Sensory Thresholds and Response Bias in the Detection of Auditory Signals

Abstract

Responses in an auditory-detection experiment are assumed to be determined in two stages: a detection stage, in which the auditory signal is transformed into some physiological representation, and a decision stage, in which the response is generated, using the output of the detection process and the observer's motivations and expectations, as well. Three models for detection of an auditory signal are considered: a low-threshold model, the neural quantum theory, and a continuous model, signal-detectability theory. Several decision models are applied to the detection models, and their predictions for psychometric functions and ROC curves in yes-no and temporal forced-choice experiments are examined, both theoretically and experimentally. Although the experiments use as a signal a brief increment in the amplitude of a sinewave, the models are not restricted to this situation. The decision model applied to the neural quantum theory provides an explanation for the way in which the psychometric functions of quantum theory are transformed into nearly ogival functions by changes in experimental procedure. The experiments strongly support the existence of a low differential threshold by all measures examined: the locations of the ROC curves, the characteristics of the psychometric functions, and the shape of the temporal forced-choice ROC curves.