Intensity Discrimination Task Research Articles

Relational and absolute cues in auditory discrimination by monkeys

Rhesus monkeys were trained to make auditory frequency, intensity, and duration discriminations. Initial training was carried out with a procedure which allowed the utilization of either relational cues or absolute cues. Later tests with similar auditory parameters allowed only the utilization of relational cues. Performance on these latter tests indicated that relational rather than absolute cues had been utilized when both types were available on the frequency and intensity discrimination tasks. However, absolute rather than relational cues were apparently utilized in making duration discriminations.

Comparison of Performance in Three Paradigms for the Study of Intensity Discrimination

Performances in the following auditory intensity discrimination paradigms were compared: (1) 2IFC; (2)single-interval rating with an intensity cue preceding each observation interval; (3) single-interval rating with no cue. ROC curves obtained in the single-interval tasks can be well fitted by assuming that the underlying distributions are both Gaussian and have equal variance. No large difference was observed between performance in the cue and the no-cue conditions. The normalized separation of the means of the decision variable for 2IFC was approximately twice the corresponding estimate for the single-interval conditions, i.e., d2 = 1.91d1. This is consistent with the hypothesis that the observer bases his decisions on the difference between the observed input and a noisy stored reference in certain intensity discrimination tasks. This hypothesis can be incorporated easily into most models of intensity discrimination and can account for the familiar result that d2 = √d1 for simple detection. [Supported by an NIH Predoctoral Fellowship and by the Information Sciences Directorate, Air Force Office of Scientific Research.]

Intensity discrilnination: Performance in three paradigms

Performance in the following auditory intensity-discrimination paradigms was compared: (1) 2IFC, (2) single-interval rating with an intensity cue preceding each observation interval, and (3) single-interval rating with no cue. ROCs obtained in the single-interval conditions could be well approximated by assuming that the underlying distributions were both normal and had equal variance. No large difference was observed between performance in the cue and the no-cue conditions. The normalized separation of the means for 2IFC was approximately twice the corresponding estimate for the single-interval conditions. i.e., d2 = 1.91 d1. This is consistent with the hypothesis that the O in intensity-discrimination tasks bases his decisions on the difference between the observed input and that of a noisy stored reference. The familiar result that d2 = (2)1/2 d1 can be predicted for simple detection.

Differential Effects of Cortical Lesions upon Various Types of Auditory Discriminations in the Monkey

Following preablation training on frequency, intensity, duration, and complex spectral difference discrimination tasks at three different frequencies, postablation performance was determined. Variations in the testing procedure were also introduced to determine the extent to which changes in discrimination performance reflected the specific nature of the discrimination task. For most animals, bilateral ablations of the primary auditory area produced amnesia, though occasionally this did not occur. (Presumably, the lack of even temporary amnesia reflects incomplete ablations, though final histopathological evaluations are not yet available.) For some animals, amnesia proved to be temporary in the sense that the discrimination tasks could be relearned (though they did not reappear spontaneously), while for others, discrimination performance was permanently affected. The various tasks can be ranked in terms of the probability that the lesion would produce either temporary or permanent amnesia, and these ranks are related to the initial ease of learning. However, since significant individual differences appeared in the ease of initial learning the various discrimination tasks, such a ranking is only of limited accuracy for the group of experimental animals as a whole. It was also found that varying the manner in which the discrimination tasks were structured often significantly altered the accuracy of postablation performance. It is clear that some type of explanative principle similar to Neff's theory of neural habituation for ablated animals is needed.