Ear differences for same-different reaction times to monaurally presented speech

Subjects were played sequences of two consonant-vowel syllables which they had to judge as “same” or “different.” The first syllable was always played binaurally and the second came either to the left or to the right ear. The two syllables were always on different pitches. Subjects were faster in judging the syllables “different” when the second syllable came to the right than to the left ear, but there was no ear difference for “same” judgments. This experiment suggests that ear differences can be obtained under monaural stimulation on a task involving a simple phonetic judgment. It also suggests that some process of categorization is necessary in tasks which show left hemisphere superiority for verbal material.