Figure 1.

Same-different task and behavioral performance. (A) Following two to four presentations of the reference stimulus, a test stimulus was presented. The reference stimulus was always one of the two prototype spoken words (bad or dad). The test stimulus was a morphed version of the prototypes. If the monkeys perceived that the reference and test stimuli were the same, they made a saccade to a leftward target. If the monkeys perceived that the reference and test stimuli were different, they made a saccade to a rightward target. (B) Spectrographic representations of the prototype spoken words and two of the morphs. In this example, the reference stimulus is bad. Consequently, it is the 100% morph, whereas dad is the 0% morph; see Section “Materials and Methods” for more details. When the reference stimulus is the spoken word dad, the morph percentages are reversed (e.g., the 0% morph is bad and the 100% morph is dad). The axes for all of the spectrograms are seen in the leftmost spectrogram. (C) The average performance of the monkeys from those recording sessions reported in this manuscript. The monkeys' performance is shown as a function of the reference stimulus: the prototype spoken word bad (left column) or dad (right column). A 0% morph means that the test stimulus was a different prototype than the reference stimulus (e.g., the reference stimulus was the prototype bad and the test stimulus was the prototype dad). A 100% morph means that the test and reference stimuli were the same (e.g., both were the prototype dad). Other values represent morphed stimuli between these two extremes. Error bars are standard error of the means.