Learning-related shifts in generalization gradients for complex sounds

Abstract

Learning to discriminate stimuli can alter how one distinguishes related stimuli. For instance, training an individual to differentiate between two stimuli along a single dimension can alter how that individual generalizes learned responses. In this study, we examined the persistence of shifts in generalization gradients after training with sounds. University students were trained to differentiate two sounds that varied along a complex acoustic dimension. The students were subsequently tested on their ability to recognize a sound that they had experienced during training when it was presented among several novel sounds varying along this same dimension. Peak shift was observed in Experiment 1, in which generalization tests immediately followed training, and in Experiment 2, in which the tests were delayed by 24 h. These findings further support the universality of generalization processes across species, modalities, and levels of stimulus complexity. They also raise new questions about the mechanisms underlying learning-related shifts in generalization gradients. The sound stimuli from this study are available as .wav files from http://lb.psychonomic-journals.org/content/supplemental.

Figure 1

Spectrograms of the stimuli used in Experiments 1 and 2.

Figure 2

The average proportion of S+ responses to each Hz value for the discrimination and identification groups in Experiment 1. Error bars depict the standard error of the mean.

Figure 3

The average S+ response proportions to each Hz value for the discrimination and identification groups in Experiment 2 a) without a delay between training and test and b) with a 24 hr. delay between training and test. Error bars depict the standard error of the mean.