Effects of event rate and display time on sustained attention in hyperactive,normal, and control children

Two experiments were conducted to determine whether hyperactive boys have a unique deficit in sustained attention. Groups with DSM-III diagnoses of attention deficit disorder (ADDH), conduct disorder (CD), ADDH+CD, and learning disorder were compared with normal controls on the Continuous Performance Task. In Experiment 1, stimulus presentation rate (stimulus onset asynchrony, SOA) and display time were varied to manipulate attentional demand, and speed and accuracy of performance were measured. The ADDH group was uniquely affected, with less accurate performance at the fastest and slowest SOA. To distinguish the effects of time on task and SOA, the duration of each SOA condition was held constant in Experiment 2. The poorer performance of the ADDH group at the fastest SOA was no longer evident. This finding indicates that the deficit of sustained attention in boys who have ADDH is associated with a greater susceptibility to refractory effects, which is influenced by practice.This research was supported by the Ontario Mental Health and Ruth Schwartz Foundations through a graduate fellowship awarded to P. Chee and a research grant to R. Schachar, G. Logan, and R. Wachsmuth. Dr. Schachar was also supported by the Canadian Psychiatric Research Foundation. This article is based, in part, on a doctoral dissertation submitted by the first author to the Ontario Institute for Studies in Education. The authors thank Dr. John Lovering and the staff of the Departments of Psychiatry and Psychology, The Hospital for Sick Children, for their cooperation in the conduct of this study. This paper was prepared with the assistance of the Medical Publications Department, The Hospital for Sick Children, Toronto.     

Incidental learning,attention, and curiosity in squirrel monkeys calorie deprived as infants

The long-term effects of infantile malnutrition on information processing were studied in squirrel monkeys. From 2 through 8 weeks of age, four low-calorie infants were fed reduced amounts of a high protein diet, limiting their mean body weight gain to 23% of that of four well-fed controls, with all of this gain occurring during the first 2 weeks on the low-calorie diet. Thereafter, both groups received the standard diet ad libitum. At 68 weeks of age, incidental learning was tested by introducing shape cues that were redundant to the solution of a previously learned, two-choice, color discrimination. Removal of the color cues showed that the low-calorie monkeys had learned significantly less about the shape cues than had the controls. The basis for this incidental learning failure was then examined with an embedded-figures dicrimination, to measure attentional ability, and a novel stimulus substitution task, to measure curiosity. The groups did not differ in detecting embedded figures, but the low-calorie monkeys were significantly less likely than controls to select or handle novel stimuli that had been substituted for previously learned discriminative cues. It was concluded that undernutrition in infancy may induce a long-term strategy of only learning information which leads to an immediate reward, while suppressing the acquisition of information due to intrinsic curiosity.     

Laterality and selective attention in hyperactive children

Laterality and selective attention were investigated in a group of 20 hyperactive children and their matched controls using a dichotic listening task. There was a strong rightear advantage for both groups indicating that hyperactive children were not different from normal children in hemispheric specialization for verbal stimuli. In the selective attention experiment hyperactive children were again not different from normal children in their ability either to select the input designated as relevant or to resist the distraction of input designated irrelevant. Both groups gave more correct responses from the right ear than from the left ear, and more intrusions from the right ear than from the left. The results do not suggest abnormalities of lateralization for verbal material or indicate the existence of a selective attentional deficit. It is suggested that such reported deftcits may be situation or taskspecific.     

Auditory attention switching in hyperactive children

The ability to rapidly reorient attention in the auditory modality was studied in hyperactive children. Hyperactive and nonhyperactive subjects matched on age, sex, and IQ listened to dichotically presented lists for prespecified targets. Reorientation was studied by comparing performance on trials requiring subjects to reorient their attention during a list to performance on trials requiring no switching of attention. The results indicate that although nonhyperactive children were temporarily disrupted by the switch, they eventually reoriented to the cued ear. In contrast, once hyperactive children were disrupted by the switch, they did not reorient to the cued ear. As the pattern in performance comparing hyperactive and nonhyperactive subjects resembles the pattern previously found in comparing younger and older subjects, these results are consistent with the hypothesis that the auditory reorientation skills of hyperactive children are developmentally immature.     

Focused attention in pervasively hyperactive children

This experiment was designed to investigate the hypothesized distractibility of hyperactive children in a focused attention task. Distractibility was defined in terms of Shiffrin and Schneider's model of focused attention as the ability to ignore irrelevant in favor of relevant information. Failure to inhibit processing of irrelevant information indicates a focused attention deficit. Task efficiency in all children decreased when irrelevant information was presented. The mean reaction time, within-subject variance of reaction time, and error percentage all increased compared with a nondistraction condition. Thus, the demands of focused attention, as formulated in the model, were measured optimally. Since hyperactives and controls did not differ significantly with respect to task efficiency in the distraction condition, a focused attention deficit in hyperactives was not demonstrated. The hyperactives did nevertheless make more errors and their responding was more variable than the controls. However, the difference in error percentages between hyperactives and controls was associated with the difference in IQ. It is speculated that the variable responding in hyperactives is caused by a less optimal state of performance unrelated to distractibility.The authors wish to thank L. Leertouwer for making the drawings. This research was supported by grants from the Netherlands Foundation for the Advancement of Pure Research (ZWO) and the Professor Duijker Fund.     

Attaining and maintaining preparation: A comparison of attention in hyperactive,normal, and disturbed control children

The hypothesis that hyperactive children have a deficit in sustained attention was investigated. Eighteen children who had attention deficit disorder with hyperactivity (ADDH), aged 7 to 11 years, were compared with children who had conduct disorder (n = 15), mixed conduct disorder and ADDH (n = 26), emotional disorder (n = 18), or learning disability (n = 22), and with normal controls (n = 15). The subjects were tested on three versions of the Continuous Performance Task. Sustained attention was assessed from performance with increasing time on task and from ability to prepare attention in response to a warning. Performance of all subjects deteriorated with increasing time and improved with the opportunity to prepare attention. Hyperactive subjects were not more adversely affected by increasing time, nor did they benefit less than controls from the opportunity to prepare attention. Data reanalysis after rediagnosis according to ICD-9 criteria did not change the results. This study did not confirm the hypothesis that hyperactive children have a unique sustained attention deficit.     

Temperament, distraction, and learning in toddlerhood

The word- and nonword-learning abilities of toddlers were tested under various conditions of environmental distraction, and evaluated with respect to children's temperamental attentional focus. Thirty-nine children and their mothers visited the lab at child age 21-months, where children were exposed to fast-mapping word-learning trials and nonlinguistic sequential learning trials. It was found that both word- and nonword-learning were adversely affected by the presentation of environmental distractions. But it was also found that the effect of the distractions sometimes depended on children's level of attentional focus. Specifically, children high in attentional focus were less affected by environmental distractions than children low in attentional focus when attempting to learn from a model, whereas children low in attentional focus demonstrated little learning from the model. Translationally, these results may be of use to child health-care providers investigating possible sources of cognitive and language delay.     

Evidence for a cognitive control network for goal-directed attention in simple sustained attention

The deterioration of performance over time is characteristic for sustained attention tasks. This so-called “performance decrement” is measured by the increase of reaction time (RT) over time. Some behavioural and neurobiological mechanisms of this phenomenon are not yet fully understood. Behaviourally, we examined the increase of RT over time and the inter-individual differences of this performance decrement. On the neurophysiological level, we investigated the task-relevant brain areas where neural activity was modulated by RT and searched for brain areas involved in good performance (i.e. participants with no or moderate performance decrement) as compared to poor performance (i.e. participants with a steep performance decrement). For this purpose, 20 healthy, young subjects performed a carefully designed task for simple sustained attention, namely a low-demanding version of the Rapid Visual Information Processing task. We employed a rapid event-related functional magnetic resonance imaging (fMRI) design. The behavioural results showed a significant increase of RT over time in the whole group, and also revealed that some participants were not as prone to the performance decrement as others. The latter was statistically significant comparing good versus poor performers. Moreover, high BOLD-responses were linked to longer RTs in a task-relevant bilateral fronto-cingulate-insular-parietal network. Among these regions, good performance was associated with significantly higher RT-BOLD correlations in the pre-supplementary motor area (pre-SMA). We concluded that the task-relevant bilateral fronto-cingulate-insular-parietal network was a cognitive control network responsible for goal-directed attention. The pre-SMA in particular might be associated with the performance decrement insofar that good performers could sustain activity in this brain region in order to monitor performance declines and adjust behavioural output.     

Schizotypy and sustained attention

We examined sustained attention in 32 schizotypic and 43 normal control subjects from a large, randomly ascertained nonclinical university population. Schizotypy status was determined with the Perceptual Aberration Scale. Sustained attention was measured with the Continuous Performance Test-Identical Pairs. Schizotypic subjects displayed significantly poorer sustained-attention performance than did control subjects, as measured by d and overall hit rate. Although schizotypic subjects evidenced greater levels of anxiety and depression, sustained-attention performance was not significantly associated with these mental state factors. Our results provide evidence for a subtle sustained-attention deficit among schizotypes and are interpreted in light of previous attention research with actual schizophrenic patients as well as children at risk for schizophrenia. Utility of the psychometric high-risk strategy in psychopathology research is discussed.     

Search asymmetry, sustained attention, and response inhibition

In the present experiment, we used search asymmetry to test whether the sustained attention to response task is a better measure of response inhibition or sustained attention. Participants performed feature present and feature absent target detection tasks using either a sustained attention to response task (SART; high Go low No-Go) or a traditionally formatted task (TFT; high No-Go low Go) response format. In addition to performance, we employed functional near infrared spectroscopy (fNIRS) to measure lateral cerebral oxygenation levels and self-reports of Tense Arousal, Energetic Arousal, task related and unrelated thoughts occurring during the tasks. Detections were lower and reaction times longer in the feature absent search than the feature present search regardless of response format. Detections were lower, but reaction times shorter in the SART than the TFT regardless of feature search. Greater right than left frontal hemisphere activation occurred in the SART than the TFT. In addition, the SART was more fatiguing based on self-reports than the TFT, but there were no differences in Task-Unrelated Thoughts across task conditions. Overall, the results suggest the SART places high response inhibition, not necessarily sustained attention, demands on participants.     

Incidental cue learning in rats

Continuity theories of discrimination learning appear to say that animals learn equally about all cues impinging upon their receptors; noncontinuity theories that they learn about only one cue at a time. Experiment I showed that neither of these positions is correct: rats trained to attend to one cue learned less about a subsequently introduced incidental cue than rats given no such pretraining; but attention to one cue did not totally prevent learning about the other. A second experiment established that if rats are trained with one cue, and a second cue is then also made relevant, the amount learned about this second cue varies directly with (a) the abruptness with which it is introduced, and (b) the difficulty of the original discrimination.     

The relationship between sustained attention,attentional selectivity,and capacity

The Theory of Visual Attention (TVA; Bundesen, 1990) provides a quantitative account of visual attentional selectivity and capacity but does not include a parameter relating to sustained attention. We conducted two studies to examine the relationship between sustained attention and the TVA parameters relating to selectivity and capacity. In the first study (n=46; mean age=41, SD=10), we investigated the effects of self alerting during a combined whole and partial report task (CombiTVA). In the second study, 70 participants (aged 20–69), performed the CombiTVA and the Sustained Attention to Response Task (Robertson, Manly, Andrade, Baddeley, & Yiend, 1997). The results indicated that attentional selectivity and capacity were unaffected by self alerting, unrelated to sustained attention ability and robust to the adverse effects of time-on-task. These findings are in keeping with the idea of independent functions relating to sustained attention and attentional selectivity and capacity.     

Dextroamphetamine and placebo practice effects on selective attention in hyperactive children

Three groups of three boys referred to a hospital study unit for evaluation of hyperactive behavior were tested on a classification task involving selective attention while on either dextroamphetamine (D) or placebo (P). In two sessions, groups had D first, P second (DP), or PD, or PP. Amphetamine reduces response times in general and reduces interference due to orthogonally varying irrelevant information. Practice while on placebo improves performance in a subsequent placebo session. Practice while on amphetamine does not, however, improve performance in the subsequent session on placebo. Assessment of the extent of the drug-state-related practice effect is necessary for evaluation of long-term benefits of dextroamphetamine therapy in these children.Thanks go to Ramona Roberts for assistance in running subjects. The University of Maryland Computer Science Center provided the computer facilities for data analysis.     

Event asynchrony and signal regularity in sustained attention

Subjects monitored the repetitive presentation of a vertically oriented line of light (background events) for occasional increments in the height of the line (critical signals). Signals for detection occurred in either a temporally regular or an irregular manner and were blended within a background of temporally synchronous (regular) or asynchronous (irregular) background events. The vigilance decrement, as reflected by a decline in perceptual sensitivity (A‘), during the watch was eliminated when critical signals appeared regularly within a synchronous event context. By contrast, in the context of event asynchrony, regular signal appearances exacerbated the decrement. The results highlight the importance of event asynchrony as a factor in vigilance performance, and link vigilance to a growing list of psychological processes that are dependent upon contextual rhythmicity. This report was completed while Joel S. Warm was a National Science Foundation senior postdoctoral fellow at the National Institute of Occupational Safety and Health Taft Laboratory, Cincinnati, Ohio.