Rachel J. Yapp¹ (), Nadja Jankovic¹, Aaron A. N. Richardson¹, Thomas M. Spalek¹; ¹Simon Fraser University

Alerting is the facilitation of a response to a target when it is preceded by a brief non-informative cue. Although auditory tones are often used as the cue in the literature, a brief luminance increase has been shown to produce similar facilitation. While this visual cue reliably speeds responses, it is unknown whether both increases and decreases in display intensity produce alerting. Three experiments are presented to explore this question. In Experiment 1, a brief (33 ms) white flash preceded the presentation of a visual search display at one of four stimulus onset asynchronies (SOAs: 50, 100, 150, 200 ms). Robust alerting was observed at the three longer SOAs. Experiment 2 was a replication of Experiment 1, except that the white flash was replaced by a black flash. Alerting was observed at the 150 and 200 ms SOAs, but not at 100 ms. Although this finding is consistent with the idea that luminance offset-transients are processed slower than luminance onset-transients, another possibility is that the alerting was not due to the offset-transient but rather was due to the onset-transient produced as the black screen returned to the grey background luminance 33 ms later. Experiment 3 tested these two possibilities by extending the black-flash duration to 83 ms while keeping everything else constant. If alerting was in response to the offset-transient, then that occurs at the same point as in Experiment 2, and so the same results should be observed. If, however, the alerting is due to the onset-transient, then because this transient occurs 50 ms later in Experiment 3 than in Experiment 2, we would expect to see a further shift of 50 ms in the pattern of results. The results revealed alerting only at 200 ms, which is consistent with the notion that only onset-transients, not offset-transients, produce alerting.