John R. Platt

Percentile Reinforcement: Paradigms for Experimental Analysis of Response Shaping1

Publisher Summary Conditioning paradigms allow experimental control of selected classes of variables, which potentially affect behavioral change. Instrumental or operant conditioning paradigms allow examination of how the consequences of an organisms behavior change subsequent behavior. This chapter presents a class of conditioning paradigms, which offer considerable promise for experimentally analyzing a class of variables that has long been accepted as fundamental to behavior change, but which remained inextricably confounded within traditional paradigms of instrumental and operant conditioning. Additionally, some early results utilizing these new paradigms are reviewed, and some examples of applications of these paradigms to specific problems in behavior theory are proposed. The paradigms presented in this paper have been developed to deal with problems of controlling contact with, and selectiveness of reinforcement criteria during response shaping, but similar behavior dependent schedules seem particularly well suited to a number of problem areas in which effects of behaviorally confounded relationships between events have to be separated.

Parametric manipulation of interresponse-time contingency independent of reinforcement rate.

Pecking of pigeons was reinforced under a modified interval-percentile procedure that allowed independent manipulation of overall reinforcement rate and the degree to which reinforcement depended on interresponse-time duration. Increasing the contingency, as measured by the phi coefficient, between reinforcement and long interresponse times while controlling the overall rate of reinforcement systematically increased the frequency of those interresponse times and decreased response rate under both of the reinforcement rates studied. Increasing reinforcement rate also generally increased response rate, particularly under weaker interresponse-time contingencies. Random-interval schedules with comparable reinforcement rates generated response rates and interresponse-time distributions similar to those obtained with moderate-to-high interresponse-time reinforcement contingencies. These results suggest that interresponse-time reinforcement contingencies inherent in random-interval and constant-probability variable-interval schedules exercise substantial control over responding independent of overall reinforcement rate effects. The interresponse-time reinforcement contingencies inherent in these schedules may actually mask the effects of overall reinforcement rate; thus differences in response rate as a function of reinforcement rate when interresponse-time reinforcement is eliminated may be underestimated.

Effect of frequency, timbre, experience, and feedback on musical tuning skills

Subjects with tuning experience were superior to nontuners in a pitch-matching task at all but the lowest of five frequencies tested. Performance was better for adjustment of simple (sine-wave) tones to match simple tones than for adjustment of complex (string-timbre) tones to match simple tones. A comparison of constant errors showed that both tuners and nontuners heard complex tones as sharp relative to simple tones. Additional testing with 2 of the subjects indicated that the first overtone of the complex tone was sufficient to produce this effect. Repetition of the pitch-matching task over 6 days produced some improvement in performance. A second experiment showed that auditory and visual feedback improved tuning accuracy for complex comparison tones about 4.5 cents more than did practice without feedback, but no effect was observed for simple comparison tones. This experiment also indicated that musical experience, rather than tuning experience perse, was responsible for the effects of prior experience, and that tuning was more accurate when the standard was a complex tone and when the standard and comparison tones had the same timbre. The relevance of these data to musical tuning skills and to theories of complex pitch perception is discussed.

Contiguity and contingency in the acquisition and maintenance of an operant

Abstract Three experiments compared the effects of nondifferential and differential reinforcement of response location on a circular dimension. Rats were required to operate a vertical joystick to produce food. When food was delivered immediately after responses, but independent of response location, the spatial concentration of responding was low and no progressive changes were observed. Traditional and percentile schedules of differential reinforcement for response location produced highly reliable acquisition of spatially concentrated responding. Once concentrated responding had been established, nondifferential reinforcement was sufficient to maintain it in some subjects. Since only the differential reinforcement schedules established a contingency with respect to response location, it was concluded that this relationship was necessary for acquisition, but that response-reinforcer contiguity may be sufficient for maintenance. This conclusion is consistent with the view that operant conditioning is a contiguity-based process, but that contingencies are required to produce reliable contiguity between reinforcers and particular responses.

Rhythm perception and differences in accent weights for musicians and nonmusicians

In order to investigate the contribution of harmonic—temporal and structural features to the perception of musical rhythm, three experiments were conducted in which a harmonic and a temporal accent were pitted against each other in such a way as to form five possible patterns. In three experiments, the temporal structure of various chord progressions was manipulated in an effort to determine the harmonic contributions to the inference of meter. The final experiment differed from the first two in the use of nondiatonic progressions that implied an unlikely key modulation. In all experiments, musicians and nonmusicians were requested to report perceived rhythm patterns in an attempt to determine the relative salience of various accents. Results indicated that changes in the temporal structure led to predictable change in an inferred meter, and that all diatonic chord progressions led to similar patterns of responses in which coincidences of harmonic, temporal, and metrical accents were perceptually salient events. Unusual progressions implying key modulations resulted in a qualitatively distinct pattern of results, and, in all experiments, amount of formal musical training was found to be a good predictor of the use of harmonic cues.

Spectral-motion aftereffects and the tritone paradox among Canadian subjects

The effect of spectral motion on the tritone paradox was investigated by pretesting subjects residing in southwestern Ontario, Canada, on the tritone task, presenting them with a continuous ascending or descending chromatic scale created using Shepard tones, and then retesting them on the tritone task. Results indicated a negative-motion aftereffect that affected the orientation of the pitch class circle. Differential effects of perceived pitch height on the lower portion of the pitch class circle and of adaptation on the upper portion of the pitch class circle were found in the pre- and postadaptation data, respectively. The implications of this dissociation are discussed. In addition, since our subjects lived relatively close to the U.S. border, the experimental pretests allowed us to examine the hypothesis that a canonical American pitch template similar to that found among “Californian” subjects (Deutsch, 1991) is propagated by linguistic influences of media such as television and radio (Ragozzine & Deutsch, 1994). A survey of our subjects indicated that overall, the majority of time engaged in listening to the radio and watching television or movies was spent with American sources. Despite this, and despite the fact that subjects had widely varying language and cultural backgrounds, a tight distribution of peak-pitch classes was found that is indicative of a “British” pitch template (Deutsch, 1991) for every subject tested.

Adjustment of successive and simultaneous intervals by musically experienced and inexperienced subjects

A single-stimulus adjustment technique was used to test the accuracy with which musically experienced and inexperienced subjects could intone musical intervals. We were particularly interested in the relationship between any improved accuracy resulting from musical training and interval properties, such as size or musical consonance, that could provide clues as to the mechanism of the improvement. The range of adjustment was restricted to a single chromatic interval to obviate the need for categorical interval labels. The intervals were selected so that the roles of both interval size and musical consonance could be tested. Simultaneous (harmonic) and successive (melodic) intervals, composed of both simple and complex tones, were examined. The experienced subjects were generally more accurate in their mean settings, although there was a slight tendency to stretch the smaller intervals. The inexperienced subjects tended to compress all intervals, expecially the larger ones. The experienced subjects were also more consistent in their settings, with the degree of consistency relating directly to the musical consonance of the interval. The inexperienced subjects, on the other hand, were also affected by absolute interval size and sensory consonance, displaying more consistency for smaller intervals and with simultaneous complex tones.

Differential reinforcement of interresponse times with controlled probability of reinforcement per response

Abstract Pigeons were presented food after interresponse times (IRTs) longer or shorter than a fixed percentage of their most recent IRTs. This procedure controlled probability of reinforcement per response while still allowing different classes of IRTs to be reinforced differentially. Support was found for IRT-reinforcement theory in that response rates were determined by the degree and direction of differential reinforcement of IRTs, but were relatively independent of probability of reinforcement per response and of the length of the control systems IRT memory. Stimulus control of these differential response rates was also demonstrated.

Detection of Implied Harmony Changes in Triadic Melodies

Three experiments investigated the cues used by musicians and nonmusicians asked to rate their confidence that an implied harmony change had or had not occurred at a specified point in pseudo- randomly generated, isochronous, triadic melodies that conformed to the rules of elementary classical harmony. In the first experiment, a single melody note followed the putative point of harmony change, and subjects9 responses were predictable on the basis of whether this note was contained in the previous triad and the size of the melodic interval between this note and the one preceding it. Musicians were relatively more influenced by the former factor, and nonmusicians, by the latter one. In the second experiment, five to seven melody notes followed the putative point of harmony change, which greatly reduced control by the harmonic relationship of the first of these to the previous triad, but the effect of melodic interval size persisted. The third experiment verified the findings of the first two by using the cues that had been identified in them as design variables and evaluating their effect with conventional analytic statistics. This experiment also parametrically manipulated the number of notes after the putative point of harmony change and showed that maximum confidence concerning the occurrence of an implied harmony change was reached with the first note that did not belong to the previous triad. Possible mechanisms for use of these cues to implied harmony changes are discussed, and directions for future research are indicated.

Perceived pitch class of isolated musical triads.

A paired-comparisons task was used to determine which note of a pure-tone triad sounded most similar to the triad. Musically inexperienced Ss showed no systematic preference, experienced Ss consistently preferred the highest note in the triad, and professional musicians split equally between preferring the highest note and the root note. Preference for the root note shifted to preference for the highest note as the triad type became increasingly inharmonic, suggesting that the former depended on inference of a missing fundamental. When Ss were asked to vocally reproduce the pitch they heard when listening to a triad, similar results were obtained, except that a root-note preference was not detectable in Ss with less musical experience. Preference for the root note was also facilitated by use of octave-replicated tones, and this increase was shown to be due to obscuring of pitch-height cues, rather than harmonic complexity.