Factors in the discrimination of tonal patterns. I. Component frequency, temporal position, and silent intervals

Factors which determine the discriminability of tonal sequences, or patterns, were investigated in five experiments. The patterns were generally sequences of ten 40-msec tonal components, which ranged in frequency from 256 to 900 Hz, or from 500 to 1500 Hz, in equi-log intervals. Highly trained (15 to 60 h of training prior to collecting experimental data) listeners’ abilities to detect changes in the frequency of single tonal components in these patterns were measured using a same–different psychophysical method. The just-detectable values of Δf (d′=1.0) were only slightly larger than for single 40-msec tones presented in isolation for tonal components at the end of the temporal sequences (a ’’recency’’ effect). Performance was systematically worse for earlier components, the just-detectable Δf increasing by four to five times from the end of the pattern to the beginning (no ’’primacy’’ effect). The ’’recency’’ effect was interpreted as a matter of later arriving components interfering with frequency resolution for earlier ones, since a brief silent period (80 to 120 msec) following an early component led to as precise discrimination for that early component as for the last one in the sequence. The higher-frequency components in a given pattern were resolved much more accurately than the lower-frequency components for patterns with overall bandwidths of 250 to 900 Hz and also when the bandwidths were raised from 500 to 1500 Hz. Subject Classification: 65.22, 65.75, 65.64.