Roles of the qualities and locations of stimuli and responses in simple associative learning

The Quality-Location Phenomenon is defined by the previous research of Lawicka (1964 and 1969) in which dogs easily learn go/no-go tasks to differences in stimulus quality and go-left/go-right tasks to differences in stimulus location whereas the opposite pairings of tasks and stimulus attributes are difficult to learn. The Lawicka-Konorski explanation in terms of drive differentiation and response selection is described, and a new hypothesis, the Quality-Location Hypothesis, is offered. This hypothesis states that the quality of a stimulus best serves as a cue for the quality of a response, whereas the location of a stimulus best serves as a cue for the location of a response. The evidence for the hypothesis is reviewed, and experimental considerations for its evaluation are mentioned.     

The roles of vibration amplitude and static force

Previous work (Verrillo, 1963, 1968) has shown that when measured as a change in absolute threshold, spatial summation occurs only at vibration frequencies above 40 Hz. The present study measured vibrotactile spatial summation at suprathreshold amplitudes. A matching task was used to investigate the effect of varying contactor size on sensory magnitude at three different vibration frequencies. Unlike the threshold data, increasing contactor size resulted in increases in sensory magnitude at 25 and 40 Hz as well as at 160 Hz. The amount of summation varied directly with amplitude for the two lower frequencies. In a second experiment, the effect of increasing static force, independent of contactor size, was investigated. The results indicated that the spatial summation effects noted in the first experiment may be due to increases in static force and not contactor area. The implications of these results for the concept of spatial summation and for the duplex mechanoreceptor hypothesis are discussed.     

Vibrotactile spatial summation

By means of a two-interval, forced-choice technique, absolute thresholds were obtained at several sites on the skin for short bursts of mechanical vibration. The difference between the energy required for a single vibrator, in dB, to reach threshold and the energy required for two vibrators presented successively to reach threshold was taken as the measure of probability summation. Spatial summation was computed as the difference between the energies required for threshold for the two vibrators presented successively and simultaneously. Both probability summation, 0.52 dB lowering in threshold, and spatial summation, 1.94 dB lowering in threshold, remained constant as a function of the distance between the two vibrators on the thigh. Similar amounts of summation were obtained unilaterally and bilaterally on the fingers. When the frequency of vibration was lowered to 9 Hz, no spatial summation was found. When the frequencies of vibration at the two test sites were different, 160 Hz at one locus, 360 Hz at the other locus, there was no spatial summation.     

Vibrotactile loudness addition

Os adjusted the intensity of vibration at a single locus on the right hand to a value equal in vibratory loudness to various patterns of vibration on the left hand. The patterns were created by 1 to 5 equated vibration generators, varied with respect to sensation level and distances among the vibrators. The results were: (a) increasing from 1 to 5 vibrators produced a doubling in vibratory loudness, (b) neither loudness level of the components nor distance among vibrators had any effect on the slope of the overall loudness growth function. Os also adjusted the intensity of a white noise to equal in magnitude the patterns of vibration presented (a) to the left hand as before and(b) to loci distributed over the surface of the body. The results were the same as those obtained using a single vibrator as standard. The specific loci stimulated did not appear to have any effect on vibrotactile loudness addition.