Efficiency of visual selection in duplex and conjunction conditions in partial report.

Factors that determine the efficiency of visual selection were investigated in two precued partial-report experiments. There were four selection conditions: a color condition (e.g., selecting purple letters among blue letters), a class condition (e.g., selecting letters among digits), a duplex condition (e.g., selecting purple letters among blue digits; that is, the targets differed from the distractors both in color and in alphanumeric class), and a conjunction condition (e.g., selecting purple letters among blue letters and purple digits; that is, the targets differed from the distractors either in color or in alphanumeric class). The efficiency of visual selection was highest in the duplex condition and lowest in the conjunction condition. The difference in performance across the different selection conditions within subjects was accounted for by variation in the value of a single parameter of the fixed-capacity independent race model (FIRM) proposed by Shibuya and Bundesen (1988), which assumes independent parallel processing, limitations in both processing capacity and storage capacity, and time-invariant selectivity. By assuming that the factors that determine the efficiency of selection in the color and class conditions also underlie the efficiency of selection in the duplex and conjunction conditions, an extension of FIRM, FIRM+, accounted for the relationship with respect to efficiency of selection among the different conditions.