1996 Paper

In an attempt to further understand hyperactivity in children of six and under a group of researchers decided to undertake an intensive study. Referrals to an Educational psychologist in the North of England were monitored. Every instance of a child diagnosed as showing signs of hyperactivity under the age of six was noted over a period of eight months. Each child's parents were written to and consent was sought to run each child on a battery of tests on various cognitive and perceptual abilities. By the end of eight months the researchers had ear-marked a cohort of 46 hyperactive children and began to collect the data. At the same time they liaised with a primary school in the area close to the University and were able to select control children from the school. For each hyperactive child in the experiments cohort a control child was selected from the primary school such that this pair of children were matched for chronological age.

Overall, twenty tests were used in the test battery. Each child was tested in two separate sessions because of the time needed to administer the tests. Each child was tested on the same order of tests so as to ensure that all children were treated the same. Testing was straight-forward for the control children because each child was tested in the classroom during a period set aside for play activities. Each of the hyperactivity children was tested at home. This was because these children came from many different parts of the North of England and it would have proved quite difficult to liaise with all the different schools concerned.

The data from each of the twenty tests were analysed in separate unrelated sample t-tests. The results are shown in Table 1.

Table 1. Results of unrelated sample t-tests comparing the hyperactive and control children for each of the 20 tests included in the test battery.

Test Level of significance
1. Block Design n.s.
2. Speech rate n.s.
3. Memory span (Forward span - numbers) n.s.
4. Memory span (Forward span - words) n.s.
5. Memory span (Backward span - numbers) n.s.
6. Memory span (Backward span - words) n.s.
7. Visual memory n.s.
8. Rhyme judgement n.s.
9. Odd-man-out (Words) n.s.
10. Odd-man-out (Numbers) n.s.
11. Name-Picture matching n.s.
12. Picture-name matching n.s.
13. Verbal definitions p < .05
14. Auditory gap detection n.s.
15. Auditory intensity discrimination n.s.
16. Auditory frequency discrimination n.s.
17. Auditory vigilance task p < .001
18. Visual vigilance task n.s.
19. General knowledge p < .01
20. Spelling n.s.

Three tests showed a statistically significant difference. Where the Verbal definitions task was concerned, it was found that the control children were able to define significantly more words correctly than were the hyperactive children. In addition, the control children scored more items correct on the General Knowledge task than the hyperactive children. However, rather surprisingly, the hyperactive children were better at the auditory vigilance task than were the control children. This final result was contrary to the researchers initial hypothesis for they had predicted that on the vigilance tasks the control children should have been better than the hyperactive children. The argument being that hyperactive children possess an attentional deficit that causes them to be unable to concentrate for even quite brief periods of time.

Given that the test battery produced such inconclusive results, the researchers began to examine the hyperactive children in more detail. Now each child in the hyperactive group was rated on a newly-devised hyperactivity scale. The aim was to examine the causes of hyperactivity in terms of both general knowledge and auditory vigilance. To this end both the original general knowledge scores and the auditory vigilance scores were correlated with rated hyperactivity. Table 2 shows the correlation values and Table 3 gives summary statistics for these three tests tests. From this pattern of results the researchers concluded that overall hyperactivity was caused by poor general intellectual ability.

Table 2. Pearson product moment correlations between the original tests and rated hyperactivity.

r Significance level
General Knowledge 0.56 p < .001
Auditory Vigilance 0.30 p < .05

Table 3. Means and standard deviations for the hyperactivity rating, general knowledge and auditory vigilance, hyperactive group only.

Test Mean SD
Rated Hyperactivity 25 12.5
Possible total score = 60
General Knowledge 35 24.5
Possible total score = 60
Auditory Vigilance 72.5 1.5
Possible total score = 75

As a final exercise the researchers decided to explore in more detail the possible relationship between general intellectual ability and hyperactivity. In order to obtain hyperactivity scores for both groups they re-contacted the children in the normal group and rated each of them on the hyperactivity scale. Having done this, they then divided the total sample of participants into four equal sized groups. Both hyperactive and normal groups were divided up according to their General Knowledge test scores. A median split was carried out in each group such that the half of the children in that group having the highest general knowledge scores were designated as good general knowledge and the remainder as poor general knolwedge. The mean hyperactivity ratings for these four groups are given in Table 4. A 2 x 2 completely randomised design (between subjects) analysis of variance was carried out to evaluate these data. The first factor of interest was type of child (i.e., hyperactive vs. normal) and the second factor of interest was level of general knowledge (good vs. poor).

Table 4. Mean hyperactivity ratings scored out of a possible total of 60 and standard deviations for the participants when divided according to their general knowledge ability and whether they were diagnosed hyperactive or not.

Type of childHyperactive Normal
Level of general knowledge Good PoorGoodPoor
Mean 5.0 45.0 3.0 6.0
SD 1.4 15.8 0.91.1

This analysis revealed a statistically significant main effect of type of child (F(1, 87) = 15.6, p < .01), and a statistically significant main effect of level of general knowledge (F(1, 87) = 10.96, p < .01). In addition the type of child by level of general knowledge interaction also reached statistical significance (F(1, 87) = 130.4, p < .01). From this pattern of results the researchers concluded that general knowledge was a good indicator of hyperactivity, but only for those children that had already been referred to an Educational Psychologist. For the normal population of young children there was no causal link between intellectual ability and hyperactivity.

[Back to Criticise-the-Experiment List] [Back to Main Page]