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Biomedical subjects

C P Shimp

Publications and source records attributed to C P Shimp.

At least 19 recordsLinked to original sources
PubMed1999

Tolerance in a rigorous science.

Scientists often evaluate other people's theories by the same standards they apply to their own work; it is as though scientists may believe that these criteria are independent of their own personal priorities and standards. As a result of this probably implicit belief, they sometimes may make less useful judgments than they otherwise might if they were able and willing to evaluate a specific theory at least partly in terms of the standards appropriate to that theory. Journal editors can play an especially constructive role in managing this diversity of standards and opinion.

Interprofessional Relations↗
PubMed1999

The randomization procedure in the study of categorization of multidimensional stimuli by pigeons.

Pigeons categorized rectangles varying in both height and width in an adaptation of a method used by Ashby and colleagues for the cognitive and neuropsychological analysis of human decision bounds for ill-defined categories. Optimal decision bounds were defined in a stimulus space in which the point (x,y) corresponded to a rectangle with width x and height y. Four tasks defined the following 4 optimal bounds: x = y, x = c, x = y + d, and (x-a)2 + (y-b)2 = r2, where a, b, c, d, and r were constants given by a task. Estimated decision bounds for individual pigeons conformed approximately to the optimal decision bound in each of the 4 tasks. The new method suggests a way to (a) integrate the disparate literature on ill-defined visual concepts and on optimal performances in nonhuman animals; (b) compare how humans and nonhuman animals categorize ambiguous, multidimensional configural stimuli; (c) model how nonhuman animals categorize naturalistic stimuli; and (d) infer that pigeons' categorizations of naturalistic stimuli may be remarkably close to optimal.

Animals↗
PubMed1998

Priming of attention to local or global levels of visual analysis.

Humans can shift attention between parts and wholes, as shown in experiments with complex hierarchical stimuli, such as larger, global letters constructed from smaller, local letters. In these experiments, a target stimulus appears at either the local or the global level, with a distractor at the other level. A shift of attention between levels is said to be demonstrated through a form of priming, whereby targets at one level are presented with a higher probability than at the other level. This base-rate type of priming can facilitate speed of responding to targets, as seen in shorter reaction times to targets at the primed level. Experiment 1 demonstrated such a priming effect in pigeons. Experiment 2 confirmed this priming, by showing that accuracy remained high for familiar targets, at either level, even when distractors at the other level were novel.

Animals↗
PubMed1994

Molar function depends on molecular structure of behavior.

Pigeons chose between green side keys, then waited a shorter or longer time before pecking a center key, and finally chose between red side keys. Two successive left choices (to green and then red) with a shorter wait intervening, or 2 successive right choices with a longer wait intervening, were intermittently reinforced with food. The 2 required waiting times and the relative frequency of reinforcement for the shorter reinforced pattern were varied. Molar preference, defined in terms of coherent responses that satisfied the molecular reinforcement contingency, conformed to the highly adaptive matching level, but molar preference, defined in terms of incoherent responses, did not. The molar matching result therefore generalizes to responses with complex molecular structures provided that analyses distinguish between coherent and incoherent responses. The results are compatible with the idea that awareness can facilitate adaptation.

Animals↗
PubMed1993

Behavioral and computational models of spatial attention.

Pigeons pecked for food in a spatially cued choice reaction time (RT) task. A brief (50-ms) white light appeared on a left or right key and probabilistically predicted the location (on either the left or right key) of a subsequent target stimulus. The time between cue and target onset (stimulus onset asynchrony), the base rate of left cues, and the probability that the cue correctly predicted the target (cue validity) were experimentally varied. The mean RT to respond to the target key was faster on correctly cued trials (defining a validity effect), decreased for both valid and invalid trials as stimulus onset asynchrony increased (defining an alerting effect), showed a variety of base-rate effects, and did not depend on cue validity. It is shown with a computational-processing model that dynamic interactions of short-term and associative memory processes are sufficient to produce these attentionlike empirical phenomena.

Animals↗
PubMed1992

Computational behavior dynamics: an alternative description of Nevin (1969).

A computational processing behavior-dynamic model was instantiated in the form of a computer program that "behaved" on the task developed by Nevin (1969). In this classic discrete-trials experiment, the relative frequency of choosing a response alternative matched the relative frequency of reinforcement for that alternative, the local structure of responding was opposite that predicted by momentary maximizing (i.e., the probability of a changeover decreased with run length), and absolute and relative response rates varied independently. The behavior-dynamic model developed here qualitatively reproduced these three results (but not in quantitative and specific detail) and also generated some interesting, as-yet-untested predictions about performance in Nevin's task. The model was discussed as an example of a stochastic behavior-dynamic alternative to algebraic behavior theory.

Animals↗
PubMed1990

Local patterns in human operant behavior and a behaving model to interrelate animal and human performances.

College students pressed buttons for points delivered according to molecular concurrent reinforcement contingencies similar to those used in previous experiments with animal subjects. Relative frequency of reinforcement and the relative and absolute durations of two reinforced patterns of button pressing were experimentally varied. Qualitative effects of all three variables resembled those obtained previously with animals. Computer simulation of a cognitive processing model described these qualitative effects. A similar model was used previously to describe corresponding behavior in pigeons. Therefore, similar cognitive processing may underlie the local temporal patterning of animal and human operant behavior maintained by this concurrent reinforcement contingency.

Adult↗
PubMed1990

Preference as a function of absolute response durations.

The durations of 2 responses, 2 categories of reinforced nondiscriminated interresponse times, were varied while their relative durations were held approximately constant, with the longer about 2 1/2 times longer than the shorter. Three pigeons pecked for food. Reinforcers for the shorter and longer responses were arranged by a concurrent variable-interval, variable-interval schedule. Preference for the shorter response increased when both were lengthened. These results, taken together with previous results for discriminated interresponse times, show that preference for the shorter of 2 responses depends on their absolute durations, whether they are discriminated or not and regardless of autoshaped key pecks that may occur in the discriminated case. Time-allocation-matching was not generally obtained. The results qualitatively agree with an associative learner, a computational processing model derived from a molecular analysis of behavior.

Animals↗
PubMed1989

Preference for starting and finishing behavior patterns.

Pigeon's key pecking was reinforced with food in two experiments in which the correspondence between preference for starting one of two reinforced behavior patterns and the likelihood of finishing it subsequently was examined. Reinforcers were scheduled according to concurrent schedules for two classes of interresponse times, modified such that reinforcers followed a center-key peck terminating either a shorter interresponse time started by a left-key peck or a longer interresponse time started by a right-key peck. In Experiment 1, the times when reinforcers potentially were available were not discriminated, whereas in Experiment 2 they were. Absolute reinforced pattern durations were varied. The relative frequency of starting a particular pattern was highly correlated with relative frequency of that completed pattern in both experiments. Other relations between starting and finishing a pattern depended on whether reinforced interresponse times were discriminated. For instance, preference for starting a pattern sometimes correlated negatively with the likelihood of subsequently completing it. The present experiments are described as capturing part of the ordinary language meaning of "intention," according to which an organism's behavior at one moment sets the occasion for an observer to say that the organism "intends" in the future to engage in one behavior rather than another.

Animals↗
PubMed1985

An infrared system for the detection of a pigeon's pecks at alphanumeric characters on a TV screen: the dependency of letter detection on the predictability of one letter by another.

Three pigeons pecked at letters of the alphabet and at the symbol "?" displayed on a computer-driven cathode ray screen. A 4 by 4 matrix of infrared emitting and detecting diodes and associated circuitry identified the location of a pigeon's responses to the screen. Responses at the target letter T were probabilistically reinforced with food whenever T appeared in a string of three letters in the middle of the screen. Responses at the symbol "?" appearing below this string were probabilistically reinforced whenever T did not appear. The letter F anywhere in the three-character string either strongly predicted the occurrence of the target letter T, in two conditions, or predicted its nonoccurrence, in a third. This manipulation of the frequency with which the familiar letter F predicted T was shown to change the function relating probability of a correct peck at the symbol "?" to the number of Fs in the string. This effect may be interpreted as an instance of the phenomenon where an organism's acquired knowledge changes what it sees.

Animals↗
PubMed1985

Local temporal pattering of operant behavior in humans.

Button pressing by 44 college students intermittently produced points and the words "GOOD" or "POOR" on a computer screen. The events were arranged according to a paced random-interval 10-s schedule in which the target interresponse-time categories were 1 to 3, 3 to 5, or 6 to 12 s. The degree to which instructions specified certain aspects of the contingency (e.g., whether response spacing was critical) was also varied, and in some conditions the experimenter prompted specifically paced responses during the first 2 min of the session. The procedures shaped the local patterning of behavior of some subjects in less than 30 min of exposure to the contingencies. Most subjects who, in a postexperimental questionnaire, accurately identified the schedule contingencies also responded more accurately than those whose verbal descriptions were inaccurate or imprecise.

Journal Article↗
PubMed1984

Timing, learning, and forgetting.

A computer-simulation model (AL) was developed for molecular and molar operant conditioning data. AL assumes a simple forgetting rule and all-or-nothing associations between memory representations of responses and reinforcers. AL describes acquisition and steady-state behavior in both concurrent interresponse time (IRT) schedules and in ordinary concurrent schedules. It describes functions relating the relative frequency of an IRT to IRT duration and to reinforcement frequency. AL accurately predicts for ordinary concurrent variable-interval schedules that the log ratio of responses to the two alternatives is a linear function of the log ratio of the reinforcers they deliver, and that the slope of this straight line approximates the degree of undermatching that characterizes the behavior of real animals. In addition, AL successfully describes the fact that in real data of Nevin, Heyman, and others, the probability of a changeover from one response to the other is roughly independent of the number of consecutive responses to the same alternative preceding the changeover. A previous version of AL assimilated data on temporal psychophysics, such as that animals bisect two temporal intervals at the geometric mean, and that the Weber fraction in DRL schedules is approximately constant. AL therefore describes transient and steady-state molecular and molar performances as well as data on temporal psychophysics.

Animals↗
PubMed1984

Cognition, behavior, and the experimental analysis of behavior.

A case history illustrates how one research program in the experimental analysis of behavior evolved somewhat differently from the modal research program represented in this journal. A chief issue that seems to be responsible for this difference is the role attributed to theory in behavioral research: Skinner's views on the nature and function of theory and on the nature of observation combine to produce a certain kind of picture of behavior. The classic conception of reinforcement contingencies is tied to this particular picture. But this picture may be incompatible with, and certainly is different from, other possible pictures. Reinforcement contingencies that place greater emphasis on the local temporal patterning of behavior seem tied to some of these alternative pictures of what behavior is. These other pictures encourage a wide range of theoretical approaches, including cognitive ones, various kinds of mathematical analyses, and computer-simulation methods to characterize entire behavior streams. In the future, perhaps the experimental analysis of behavior will accept a somewhat different range of views on the nature and function of theory, a correspondingly different set of experimental methods, and alternative ways of talking about behavior.

Journal Article↗
PubMed1983

The local organization of behavior: dissociations between a pigeon's behavior and self-reports of that behavior.

The purpose of the experiment was to study the relation between what an organism does in a setting that demands temporal patterning of behavior and what it reports it has done. More specifically, a pigeon produced two classes, shorter and longer, of temporal patterns of key pecks (interresponse times) on a center key. Occasionally, a symbolic matching-to-sample probe arranged on side keys asked the pigeon whether its most recent pattern was a shorter or longer one. The longer reinforced pattern was always three times as long as the shorter one and the two patterns were reinforced equally often. Absolute duration of reinforced patterns was varied. In some conditions, interresponse-time distributions on the center key were bimodal, indicating a clear behavioral adaptation to the contingency, yet a bird did not report very well by appropriate side-key responding what its most recent interresponse time had been. In other conditions, the interresponse-time distributions were less clearly bimodal, yet a bird reported more accurately its previous interresponse time as shorter or longer. Thus, there was a dissociation between how well behavior on the center key conformed to the schedule requirement and how well a bird reported what it was doing on the center key. In addition, as absolute duration of the reinforced patterns was increased, a bird categorized its most recent pattern less well even as its preference for the shorter pattern increased dramatically. These results were interpreted as an example of the phenomenon of dissociation between tacit knowledge and knowledge.

Color Perception↗
PubMed1982

Choice and behavioral patterning.

Ten pigeons pecked left and right keys in a discrete-trials experiment in which access to food was contingent upon changeovers to the right key after particular runs of left-key pecks. In each of three sets of conditions, two run lengths were reinforced according to a concurrent variable-interval schedule: reinforcement followed runs of either 1 or 2, 1 or 4, or 2 or 4 left-key pecks preceding changeovers. The intertrial interval separating successive pecks was varied from .5 to 10.0 sec, and the relative frequency of reinforcement for the shorter of the two reinforced runs was varied from 0 to .75. The contingencies established local behavioral patterning that roughly approximated that required for reinforcement. For a fixed pair of reinforced run lengths, preference for the shorter of the two frequently increased as the intertrial interval increased and therefore as the minimum temporal durations of both reinforced runs increased. Preference for the shorter of the two also increased as its corresponding relative frequency of reinforcement increased. Both of these effects on preference were qualitatively similar to corresponding effects in previous research with two different kinds of reinforced behavioral patterns, interresponse times and interchangeover times. In all these experiments, analytical units were found in the temporal patterns of behavior, not in the behavior immediately contiguous with a reinforcer. It is suggested that a particular local temporal pattern of behavior is established to the extent to which it is repeatedly remembered when reinforcers are delivered, regardless of whether the delivery of a reinforcer is explicitly contingent upon that pattern.

Journal Article↗
PubMed1981

The local organization of behavior: discrimination of and memory for simple behavioral patterns.

A procedure was developed to enable nonverbal organisms to report what they remember of the temporal organization of their recent behavior. A baseline behavior with known temporal structure was established by a concurrent variable-interval variable-interval schedule for two temporal patterns of behavior (two different classes of reinforced inter-response times). The five pigeon subjects emitted these two temporal patterns on a center key and were occasionally given a short-term memory probe for their most-recently-emitted pattern. The probes consisted of symbolic delayed matching-to-sample tests, in which a response on a green side key was reinforced if the most recent pattern belonged to the shorter reinforced class, and a response to a red side key was reinforced if the most recent pattern belonged to the longer reinforced class. All subjects could report with over ninety percent accuracy what their most recently emitted behavioral pattern was when a retention interval separating the pattern from the memory probe was only .1 seconds. The retention interval was then manipulated, and it was found that recall for a pattern was frequently above chance after a delay of as much as eight seconds. Thus, pigeons can remember their most recent interresponse time not only right after it is emitted, but for several seconds thereafter. In other conditions, the patterns themselves were manipulated. It was found that as the patterns became more similar, discrimination became poorer. These results agree with the view that reinforcement tends to organize and integrate the local structure of behavior to the extent to which that structure is remembered.

Animals↗
PubMed1977

Short-term memory in the pigeon: delayed-pair-comparison procedures and some results.

A discrete-trials, delayed-pair-comparison procedure was developed to study visual short-term memory for tilted lines. In four experiments, pigeons' responses on left or right keys were reinforced with food depending on whether a comparison stimulus was or was not the same as a standard stimulus presented earlier in the same trial. In Experimental I, recall was an increasing function of the exposure time of the to-be-remembered stimulus and was a decreasing function of the retention interval. In Experiment II, retroactive interference was investigated: recall was poorer after a retention interval during which was presented either a tilted line or contextual stimuli in the form of the illuminated experimental chamber. In Experiment III, a subject was required to engage, throughout the retention interval, in one or the other of two different behaviors, depending on which of two stimuli a subject was to remember. This mnemonic strategy vastly improved recall after 15- and 20-second retention intervals. In Experiment IV, the opposite end of the performance continuum was studied: by combining the effects of a larger stimulus set and the effects of what presumably was an increased memory load, performance was reduced to approximately chance levels after retention intervals shorter than 1 second.

Animals↗