Auditory inspection time and intelligence

The relationship of intelligence to auditory inspection time (AIT) was investigated using tasks derived from the spatial-location method reported by Parker, Crawford, and Stephen (1999). Stereo tone bursts were phase-shifted to create lateralized auditory stimuli, and a high-efficiency staircase was used to systematically vary the duration of the stimulus and determine reliable identification thresholds. As reported by Parker et al., all subjects could complete the task and log(AIT) correlated significantly with the general ability (assessed using Ravens Matrices: r=−0.53). This was independent of pitch discrimination ability. A second experiment examined the reliability of the task in a test-retest design. Test-retest reliability was 0.88, and there was no evidence for learning or practice effects on the task. A modified version of the task was constructed which cued location using binaural differences in volume instead of phase. While the volume and phase-coding methods derive from distinct brain systems, volume IT correlated with phase IT (r=0.75). It is concluded that auditory inspection time for spatial location is able to be assessed rapidly, reliably, and with high precision, and lends support to the role of processing speed differences as basic to differences in intelligence.