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The common brushtail possum (Trichosurus vulpecula) has been reported to eat vegetation, fruit, invertebrates, and occasionally fungi, eggs and meat. The relative preference between food types found in the wild, however, has not been investigated systematically in a controlled laboratory study. This research investigated captive possums’ food choice using two different methods of preference assessment. The first experiment involved a single stimulus assessment of possums’ (n = 20) consumption of individually presented food items. More than 75% of possums consumed berries, locusts and mushrooms but fewer than 50% of possums consumed fivefinger, raw chicken and eggs. The second experiment that used a paired stimulus assessment to establish relative preference for those foods revealed that no single food was preferred by all possums. Overall locusts were the most preferred food, followed in order of preference by berries, egg, mushrooms, chicken and foliage. The single stimulus preference assessment confirmed the palatability of foods. The paired stimulus assessment provided a rank order of food preferences.

In the present experiment, an attempt was made to extend the base of evidence for the assumption of the behavioral theory of timing that pacemaker rate is determined by reinforcement rate. Pigeons discriminated the first half from the second half of a 50-sec trial in a free-operant psychophysical procedure. Left-key responding was reinforced at variable intervals during the first 25 sec, and right-key responding was reinforced at variable intervals during the second 25 sec. The rate of “extraneous” reinforcers delivered at variable intervals following responses to a center key was manipulated independently of performance in the temporal discrimination. Quantitative estimates of pacemaker rate were not directly proportional to extraneous rate of reinforcement, whether extraneous reinforcers were available during the intertrial interval, the entire session, or the trial only. Instead, estimates of pacemaker rate were inversely related to the rate of extraneous reinforcement, which suggests that pacemaker rate is determined by the ratio of the rate of reinforcement for the timing response relative to other sources of reinforcement.

In the behavioral theory of timing, pacemaker rate is determined by overall rate of reinforcement. A two-alternative free-operant psychophysical procedure was employed to investigate whether pacemaker period was also sensitive to the differential rate of reinforcement. Responding on a left key during the first 25 s and on a right key during the second 25 s of a 50-s trial was reinforced at variable intervals, and variable-interval schedule values during the two halves of the trials were varied systematically. Responding on the right key during the first 25 s and on the left key during the second 25 s was not reinforced. Estimates of pacemaker period were derived from fits of a function predicted by the behavioral theory of timing to right-key response proportions in consecutive 5-s bins of the 50-s trial. Estimates of pacemaker period were shortest when the differential reinforcer rate most strongly favored right-key responses, and were longest when the differential reinforcer rate most strongly favored left-key responses. The results were consistent with the conclusion that pacemaker rate is influenced by relative reinforcer rate.

The assumption by the behavioral theory of timing that pacemaker rate is proportional to reinforcer density was tested in 2 experiments. Pigeons discriminated between the 1 st and 2nd halves of a 50-s trial. Responses on a left key were reinforced at variable intervals for the first 25 s of the trial, and right-key responses were reinforced at variable intervals during the second 25 s. In Experiment 1, overall reinforcement rate was varied by manipulating the intertrial interval (ITI) duration. Pacemaker rate, estimated by fitting predictions to psychometric functions, was an inverse function of ITI. In Experiment 2, reinforcer duration was manipulated as a means of altering reinforcer density. Pacemaker rate was found to be directly related to reinforcer duration

In the behavioral theory of timing, pulses from a hypothetical Poisson pacemaker produce transitions between states that are correlated with adjunctive behavior. The adjunctive behavior serves as a discriminative stimulus for temporal discriminations. The present experiments tested the assumption that the average interpulse time of the pacemaker is proportional to interreinforcer interval. Responses on a left key were reinforced at variable intervals for the first 25 s since the beginning of a 50-s trial, and right-key responses were reinforced at variable intervals during the second 25 s. Psychometric functions relating proportion of right-key responses to time since trial onset, in 5-s intervals across the 50-s trial, were sigmoidal in form. Average interpulse times derived by fitting quantitative predictions from the behavioral theory of timing to obtained psychometric functions decreased when the interreinforcer interval was decreased and increased when the interreinforcer interval was increased, as predicted by the theory. In a second experiment, average interpulse times estimated from trials without reinforcement followed global changes in interreinforcer interval, as predicted by the theory. Changes in temporal discrimination as a function of interreinforcer interval were therefore not influenced by the discrimination of reinforcer occurrence. The present data support the assumption of the behavioral theory of timing that interpulse time is determined by interreinforcer interval.

Food and sounds (white noise, a food call and the sound of other chicks) were used in an attempt to establish conditioned place preferences with domestic hen chicks. Thirty-two chicks were randomly allocated to one of the 4 groups, and exposed to a 3-compartment apparatus to establish a baseline of their movements across 4 15-min sessions. They were then confined to one compartment and provided with free access to food or exposed to one sound for 15 min and then they were confined to the alternate compartment with no food or sound for 15 min. This process was repeated 3 times. Post-conditioning test sessions showed a conditioned place preference towards the area associated with food and away from the area associated with white noise. After conditioning, chicks showed no preference for spending time in the side associated with the food call or the sounds of other chicks; however, they entered a compartment first more often when it was associated with the food call and less often when it was associated with chick-sounds. Overall, these results showed that it was possible to use the conditioned place preference procedure to assess the effects of sounds and that the procedure has potential use for assessing other environmental stimuli.

This article reports two studies assessing the influence of self-efficacy, outcome expectancies and aversive feedback on different aspects of adherence. Study 1 employed a computer simulation of physiotherapy to test experimentally the effects of aversive feedback (i.e., loud noise) experienced during simulated therapy on adherence behaviour in a student population. Study 2 examined whether similar effects of aversive feedback (i.e., pain) experienced during physiotherapy in a clinical setting would be observed in a longitudinal questionnaire study of predictors of adherence. In both studies, self-efficacy and outcome expectancies were assessed at baseline and after experience of the task (performing simulated or actual physiotherapy). Study 1 found that self-efficacy and outcome expectancies predicted persistence with simulated physiotherapy (i.e., completing the experimental session), whereas aversive feedback influenced adherence during sessions (i.e., correct response rate). Study 2 found that self-efficacy and outcome expectancies predicted persistence with actual physiotherapy (i.e., completing the prescribed number of sessions). Aversive feedback and outcome expectancies influenced adherence during sessions. We conclude that different factors predict different aspects of adherence behaviour. It is therefore important to measure both persistence over time and adherence during sessions, and to investigate the predictors of each dimension of adherence.

Discrete-trial training (DTT) relies critically on implementation by trained tutors. We report three experiments carried out in the development of "DTkid"--interactive computer simulation software that presents "SIMon", a realistic virtual child with whom novice tutors can learn and practise DTT techniques. Experiments 1 and 2 exposed groups of participants either to DTkid training or to a control task. Participants in the former groups demonstrated significantly greater procedural and declarative knowledge of DTT. Experiment 3 confirmed this finding, further demonstrating that observation of DTkid training trials alone was sufficient to enhance participants' declarative and procedural knowledge of DTT. Results indicate that DTkid offers the potential for an effective means of teaching DTT skills to novice tutors of children with autism.

Please cite this article in press as: Bizo, L.A., et al., Corrigendum to “The failure of Weber’s law in time perception and production” [Behav. Process. 71 (2–3) (2006) 201–210]. Behav. Process. (2013), http://dx.doi.org/10.1016/j.beproc.2013.08.014 The authors regret that the parameters of Eqs. (16) and (17) reported on p. 206 for the categorization task are wrong. The median values ver the 12 subjects are m = 2.8, A = 0.31, B = 0.12, with semi-interquartile ranges of 0.15, 0.05, and 0.04 respectively. We thank Dr. Todd orowitz for alerting us to that error.

Seven pigeons were trained to respond on one key during the first half of a 60-s trial, and on another during the second half, to test the prediction that the rate of the internal pacemaker should slow in the absence of reward. The relative probability of responding was well-described by Erlang distributions, which yielded as parameters the period of the pacemaker and the criterial number of counts for switching to the second key. During a subsequent period of extinction the period increased linearly with time in extinction, and the criterial count decreased. This slowing of the pacemaker was predicted by the Behavioral Theory of timing, but not by other theories.

Predictions of P. R. Killeen's (1994) mathematical principles of reinforcement were tested for responding on ratio reinforcement schedules. The type of response key, the number of sessions per condition, and first vs. second half of a session had negligible effects on responding. Longer reinforcer durations and larger grain types engendered more responding, affecting primarily the parameter alpha (specific activation). Key pecking was faster than treadle pressing, affecting primarily the parameter delta (response time). Longer intertrial intervals led to higher overall response rates and shorter postreinforcement pauses and higher running rates, and ruled out some competing explanations. The treadle data required a distinction between the energetic requirements and rate-limiting properties of extended responses. The theory was extended to predict pause durations and run rates on ratio schedules.

Publisher Summary This chapter interprets Aristotle's four causes, which he called material, final, efficient, and formal as questions about what (description/ definition and substrate), why (function), how (mechanism), and like (analogs and models). These four causes organize the analysis of time and timing. Time is not a fourth dimension—although it may be measured on one. It is not itself a cause—even though effects unfold in time. Time was not discovered; it was invented. The conceptions of time that have been invented by physicists have been adopted by society at large, so that there is a good correlation between the physicist's time— SI time—and that on our clocks—Big Ben Time. Both times are measured on cyclic interval scales. An animal is only said to be timing while it is involved in activities that in the past have been reinforced for improving temporal judgments.