Abstract
Purpose: We have previously shown (ARVO, 2000, 2001) that active attention has an effect on passive attention. This study investigates the effects of active attention on the detection of the pop-out target with a dual task condition that requires a subject to pay attention to a RSVP stream voluntarily. The goal of this study is to clarify how active attention affects the detection of the pop-out target.
Method: First, RSVP stream was presented on the center of the monitor. Then a pop-out search array consisted of twenty-four items was presented (30ms) around RSVP stream. Subjects pressed one of two keys to report whether the pop-out target was presented or not. Five subjects were tested in two experiments. In dual-task condition of the first experiment subjects had to detect the RSVP target which color was different from other stimuli in addition to report the presence of a pop-out target. In dual-task condition of the second experiment subjects had to detect the RSVP target which shape was different from other stimuli in addition to report the presence of a pop-out target. RSVP stream had nine items which color was red, green or blue and shape was circle, triangle or square. Half the trial contained one uniquely colored stimulus and half contained no pop-out target in a pop-out search array.
Result: When subjects attended a color feature to detect the RSVP target (dual-task condition of first experiment), their performances in the detection of the pop-out target were not impaired. However when subjects attended a shape feature to detect the RSVP target (dual-task condition of second experiment), their performances in the detection of the pop-out target were impaired.
Conclusion: In our experiments a pop-out target was uniquely colored stimulus and subject's performances in detection of the pop-out target were impaired when they attended a shape, but were not impaired when they attended a shape. This suggests that active attention affects a feature module which subjects do not attend.