PubMed1983
The spans of apprehension of learning-disabled and normal boys were compared by means of a forced-choice letter-recognition task involving tachistoscopic exposures of letter displays. This task provides an estimate of the span that is relatively insensitive to memory or motivational influences. In Experiment 1, the spans of learning-disabled and normal boys were compared under 4 information conditions: with no noise letters present or with 2, 4, or 8 noise letters present. Experiments 2-4 examined 3 possible interpretations of the deficit in the span of apprehension observed for learning-disabled boys in Experiment 1. In Experiment 2, the possibility that the noise letters were more distracting for learning-disabled boys was examined by varying the amount of physical similarity and redundancy between the signal and noise letters. In Experiment 3, the possibility that the visual afterimage of the letter displays faded more rapidly for the learning-disabled boys was examined. In Experiment 4, the possibility that the learning-disabled boys were slower to pick up information from the decaying afterimages was examined. The results of these three experiments indicated that the decreased spans of apprehension observed for the learning-disabled boys in Experiment 1 resulted either from greater distractiveness or from the slower pickup of information, or both. The implications for visual training are discussed.