Interference and Inhibition in Tasks of Selective Attention by Persons With and Without Mental Retardation

Inhibition deficits in individuals with intellectual disability: a meta-regression analysis

BACKGROUND

Individuals with intellectual disabilities (ID) are characterised by inhibition deficits; however, the magnitude of these deficits is still subject to debate. This meta-analytic study therefore has two aims: first to assess the magnitude of inhibition deficits in ID, and second to investigate inhibition type, age, IQ and the presence/absence of comorbid problems as potential moderators of effect sizes.

METHOD

Twenty-eight effect sizes comparing ID and age matched normal controls on inhibition tasks were included in a random effects meta-regression. Moderators were age, IQ, inhibition type and presence/absence of comorbid disorder.

RESULTS

The analysis showed a medium to large inhibition deficit in ID. Inhibition type significantly moderated effect size, whereas age and comorbid disorder did not. IQ significantly moderated effect size indicating increasing effect size with decreasing IQ, but only in studies that included a sample of ID participants with mean IQ > 70. The analysis indicated comparable deficits in behavioural inhibition and interference control, but no significant deficits in cognitive inhibition and motivational inhibition.

CONCLUSIONS

These results indicate that ID is characterised by a medium to large inhibition deficit in individuals with ID. ID seems not to be characterised by deficits in cognitive and motivational inhibition, which might indicate that distinct processes underlie distinct inhibition capacities.

Math practice and its influence on math skills and executive functions in adolescents with mild to borderline intellectual disability

Adolescents with mild to borderline intellectual disability (MBID) often complete schooling without mastering basic math skills, even though basic math is essential for math-related challenges in everyday life. Limited attention to cognitive skills and low executive functioning (EF) may cause this delay. We aimed to improve math skills in an MBID-sample using computerized math training. Also, it was investigated whether EF and math performance were related and whether computerized math training had beneficial effects on EF. The sample consisted of a total of 58 adolescents (12-15 years) from special education. Participants were randomly assigned to either the experimental group or a treatment as usual (TAU) group. In the experimental condition, participants received 5 weeks of training. Math performance and EF were assessed before and after the training period. Math performance improved equally in both groups. However, frequently practicing participants improved more than participants in the control group. Visuo-spatial memory skills were positively related to addition and subtraction skills. Transfer effects from math training to EF were absent. It is concluded that math skills may increase if a reasonable effort in practicing math skills is made. The relation between visuo-spatial memory skills provides opportunities for improving math performance.

Adaptive force control in grasping as a function of level of developmental disability

BACKGROUND

The adaptation to the task demands of grasping (grip mode and object mass) was investigated as a function of level of developmental disability.

METHODS

Subjects grasped objects of different grip widths and masses that were instrumented to record grip forces.

RESULTS

Proportionally, fewer participants from the profound compared with moderate and severe disability groups were able to complete the prehensile tasks. Nevertheless, all participants who completed the task showed adaptive grasping behaviour in terms of level and variability of force produced. There was higher absolute and relative force variability in low mass tasks that was enhanced with greater level of developmental disability.

CONCLUSIONS

The findings show task relevant adaptive grasping control with inhibition of force output at very-low-force conditions being the primary performance deficit of the profound disability group as a function of level of developmental disability.