Imitation of conditional discriminations in pigeons (Columba livia)

In the present experiments, the 2-action method was used to determine whether pigeons could learn to imitate a conditional discrimination. Demonstrator pigeons (Columba livia) stepped on a treadle in the presence of 1 light and pecked at the treadle in the presence of another light. Demonstration did not seem to affect acquisition of the conditional discrimination (Experiment 1) but did facilitate its reversal of the conditional discrimination (Experiments 2 and 3). The results suggest that pigeons are not only able to learn a specific behavior by observing another pigeon, but they can also learn under which circumstances to perform that behavior. The results have implications for proposed mechanisms of imitation in animals.     

Social learning and innovation are positively correlated in pigeons (<Emphasis Type="Italic">Columba livia</Emphasis>)

When animals show both frequent innovation and fast social learning, new behaviours can spread more rapidly through populations and potentially increase rates of natural selection and speciation, as proposed by A.C. Wilson in his behavioural drive hypothesis. Comparative work on primates suggests that more innovative species also show more social learning. In this study, we look at intra-specific variation in innovation and social learning in captive wild-caught pigeons. Performances on an innovative problem-solving task and a social learning task are positively correlated in 42 individuals. The correlation remains significant when the effects of neophobia on the two abilities are removed. Neither sex nor dominance rank are associated with performance on the two tasks. Free-flying flocks of urban pigeons are able to solve the innovative food-finding problem used on captive birds, demonstrating it is within the range of their natural capacities. Taken together with the comparative literature, the positive correlation between innovation and social learning suggests that the two abilities are not traded-off.     

Visually guided capture of a moving stimulus by the pigeon (Columba livia)

Although the pigeon is a popular model for studying visual perception, relatively little is known about its perception of motion. Three experiments examined the pigeons’ ability to capture a moving stimulus. In Experiment 1, the effect of manipulating stimulus speed and the length of the stimulus was examined using a simple rightward linear motion. This revealed a clear effect of length on capture and speed on errors. Errors were mostly anticipatory and there appeared to be two processes contributing to response locations: anticipatory peck bias and lag time. Using the same birds as Experiment 1, Experiment 2 assessed transfer of tracking and capture to novel linear motions. The birds were able to capture other motion directions, but they displayed a strong rightward peck bias, indicating that they had learned to peck to the right of the stimulus in Experiment 1. Experiment 3 used the same task as Experiment 2 but with naïve birds. These birds did not show the rightward bias in pecking and instead pecked more evenly around the stimulus. The combined results indicate that the pigeon can engage in anticipatory tracking and capture of a moving stimulus, and that motion properties and training experience influence capture.     

Use of slope and feature cues in pigeon (Columba livia) goal-searching behavior

Terrain slope provides a directional frame of reference for reorientation and navigation, similar to cardinal directions. Previous studies have shown that, in a goal location task, slope is a very salient cue and that pigeons tend to rely on it even if it is not the most informative cue. Such a strong dependence on one type of information, when there are more effective predictors of reward, is a key premise for a modular view of information processing. Here we tested the provocative hypothesis of a "slope module" for reorientation in slanted environments. Pigeons had to solve a goal location task using slope or another, theoretically salient cue: a beacon feature. Overall, searching behavior was controlled almost equally by the two cues. The fact that, for the first time, slope failed to capture most of the associative strength allows us to reject a strong modularity view and suggests instead that there is competition between cues based on salience. As an interesting additional finding, the reliance on slope and the feature was affected by training location (uphill vs. downhill), suggesting the possibility of a modulatory role of effort on the cue-weighting mechanism of reorientation.     

Limits of visual acuity in the frontal field of the rock pigeon (Columba livia)

The eye of the rock pigeon is typical of a granivorous lateral-eyed bird, in that it has both a laterally projecting central fovea and a second high-density cellular area in peripheral retina (area dorsalis) which projects to the binocular frontal field below the beak. Such a dual system is faced with potentially different optical restraints arising from central and peripheral vision. We asked whether the frontal axis can support high resolution vision from a refractive resting position (predicted to be 25-33 cm; Fitzke et al, 1985 Journal of Physiology 369 33-44) to some near point of accommodation. We measured the visual acuity on the frontal axis in five pigeons using an operant discrimination of high-contrast square-wave gratings at a series of distances from 7 to 80 cm from the eye. The peak average acuity was 11.04 cycles deg(-1), which occurred 10 cm from the eye. The average of the maximum acuity of each bird at 10 cm was 12.8 +/- 1.1 cycles deg(-1), a value equal to the Nyquist frequency calculated from the peak ganglion cell density of the area dorsalis. However, this maximum acuity was restricted to a narrow depth in space, located around 10 cm from the eye, and at greater distances fell exponentially such that acuity was 50% of its maximum at 35 cm and less than 1 cycle deg(-1) at 100 cm. We propose that the range of high-acuity vision is limited in the frontal field by either increased refractive power and/or inaccuracy in frontal accommodation, and is optimized for a preferred far point located 10 cm from the eye.     

Context controls access to working and reference memory in the pigeon (Columba livia)

The interaction between working and reference memory systems was examined under conditions in which salient contextual cues were presented during memory retrieval. Ambient colored lights (red or green) bathed the operant chamber during the presentation of comparison stimuli in delayed matching‐to‐sample training (working memory) and during the presentation of the comparison stimuli as S+ and S‐ cues in discrimination training (reference memory). Strong competition between memory systems appeared when the same contextual cue appeared during working and reference memory training. When different contextual cues were used, however, working memory was completely protected from reference memory interference.     

The spontaneous interconnection of four repertoires of behavior in a pigeon (Columba livia)

A pigeon was trained to peck a small facsimile of a banana placed within its reach, to climb onto a box, to open a door, and to push a box toward targets. When confronted with a new situation-the banana was placed out of reach, and the box was placed behind the door-the four repertoires came together rapidly to produce a humanlike solution to the problem. A tentative account of the performance is offered in terms of empirically validated principles.     

Functional lateralization, interhemispheric transfer and position bias in serial reversal learning in pigeons (Columba livia)

In the present study we investigated lateralization of color reversal learning in pigeons. After monocular acquisition of a simple color discrimination with either the left or right eye, birds were tested in a serial reversal procedure. While there was only a slight and non-significant difference in choice accuracy during original color discrimination, a stable superiority of birds using the right eye emerged in serial reversals. Both groups showed a characteristic ‘learning-to-learn’ effect, but right-eyed subjects improved faster and reached a lower asymptotic error rate. Subsequent testing for interocular transfer demonstrated a difference between pre- and post-shift choice accuracy in pigeons switching from right to left eye but not vice versa. This can be accounted for by differences in maximum performance using either the left or right eye along with an equally efficient but incomplete interocular transfer in both directions. Detailed analysis of the birds’ response patterns during serial reversals revealed a preference for the right of two response keys in both groups. This bias was most pronounced at the beginning of a session. It decreased within sessions, but became more pronounced in late reversals, thus indicating a successful strategy for mastering the serial reversal task. Interocular transfer of response patterns revealed an unexpected asymmetry. Birds switching from right to left eye continued to prefer the right side, whereas pigeons shifting from left to right eye were now biased towards the left side. The results suggest that lateralized performance during reversal learning in pigeons rests on a complex interplay of learning about individual stimuli, stimulus dimensions, and lateralized response strategies. Received: 4 June 1999 / Accepted after revision: 18 August 1999     

Symmetry and transitivity of conditional relations in monkeys (Cebus apella) and pigeons (Columba livia)

In Experiment 1 six monkeys were tested with discriminative relations that were backward relative to their training in a 0-second conditional (“symbolic”) matching procedure. Although there was some indication of backward associations, the evidence was generally weak, and statistical evaluations did not reach conventional significance levels. Unlike children, who show backward associations to the point of symmetry, monkeys and pigeons display at best only weak and transient backward associations. In Experiment 2 associative transitivity was assessed across two sets of conditional matching tasks. All four monkeys tested demonstrated strong transitivity. In contrast, in Experiment 3 there was no evidence of transitivity in three pigeons tested under conditions closely comparable to those of Experiment 2. These results may identify some key features of interspecies differences and contribute to analyses of serial learning in animals.     

Trigeminal nerve and eating in the pigeon (Columba livia): neurosensory control of the consummatory responses.

Electrophysiological, neurobehavioral, and cinematographic techniques were used to study the role of the trigeminal nerve in the neurosensory control of eating. Analaysis of single-unit data recorded in the pigeon's trigeminal ganglion indicates that the trigeminal nerve provides somatosensory inputs from the oral region that signal the location and movement of food and monitor the extent of mouth opening. Trigeminal deafferentation, although it does not affect pecking or swallowing, severly impairs the efficiency of eating. Cinematographic analysis shows that the impairment is due to disruption of the neurosensory control of mandibulation-the process by which grain is grasped at the beak tip and moved to the back of the mouth.     

Social influence in pigeons (Columba livia): the role of differential reinforcement

Socially-influenced learning was studied in observer pigeons that observed a demonstrator in an adjacent chamber performing a target response comprising standing on a box and pecking a key 10 times. In Experiment 1 there was no evidence for social learning in the absence of reinforcement of the observer's behavior. When the target response was already established in the observer's repertoire, but was not differentially reinforced in relation to the demonstrator's behavior, rates of extinction were not influenced by the demonstrator's behavior (Experiment 2). Reinforcement of the observer's target response in the presence of the modeled target response, and not in its absence, resulted in control of the observer's responding by the behavior of the demonstrator (Experiments 3 and 4). This control was extended in Experiment 5 to deferred responses that occurred following a delay since the demonstrator's target responses. The acquisition of social influence depended on differential reinforcement of the observer's target response, with the demonstrator's target behavior serving as the explicit discriminative stimulus.     

Discrimination of moving video images of self by pigeons (<Emphasis Type="Italic">Columba livia</Emphasis>)

The ability to recognize self has been known to be limited to some animal species, but previous research has focused almost exclusively on the animal's reaction to a mirror. Recent studies suggest that the temporal contingency between a subject's action and the corresponding visual scene reflected in a mirror plays an important role in self-recognition. To assess the roles of visual-proprioceptive contiguity in self-recognition, we explored whether pigeons are able to discriminate videos of themselves with various temporal properties. We trained five pigeons to respond to live video images of themselves (live self-movies) and not to video filmed during previous training sessions (pre-recorded self-movies). Pigeons learned to peck trial-unique live self-movies more frequently than pre-recorded self-movies. We conducted two generalization tests after pigeons learned to discriminate between the two conditions. First, discrimination acquired during training sessions was transferred to a test session involving live self-movies and new pre-recorded self-movies. Second, the same pigeons were tested in extinction procedure using delayed live self-movies and new pre-recorded self-movies. Although pigeons responded to delayed presentations of live self-movies more frequently than to new pre-recorded self-movies, the relative response rate to delayed presentation of live self-movies gradually decreased as the temporal discrepancy between pigeons' own behavior and the corresponding video increased. These results indicate that pigeons' discrimination of self-movies with various temporal properties was based on the temporal contiguity between their behavior and its visual feedback. The methodology used in the present experiment is an important step toward improving the experimental analysis of self-recognition in non-human animals.     

Local rather than global processing of visual arrays in numerosity discrimination by pigeons (Columba livia)

A series of experiments investigated which stimulus properties pigeons use when they discriminate pairs of visual arrays that differ in numerosity. Transfer tests with novel stimuli confirmed that the birds’ choices were based on relative differences in numerosity. However, pigeons differed from other species in the non-numerical cues that affected their choices. In human and non-human primates, numerical discrimination is often influenced by continuous variables such as surface area or overall stimulus brightness. Pigeons showed little evidence of using those cues, even when summed area and brightness had been correlated with numerosity differences and reward outcome. But when array-element sizes were asymmetrically distributed across numerosities, the birds readily utilized information about item sizes as an additional discriminative cue. These novel results are discussed in relation to pigeons’ tendency to focus on local, rather than global dimensions when they process other non-numerical complex visual stimuli. The findings suggest there may be inter-specific differences in the type of perceptual information that provides the input stage for mechanisms underlying numerical processing. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Matching and oddity relational learning by pigeons (<Emphasis Type="Italic">Columba livia</Emphasis>): transfer from color to shape

Relational learning, as opposed to perceptual learning, is based on the abstract properties of the stimuli. Although at present there is no doubt that pigeons are capable of relational behavior, this study aims to further disclose the conditions under which it occurs. Pigeons were trained in an outdoor cage on a matching-to-sample or an oddity-from-sample task, with colored cardboard stimuli presented horizontally. The apparatus involved three sliding lids on which the stimuli were drawn and which, when displaced, revealed the reinforcement. The lids were either adjacent to each other or somewhat separated. Training sessions involved two colors, and test sessions six different colors (same dimension test), or six different shapes (different dimension test). One group of birds trained under the ‘adjacent’ condition failed when tested with new stimuli, but succeeded in both dimension tests after training under the ‘separate’ condition. Two other groups of birds succeeded in all tests after training under the latter condition. These results show that depending on procedural details, pigeons are or are not able to transfer from one visual dimension to another, thus extending previous related findings.     

A comparative study of geometric rule learning by nutcrackers (Nucifraga columbiana), pigeons (Columba livia), and jackdaws (Corvus monedula)

Three avian species, a seed-caching corvid (Clark's nutcrackers; Nucifraga columbiana), a non-seed-caching corvid (jackdaws; Corvus monedula), and a non-seed-caching columbid (pigeons; Columba livia), were tested for ability to learn to find a goal halfway between 2 landmarks when distance between the landmarks varied during training. All 3 species learned, but jackdaws took much longer than either pigeons or nutcrackers. The nutcrackers searched more accurately than either pigeons or jackdaws. Both nutcrackers and pigeons showed good transfer to novel landmark arrays in which interlandmark distances were novel, but inconclusive results were obtained from jackdaws. Species differences in this spatial task appear quantitative rather than qualitative and are associated with differences in natural history rather than phylogeny.     

Representation of serial order in pigeons (Columba livia)

In Experiment 1, 2 groups of pigeons were trained to respond to either a 4-item (A→B→C→D) or 5-item (A→B→C→D→E) list. After learning their respective list, half of the subjects were trained on a positive pair with reinforcement provided when pairs were responded to in the order true to that of the original sequence (4-item: B→C; 5-item: B→D). The remaining subjects were trained on a negative pair with reinforcement provided for responding to the pairs in the order opposite to that learned in the original sequence (4-item: C→B; 5-item: D→B). Subjects in the positive pair condition learned their respective pair faster than did subjects in the negative pair condition. In Experiment 2, after reaching criterion on a 4-item list, subjects received 16 BC probe trials spread across 4 sessions of training. Subjects performed significantly above chance on the probe trials. The performance of our subjects in Experiments 1 and 2 demonstrates that, similar to monkeys, pigeons form a representation of the lists that they learn.     

Pigeons (Columba livia) integrate visual motion using the vector average rule: effect of viewing distance

Animal Cognition - Integrating local motion signals detected by the primary motion detector is crucial for representing a rigid, two-dimensional motion. The nature of motion integration has been...     

Conditioned suppression/avoidance as a procedure for testing hearing in birds: The domestic pigeon (Columba livia)

Although the domestic pigeon is commonly used in learning experiments, it is a notoriously difficult subject in auditory psychophysical experiments, even those in which it need only respond when it detects a sound. This is because pigeons tend to respond in the absence of sound—that is, they have a high false-positive rate—which makes it difficult to determine a pigeon’s audiogram. However, false positives are easily controlled in the method of conditioned suppression/avoidance, in which a pigeon is trained to peck a key to obtain food and to stop pecking whenever it detects a sound that signals impending electric shock. Here, we describe how to determine psychophysical thresholds in pigeons using a method of conditioned suppression in which avoidable shock is delivered through a bead chain wrapped around the base of a pigeon’s wings. The resulting audiogram spans the range from 2 to 8000 Hz; it falls approximately in the middle of the distribution of previous pigeon audiograms and supports the finding of Kreithen and Quine (Journal of Comparative Physiology 129:1–4, 1979) that pigeons hear infrasound.     

Degree of representation of the matching concept in pigeons (Columba livia)

In Experiment 1, 12 pigeons (Columba livia) were trained on a simultaneous matching-to-sample task with 2 stimuli and then tested with 2 novel stimuli. Half of the birds were trained with a fixed ratio schedule requirement of 1 (FR1) or 20 (FR20) pecks on the sample stimulus. None of the birds showed any evidence of concept-mediated transfer. In Experiment 2, 12 pigeons were trained with 3 stimuli and then tested with the same novel stimuli used in Experiment 1. Half of the birds in each group were trained with either an FR1 or FR20 requirement on the sample stimulus. Two of the FR20 birds showed high levels of transfer to the novel stimuli similar to that of monkeys in a previous study.