Hank Davis

Hank Davis
University of Guelph | UOGuelph · Department of Psychology

PhD

About

171
Publications
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2,850
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Publications

Publications (171)
Article
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Twelve Long-Evans rats were individually trained on different schedules of reinforcement and then run in pairs in a two-lever cage. Results indicated that various classes of social behavior could be experimentally produced and studied in the same manner as individual behavior by manipulating schedules of reinforcement
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Data from a recent conditioned suppression experiment by Weiss & Strongman (1969) are reexamined to determine the basis for postshock response bursts. The present paper debates Weiss and Strongman’s conclusion that such responding represents “attack” or aggressive behavior. Using data from other conditioned suppression studies, it is argued that po...
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Although a variety of experimental procedures have shown considerable evidence of “counting” in animals, there is no evidence of numerical competence when conspecifics are used as test stimuli. Here, we report evidence of a relative numerousness (2 vs. 4) judgment by rats that were required to discriminate the number of free-ranging conspecifics in...
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Conditioned suppression is often regarded as an ideal procedure for studying the interaction between operant and Pavlovian conditioning. The present paper surveys the results of 103 conditioned suppression experiments with regard to differences in a number of key procedural and parametric variables (e.g., on- vs. off-baseline training, number of se...
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In Experiment I, the performance of male and female Wistar albino and Long Evans hooded rats was compared on a leverpress shock escape procedure. Consistent superiority of Long-Evans over Wistar subjects emerged in measures of escape latency and percentage of session time spent in contact with the lever. Lower escape latencies recorded for females...
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Three experiments were performed to explore the relationship between leverpress escape behavior and pituitary-adrenal activity. In Experiment 1, concentrations of plasma corticosterone increased from basal levels during exposure to the shock escape procedure, but were substantially decreased following the 15th escape conditioning session. In Experi...
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Long Evans rats obtained a high frequency of reinforcement during initial exposure to a schedule which reinforced only responses spaced by at least 10 sec (DRL 10) provided this schedule was part of a two lever concurrent Fixed Ratio-DRL 10 schedule on which (1) the animal had received Fixed Ratio pretraining and (2) the animal needed 10 or more se...
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Four rats were trained to stable performance on a schedule which reinforced only bar presses exceeding an inter-response time of ten sec. (DRL 10 sec). The trained animals, when performing in the presence of other animals, emitted responses having shorter inter-response times than when alone, and as a consequence received fewer reinforcements than...
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The properties of leverholding occurring under à procedure in which subjects were required to remain in continuous contact with the lever to avoid shock were examined and compared to nonreinforced leverholding which occurred under a traditional shock escape procedure. Long-Evans rats, exposed to either the avoidance or escape procedure, were run un...
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Much recent research on superstitious behavior involves a procedure in which an instrumental response is pretrained and its rate of occurrence later recorded during a schedule of nonresponse-contingent reinforcement. It is argued that because this procedure fails to take into account the variety of alternative behaviors which might simultaneously b...
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We previously reported that rats were able to discriminate among two, three, and four sequentially presented auditory stimuli (Davis & Albert, 1986). In the present paper, we describe our failure to transfer this numerical discrimination to visual stimuli and to establish the same discrimination using visual stimuli in naive animals. These negative...
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Using a conditioned suppression procedure, previous research has demonstrated that rats can use unsignaled shock occurrences to predict subsequent periods free from shock (Davis, Memmott, & Hurwitz, 1975). This stimulus arrangement, termed an autocontingency (if shock, then no shock), does not exert behavioral control if a traditional tone-shock co...
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Varying degrees of aggressive interaction appeared in all four pairs of Ss run in a two lever cage under different conditions of extinction. The nature of the aggression (ranging from postural threat to an animal’s being chased from the cage) appeared to be related to the amount of extinction for each pair; i.e. where both animals were being exting...
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Two pairs of harbor (Phoca vitulina) and three pairs of gray (Halicboeruls grypus) seals were exposed to one of three human handlers for 15 min, twice a day, for a total of six sessions. Following habituation to the familiar handler, animals were then exposed to a novel human for 7 min, and then retested for 7 min with the familiar human. In all ca...
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Anecdotal reports suggest that insects can be "tamed" with frequent human contact. In the present experiment, repeated handling of Madagascar hissing cockroaches by the same person resulted in habituation of the hissing response in ten of 12 subjects. These subjects were then handled by a novel person in order to determine whether habituation might...
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Although it draws nearly universal disdain, sensational news continues to attract a wide audience for reasons that are not fully understood. We examined sensational front-page newspaper stories from eight countries, published between 1700 and 2001. The 736 stories that we collected were sorted thematically, and 12 categories emerged. An analysis of...
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Although it draws nearly universal disdain, sensational news continues to attract a wide audience for reasons that are not fully understood. We examined sensational front-page newspaper stories from eight countries, published between 1700 and 2001. The 736 stories that we collected were sorted thematically, and 12 categories emerged. An analysis of...
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A growing body of evidence suggests that animals of various species can discriminate among the humans with whom they have regular contact. This discriminative ability has considerable implications for research. Because animal life is hedonistic, there is a strong incentive for animal subjects to predict the events that bring them pleasure and pain....
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To date, a wide range of interdisciplinary scholarship has done little to clarify either the why or the how of empathy. Preston & de Waal (P&deW) attempt to remedy this, although it remains unclear whether empathy consists of two discrete processes, or whether a perceptual and motor component are joined in some sort of behavioral inevitability. Alt...
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1. We demonstrate that Barred-Rock and Isa-Brown hens can discriminate between the presence of 2 different humans and use this information as a cue for whether or not to make an operant response. 2. This demonstration in domestic fowl, the first of its kind in any avian subject, is consistent with a growing body of evidence that many species, inclu...
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To predict when food reward was available, 12 New Zealand White rabbits were trained to discriminate between two humans. All subjects had significantly higher response rates and greater behavioral arousal in the presence of the positive stimulus person. The ability to discriminate between individual humans sets the stage for unanticipated Pavlovian...
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Holstein–Friesian dairy cattle were tested for their ability to use individual humans as discriminative stimuli for the performance of an operant response. Nine animals demonstrated their ability to tell people apart by successfully learning to confine their responding to the presence of a handler who reinforced a nose press response (S+ handler),...
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A growing literature suggests that animals of various species can discriminate between individual humans. In the present study, 15 experimentally naive sheep were rewarded for making a nosepress response in the presence of one handler (S+) and non-reinforced for this behavior in the presence of a second person (S−). All animals responded significan...
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A growing literature suggests that animals of various species can discriminate between individual humans. In the present study, 15 experimentally naive sheep were rewarded for making a nosepress response in the presence of one handler (S+) and non-reinforced for this behavior in the presence of a second person (S−). All animals responded significan...
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Many “higher” animals are commonly assumed to distinguish between individual humans. This belief is based largely on anecdotal reports; in reality, there is little empirical evidence to support human recognition in nonhuman species. We report that laboratory rats consistently chose a familiar human over an unfamiliar human following fourteen and fi...
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Although rats are a much maligned species, it appears that their intelligence has been underestimated. This paper surveys evidence of cognition in rats from traditional categories (e.g. temporal and numerical competence) as well as from less ordinary test situations (e.g. transitive inference; recognition of individual humans). Although rats may no...
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Geary suggests that implicit mathematical principles exist across human cultures and transcend sex differences. Is such knowledge present in animals as well, and is it sufficient to account for performance in all species, including our own? I attempt to trace the implications of Gearys target article for comparative psychology, questioning the excl...
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The finding that women are attracted to men older than themselves whereas men are attracted to relatively younger women has been explained by social psychologists in terms of economic exchange rooted in traditional sex-role norms. An alternative evolutionary model suggests that males and females follow different reproductive strategies, and predict...
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A campus-wide memorial service was held to acknowledge the contribution of animals to excellence in research and teaching at the University of Guelph. The conception, rationale behind, and execution of this project are described, including the actual text of the service, as a model for other animal-using institutions. Such rituals can play an impor...
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Although Piagetian theory proposes that the ability to make transitive inferences is confined to humans above age 7, recent evidence has suggested that this logical ability may be more broad based. In nonverbal tests, transitive inference has been demonstrated in preschool children and 2 species of nonhuman primates. In these experiments, I demonst...
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We report a case study of Christine, an intelligent 30-year-old woman with a developmental learning disability. Psychometric evaluation and extensive interviews revealed several findings: most notably, evidence of anomia, auditory processing problems, difficulty acquiring reading and spelling skills, and an extremely poor sense of number. In additi...
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Although animals are widely employed as research subjects, only recently have we acknowledged the bond that frequently, perhaps inevitably, develops between subject and researcher. Whatever the qualities of this relationship, an increasing body of evidence suggests that it may result in profound behavioral and physiological changes in the animal su...
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Rats were trained to leave an array of food after they had consumed a fixed number (three, four, or five) of food items. This discrimination remained in effect despite a shift from 45-mg Noyes pellets to larger and irregularly sized sunflower seeds. The present demonstration replicates work first reported 50 years ago by Otto Koehler and his associ...
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Rats trained to eat a fixed number of food items from a larger array began to consume additional pieces of food when the experimenter was no longer available to punish errors (Davis & Bradford, 1988). When such departures from "correct" behavior are viewed in terms of Kohlberg's (1976) schema of moral development, it appears that rats are functioni...
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Three experiments were performed to test if tactile stimuli could serve as the basis for a numerical discrimination in rats ( Rattus norvegicus). In Experiment 1, touch delivered symmetrically to both sides of the animal's body yielded no evidence of numerical discrimination. In Experiment 2, the restriction of tactile cues to one side of the anima...
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Numerical competence is one of the many aspects of animal cognition that have enjoyed a resurgence of interest during the past decade. Evidence for numerical abilities in animals has followed a tortuous path to respectability, however, from Clever Hans, the counting horse, to modern experimental studies. Recent surveys of the literaturereveal theor...
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Rats were trained to leverpress in a conventional operant test chamber; however, their behavior was rewarded solely by social interaction with a human being. This training was successful for half the subjects tested; success was confined to animals for which social interaction had occurred prior to training. Similar findings with other species are...
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Four rats were trained to perform two numerical discriminations during the same experimental session. As in a previous study (Davis & Bradford, in press), one of these tasks required the animal to enter a target tunnel solely on the basis of its ordinal position in an array of six tunnels. Of primary interest here is the fact that the subjects were...
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Three rats were trained under a discrimination procedure in which responding was reinforced only following the repeated presentation of three bursts of white noise (S+). S− consisted of presentations of either two or four bursts of noise. All animals responded significantly more in the presence of S+ and, in two cases, showed lower response rates t...
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Three experiments were performed to explore the rat's ability to count objects in its environment. Previous research demonstrating counting behavior in animals has typically involved overtraining or extreme motivational conditions in which food or safety were at a premium. In the present experiments, a simulated natural environment was employed in...
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This paper reports the establishment of a discrimination based upon the number three in a male raccoon. Following a 6-month training period, the subject was able to select a clear Plexiglas cube containing 3 objects (grapes or small metal bells) from an array of cubes containing 1, 2, 3, 4, and 5 items. The results confirm previous reports of “inte...
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Previous research has shown that unsignaled shock may accelerate positively reinforced operant responding if each shock signals a subsequent shock-free period. In order to explore the boundary conditions of this effect, two experiments were performed. In Experiment 1, pairs of unsignaled shocks separated by 15, 30, 60, or 120 seconds resulted in su...
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It is argued that the conventional A/(A+B) ratio is an inappropriate tool for both the description and analysis of conditioned suppression. Conditioned suppression is a procedure that generates two separate dependent variables that cannot be meaningfully collapsed into a single index. Using a relatively simple experiment, we demonstrate that the pr...
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Following training on a variable-interval food-reinforcement schedule, rats were exposed to three unsignaled shocks during each 30-min session. Although leverpressing was initially suppressed, responding was significantly accelerated following offset of the third shock, regardless of when in the session it occurred. Control sessions in which only t...

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