(sagittal), became available to clinicians and brain scientists only in the last decade. In (a), the dotted line demarcates the temporal lobe (T); the top portion (superior surface) of the temporal lobe houses the auditory area in man. In (b), the arrows indicate the extent of the corpus callosum, the semilunar bundle of nerve fibers which connects the left and right hemispheres. In split-brain patients, the callosum is cut.

Because the term “timbre” is ambiguously defined in psychoacoustics as that attribute of sound which distinguishes two different sounds of the same pitch and loudness (American Standards Association 1960), yet is usually defined in music to denote the distinctive tonal quality produced by a particular musical instrument (Apel 1972), let us consider the nature of the stimuli used in Seashore’s Timbre Test and if, in fact, this task measures musical talent. The Seashore Timbre Test contains five blocks of ten trials, each of which requires subjects to determine if two successive complex tones sound the same or differ in “tonal quality”. The stimuli are essentially steady-state spectra composed of a 500 cycle per second (cps) fundamental and its first five harmonics. In half the trials, the standard and comparison differ by the reciprocal intensities of the third and fourth harmonics, with overall intensity remaining constant. The blocks became increasingly difficult over the course of the test in that the reciprocal intensities differ by 10dB in the first block and 4dB in the fifth block. While other physical features of the complex tones are not specified in the test booklet, spectrographic analysis of a digital sample of one of the test stimuli shows a stimulus duration of 1148msec, with an attack time of 160msec and a release time of 148msec (Tramo & Gazzaniga 1991).