Abstract

Widmann, A., Scharf, B., & Schröger, E. (2000). Frequency and Location Discrimination: Which is Faster? In A. Schick, M. Meis & C. Reckhardt (Eds.), Contributions to Psychological Acoustics, Results of the Eight Oldenburg Symposium on Psychological Acoustics (pp. 373-380). Oldenburg: Bibliotheks- und Informationssystem der Universität Oldenburg.

Frequency and Location Discrimination: Which is Faster?

It is debatable whether frequency information is processed faster than location information or vice versa. In a Go/Nogo task, Scharf, Possamaï, and Bonnel (personal communication) found evidence suggesting that frequency discrimination is faster than location discrimination. In contrast, Schröger and Wolff (1997) presented evidence suggesting that location discrimination is faster. To choose between these two contradictory predictions, we designed an experiment in which we carefully equated discriminability (in terms of just noticable differences or jnds) and the type of discrimination task. In 10 subjects the 0.90 jnd (stimulus difference required for 90% correct) was first determined in a weighted up-down adaptive procedure (two-interval forced choice), separately for frequency and lateralization (based on interaural time difference). Next, in reaction time (RT) measurements, for each subject, stimuli were separated either by these jnd-values ("difficult" condition) or by 5 times these values ("easy" condition). In three different RT tasks subjects had to discriminate frequency and location (blocked presentation). The mean RTs ranged from 314 to 559 ms and were about the same for location and frequency discrimination in all three tasks. These means as well as the cumulative RT distributions did not indicate that one feature was discriminated significantly faster than the other feature at a behavioral level in any of the tasks. Accordingly, neither of our predictions is confirmed. It seems that both auditory features are available to cognitive discrimination operations at about the same time.



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