Time perception: modality and duration effects in attention-deficit/hyperactivity disorder

Journal of Abnormal Child Psychology,  Oct, 2005  by Maggie E. Toplak,  Rosemary Tannock

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We also examined whether estimated full-scale IQ was a significant covariate of performance on the control tasks. Estimated full-scale IQ did not enter as a significant covariate on the visual control task, but did on the auditory control task, F(1, 87) = 13.81, p = .0001. The lack of group differences were maintained even after IQ was entered as a covariate. Effect sizes were re-calculated with the adjusted means, and a small effect size was maintained on the visual control task (shown in Table II).

Reading Ability

Recognizing the potentially important contribution of reading ability in our experimental measures, we conducted a preliminary comparison of performance between our adolescents who only met criteria for ADHD and adolescents who met criteria for ADHD and a reading disorder. These two groups did not differ on any of the experimental time perception measures. There were, as would be expected, differences on auditory span memory, reading ability, and language ability.

ADHD Subtype

As 46% of our ADHD sample met criteria for the Inattentive subtype, and 54% met criteria for the Combined subtype, we compared duration discrimination performance in these groups. Overall, no differences between subtype were obtained on the duration discrimination and control tasks. This was not unexpected given that both of these groups had clinically significant inattention symptoms, which previous research has shown to be associated with cognitive difficulties (Chhabildas, Pennington, & Willcutt, 2001).

Correlational Analyses

Correlations Between Duration Discrimination and Standardized Measures

We performed correlational analyses in order to specifically investigate relationships between the duration discrimination threshold and memory (memory span and working memory). However, we also conducted analyses between duration threshold and other clinical measures, including, reading and language ability, and severity of behaviour symptoms. These correlations were performed separately in the ADHD and control samples, as our previous work has indicated that cognitive and behavioural variables may be associated differently in clinical and control samples (see Toplak et al., 2003). These correlations are displayed in Table III.

Few associations were obtained with age, estimated full-scale IQ, reading and language ability, and the behaviour ratings, which was unexpected. Two of the three associations obtained with the behaviour ratings were obtained in the control sample, perhaps because there was a wider range of scores from parent and teacher reports in the control sample, whereas ratings tended to be clinically elevated and therefore reflecting ceiling scores in the ADHD sample. The most striking pattern was the relationships between measures of memory and duration threshold. Notably, duration threshold for the visual tasks was related to auditory-verbal and visual-spatial memory in the ADHD group but not in the control group. In order to understand this pattern of associations further, we performed regression analyses with the duration discrimination tasks.