The Scrambled Stream Effect and the Importance of a Subjective Sequence Beginning for Serial Order Memory ((A. O. Holcombe & N. Kanwisher)) Department of Psychology, Harvard University, Cambridge, MA, 02138.
Warren, Obusek, Farmer, & Warren (1969) found that it was more difficult to report the relative order of a rapid four-sound sequence when that sequence was presented repeatedly without pause than when it was presented once. We first demonstrate that a similar scrambled-stream effect can occur with visually presented letters. Our subsequent investigations suggest that the lower performance in the repeated condition is due to difficulty apprehending the serial order rather than identifying or remembering the individual letters. Crucially, we find that the difficulty only occurs when the stream is "faded in", with the first few items presented indistinctly and the subsequent items gradually presented more clearly, so that the sequence does not appear to have a beginning item. This can be explained by those theories of short-term order memory which imply that a beginning, but not an end, is required for encoding order. Finally, we report work which begins to elucidate more specifically the conditions of the stimulus and mental set required for this initiation-of-encoding process.
Supported by NIMH grant 45245 to N. Kanwisher