Bayesian analysis of foraging by pigeons (Columba livia).

In this article, the authors combine models of timing and Bayesian revision of information concerning patch quality to predict foraging behavior. Pigeons earned food by pecking on 2 keys (patches) in an experimental chamber. Food was primed for only 1 of the patches on each trial. There was a constant probability of finding food in a primed patch, but it accumulated only while the animals searched there. The optimal strategy was to choose the better patch first and remain for a fixed duration, thereafter alternating evenly between the patches. Pigeons were nonoptimal in 3 ways: (a) they departed too early, (b) their departure times were variable, and (c) they were biased in their choices after initial departure. The authors review various explanations of these data. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The oblique effect in pigeons (Columba livia).

The oblique effect—the greater discriminability of lines in the main axes orientation compared with obliquely oriented ones—was investigated in 3 experiments in which pigeons (Columba livia) were trained on 2-choice discrimination tasks. In Experiment 1, the reaction times (RTs) of separate groups of 4 pigeons trained to discriminate between a horizontal and a vertical line were significantly faster than pigeons trained to discriminate between 2 oblique lines. In Experiment 2, pigeons trained to concurrently discriminate between the 2 oblique and the horizontal and vertical lines did not show clear RT differences. However, in Experiment 3, the RT results of the 1st experiment were replicated with pigeons trained as in Experiment 1 but with stimuli consisting of 3 dots aligned along the main axes or obliquely. The results are discussed in terms of response measures, biasing habitats, and greater confusability of oblique lines that is due to these lines being mirror images. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Head and eye movements in unrestrained pigeons (Columba livia).

Head and eye movements were simultaneously recorded during locomotory and pecking behavior of 4 pigeons, which were trained to traverse a conditioning chamber, with a pecking key and a food dispenser at each end. Each trial involved key pecking, walking, and feeding. Head movements were registered with a skull-mounted miniature accelerometer, and eye movements were recorded with implanted electrooculogram (EOG) electrodes. An almost perfect temporal coordination between head and eye movements was observed during both walking and feeding bouts. During walking, head movements primarily provide retinal image stability, and eye movements support visual scanning. During feeding, head movements mainly subserve the grasping of food items, and eye movements maintain visual fixation on them. Because the eyes are reflexively closed during the middle phase of pecks, the head and eye movements are then under ballistic control. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mental rotation in pigeons (Columba livia)?

Previous research has shown pigeons to be insensitive to the orientation of visual test stimuli both for response latency and for discrimination ratio. Discrimination of stimulus orientation has been more difficult to learn than discrimination of small arbitrary differences between stimuli. This has suggested that the visual processing of pigeons is orientation invariant, which would obviate the need for mental rotation such as is often observed in studies with human subjects. Contrary to previous findings, the current experiment obtained linear effects of orientation on response latency and discrimination ratio, with a go/no-go procedure. Pigeons (Columbia livia) first learned to discriminate among line drawings of similar objects and then were tested with rotated versions of the drawings. The pattern of data is similar to that found in studies of human recognition of rotated objects. One speculative explanation of this finding is the mental rotation of stimuli by pigeons. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of reinforcement in spaced-trial operant learning in pigeons (Columba livia).

The author designed 3 experiments to study pigeons' adjustment to unexpected shifts in reinforcer magnitude with a single trial per day. Extinction was faster or poorer after training with a small magnitude (1 food pellet) than after training with a large magnitude (10 or 15 pellets). A shift from 15 to 1 pellet was accompanied by a gradual adjustment, with no indication of a successive negative contrast effect. Pigeons discriminated the reinforcer magnitudes but yielded no evidence of spaced-trial simultaneous negative contrast. Moreover, extinction was faster for a stimulus paired with 1 pellet than for a stimulus paired with 15 pellets. The results can be interpreted in terms of simple strengthening-weakening learning rules and without reference to anticipatory frustration. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rapid acquisition of a novelty versus familiarity concept by pigeons (Columba livia).

Pigeons performed a successive discrimination task in which responding to novel slides was rewarded, and responding to familiar slides, seen once previously, was not rewarded. In Experiment 1, naive Ss initially responded more rapidly to familiar slides, but all Ss learned to respond more rapidly to novel slides within a few sessions. In Experiment 2, Ss transferred immediately to novel trial sequences. Experiment 3 showed that both increased retention intervals and interpolated slide presentations impaired recognition. Experiment 4 showed that Ss treated duplicate slides as familiar and confirmed that Ss were using a "novelty versus familiarity" concept. The authors conclude that such a concept is readily available to pigeons. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Discrimination of duration ratios by pigeons (Columba livia) and humans (Homo sapiens).

Humans were trained on 2 versions of a 2-alternative, forced-choice procedure. First, Ss judged which of 2 successive stimulus durations was longer. Second, Ss judged whether the ratio of the 2 durations was less or greater than a criterion ratio (e.g., 2:1). Accuracy was significantly lower for the task in which the judgment was made according to the ratio of the 2 durations. This result is different than that obtained by J. G. Fetterman et al (1989), who trained pigeons on a similar pair of tasks and found that pigeons' performance was comparable for the 2 discriminations. Comparisons of the pigeon and human data suggest that humans were more accurate than pigeons when the judgment involved which duration was longer, but that accuracy was comparable for the ratio-based task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The influence of hippocampal lesions on the discrimination of structure and on spatial memory in pigeons (Columba livia).

Pigeons (Columba livia) were trained with a spatial structural discrimination, which was based on the spatial relationship among the components of a pattern, and a feature-binding structural discrimination, which was based on how different visual features within a pattern were combined. Neither discrimination was impaired by damage to the hippocampus and area parahippocampalis. The lesions impaired performance on a spatial working memory and a spatial reference memory task in open field. The results indicate an intact hippocampus is not essential for the solution of structural discriminations in pigeons and the hippocampus is important for processing some types of spatial information--that used in navigation, but not other types--that used in spatial structural discriminations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Flexible serial response learning by pigeons (Columba livia) and humans (Homo sapiens).

Experimental tasks designed to involve procedural memory are often rigid and unchanging, despite many reasons to expect that implicit learning processes can be flexible and support considerable variability. A version of the serial response time (SRT) task was developed, in which the locations of targets were probabilistically determined. Targets appeared in locations according to both a structured sequence and a cue validity parameter, and the time to respond to each target was measured. Pigeons (Columba livia) and humans (Homo sapiens) both showed response time facilitation at the highest tested value for cue validity, and the magnitude of that facilitation gradually weakened as cue validity was decreased. Both species showed evidence that response times were largely determined by the local predictabilities of individual cue locations. In addition, humans showed some evidence that explicit knowledge of the sequence affected response times, specifically when cue validity was 100%. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Abstract-concept learning carryover effects from the initial training set in pigeons (Columba livia).

Three groups of pigeons were trained in a same/different task with 32, 64, or 1,024 color-picture stimuli. They were tested with novel transfer pictures. The training-testing cycle was repeated with training-set doublings. The 32-item group learned the same/different task as rapidly as a previous 8-item group and transferred better than the 8-item group at the 32-item training set. The 64- and 1,024-item groups learned the task only somewhat slower than other groups, but their transfer was better and equivalent to baseline performances. These results show that pigeons trained with small sets (e.g., 8 items) have carryover effects that hamper transfer when the training set is expanded. Without carryover effects (i.e., initial transfer from the 32- and 64-item groups), pigeons show the same degree of transfer as rhesus and capuchin monkeys at these same set sizes. This finding has implications for the general ability of abstract-concept learning across species with different neural architectures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sound localization in pigeon (Columba livia).

The presence of a binaurally activated nucleus (nucleus laminaris) in the hindbrain of birds suggests that they may be capable of binaural sound localization. In this report, after verification that pigeons were capable of either homing or scanning for the source of a sound, 5 Ss were also shown to be (a) capable of localizing a single burst of noise whose duration was too brief for homing or scanning; (b) capable of using either binaural time or intensity disparities for the localization of brief tones; (c) capable of localizing a single tone-pip throughout their frequency range of hearing from 125 Hz to 8 kHz, though having considerable difficulty in their midfrequency range (1–2 kHz); and (d) capable of localizing a single brief burst of narrow band noise even in their midfrequency range. It is concluded that the capacity of pigeons to localize brief sounds and to use binaural disparity cues for doing so is not qualitatively different from that of mammals and, therefore, that the nucleus laminaris or some similar brain-stem nuclei in pigeons are probably analogous in their contribution to sound localization to the superior olivary complex in mammals. (55 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The discrimination of natural movement by budgerigars (Melopsittacus undulates) and pigeons (Columba livia).

Three experiments examined the ability of birds to discriminate between the actions of walking forwards and backwards as demonstrated by video clips of a human walking a dog. Experiment 1 revealed that budgerigars (Melopsittacus undulates) could discriminate between these actions when the demonstrators moved consistently from left to right. Test trials then revealed that the discrimination transferred, without additional training, to clips of the demonstrators moving from right to left. Experiment 2 replicated the findings from Experiment 1 except that the demonstrators walked as if on a treadmill in the center of the display screen. The results from the first 2 experiments were replicated with pigeons in Experiment 3. The results cannot be explained if it is assumed that animals rely on static cues, such as those derived from individual postures, in order to discriminate between the actions of another animal. Instead, this type of discrimination appears to be controlled by dynamic cues derived from changes in the posture of the demonstrators. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Orientation invariant pattern recognition by pigeons (Columba livia) and humans (Homo sapiens).

The orientation invariance of visual pattern recognition in pigeons and humans was studied using a conditioned matching-to-sample procedure. A rotation effect, a lengthening of choice latencies with increasing angular disparities between sample and comparison stimuli, was replicated with humans. The choice speed and accuracy of pigeons was not affected by orientation disparities. Novel mirror-image stimuli, rotation of sample shapes, a delayed display of comparison shapes, and a mixed use of original and reflected sample shapes did not lead to a rotation effect in pigeons. With arbitrarily different odd comparison shapes, neither humans nor pigeons showed a rotation effect. Final experiments supported the possibility that the complete absence of a rotation effect in pigeons is because they are relatively better than humans at discriminating mirror-image shapes compared with arbitrary shapes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Trigeminal deafferentation and feeding behavior patterns in the pigeon (Columba livia).

Data from a study with 11 White Carneaux pigeons show that after an aphagic period, trigeminally deafferented Ss regulated body weight at reduced levels. The deficit involved was characterized by comparing feeding patterns of deafferented and food-deprived birds with equivalent weight losses. Deafferented Ss showed disproportionate increases in meal size during the early portion of the feeding period but abnormally rapid attenuation of feeding activity in the course of the day, which led to a reduced overall level of food intake. Trigeminal input appears to influence both the size of bouts and the frequency of bout initiation. Findings are discussed in relation to the homeostatic model of intake control and within the framework of food conditioning. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Imitation and Affordance Learning by Pigeons (Columba livia).

The bidirectional control procedure was used to determine whether pigeons (Columba livia) would imitate a demonstrator that pushed a sliding screen for food. One group of observers saw a trained demonstrator push a sliding screen door with its beak (imitation group), whereas 2 other groups watched the screen move independently (possibly learning how the environment works) with a conspecific either present (affordance learning with social facilitation) or absent (affordance learning alone). A 4th group could not see the screen being pushed (sound and odor control). Imitation was evidenced by the finding that pigeons that saw a demonstrator push the screen made a higher proportion of matching screen pushes than observers in 2 appropriate control conditions. Further, observers that watched a screen move without a demonstrator present made a significantly higher proportion of matching screen pushes than would be expected by chance. Thus, these pigeons were capable of affordance learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential effects of visual context on pattern discrimination by pigeons (Columba livia) and humans (Homo sapiens).

Three experiments examined the role of contextual information during line orientation and line position discriminations by pigeons (Columba livia) and humans (Homo sapiens). Experiment 1 tested pigeons' performance with these stimuli in a target localization task using texture displays. Experiments 2 and 3 tested pigeons and humans, respectively, with small and large variations of these stimuli in a same-different task. Humans showed a configural superiority effect when tested with displays constructed from large elements but not when tested with the smaller, more densely packed texture displays. The pigeons, in contrast, exhibited a configural inferiority effect when required to discriminate line orientation, regardless of stimulus size. These contrasting results suggest a species difference in the perception and use of features and contextual information in the discrimination of line information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spared feature-structure discrimination but diminished salience of environmental geometry in hippocampal-lesioned homing pigeons (Columba livia).

Homing pigeons (Columba livia) were trained to locate a goal in one corner of a rectangular arena by either its shape (geometry) or the left-right configuration of colored features located in each corner (feature structure). Control and hippocampal-lesioned pigeons learned at a similar rate, but the control birds made proportionally more geometric errors during acquisition. On conflict probe trials, the control birds preferred geometrically correct corners, whereas the hippocampal-lesioned birds displayed a greater preference for the correct corner defined by feature structure. On geometry-only probe trials, both groups demonstrated an ability to identify the goal location. Hippocampal lesions do not interfere with goal recognition by the feature structure of local cues but diminish the salience of arena shape. (PsycINFO Database Record (c) 2010 APA, all rights reserved)