Andrejkova Gabriela¹, Best Virginia², Barbara G. Shinn-Cunningham³, Kopco Norbert4
¹P.J. Safarik University, ²Boston University, ³Boston University, 4P.J. Safarik University
A previous study of sound localization with a preceding 1-click distractor showed the following interesting results [Kopčp, Best, and Shinn-Cunningham (2007). J. Acoust. Soc. Am. 121, 420-432]: (1) the 1-click distractor affects response bias and response variance for the distractor-target inter-stimulus of up to 400 ms, and (2) localization responses are biased away from the distractor position even on interleaved control trials in which the target is presented alone. Neural mechanisms operating on time scales of milliseconds to tens of seconds are likely to cause to these effects. The current study examined how perceptual organization affects target localization performance in an anechoic and a reverberant room. Sound localization was examined for 2-ms click target stimuli from 7 different positions. On 80% of trials the target was preceded by a distractor, designed either to be grouped with the target (distractor was an identical 2-ms click) or to be perceived in a separate stream (an isochronous train of 8 clicks whose inter-click-interval was different from the distractor-target inter-stimulus-interval). As hypothesized, the 1-click distractor affected target localization more than the 8-click distractor. On the other hand, the biases in the control trials were greater for the 8-click distractor. These results indicate that performance is influenced by both top-down mechanisms like streaming and bottom-up mechanism like stimulus distribution-based adaption.
[Work supported by APVV-0452-12 and R01DC009477.]
Keywords: Sound Localization, Contextual Effect