Sociability and gazing toward humans in dogs and wolves: Simple behaviors with broad implications.

Sociability, defined as the tendency to approach and interact with unfamiliar people, has been found to modulate some communicative responses in domestic dogs, including gaze behavior toward the human face. The objective of this study was to compare sociability and gaze behavior in pet domestic dogs and in human-socialized captive wolves in order to identify the relative influence of domestication and learning in the development of the dog-human bond. In Experiment 1, we assessed the approach behavior and social tendencies of dogs and wolves to a familiar and an unfamiliar person. In Experiment 2, we compared the animal's duration of gaze toward a person's face in the presence of food, which the animals could see but not access. Dogs showed higher levels of interspecific sociability than wolves in all conditions, including those where attention was unavailable. In addition, dogs gazed longer at the person's face than wolves in the presence of out-of-reach food. The potential contributions of domestication, associative learning, and experiences during ontogeny to prosocial behavior toward humans are discussed.

The canid genome: behavioral geneticists' best friend?

We review a range of studies on the genetic contribution to behavior in canid species. We begin by identifying factors that make canids a promising model in behavioral genetics and proceed to review research over the last decade that has used canids to identify genetic contributions to behavior. We first review studies that have selectively bred dogs to identify genetic contributions to behavior and then review studies that estimate heritability from populations of non-laboratory bred dogs. We subsequently review studies that used molecular genetics to identify gene-behavior associations and note associations that have been uncovered. We then note challenges in canid behavioral genetics research that require further consideration. We finish by suggesting alternative phenotyping methods and identify areas in which canids may have as yet unexploited advantages, such as in gene-environment interaction studies where genetic factors are found to moderate the effects of environmental variables.

A review of domestic dogs' (Canis familiaris) human-like behaviors: or why behavior analysts should stop worrying and love their dogs.

Dogs likely were the first animals to be domesticated and as such have shared a common environment with humans for over ten thousand years. Only recently, however, has this species' behavior been subject to scientific scrutiny. Most of this work has been inspired by research in human cognitive psychology and suggests that in many ways dogs are more human-like than any other species, including nonhuman primates. Behavior analysts should add their expertise to the study of dog behavior, both to add objective behavioral analyses of experimental data and to effectively integrate this new knowledge into applied work with dogs.

Effects of d-amphetamine on the behavior of pigeons exposed to the peak procedure.

The effects of d-amphetamine on pigeons' key-pecking under the peak interval (PI) procedure were investigated in two experiments. In experiment I the effects of doses of d-amphetamine from 0.75 to 3.0 mg/kg on responding under PI 30 and 45 s were studied for 10 successive days. Reductions in peak time and wait time were observed at both PI values and an increase in the width was found at PI 30 s. There was no evidence of tolerance. In experiment II, pigeons exposed to a PI 45 s schedule were administered doses of D-amphetamine of 1.5 and 3.0 mg/kg for 30 successive days. Reductions in peak time and wait time were found here. Evidence of tolerance was found in wait time, peak time and width of the distribution at the higher dose. In both experiments a rate-dependent effect of the drug was found in the portion of each peak trial before the time that food was delivered on reinforced trials; this effect was weaker after the customary time of food delivery. The rate-dependent effect for responses before food time, combined with little effect of the drug on responses after food time, is shown by simulation to be sufficient to account for the reduction in peak time, without the need to appeal to an internal clock mechanism.

Effects of D-amphetamine on temporal discrimination in pigeons.

Two experiments used a matching to sample of durations procedure to examine changes in temporal discrimination evoked by D-amphetamine (0.75, 1.50, 2.25 and 3.0 mg/kg i.m.) in pigeons. Responses to one key color were reinforced after long (8-s) stimuli: responses to the alternative key color were reinforced after short (2-s) stimuli. Stimuli of intermediate duration were reinforced in Experiment 1 and were not reinforced in Experiment 2. Sigmoid functions relating percent of choices of the key reinforced after long-duration stimuli to the duration of stimulus presented were fit by a cumulative normal function. In addition to a parameter giving the left/right position of the sigmoid curves (which indexes temporal perception), this function also provided estimates of the range and slope of the curve (measures of stimulus control). The results showed that, contrary to many published reports, amphetamine had no effect on the left/right positioning of the sigmoid curve. There was, however, an effect of amphetamine on stimulus control, as shown by the general flattening of the psychophysical functions. Little evidence of tolerance to the drug's behavioral effects was found after 30 consecutive days of behavioral testing under amphetamine.

Studies of learning and problem solving in two species of Australian marsupials.

This article reviews the authors' recent work with two species of Australian marsupials on several learning and conditioning experiments. The quokka (Setonix brachyurus) is a cat-sized herbivorous wallaby that inhabits offshore islands around south-western Australia. The fat-tailed dunnart (Sminthopsis crassicaudata) is a mouse-sized carnivorous marsupial that inhabits much of inland Australia. Both species were successful in learning simple discriminations, learning sets and reversal sets. Quokkas and dunnarts were also tested on two configural discrimination tasks: transverse patterning and negative patterning; only the dunnarts successfully solved these tasks. Dunnarts were also the only species to show one-trial learning in reversal set training. Dunnarts may be particularly useful subjects in future studies of brain-behavior relationships, since these animals have some interesting neuroanatomical features, demonstrate a wide range of fast learning abilities, and as pouch young, can be accessed during early developmental stages.

Detour behavior in the Quokka (Setonix brachyurus).

Four quokkas (Setonix brachyurus) were tested in their natural environment for the ability to progress around a barrier to a desired goal object (food). Symmetrical and asymmetrical barriers were used with different lengths of side arm. Three quokkas showed significant tendencies to progress either left or right around the barrier, though this laterality declined as the length of the side arm of the barrier was extended. One quokka showed no behavioral laterality and this animal was also the only one to show spatial reasoning (spontaneous selection of the shorter route on first presentation of the asymmetrical barrier) as opposed to spatial learning (progressive improvement in choice of the shorter route with repeated experience).

Configural learning in two species of marsupial (Setonix brachyurus and Sminthopsis crassicaudata).

Four experiments examined the ability of quokkas (Setonix brachyurus) and fat-tailed dunnarts (Sminthopsis crassicaudata) to solve 2 configural tasks: transverse and negative patterning. Transverse patterning requires the simultaneous solution of 3 overlapping discrimination problems (A+ B-, B+ C-, C+ A-). Both species could solve the nonoverlapping (elemental) version of this task (U+ V-, W+ X-, Y+ Z-), but only dunnarts solved the transverse patterning task. Negative patterning requires conditioned responses to 2 stimuli when presented separately but not together (A+, B+, AB-). Both species formed a selective conditioned response to A+ and B+ stimuli and inhibited responding to a simple nonreinforced stimulus (C-), but only dunnarts successfully inhibited responding to the AB- compound to solve the negative patterning task. These experiments are the first to demonstrate configural learning in a marsupial.

Quokkas (Setonix brachyurus) demonstrate tactile discrimination learning and serial-reversal learning.

Two male quokkas (Setonix brachyurus: a herbivorous macropod marsupial) were trained to discriminate pairs of stimuli in the laboratory. Quokkas indicated their choice by pulling on 1 of 2 simultaneously presented cords. The quokkas' discrimination abilities were tested on 6 tactile and 6 visual discrimination tasks. Correct responses were rewarded with food. For both quokkas, all tactile tasks were learned to a criterion of 75% correct in up to 4 20-trial sessions. No visual task maintained criterion performance in 4 sessions. One tactile discrimination was reversed 10 times. After the 1st reversal, the error rate declined sharply and fell to a level well below the initial discrimination.

Visual discrimination learning and strategy behavior in the fat-tailed dunnart (Sminthopsis crassicaudata).

Fat-tailed dunnarts (Sminthopsis crassicaudata) were trained on visual discrimination learning-set, reversal-set, and spatial delayed-alternation tasks. The learning set involved 36 2-way black-and-white pattern discriminations and 5 probe reversals. Ten reversals of a black-and-white pattern discrimination were followed by 5 novel tasks. Spatial alternation was tested at delays up to 20 s. Learning-set and reversal-set formation, including 1-trial learning and spontaneous transfer from learning set to reversals and vice versa, was found. Learning-set-experienced dunnarts showed no retention of previously learned tasks 1 week after testing but demonstrated consistently high Trial 2 performance, indicating the retention of a response strategy. Delayed-alternation tasks were learned up to 10-s delays. These results provide the first evidence of a visually guided "win-stay, lose-shift" strategy in a marsupial.

ERP correlates of response inhibition to elemental and configural stimuli in a negative patterning task.

OBJECTIVE: The present experiment examined the ERP correlates of response inhibition to elemental and configural Nogo stimuli in a Go/Nogo task. DESIGN AND METHODS: Event-related potentials (ERPs) were recorded while 8 subjects completed a visual Go/Nogo task. Nogo stimuli required the inhibition of a response to stimuli that differed from Go stimuli (A+, B+) either on the basis of each of two physical features (elemental Nogo stimuli; CD-) or on the basis of the conjunction of features represented in the Go stimuli (configural Nogo stimuli; AB-). Behavioural data and ERP component measures (amplitude and latency) were analysed using analysis of variance. RESULTS: An enhanced N2 component and an enhanced fronto-centrally distributed P3 component were elicited following elemental Nogo stimuli relative to Go stimuli, consistent with a number of studies examining ERPs during Go/Nogo tasks. In contrast, an enhanced late frontal negative/parietal positive slow wave was elicited following configural Nogo stimuli relative to Go stimuli. CONCLUSIONS: These results cast doubt on the interpretation of the N2 enhancement as reflecting response inhibition processes per se. The pattern of results was interpreted as providing support for the unique cue model of learning rather than the configural model of learning and was discussed in the context of a recent model of executive functioning.

Preserved negative patterning and impaired spatial learning in pigeons (Columba livia) with lesions of the hippocampus.

Pigeons (Columba livia) with bilateral electrolytic lesions of the hippocampus and area parahippocampalis were compared with control pigeons on 2 tasks: negative patterning and delayed spatial alternation. Negative patterning demands configural stimulus representations for its successful solution. The only effect of hippocampal lesions on this task was an increased response rate to the rewarded stimuli. On the delayed spatial alternation task, hippocampal birds showed deficits relative to controls. Differences in the results of prior studies on negative patterning appear to be due to different response requirements to the nonreinforced stimuli. These results are consistent with prior work with rats and suggest that the avian hippocampus is essential for spatial memory and response inhibition but is not involved in configural learning.

Effects of occasional short interfood intervals on temporal control in pigeons.

This study explored pigeon memory for short time intervals. Occasional (one per session) shorter-than-usual interfood intervals (IFIs) were interspersed in series of longer IFIs. In phase 1, the shorter IFIs were of a magnitude that varied from daily session to session. In phase 2, the shorter IFIs were of one magnitude for 20 consecutive daily sessions. Analysis of the results of both experiments showed that pigeons' memory for an IFI was not restricted to the immediately preceding interval but rather decayed exponentially with a half-life of around three intervals. This effect did not take time to develop and did not change over the course of training. These results have implications for the memory component of both clock and non-clock-based theories of animal timing.

Pigeon transitive inference: Tests of simple accounts of a complex performance.

This study addressed pigeons' abilities to form transitive inferences and the mechanism by which they do so. Subjects were trained on four operant discriminations in a 5-term series-A + B - , B + C - , C + D - and D + E - (where [ + ] denotes reward, and [ -] non-reward in choice). In unreinforced tests, choice of B over D is evidence of transitive inference formation. Training proceeded without the subjects being presented the training pairs in blocks. Results show that randomized training degrades the performance of pigeons, just as it does human subjects, but that some subjects can still respond transitively under these conditions. In addition, the results support reinforcement models of transitive inference performance.

Dynamics of waiting in pigeons.

Two experiments used response-initiated delay schedules to test the idea that when food reinforcement is available at regular intervals, the time an animal waits before its first operant response (waiting time) is proportional to the immediately preceding interfood interval (linear waiting; Wynne & Staddon, 1988). In Experiment 1 the interfood intervals varied from cycle to cycle according to one of four sinusoidal sequences with different amounts of added noise. Waiting times tracked the input cycle in a way which showed that they were affected by interfood intervals earlier than the immediately preceding one. In Experiment 2 different patterns of long and short interfood intervals were presented, and the results implied that waiting times are disproportionately influenced by the shortest of recent interfood intervals. A model based on this idea is shown to account for a wide range of results on the dynamics of timing behavior.

Transverse patterning in pigeons.

The ability of pigeons to form configural stimulus representations was assessed in two operant discrimination experiments. In Experiment 1 the transverse patterning problem of Spence (1952) was trained. In Phase 1, subjects had to choose stimulus A on A + B - trials; B + C - trials were added in Phase 2. In Phase 3, the first two pairs were combined with C + A - trials. The success of the subjects was simulated by a model assuming that elemental and configural stimulus representations coexist in a stable proportion, even in the phases of the experiment which do not require configural stimulus representations for successful solution. Experiment 2 replicated the first two phases of Experiment 1, but trained A + C - in Phase 3. Comparison of the results of this experiment with simulations of the model showed that elemental and configural stimulus representations coexisted in similar proportions as in Experiment 1, even though they were not necessary for successful task solution.

Waiting in pigeons: the effects of daily intercalation on temporal discrimination.

Pigeons trained on cyclic-interval schedules adjust their postfood pause from interval to interval within each experimental session. But on regular fixed-interval schedules, many sessions at a given parameter value are usually necessary before the typical fixed-interval "scallop" appears. In the first case, temporal control appears to act from one interfood interval to the next; in the second, it appears to act over hundreds of interfood intervals. The present experiments look at the intermediate case: daily variation in schedule parameters. In Experiments 1 and 2 we show that pauses proportional to interfood interval develop on short-valued response-initiated-delay schedules when parameters are changed daily, that additional experience under this regimen leads to little further improvement, and that pauses usually change as soon as the schedule parameter is changed. Experiment 3 demonstrates identical waiting behavior on fixed-interval and response-initiated-delay schedules when the food delays are short (less than 20 s) and conditions are changed daily. In Experiment 4 we show that daily intercalation prevents temporal control when interfood intervals are longer (25 to 60 s). The results of Experiment 5 suggest that downshifts in interfood interval produce more rapid waiting-time adjustments than upshifts. These and other results suggest that the effects of short interfood intervals seem to be more persistent than those of long intervals.

Dynamics of time discrimination.

Pigeons tracked sinusoidal sequences of interfood intervals (IFIs) by pausing in each interval for a time proportional to the preceding interval. Schedules with either long (30-90 s) or short (5-15 s) values, with variable numbers of cycles and starting phase each day, were tracked about equally well. Tracking was apparently immediate and did not improve across sessions. Experiment 2, in which long and short series were presented on alternate days, showed that tracking on long was more impaired than on short. Experiment 3 showed that occasional presentation of a short IFI in a series of fixed, longer IFIs caused a reduction in waiting time in the next IFI. These effects are evidence for a fast-acting timing mechanism in which waiting time in the IFI N + 1 is strongly determined by the preceding IFI, N. Earlier IFIs have some cumulative effect, but the details remain to be elucidated.