mussap-detectingcollinear-1999.pdf (181.61 kB)
Detecting collinear dots in noise
journal contribution
posted on 1999-12-01, 00:00 authored by S P Tripathy, Alexander MussapAlexander Mussap, H B BarlowWe estimated the sensitivity for detecting a row of collinear target elements (usually dots) by measuring the maximum density of randomly positioned noise elements that allowed 75% correct detection of the orientation of alignment (binary choice: horizontal versus vertical) of the target elements. We varied the number of target elements, their mode of generation, and their accuracy of positioning. As reported previously (Moulden (1994) Higher-order processing in the visual system. Ciba Foundation Symposium 184. Chichester: Wiley), target detection improved rapidly until the number of target elements reached about seven, and then improved more slowly beyond this point. However, this break was reduced (and often removed entirely) when the target array was formed by repositioning pre-existing noise elements lying close to the target location, rather than by superimposition of additional target elements onto the noise array. This almost linear slope of improvement, coupled with the observation that target detection was disrupted more by random jitter of target elements at right angles to their axis of alignment than by jittering along this axis, argues against a two-stage process of perceptual grouping (Moulden, 1994) and supports instead an explanation based on the operation of a single mechanism. This single mechanism explanation is further supported by the observation that intrinsic positional uncertainty (estimated from the results of jitter experiments) was independent of target element number. Additional experiments showed that target detection is facilitated by aperiodic noise dots that fall close to the target axis. The results are discussed in relation to alternative explanations of perceptual grouping.
History
Journal
Vision researchVolume
39Issue
25Pagination
4161 - 4171Publisher
ElsevierLocation
Kidlington, Eng.Publisher DOI
Link to full text
ISSN
0042-6989eISSN
1878-5646Language
engPublication classification
C1.1 Refereed article in a scholarly journalCopyright notice
1999, ElsevierUsage metrics
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