Control of responding by the location of sound: role of binaural cues.

In auditory localization experiments, where the subject observes from a fixed position, both relative sound intensity and arrival time at the two ears determine the extent of localization performance. The present experiment investigated the role of binaural cues in a different context, the sound-position discrimination task, where the subject is free to move and interact with the sound source. The role of binaural cues was investigated in rats by producing an interaural imbalance through unilateral removal of the middle auditory ossicle (incus) prior to discrimination training. Discrete trial go-right/go-left sound-position discrimination of unilaterally incudectomised rats was then compared with that of normal rats and of rats with the incus of both sides removed. While bilateral incus removal affected binaural intensity and arrival times, the symmetry of sound input between the two ears was preserved. Percentage of correct responses and videotaped observations of sound approach and exploration showed that the unilateral rats failed to localize the sounding speaker. Rats with symmetrical binaural input (normal and bilaterally incudectomised rats) accurately discriminated sound position for the duration of the experiment. Previously reported monaural localization based upon following the intensity gradient to the sound source was not observed in the unilaterally incudectomised rats of the present experiment. It is concluded that sound-position discrimination depends upon the use of binaural cues

Auditory discrimination: the Konorski quality-location effect.

Konorski showed that when a go/no-go procedure was used, sound quality discriminations were rapidly acquired and sound location discriminations were slowly acquired. These findings have been interpreted as a general constraint on the acquisition of auditory discriminations (quality-location effect). However, experiments carried out within an evolutionary framework (Harrison, 1984) have shown that the rate of acquisition of sound location discriminations varies widely as a function of the inclusion or exclusion of naturalistic features. These data suggest that Konorski's findings were a function of the special conditions of the experiments. The first purpose of the present experiments was to assess whether rats showed the effects noted by Konorski when studied under similar conditions. The second purpose was to study the effect of manipulating two natural features (novelty and stimulus-response adjacency) to assess whether the acquisition rates of quality and location discriminations could be greatly modified or made approximately equal, or both. When a go/no-go procedure was used and the other conditions were similar to those of Konorski, rats acquired a quality discrimination but did not acquire a location discrimination. However, when the S+ or S- were presented through a closely adjacent speaker, the sound location discrimination was acquired as rapidly as the quality discrimination. Finally, preexposing the animal to either S+ or S- retarded the rate of or prevented the acquisition of the quality discrimination. The experiments showed that the quality-location effect was determined primarily by the conditions used in Konorski's experiments, and that the effect is not a general constraint on learning

Formação de classes funcionais de estímulos musicais

O objetivo deste experimento foi verificar o efeito do treino discriminativo sobre a formação de classes funcionais de melodias em andamentos e modos diferentes. Nove estudantes universitários do 2° período da graduação em Psicologia foram divididos em três grupos: Modo, Andamento ou Misto. O software SomPsi, produzido especialmente para este estudo, treinou os participantes e gerou relatórios com informações sobre os desempenhos, nas quatro fases do procedimento. O treino proposto mostrou-se eficiente para a formação das classes funcionais de estímulos sonoros musicais. Observou-se que agrupamentos de estímulos pela propriedade andamento foram mais facilmente discriminados que os agrupados pela melodia. A manipulação combinada das duas propriedades, em condição convergente, permitiu desempenho superior dos participantes. A rápida formação de classes funcionais e equivalentes de estímulos musicais, a partir de procedimentos de ensino automatizado de relações condicionais entre estímulos musicais, indica a possibilidade de uso desse procedimento na iniciação à música