Pigeons were rnn on fixed ratio schedules that alternated between pairs of long and pairs of short ratios. Length of ratio was differentially cued. The longest pause in response preceded the longer ratio. However, sequential effects were observed. These suggested a contrast effect rather than a direct relation between amount of responding preceding a pause and pause duration.The postreinforcement pause (PRP) has frequently been shown to be the property of behavior controlled by fixed-ratio (FR) scheduies-reinforcement of every nth response-most sensitive to experimental manipuiation. FR length (Boren, 1961), response effort (Notterman & Mintz, 1965), drive level (Sidman & stebbins, 1954), and number of reinforcements (Mintz, Mourer, & Weinberg, 1966a) are a few among the variety of variables shown systematically to affect pause duration.Since both effort of individual response, and the number of responses in the FR exert great influence on pause duration, total energy expenditure in achieving reinforcement suggests itself as an important determinant of pausing. However, the reguiarity of the FR scheduie, as opposed to, say, a variable ratio (VR) averaging equal length, is also important. Ferster & Skinner (1957) suggest a discriminative basis for the PRP. Response is least likely when its contingent reinforcement is least likely. Extensive training on FR establishes the reinforcement itself as the stimuius systematically preceding the lowest probability of subsequent reinforcement.Further evidence· for the importance of stimuius control in the FR performance has been shown in chained scheduies or related procedures where different stimuii are reguiarly correlated with different component responses in the sequence leading to reinforcement (Ferster & Skinner, 1957;Thomas, 1964;Mintz, Mourer, & Weinberg, 1966b). In general, when the S is provided with exteroceptive stimuii correlated with the beginning of the FR sequence, control of the behavior is weaker than when cues that have been related to closer proximity to reinforcement are presented.The present study is concerned with an analysis of PRP duration as it is influenced by FR length. The PRP occurs when one FR cycle has just been completed and a new one has begun. Our interest is to isolate the effects of the length of the preceding and the present FR on this pause.Psychon. Sci., 1967, Vol. 9 (7 A) MethodThe Ss were two aduit male White Carneaux pigeons. S24 was experimentally naive and S10 had a prior history of FR reinforcement on a white key. Both Ss were maintained at 80% of their ad lib feeding weights.The apparatus was a standard Lehigh Valley two key operant chamber for pigeons; only the right hand key was used.Both birds were run on two-component muitiple FR scheduies that followed a fixed pattern. Pairs of each ratio length were reguiarly alternated. For S10 the pattern was FR50-FR50-FR20-FR20 etc; S24 ran on FR40-FR40-FR20-FR20 etc. The longer FR was cued by a red key light, the shorter by a green key light for both Ss. During the 3.5 sec periods of ...

Pigeons were maintained on a fixed ratio (FR 9) schedule of reinforcement for correct matchingto-sample responses. Included in the test situation was a vertical array of lights, illuminated in relation to the successive steps of the fixed ratio. All five subjects showed regular decrements in matching errors across the sequence of unreinforced responses within the ratio cycle. In the form of a randomly introduced probe, the stimulus situation (array of lights) appropriate to having seven of the FR 9 steps already completed was occasionally introduced at the beginning of an FR cycle. Reinforcement followed the illumination of the two remaining lights by two correct matches. The number of errors in this probe condition was sharply lower than the errors characteristic of the first two steps of the basic FR 9.When maintained with reinforcement for every nth response (fixed-ratio), behavior frequently varies cyclically between successive reinforcements. For a color matching-to-sample situation, Nevin, Cumming, and Berryman (1963) report increases in the relative frequency of correct matches across the unreinforced sequences of a fixed ratio (FR). Variations in such properties of response as peak force, duration, and time integral of force have also been noted in FR behavior (Mintz, 1962;Notterman and Mintz, 1965). When the schedule of reinforcement requires a particular variation of the response to be emitted, the probability of this subclass has been shown to increase systematically across the unreinforced response sequences in FR cycles (Birch, 1964;Notterman and Mintz, 1965). The rate of response may also vary cyclically when performance is maintained with fixed ratio reinforcement. The pause and run pattern is a well-known characteristic of FR behavior. If a change in some exteroceptive stimulus is correlated with the steps of the ratio, changes in response rate across the unreinforced sequence tend to be pronounced (Ferster and Skinner, 1957).

Weber ratios were obtained for visual velocity discrimination under three topographic conditions with the same subjects and psychophysical procedures. The conditions differed regarding the presence of either temporal or spatial cues, these being correlated in magnitude with stimulus velocity. Systematic effects of the cues upon the level of velocity discrimination were noted.

Food pellet reinforcement for rats was made contingent upon the peak force of a bar-pressing response falling within restricted limits. Two such "bands," 5 to 10 grams and 15 to 20 grams, were established, the momentarily correct "band" indicated by one of two exteroceptive stimulus values. Peak force of response tended to conform to the reinforcement requirements, the two stimulus values setting the occasion for differentiated distributions of response force.

Sharp decline in response force after reinforcement and progressive force elevation over a sequence of unreinforced responses were observed for subjects in a fixed ratio lever-press situation. It is suggested that these systematic variations in force level may provide, through feedback, discriminable cues for behavioral regulation.