Following variable interval training a pigeon was reinforced for responding to S+ (1099 cps tone) but was not reinforced for responding during S-(no tone). When discrimination was stable test stimuli were introduced at preselected (formerly S-) periods. Interresponse time (IRT) distributions were obtained during presentation of stimuli. Minimal changes occurred in the IRT distributions for test stimuli relative to those for S+. Problem Jenkins & Harrison (1960) studied the effects of differential and nondifferential training on auditory generalization in the pigeon finding that steeper gradients were obtained following differential training. Guttman & Kalish (1956) found in studying wavelength gradients that as the test stimulus values deviated more from the training stimulus pigeons generally responded more slowly. What does responding more slowly mean? In steady state generalization where more reinforcements are received at 550 millimicrons than at other wavelengths "short IRT peaks" seem insensitive to stimulus variation. Fewer intermediate IRT's occur at or near 550 millimicrons than elsewhere (Blough, 1963). The purpose of this study consisted in obtaining separate IRT distributions for responses emitted to test stimuli so that response patterning as well as rate changes could be investigated. Use of a probe technique in generalization testing results in at least two advantages: (1) Interaction of test tones via serial effects on responding may be evaluated. (2) Total number of reinforcements possible during S+ presentation is not attenuated making interaction effects of extinction less likely (Skinner, 1950). Method The S was one experimentally naive white Carneaux pigeon maintained at 80% of its free feeding weight. A standard one cubic foot experimental chamber containing a one key response panel was used. Chamber and response key illumination was provided by white and green 7-watt lamps, respectively. Access to grain for 4.5 sec. was accompanied by magazine light onset and extinction of the chamber and key lamps. Standard programming equipment was used. Pure tones were delivered through a ceiling mounted speaker at 80 db amplification. Twenty-five sessions of variable interval VI 30-sec. and VI 1-min. schedules of reinforcement in the presence of a 1099 cps tone preceded discrimination training. From session 26 responding was reinforced on a VI 1 schedule in the presence of 1099 cps tone (S+) and not reinforced in the absence of tone (S-). Working periods ,

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AbstraetThree pigeons were exposed to an FR-10 conditioned reinforcement probe superimposed over baselines generated by DRL schedules. Response rates increased when the probes were introduced. ProblemFindley & Brady (1965) have reported facilitative effects of response contingent magazine lightpresentations during large fixed ratio contingencies. In that study response rates were substantially increased by adding a concurrent FR-400 schedule of magazine light delivery to an FR-4000 food schedule.The present study is the first in a series of attempts to demonstrate this effect when the high rates produced by the conditioned reinforcement contingency do not increase reinforcement density, without using programmed extinction as a baseline (Kelleher, 1961). SubjectsThe Ss were three adult silver king pigeons which were maintained at 80% of their ad. lib. body weight. They had extensive histories, Le., several hundred hours, of both DRL-20 sec. and DRL-30 sec. schedules of food reinforcement. ApparatusA standard one cubic foot experimental chamber was used . Illumination of the entire chamber was provided by a 7-w lamp located opposite the response panel near the ceiling. The translucent plastic response key, 8-3/4 in from the floor on the midline of the response panel, was illuminated by a green 7-w lamp. The aperture to the grain magazine was centered 2 in from the floor immediately under the key. Programming was accomplished with standard relay equipment. ProcedureThe Ss were exposed to a DRL-20 sec. schedule of food reinforcement until their intrasession rates of responding were relatively consistent, and the intersession variability was small. The DRL schedule specifies a minimum interresponse time, or pause length, and in this experiment each response was reinforced whose latency was equal to or exceeded the specified value. Reinforcement was a 4.5 sec. access to grain.A probe (conc. DRL-20 sec. FR-10) was introduced within several sessions. The DRL contingency was unchanged by the probe, and every tenth response produced a 2 sec. blackout of the box during which the magazine light was illuminated. These stimulus conditions were identical to those which occurred at food reinforcement on the DRL schedule except the grain Psychon. Sci. , 1965, Vol. 3 JOHN J. RANDOLPH AND WILLIAM R. SEWELL UNIVERSITY OF ALABAMAhopper was not elevated.Two of the three birds were re-exposed to a DRL-30 sec. schedule in the latter portion of the experiment. The probe, now conc. DRL-30 sec. FR-10, was reintroduced when the intra session variability was small enough for an adequate eValuation of the effects of the fixed ratio contingency. Results and DiscussionIncreases in response rates during the probes of the 20 sec. baseline were found for all three birds, but in two of the three cases the changes were small and transitory. The most dramatic change is shown in the first probe in Fig. 1. The segment marked with the letter A shows a food reinforcement delivered while the probe was in effect.The amount of rate change during the probes...

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