Venema, Theodore

Measures of listeners’ ability to attend to each of four possible discrimination cues were obtained. The stimuli comprised pairs (T1,T2) of 1500‐Hz, 80‐ms, 66‐dB SL tones separated by a 80‐ms silent interval [Espinoza‐Varas, J. Acoust. Soc. Am. 74, 1687–1694 (1983)]. In a three‐interval, 2AFC task, listeners discriminated a ‘‘standard’’ pair (interval 1) from a ‘‘comparison’’ pair (interval 2 or 3) containing increments in the duration (ΔT) or in the frequency (ΔF) of either T1 or T2. Each of the four possible increments was controlled by an adaptive track targeting 71‐percent‐correct thresholds (Levitt, 1971). Separate adaptive tracks were used for each increment, but all four tracks were interleaved randomly within a block of trials. That is, only one kind of increment occurred on a given trial, but all four increments alternated randomly within a block of trials. Each adaptive track terminated after 10 reversals, and thresholds were defined as the average increment value of the last five reversals. A block of trials terminated when the ten‐reversals criterion was reached with all four cues. The slope of the adaptive tracks and the thresholds reached after ten reversals provided measures of attention distribution. [Work supported by OCAST Grant No. HSO‐005 and Presbyterian Health Foundation.]