Time-of-day discrimination by pigeons,Columba livia

Pigeons were trained to discriminate between four keys. One provided food in the mornings, another provided food in the afternoons, and two never provided food. Three experiments were performed to determine whether pigeons could track food availability over a 24-h period. All the subjects appeared to demonstrate time-place associative learning. A fourth experiment was designed to investigate the mechanisms underlying the timing behavior. Lights-on time was shifted back by 6 h, and no decrease in performance was found during the first session following the phase shift. This suggests that a circadian type of timing mechanism with a self-sustaining oscillator mediates time-place learning over a period of 24 h. Further support for this notion was found in a fifth experiment, in which the subjects were tested in constant dim light. In that experiment, the subjects’ continued correct responding provides additional support for a self-sustaining circadian timer.     

Domestic pigeons (Columba livia) discriminate between photographs of individual pigeons

In two experiments, we examined the discrimination of photographs of individual pigeons by pigeons, using go/no-go discrimination procedures. In Experiments 1A and 1B, the pigeons were trained to discriminate 4 photographs of one pigeon from those of a number of pigeons. The subjects learned the discrimination, but their discriminative behavior did not transfer to new photographs taken from novel perspectives. When the pigeons were trained to discriminate between 20 photographs of five pigeons taken from four perspectives as the S+ and 20 photographs of five different pigeons as the S-, the subjects learned the discrimination, and this discriminative behavior partially transferred to new photographs taken from novel perspectives (Experiments 2A-2C). The results suggest that pigeons are able to discriminate among conspecific individuals, using stationary visual cues. This strengthens the assumption in evolutionary theory that animals can discriminate among individuals and encourages further investigation as to how this ability is used in various behaviors of animals.     

Domestic pigeons (Columba livia) discriminate between photographs of male and female pigeons

We investigated whether pigeons are able to discriminate color photographs of male and female pigeons, using a categorical discrimination procedure. In Experiments 1 and 2B, 10 out of 14 pigeons learned the discrimination. Of these, 5 pigeons showed transfer to novel stimuli, demonstrating the categorical nature of the trained discrimination. Experiment 3 showed that the discriminative behavior was based primarily on the body, as opposed to the head and the neck region. In 1 out of 3 pigeons, the discriminative behavior was maintained by the black-and-white photographs. The results suggest that some pigeons have the ability to discriminate the sex of conspecifics without behavioral cues.     

Intradimensional vs. extradimensional transfer in the discriminative learning of goldfish and pigeons

Evidence of better intradimensional than extradimensional transfer was sought in naive goldfish trained under free-operant single-stimulus conditions (Experiment I), sophisticated pigeons trained under free-operant single-stimulus conditions (Experiment II), sophisticated pigeons trained under discrete-trials choice conditions (Experiment III), and naive pigeons trained under discrete-trials choice conditions (Experiment IV). The results provide no support for attention theory.     

More evidence of robust spatial associative memory in the pigeon,Columba livia

Willson and Wilkie (1993) developed a novel procedure for assessing pigeons’ memory for the spatial location of food. Only one of four locations (consisting of an illuminated pecking key and grain feeder) provided food each day. Over days, different locations provided food. The pigeons’ tendency to revisit the location that was profitable on the previous day demonstrated memory for food-spatiallocation associations over a period of 24 h, retention longer than previously reported for this species. This basic finding was replicated and extended in three experiments. Experiment 1 demonstrated that location-food discriminations were also remembered well when established with successive rather than concurrent procedures. Experiment 2 demonstrated that pigeons can remember two location-food associations over 24 h. Experiment 3 showed that the discrimination training inherent in this paradigm is important for retention; retention was impaired when only the rewarded location was presented. Overall, this research suggests that cross-species differences in spatial memory performance may be due to quantitative rather than qualitative differences in the memory system underlying performance.     

Attempts to demonstrate magnetic discrimination by homing pigeons in flight

Eight homing pigeons, trained to fly between two elevated feeders within a flight tunnel, were tested for their ability to discriminate between two magnetic field stimuli and two acoustic stimuli, using a unitary discrete-trials procedure with successive presentation of stimuli. Magnetic stimuli consisted of the ambient magnetic field and a reduced magnetic field in which the vertical component of the field was reduced to 50% of its ambient value. Acoustic stimuli consisted of an ambient white noise and the white noise plus a tone. Stimuli were paired with food reward and either a time penalty (Experiment 1) or electric shock (Experiment 2). Although subjects could discriminate sounds with our procedures, none of the subjects demonstrated discrimination of magnetic fields. The failure of pigeons to discriminate magnetic stimuli is discussed as a consequence of either the failure to provide conditions sufficient for such discrimination or the absence of a magnetic sense in these animals.     

Artificial grammar learning in pigeons

In two experiments, we developed a new methodology for studying complex stimulus control by spatial sequences of letters generated by artificial grammars. An artificial grammar is a system of rules that defines which letter sequences or strings are “grammatical.” In Experiment 1, pigeons learned to respond differently to strings conforming to a grammar versus strings that were nongrammatical distortions. Several different criteria all suggested that performance was controlled both by some short chunks of strings shared between reinforced training strings and novel transfer strings and by more complex sequential regularities. In Experiment 2, pigeons quickly and accurately learned to respond differently to strings conforming to one or the other of two different artificial grammars. As in Experiment 1, performance was controlled both by some short chunks and by more complex sequential regularities. The results are interpreted in terms of family resemblance and pose new goals for theories of complex stimulus control.     

An investigation of ambiguous-cue learning in pigeons

Two experiments demonstrated that pigeons can solve a simultaneous discrimination in which on half the trials the positive and an ambiguous cue (A) are presented and on half the trials choice is between A and the negative stimulus. In Experiment 1, where a relatively nondistinctive A cue was used, performance on the former type of trial was superior to that shown on the latter. In Experiment 2, where a distinctive A cue was provided, this pattern of results was reversed. These findings are interpreted in terms of an approach-avoidance explanation first proposed by Leary (1958). Experiment 3 tested and confirmed a central prediction of this explanation by showing that in an orthodox simultaneous discrimination, occasional reinforcements of the negative stimulus produce less accurate performance than do nonreinforcements of the positive.     

The nature of discrimination learning in pigeons

The results from five experiments are considered in relation to two of Spence's (1937, 1938) proposals concerning discrimination learning. In Experiments 1 and 2, we investigated whether his ideas about the interaction between excitatory and inhibitory generalization gradients can be used to understand how animals solve a complex patterning discrimination. The results supported a development of his proposals as put forward by Pearce (1994), provided a modification was made to Pearce's rulefor determining the shape ofthe generalization gradient. In Experiments 3, 4, and 5, we examined whether animals would pay more attention to stimuli that are relevant, rather than irrelevant, to the solution of a discrimination. The results supported this proposal for stimuli comprising visual patterns, but not for those comprising plain colors. The results also indicated that change of attention was a consequence of preliminary receptor-exposure acts, as envisaged by Spence, and not of more central changes in attention.     

Attempts to condition homing pigeons to magnetic cues in an outdoor flight cage

An attempt was made to train 9 homing pigeons to respond to the presence or absence of bar magnets by turning either left or right after flying the length of a 20-ft outdoor flight cage. During initial training, color cues were placed in front of feeding stations on the left and right sides of the cage. The color cues were paired with magnetic cues by attaching either bar magnets or brass bars to the backs of the birds. The color cues were then deleted, leaving only the magnetic cues. Each pigeon received about 300 trials of color training followed by about 200 trials of magnet testing. When only magnetic cues remained, none of the pigeons were able to choose the correct feeder at greater than chance levels of probability.     

Extradimensional transfer in the discriminative learning of goldfish

In Experiment I, one group of goldfish (TD) was trained to discriminate blue and green while a second group (PD) was exposed to the same colors in a “pseudodiscrimination,” after which both groups were reinforced for response to a tone. The TD group subsequently showed a sharper auditory discrimination gradient than the PD group and performed better in a differentially reinforced tone discrimination. The former PD animals then were given true discrimination training and the former TD animals pseudodiscrimination training with the colors, after which the first group showed better tone discrimination than the second. These results are analogous to those found in pigeons and rats. In Experiment II, goldfish which were trained in an easy color discrimination and shifted to a more difficult tone discrimination performed better than a control group trained from the outset with the tones. This result suggests that the dimensional specificity of the processes responsible for “transfer along a continuum” cannot safely be assumed in the absence of appropriate controls.     

Observational learning of discriminative avoidance in hooded rats

To determine the aspects of an observational situation facilitating subsequent acquisition of an observed task, two experimental groups of rats were exposed to a model’s performance of a two-way discriminative shuttlebox avoidance task with a tone as the discriminative stimulus. One experimental group (OND) observed the performance of a naive demonstrator; the other experimental group (OSD) observed a skilled demonstrator. A stimulus control group (SC) was exposed to the tone with no model present; a response control group (RC) observed demonstrator running with no tone present. A naive control group (NC) received no observational experience. All groups were subsequently tested on acquisition of the task. An analysis of variance on avoidance scores and Newman-Keuls tests for differences between means revealed that OND and OSD groups performed significantly more avoidances than the control groups. Exposure to the total tone-running sequence was found to be necessary for observational learning. The results were interpreted in terms of a sensory-sensory conditioning model.

     

Stimulus selection in discriminative taste-aversion learning in the rat

In three experiments, rats were presented compound solutions consisting of a common element, saccharin, mixed with one of two different flavor elements, cinnamon and wintergreen. Rats in the experimental groups consistently received a toxicosis-inducing injection following one compound solution but not following the other compound solution. Rats in the control groups received toxicosis-inducing injections half the time following each of the compound solutions. After training in each experiment, there were tests for conditioning to the saccharin alone. The experimental groups drank significantly more than the control groups, indicating that the aversion to the partially reinforced saccharin in isolation was less when the different flavor cues were more highly correlated with reinforcement. In Experiment III, there was also a test for conditioning to the cinnamon or wintergreen flavor alone. The experimental group drank significantly less of the continuously reinforced flavor than the control group did of the partially reinforced flavor. These results are similar to those reported within more traditional conditioning paradigms.     

Testing the translational-symmetry hypothesis of abstract-concept learning in pigeons

The translational-symmetry hypothesis of abstract-concept learning was tested in a same/different (S/D) task with pairs of pictures. The translational-symmetry hypothesis proposes that subjects discriminate same trials by the simultaneous repetition of features in the two pictures (and different trials by the lack of feature repetition). Pigeons that had learned a simultaneous S/D task were tested with delays between the two pictures to remove emergent perceptual cues. In Experiment 1, we tested delays of 0 and 1 sec. The results did not show the accuracy decrease expected according to the translational-symmetry hypothesis. In Experiment 2, we expanded the delays to 2 and 6 sec. Even at the longest delay, there was no evidence of the precipitous performance decline or default strategy that would be predicted by translational symmetry. The results provide evidence against translational symmetry (or other perceptually emergent features) that might control these pigeons’ performance in our two-item S/D task.     

Conditioned inhibition in feature negative discrimination learning with pigeons

Discrimination performance was investigated with pigeons using feature negative (FN) discrimination procedures which differed in the temporal arrangement of the stimuli on S? trials. In both procedures, a single common element was presented on reinforced (S+) trials. In thesimultaneous FN procedure, a distinguishing element was presented simultaneously with the common element of S? trials. In thesequential FN procedure, the distinguishing element preceded onset of the common element on S? trials. In two experiments, the sequential FN procedure yielded better discrimination performance. In Experiment 1, a summation test designed to separate learning and performance variables indicated that sequential FN subjects had learned the negative relationship between the distinguishing element and reinforcement while simultaneous FN subjects had not. In Experiment 2, summation and acquisition tests indicated that the distinguishing element developed inhibitory properties in the sequential FN procedure but not in the simultaneous FN procedure.     

Processing of identity and conditional relations in monkeys (Cebus apella) and pigeons (Columba livid)

Learning & Behavior - As a test of differential processing of identity and conditional relations, subjects were first highly trained on 0-sec delay identity matching (IM) and conditional...     

The effect of the controllability of auditory discriminative stimuli in the performance of go/no-go discriminations by pigeons

Compared with their performance with localized (on-key) visual stimuli, pigeons are notoriously poor at performing go/no-go discriminations when keypecking for food in the presence of auditory discriminative stimuli. The difference might reflect the fact that an aversive visual onkey stimulus signaling nonreward can be escaped by looking away and not pecking, which contributes to the measure of good discriminative performance, while an auditory stimulus cannot be escaped. In Experiment 1, discriminative performance was significantly improved by providing pigeons with a response incompatible with keypecking by which they could escape a tone S+ and a tone S?. However, the pattern, frequency, and duration of escape responses were found to be insufficient to explain the improvement. In Experiment 2, it was found that the capacity to escape only S+ or only S? enhanced discriminative performance as much as the capacity to escape both. It is theorized that the Pavlovian relationship between the absence of the discriminative stimuli and the nonoccurrence of food might transfer to the instrumental relationships learned in a go/no-go discrimination. The possibility that intermittent stimuli command more attention than continuous stimuli is also considered.     

Within-event learning contributes to value transfer in simultaneous instrumental discriminations by pigeons

Following simultaneous discrimination training with pigeons, in which responding to the S−was reinforced on half of the trials and responding to the S− was never reinforced, we examined the effect on the S− of presenting the S− by itself and the effect on the S+ of presenting the S− by itself (relative to an S− or an S− for which there had been no single-stimulus presentations). For Group A−, responding to the S− presented by itself was always reinforced, whereas for Group A−, such responding was extinguished. For Group B−, responding to the S− presented by itself was always reinforced, whereas for Group B+, responding was extinguished. Although both Group A+ and Group A−tended to avoid their associated S− (relative to a control S−), Group A+ avoided its associated S− less than did Group A−. In contrast, although for Group B−, presentation of the S− alone increased the pigeons’ preference for its associated S−(relative to a control S+), for Group B−, presentation of the S−alone had little effect on its preference for its associated S+. These results suggest that presentation of one stimulus from a simultaneous discrimination has two independent and sometimes opposite effects on the other discriminative stimulus. First, it reduces the strength of within-event conditioning between the S+ and the S−, and second, if the value of the singly presented stimulus has increased, some of its newly acquired value will transfer retroactively to the stimulus with which it was originally paired.