Sensory thresholds, response biases, and the neural quantum theory

Abstract

Sensory differential thresholds are studied by models which partition the sensory process into two successive stages: a detection stage independent of motivational variables, and a decision stage which selects a response using the observer's motivations and expectations. The detection model considered is the neural quantum theory. Several decision models are applied to the detection model, and the existing psycho-physical literature relevant to thresholds is analyzed. Two aspects of the data, the psychometric function and isosensitivity curves (Receiver Operating Characteristic), are examined for three different experimental conditions: (1) the yes-no detection experiment; (2) the random presentation experiment; and (3) the two-alternative temporal forced-choice experiment. The observer's task is to decide whether a particular observation is caused by signal or noise. In one decision strategy, the rigid criterion, the observer reports a signal only if he detects an increase in the number of excited states of at leask k. Another decision strategy proposes a response bias: the observer reports a signal with probability t k if the number of excited states increases by exactly k. This model provides an explanation for the way in which the psychometric functions of quantum theory are transformed by changes in experimental procedure.