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)     

Absolute pitch: Frequency-range discriminations in pigeons (Columba livia)--comparisons with zebra finches (Taeniopygia guttata) and humans (Homo sapiens).

Absolute pitch (AP) is the ability to classify individual pitches without an external referent. The authors compared results from pigeons (Columba livia, a nonsongbird species) with results (R. Weisman, M. Njegovan, C. Sturdy, L. Phillmore, J. Coyle, & D. Mewhort, 1998) from zebra finches (Taeniopygia guttata, a songbird species) and humans (Homo sapiens) in AP tests that required classification of contiguous tones into 3 or 8 frequency ranges on the basis of correlations between the tones in each frequency range and reward. Pigeons' 3-range discriminations were similar in accuracy to those of zebra finches and humans. In the more challenging 8-range task, pigeons, like zebra finches, discriminated shifts from reward to nonreward from range to range across all 8 ranges, whereas humans discriminated only the 1st and last ranges. Taken together with previous research, the present experiments suggest that birds may have more accurate AP than mammals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pigeon (Columba livia) encoding of a goal location: The relative importance of shape geometry and slope information.

The ability to use the geometric shape of an environment as an orienting cue for goal location has been shown in many vertebrate groups. Experimentally, however, geometric spatial tasks are typically carried out on horizontal surfaces. The present study explored how learning a geometry task is affected by training on a surface extending in the vertical dimension—a slope. In a reference memory task, pigeons (Columba livia) were trained to locate a goal in an isosceles trapezoid arena. Learning on a slope proceeded more rapidly or with fewer errors than on a flat surface, presumably because of kinesthetic, vestibular, and visual information extractable from an inclined surface. Experiment 1 showed that, although the geometric shape of the arena was encoded, pigeons trained on a slope were guided by a goal representation based on the vertical and orthogonal axes of the slope to solve the task. Experiment 2 revealed that geometric learning was neither overshadowed nor facilitated by training on a slope. The data highlight a potentially important role for slope as an allocentric cue for goal location. (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)     

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)     

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)     

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)     

Foraging and spatial memory in pigeons (Columba livia).

In two experiments pigeons were studied as they foraged through a simulated patchy environment. Patches consisted of four circular groupings of feeders placed at different locations within a laboratory room. The properties of these patches varied between experiments. In Experiment 1 all feeders in all patches were baited, but the number of food pellets per feeder varied between patches. In Experiment 2 density of food was varied between patches, with 25%, 50%, 75%, or 100% of the feeders randomly baited. A number of variables that indicated pigeons' patch preferences and their behavior within patches were measured. Pigeons showed strong initial preferences for patches containing larger numbers of pellets per feeder in Experiment 1 but did not show differential preferences for patches varying in food density in Experiment 2. Within patches pigeons visited more feeders in richer patches than in poorer patches, both on initial patch entry and on repeat visits. Although pigeons showed evidence of reference and working spatial memory for patches, both experiments failed to provide evidence for the use of working spatial memory for the positions of visited and unvisited feeders within patches. The implications of these findings for spatial memory and foraging theory are discussed. (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)     

Interpreting the effects of image manipulation on picture perception in pigeons (Columba livia) and humans (Homo sapiens).

The effects of picture manipulations on humans' and pigeons' performance were examined in a go/no-go discrimination of two perceptually similar categories, cat and dog faces. Four types of manipulation were used to modify the images. Mosaicization and scrambling were used to produce degraded versions of the training stimuli, while morphing and cell exchange were used to manipulate the relative contribution of positive and negative training stimuli to test stimuli. Mosaicization mainly removes information at high spatial frequencies, whereas scrambling removes information at low spatial frequencies to a greater degree. Morphing leads to complex transformations of the stimuli that are not concentrated at any particular spatial frequency band. Cell exchange preserves high spatial frequency details, but sometimes moves them into the “wrong” stimulus. The four manipulations also introduce high-frequency noise to differing degrees. Responses to test stimuli indicated that high and low spatial frequency information were both sufficient but not necessary to maintain discrimination performance in both species, but there were also species differences in relative sensitivity to higher and lower spatial frequency information. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Information processing by pigeons (Columba livia): Incentive as information.

Experiment 1 showed that the Hick-Hyman law (W. E. Hick, 1952; R. Hyman, 1953) described the effects of anticipated reinforcement, a form of incentive, on pigeons' (Columba livia) reaction time to respond to a target spatial location. Reaction time was an approximately linear function of amount of information interpreted as probability of reinforcement, implying that pigeons processed incentive at a constant rate. Experiment 2 showed that the Hick-Hyman law described effects of incentive even when it varied from moment to moment in a serial reaction time task similar to that of M. J. Nissen and P. Bullemer (1987), and processing information about target spatial location modulated absolute reaction time and not rate of processing incentive. The results support mental continuity and provide comparative support for the idea of the economics of information in economic theory about the incentive value of information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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)     

Perception of the standard and the reversed Müller-Lyer figures in pigeons (Columba livia) and humans (Homo sapiens).

The authors compared perception of the standard and reversed Müller-Lyer figures between pigeons (Columbia livia) and humans (Homo sapiens). In Experiment 1, pigeons learned to classify 6 lengths of target lines into "long" and "short" categories by pecking 2 keys on the monitor, ignoring the 2 brackets so placed that they would not induce an illusion. In the test that followed, all 3 birds chose the "long" key more frequently for the standard Müller-Lyer figures with inward-pointing brackets (>). The subjects' responses were accountable by neither overall lengths of the figures nor horizontal gaps between the 2 brackets. For the reversed figures, effects of the brackets were absent. These results suggested that the pigeons perceived the standard Müller-Lyer illusion but not the reversed one. Experiment 2 confirmed that humans perceived both types of the illusion. Pigeons and humans may perceive the same illusory figures in different ways. (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)     

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)     

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)     

Temporal integration as a function of signal and gap intensity in rats (Rattus norvegicus) and pigeons (Columba livia).

Previous data suggest that rats (Rattus norvegicus) and pigeons (Columba livia) use different interval-timing strategies when a gap interrupts a to-be-timed signal: Rats stop timing during the gap, and pigeons reset their timing mechanism after the gap. To examine whether the response rule is controlled by an attentional mechanism dependent on the characteristics of the stimuli, the authors manipulated the intensity of the signal and gap when rats and pigeons timed in the gap procedure. Results suggest that both rats and pigeons stop timing during a nonsalient gap and reset timing after a salient gap. These results also suggest that both species use similar interval-timing mechanisms, influenced by nontemporal characteristics of the signal and gap. (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)     

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)     

Lateral hyperstriatal lesions disrupt simultaneous but not successive conditional discrimination learning of pigeons (Columba livia).

Explored, in 2 experiments, the effects of lateral vs medial laminar lesions of the hyperstriatum in pigeons; medial lesions were largely confined to the hyperstriatum accessorium, and lateral lesions to the hyperstriatum dorsale and hyperstriatum ventrale. In Exp 1, lateral, but not medial, lesions disrupted acquisition of a simultaneous conditional discrimination; both medial and lateral lesions disrupted reversal of the discrimination. The reversal deficits of the medial and lateral groups were quantitatively similar, and both groups showed exaggerated positional responding. In Exp 2, neither medial nor lateral lesions disrupted acquisition of a successive conditional discrimination. Lateral hyperstriatal damage does not obtain a general disruption of conditional learning; it is speculated that the lateral hyperstriatum may play a critical role in configural learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)