The effect of several reinforcement schedules on the variability in topography of a pigeon's key-peck response was determined. The measure of topography was the location of a key peck within a 10-in. wide by 0.75-in. high response key. Food reinforcement was presented from a magazine located below the center of the response key. Variability in response locus decreased to a low value during training in which each response produced reinforcement. Variability increased when fixed intervals, variable intervals, random intervals, or extinction were scheduled.
Four Ss were trained to press and hold down a telegraph key in the presence of a light. Subsequent release of the key during a tone was followed by water reinforcement. The schedule of reinforcement for key release was varied, and its effects on the latency (RT) of key release to the tone were studied. Both median RT and variability of RT were found to be inversely related to frequency of reinforcement as determined by the schedule.In an earlier paper (Stebbins & Lanson, 1961), we have described a technique for investigating simple reaction time (RT). The design of the classical RT experiment was adapted for use with operant-conditioning procedures. A light ("ready signal") served as the discriminative stimulus (SD1) for depression of a telegraph key (R1). After a given interval of time (foreperiod), R1 was followed by a tone (SD2). Release of the key (R2) in the presence of both tone and light was followed by water reinforcement. The latency of the key-release response to the tone was the primary dependent variable.Stable daily RT frequency distributions were generated for water-deprived rats with this method. The RT's averaged about 200 msec. In terms of variability and skew, the distributions closely resembled those commonly found with human subjects.The present experiment had a dual purpose. First, we developed the technique further. The fixed foreperiod of the earlier experiment was replaced with a variable foreperiod in an attempt to prevent the possibility of a temporal discrimination in the foreperiod. In addition, we imposed a more severe penalty (a longer time out) on "anticipatory" key-release responses to the tone, i.e., emissions of R2 to SD1 before SD2. Second, we studied the effects
Two experiments demonstrated that matching-to-sample performance was improved when an explicit observing response was required to the sample stimulus. The first experiment demonstrated that fewer training sessions were required to establish matching with than matching without such a response. The second experiment demonstrated the dependence of established matching accuracy upon this observing response and the development in two of three subjects of a new overt observing response even when none was required by the experimenter.The matching-to-sample procedure is a conditional discrimination procedure in which a standard (ST) or sample stimulus designates which of a number of comparison (CO) stimuli is correct . Analyses of behavior under this sort of conditional discrimination procedure have generally presumed the ST stimulus to exercise a logically and temporally different role than the CO stimuli. Skinner (1950) described matching-to-sample as "choosing red after being stimulated by red." Cumming and proposed that the ST exercises an "instructional" role controlling the strength of response to each of the CO stimuli. However, an alternative and more parsimonious analysis of matching-to-sample is available, and it seems worthwhile to eliminate this analysis before accepting the other. The terms of this alternative analysis become clearer once the apparatus employed in many matching-to-sample studies is described. Gen-erally, matching-to-sample is studied in the laboratory using relatively few alternative stimuli (e.g., red, green, and blue lights for color matching). Often, a three-stimulus display is used, the center display presenting the ST and the two side displays presenting the COs. Given the few stimuli and the three-key display, it is possible that the entire three- stimulus display might be acting as a unitary stimulus controlling the strengths of the responses "peck right" and "peck left" for a subject exhibiting high matching-to-sample accuracy. Depending upon the distance separating the three keys, a "unitary stimulus" analysis becomes possible: where keys are very close together, training to match-to-sample might merely be strengthening the response to the "larger" color, i.e., the side-keycenter-key area that is of homogeneous color.Although the unitary-stimulus analyses are more parsimonious than the instructionalstimulus analyses, they would be difficult to maintain if accuracy in matching-to-sample was shown to be dependent upon a separate observing response (Wyckoff, 1954) to the ST.In many matching-to-sample experiments such a separate response to the ST has been required (e.g., Riesen and Nissen, 1942;Ferster, 1960; METHOD SubjectsSix male White Carneaux pigeons were maintained throughout the experiment at 80% of their free-feeding weights. Three 435 1968, 11,[435][436][437][438][439][440][441] NUMBER 4 (JULY)
Acuity-luminance relations for a grating test object were determined with red, yellow, green, and blue narrow-band chromatic illuminants for five subjects. At intermediate and high luminance levels, acuities for blue were lower than for the other chromatic illuminants in four of the five subjects. One of these subjects also showed lower asymptotic acuity for red at high luminances. The fifth subject, who did not show lower blue acuity, exhibited lower asymptotic acuities than the other subjects. The low blue acuities observed in four of the five subjects are attributed to neural rather than dioptric factors. INDEX HEADINGS: Vision; Color vision. ALTHOUGH many studies have investigated the effect of chromatic illuminants on foveal visual acuity, conflicting results have been obtained owing to differences of test object, psychophysical method, and degree of spectral purity of the illuminants used. In addition, the chromatic aberration of the eye is a complicating factor which has been treated in different ways by different investigators. Giorgi' in his study of the effect of wavelength on critical fusion frequency has pointed out that wavelength effects may be obscured by using broad-bandpass color filters. A similar observation on the effect of bandpass for acuity can be found in the data of Ferree and Rand, 2 who report lower acuity values for red and blue illuminants than for illuminants in the center of the visible spectrum. Desaturation of the red and blue stimuli improved acuity for these illuminants, but the absolute acuity levels reached with what the authors termed an equal-saturation spectrum remained lower for the red and blue. Chromatic aberration of the eye has been treated differently by different investigators. Some, wishing to minimize dioptric factors, have employed corrections for chromatic aberration at all wavelengths tested;;35 others, wishing to know how the visual system behaves in a natural environment, have not employed a correction for chromatic aberration. 2 '6 In several experiments, a corrective lens has been used only for the blue end of the spectrum. 7. 8 Under the latter conditions, the amount of accommodation required to focus the test object varies with the wavelength of illumination.
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