Laterality effects in judgment of the identity and position of letters: A signal detection analysis

In two experiments subjects received 100 ms tachistoscopic presentations, either to left or right of fixation, of a rectangular matrix of 12 cells. On each trial three cells were filled, each with a different symbol drawn from a set of 12 letters and digits. In one (the “letter” experiment) subjects had to decide whether a particular letter (nominated at the end of the trial) had been one of the three presented. In a second (the “position” experiment) they had to decide whether a cell in the matrix (again nominated at the end of the trial) had been one of those that contained a symbol. Judgments were made on a four-point rating scale, and measures of sensitivity and response bias were calculated. In the letter experiment sensitivity was greater for presentations to right of fixation, and in the position experiment for those to left.