An experiment was performed to examine the effects of the size of target and noise letters on selective identification of a target letter. Twelve undergraduate students were required to identify a target letter on a visual display which presents a target letter alone or a target letter flanked by two noise letters. The reaction time of pressing buttons to the target letter was measured under combined conditions of size of target and noise letters. The large target letter was identified faster than the small one whether it was accompanied by noise letters or not. The large noise letters exerted stronger effects on the identification of a target letter than the small one. The rusults agreed with the prediction based on the assertion by Eriksen and Schultz (1979). Farther, it was found that the effects of size of letters varied according to the relation between target letters and noise letters and to the similarity of a target letter to noise letters.
