The effect of attention on phenomenal length.

The effect of attention of the perceived length of briefly presented peripheral lines was investigated. Attention was manipulated by engaging observers in a second concurrent task (letter identification). Observers used the method of adjustment to indicate the length of the stimulus lines. In two experiments it was found that the primary effect of attention was to reduce the variability of line length adjustments. Previously investigators had reported that attention reduces perceived line length. A third experiment suggested that these previously reported results might have been the outcome of a spatial interaction with the cue used to manipulate attention, but not the result of visual attention.