardation

Veridical and false pictorial recognition were assessed in individuals with mental retardation; groups were matched for MA and CA. Pictures were viewed in either a generative or static format at acquisition. The individuals with mental retardation and those in the MA-matched group had higher rates of false memories for critical items and lower hit rates than did their CA-matched peers. The mental retardation group demonstrated an acquiescent response bias (i.e., high novel false-alarm rate). When data were corrected for this bias, those with mental retardation had significantly lower hit rates but equivalent false-alarm rates to the MA-matched participants. Results are discussed in terms of pictorial distinctiveness and within the frameworks of activation monitoring and fuzzy trace theory.     

Differential impact of the FMR-1 full mutation on memory and attention functioning : a neuropsychological perspective

Memory and attention processing were examined in a group of 15 adult Fragile-X syndrome (FXS) males with Fragile-X mental retardation 1 (FMR-1) full mutation and compared to two control groups: a learning disabled (LD) control and a normal functioning control. Performance was assessed across a wide range of tasks including working memory, recognition memory, selective attention, sustained attention, and attentional switching. All three groups performed at a comparable level on recognition memory tasks, and the Fragile-X males and LD control group performed worse than the control group on tasks of working memory and sustained attention. On a task of executive function, the Fragile-X males demonstrated a significant deficit in comparison to the LD control group and the normal control group, but performed better than the LD control group and at a comparable level to the control group on tasks of selective attention. Molecular analyses of the lymphocyte DNA provided little evidence for a correlation between expansion size and performance on tasks of memory and attention. The findings from the present study are discussed in the context of functional neuroimaging and brain-behavior-molecular correlates.     

Implicit and explicit learning in young adults with mental retardation

We examined intelligence-related differences in explicit and implicit learning using an artificial grammar paradigm. Young adults with and without mental retardation completed a sequence-learning and identification task. For some participants, sequences were constructed following an artificial grammar; for others, sequences were random. Explicit learning was determined by ability to learn and later identify random sequences. Implicit learning was determined by the tendency to incorrectly identify new grammatical sequences as seen before, relative to new nongrammatical sequences. Participants with mental retardation did more poorly than participants without mental retardation on explicit learning but just as well on implicit learning. Results suggest that learning of complex materials, when accomplished through implicit processing, is functionally equivalent in individuals with and without mental retardation.     

Effects of age, gender, and causality on perceptions of persons with mental retardation

The present study examined the effects of age, gender, and causality on the perceptions of persons with mental retardation. Participants rated individuals with mental retardation using a semantic differential scale with three factors: activity, evaluation, and potency. Target individuals in each scenario varied on the variables of age (8, 20, 45), gender (male, female), and causality of mental retardation (genetic, self-inflicted, inflicted by others). Perceptions differed significantly according to causality, with those with mental retardation due to inheritance/genetics (Down Syndrome) evaluated most positively and those whose mental retardation was self-inflicted viewed most negatively (brain damage due to drinking cleaning fluid). Female participants gave higher ratings than male participants for target subjects on evaluation and potency factors. Implications of findings for persons with mental retardation are discussed.     

Performance of epileptic patients in continuous reaction-time situations.

Through the use of a 4-choice continuous reaction-time paradigm, the hypothesis that epiliptic patients have frequent lapses of attention was tested. Control subjects were nonepileptic mentally retarded subjects matched for IQ and CA. Experimental variables were: paced and self-paced work, massed and spaced work periods, and short or long stimulus exposition. The epileptic patients performed well as compared to the control group or to nonretarded persons with respect to reaction time, accuracy, and the occurrence of mental blocks. No abnormal disturbance of attention was clearly detected. This conclusion leads to the possibility that even for patients with severe epilepsy, some tasks can be defined that they can perform successfully.     

Detection of changes in naturalistic scenes: comparisons of individuals with and without mental retardation

Abilities of individuals with and without mental retardation to search for and detect salient changes to naturalistic scenes were investigated using the flicker paradigm. Located in areas of central or marginal interest, changes involved an object's color, shape, or presence. Individuals with mental retardation required more time to detect changes of all types, and the magnitude of the group difference was more pronounced for marginal-interest changes. Supplemental eye-tracking data from 6 participants suggested that the basis of this effect was that individuals with mental retardation tended to maintain gaze in the region of central interest for longer periods of time prior to sampling the other areas of the scene. Implications for intelligence-related differences in visual attention are discussed.     

Learning theory, intelligence, and mental development

The current state of experimental research on mental retardation was considered from a historical perspective. The early position that defined intelligence as the ability to learn was presented. Subsequent refinements were traced as intelligence was related first to stages and, subsequently, to subprocesses of learning. Research on learning in retarded persons, which mainly dates from the late 1950s, took little account of this history. The methodological errors that flawed much modern mental retardation research were made explicit. Attempts to isolate the roles of MA and of intelligence were reviewed. It was shown that with growing understanding sophisticated designs emerged. Kappauf's three-dimensional model relating performance to IQ and CA was discussed and some models of retardation presented. Research on the development of intelligence was related to these models and to the design of intervention strategies.