THE SCRAMBLED STREAM EFFECT: A DIFFICULTY IN PERCEIVING TEMPORAL ORDER IN MULTIPLY-PRESENTED SEQUENCES ((A. O. Holcombe & N. Kanwisher)) Department of Psychology, Harvard University, Cambridge, MA, 02138.
Purpose. To investigate the "scrambled stream effect": when asked to report the relative order of the letters in an RSVP stream, in certain conditions observers do worse when they see the sequence multiple times than when they see it only once. Methods. Each 20-item stream began at a very rapid rate, and decelerated to the final rate by the 9th item. In the "multiple" condition, the stream was composed of 5 iterations of the same 4-letter sequence. In the "single" condition, the 4-letter sequence was presented once, embedded in a stream of nonsense figures. The task was to report the relative order of the 4 letters. Results. Observers correctly reported the relative order more often in the single condition than the multiple condition, but correctly reported the letter identities more often in the multiple condition. Conclusions. Because the effect occurs at slow rates (4 items/sec), it is unlikely that masking or the attentional blink is responsible. We are investigating implications for temporal segmentation and endogenous temporal attention.
Supported by NIMH grant 45245 to N. Kanwisher
