Denton C L, McIntyre C W
J Abnorm Child Psychol. 1978 Mar;6(1):19-24. doi: 10.1007/BF00915778.
The spans of apprehension of hyperactive and normal boys were compared with a forced-choice letter-recognition task developed by Estes (1965). This task provides an estimate of the span which is relatively insensitive to either memory or motivational influences. The span size was the same for both groups when visual "noise" was absent. In the presence of noise, span size for the hyperactive boys decrease. Moreover, as the number of noise letters increased, the reduction in span size observed for the hyperactive boys increased. It is argued that this increasing reduction in span size represents a true deficit in attention.
