ASA 125th Meeting Ottawa 1993 May

4aMU4. The effects of training and predictability on the discrimination of sequences of tones with various frequency ranges.

Kathy Barsz

Maya Jariwala

Jeffrey E. Peter

Melissa A. Scism

Larissa A. Barnauskas

Shannon M. King

Margaret M. McCarthy

Dept. of Psychol., SUNY, Geneseo, NY 14454

Listeners discriminated sequences: two different higher frequency tones alternated with two different lower frequency tones, each 200 ms. Sequences began at a random point and repeated without pause. Predictability was manipulated by holding the standard sequence constant (PREDICTABLE) or by varying it (UNPREDICTABLE). The frequency range between the higher and lower tones was two octaves (WIDE) or a minor second (NARROW). Medium range sequences (a minor third) were presented in two contexts: with the wide range sequences (MED/W) or with the narrow range sequences (MED/N). Sequences differed only in the relationship between the higher and lower tones. Fifty listeners each discriminated the sequences in one condition (MED/N or MED/W in either a PREDICTABLE or UNPREDICTABLE block); ten returned for two extra sessions (practice). Discrimination of the wide range sequences was at chance and only improved with practice when the block was predictable, although listeners still had a difficult time. Performance on this task was affected by frequency range; performance on the narrow range sequences benefited from practice and improved predictability There was a clear practice effect for the medium sequences, but only when the block was predictable and they were presented with the narrow range sequences.