Economic and Biological Influences on Key Pecking and Treadle Pressing in Pigeons

Abstract

Pigeons were studied on a two-component multiple schedule in which the required operant was, in different conditions, biologically relevant (i.e., key pecking) or nonbiologically relevant (i.e., treadle pressing). Responding was reinforced on a variable-interval (VI) 2-min schedule in both components. In separate phases, additional food was delivered on a variable-time (VT) 15-s schedule (response independent) or a VI 15-s schedule (response dependent) in one of the components. The addition of response-independent food had different effects on responding depending on the operant response and on the frequency with which the components alternated. When components alternated frequently (every 10 s), all pigeons keypecked at a much higher rate during the component with the additional food deliveries, whether response dependent or independent. In comparison, treadle pressing was elevated only when the additional food was response dependent; rate of treadling was lower when the additional food was response independent. When components alternated infrequently (every 20 min), pigeons key pecked at high rates at points of transition into the component with the additional food deliveries. Rate of key pecking decreased with time spent in the 20-min component when the additional food was response independent, whereas rate of pecking remained elevated in that component when the additional food was response dependent. Under otherwise identical test conditions, rate of treadle pressing varied only as a function of its relative rate of response-dependent reinforcement. Delivery of response-independent food thus had different, but predictable, effects on responding depending on which operant was being studied, suggesting that animal-learning procedures can be integrated with biological considerations without the need to propose constraints that limit general laws of learning.Key words: biological effect, economic effect, contingent reinforcement, multiple schedule, response-independent food, response-dependent food, treadle press, key peck, pigeon Herrnstein's (1970) equation states that response rate varies as a function of its relative rate of reinforcement. Stated formally,c c ewhere R is rate of responding, r c is the rate of response-dependent food delivery, k is a constant representing asymptotic rate of responding, and r e is the rate of extraneous reinforcement. Extraneous reinforcement includes concurrently scheduled, dependent reinforcement, as well as response-independent food delivery and reinforcement from other alternatives (Herrnstein, 1970). It follows from Equation 1 that an increase in response-independent food delivery (r e ) would decrease the overall rate of responding (R). Indeed, response-independent food delivery generally decreases the overall rate of hu-

Disruption of Responding Maintained by Conditioned Reinforcement: Alterations in Response-Conditioned-Reinforcer Relations

“…This conclusion is strengthened in light of the fact that the observing response in Experiments 1 and 2 was a treadle press and was a key peck in Experiment 3. Key pecks can be expected to occur at higher rates than treadle presses when maintained by primary reinforcement (e.g., Green & Holt, 2003); the higher rates of treadle pressing obtained in Experiments 1 and 2, therefore, is consistent with the suggestion that the S2 had acquired aversive properties. Similarly, the procedure used in Experiments 1 and 2 (S+ only) may have functioned not as a simple FR 1 that was available intermittently, but more as a general intermittent schedule of observing due to the intervening and unsignaled Ext components during which observing had no consequences.…”

Delay discounting: Pigeon, rat, human—does it matter?

“…Preference reversals also have been obtained in studies with pigeons (Ainslie & Herrnstein, 1981; Calvert, Green, & Myerson, 2010; Green, Fisher, Perlow, & Sherman, 1981; Rachlin & Green, 1972; Rodriguez & Logue, 1988) and rats (Green & Estle, 2003). Green et al (1981) presented pigeons with choices between a smaller, sooner reinforcer and a larger, later reinforcer.…”

“…The majority of discounting studies with animals have examined choices between either different amounts of food (Green et al, 2004; Mazur et al, 1987; Rosati et al, 2007) or different amounts of plain water (Green & Estle, 2003; Reynolds et al, 2002; Richards et al, 1997). However, discounting of other reinforcers also has been studied, including choices involving sucrose (Calvert et al, 2010; Farrar et al, 2003; Freeman et al, 2012), saccharin (Freeman et al, 2009), alcohol (Mitchell et al, 2006; Oberlin & Grahame, 2009), and cocaine (Woolverton, Freeman, Myerson, & Green, 2012; Woolverton et al, 2007).…”

“…It thus may be the case that the pigeon’s ‘biological’ response (Green & Rachlin, 1975) is entrained, leading it to peck at the signal for the more immediate food reinforcer. In a test of this possibility, Holt et al (2013) compared the rate of discounting by pigeons for a delayed food reinforcer when the required response was the ‘biological’ key peck response versus a non-biological treadle-pressing response (see, Green & Holt, 2003), and reported that pigeons discounted less steeply when the choice response was treadle-pressing 4 . Therefore, the difference in the biological relevancy of key pecking for pigeons and lever pressing for rats might account for the observed species difference.…”

Within‐trial Contrast: Pigeons Prefer Conditioned Reinforcers That Follow a Relatively More Rather Than a Less Aversive Event

“…In the first A component, he found a typically higher relative level of responding that was maintained over training sessions (see also Williams, 1983). In the last A component, however, he found a higher relative level of responding primarily at the start of the component (an effect known as local contrast-see Terrace, 1966) which was not maintained over training sessions (see also Cleary, 1992;Malone, 1976; but see Green & Holt, 2003). Thus, there is evidence that behavioral contrast may be attributable primarily to the higher rate of responding in anticipation of the poorer schedule, rather than in response to the appearance of the richer schedule (Williams, 1981; see also Williams & Wixted, 1986).…”