In a change deafness manipulation using radio broadcasts of sporting events, we show that change deafness to a switch in talker increases when listeners are asked to monitor both lexical and indexical information for change. We held semantic content constant and demonstrated a change deafness rate of 85% when participants listened to the home team broadcast of a hockey game that switched midway to the away team broadcast with a different announcer. In Study 2, participants were asked to monitor either the indexical characteristics (listen for a change in announcer) or both the indexical and semantic components (listen for a change in announcer or a goal scored). Monitoring both components led to significantly greater change deafness even though both groups were alerted to the possibility of a change in announcer. In Study 3, we changed both the indexical and the semantic components when the broadcast switched from a hockey game to a basketball game. We found a negative correlation between sports expertise and change deafness. The results are discussed in terms of the nature of perceptual representation and the influence of expertise and evolution on attention allocation.

Acoustical analysis indicates that sounds generated as the rims of ellipses rotate against a fixed contactor vary regularly with ellipse shapes (defined by minor-to-major axis length ratios), potentially supporting human ability to differentiate and scale the shapes. In four experiments, we documented human ability to do so. Experiment 1 demonstrated reliable and ordinally correct shape judgments. Experiment 2 showed equivalent judgments over rotation speeds (10, 15, 20 rpm), suggesting reliance on relational information in the acoustic signal. Experiment 3 (using scalar judgments) and Experiment 4 (using multiple-choice judgments) tested perceptual learning effects. Some improvement occurred in both experiments, with a moderate advantage for multiple-choice judgments. Individual variability was notable across all experiments: Individual correlation magnitudes (actual vs. judged shape) ranged from .00 to > .9. Past research revealed associations of shape with impact noise; the current experiments are the first apparent demonstrations of human ability to associate planar object shape from friction-generated sound. Results are interpreted as consistent with Gibson's theory of information-based perception. (PsycINFO Database Record