A visual discrimination task was used to determine the effectiveness of verbal reward alone (Verbal group) vs a combination of candy and verbal reward (Combined group) with 16 middle-class 5-yr.-olds and 16 5-yr.-olds from a Head Start class. Social class proved to be the only significant variable, the performance of the higher status group being superior to that of the lower status group. Only a tendency for the verbally rewarded Ss to be superior to combined reward Ss was noted.

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Reaction times were obtained to the onset and offset of flash stimuli located in various positions in a visual field divided into two contiguous regions of white and black. With presentation of the flash stimuli in the fovea, there were no significant differences in the character of functional onset and offset RTs or in the character of the function relating RT to distance from the border. There was a border effect operative for both functions; a decrease in both onset and offset RTs appeared as the border was approached from the white side and a slight increase in both onset and offset RTs when the border was approached from the black side.Several psychophysical studies have examined the differences in response to the onset and offset of stimulation in the visual system using reaction time ( R T ) as the response measure. Rains (1961) reported no differences between RTs to the offset or the onset of a bright (344 millilambert) luminance. However, he suggested that differences may appear when a small, dim peripheral flash is employed. Pursuing this suggestion, Pease and Sticht (1965) investigated RT as a function of onset, offset, location and luminance of visual stimuli presented either foveally or peripherally. When stimuli were presented to the periphery, R T was significantly longer for the offset of the scimulus than for the onset. Bartlett, Sticht, and Pease (1968) measured onset and offset RTs to two wavebands in both the fovea and periphery. The wavebands were selected with the intention of isolating foveal and peripheral systems. RTs to onsets were significantly faster than to offsets for the peripheral data while the on-off differences for the fovea were not significant. It was further reported that the on-off differences were independent of wavelength.Single unit studies ( Baumgartner, 1961;Granit, 1955 ) have suggested that the activation of "on-off" units may play a role in the production of contrast effects. Baumgartner examined the responses of single units in the optic tract with patterns of contrasting dark and illuminated stripes. With this stimulus pattern, the "on" unit showed maximum response when its receptive field was located near the edge of an illuminated stripe. Its "off" response was greatest when its receptive field was outside the illuminated stripe. These results suggest that the functional "on" and "off" units may afford an analogy with the enhancement of boundaries by contrast.The present experiment was undertaken in order to determine if foveal onset and offset RTs would vary as a function of the proximity to a border in a 'This paper is based on the author's MA thesis resented in partial fulfillment of the requirements for that degree.