Juan D. Delius

Transitive inference formation in pigeons

Pigeons were trained with 4 pairs of visual stimuli in a 5-term series-A+ B-, B+ C-, C+ D-. and D+ E(in which plus[+] denotes reward and minus(-] denotes nonreward)-before the unreinforced test pair B D was presented. All pigeons chose Item 8, demonstrating inferential choice. A novel theory (value transfer theory), based on reinforcement mechanisms, is proposed. In Experiment 2, the series was extended to 7 terms. Performance on test pairs was transitive, and performance on training pairs accorded with the theory. The 7-term series was closed in Experiment 3 by training the flrst and last items together. In accordance with the theory, the Ss could not solve the circular series. The authors suggest that primates, including humans, also solve these problems using the value transfer mechanism, without resorting to the symbolic processes usually assumed.

Concept learning by pigeons: Matching-to-sample with trial-unique video picture stimuli

Pigeons were trained to match-to-sample with several new methodologies: a large number of stimuli, computer-drawn color picture stimuli, responses monitored by a computer touch screen, stimuli presented horizontally from the floor, and grain reinforcement delivered onto the picture stimuli. Following acquisition, matching-to-sample concept learning was assessed by transfer to novel stimuli on the first exposure to pairs of novel stimuli. One group (trial-unique), trained with 152 different pictures presented once daily, showed excellent transfer (80% correct). Transfer and baseline performances were equivalent, indicating that the matching-to-sample concept had been learned. A second group (2-stimulus), trained with only two different pictures, showed no evidence of transfer. These results are discussed in terms of the effect of numbers of exemplars on previous failures to find concept learning in pigeons, and the implications of the positive finding from this experiment on abstract concept learning and evolutionary cognitive development.

Oddity of visual patterns conceptualized by pigeons

Pigeons were trained to learn an instrumental oddity-from-sample discrimination involving visual forms. One group, the “few examples” group, dealt with 5 patterns in 40 different combinations. Another group, the “many examples” group, dealt with 20 patterns in 160 different combinations. After both groups had reached asymptotic performance and had learned to operate under partial reinforcement conditions, they were tested for transfer under extinction conditions with two different groups of 5 novel patterns, each in 40 combinations. All animals showed significant above chance transfer to both of these novel stimulus sets. Transfer performance with test stimuli of similar geometric design to training stimuli was better than performance with stimuli of markedly different design. The transfer performance of the “many examples” group was marginally better than that of the “few examples” group, even though the latter’s performance on the training stimuli was better throughout. It is concluded that pigeons can learn to employ an oddity concept and that this may be promoted by the use of many training exemplars. Furthermore, it is inferred that pigeons may normally use a mixture of strategies to solve oddity and identity problems.

A stochastic analysis of the maintenance behaviour of skylarks

The paper attempts to describe the maintenance behaviour of Skylarks Alauda arvensis using conventional qualitative and quantitative descriptive frameworks and, as a new technique, random event series analysis. It is based on behaviour records of individually marked birds which were observed in the field for extended periods. Starting from frequency analysis and using random signal analysis as a stepping stone the rationale of random event analysis is briefly explained. Some of the problems involved in considering behaviour sequences as signals and the implications of viewing animals as black box systems, particularly when only the output i.e. behaviour, is available, are reviewed. The limitations of random event analysis for dealing with non-stationarity and non-linearity are considered. A qualitative description of the maintenance behaviour follows. Some information is given on the behavioural responses to environmental stimuli, particularly to the arrival of the observer. The sequential organisation of the behaviour in terms of transition probabilities is presented next. Deviations from a null order model are found when the behaviour events are separated by less than a minute and some of the implications are briefly mentioned. In a special subsection the sequential organisation of preening is similarly treated but on the basis of too few data to give any conclusive result. Then the distribution of intervals between the various behaviour patterns are given in a matrix form and some indications of deviations of random occurrence are found and discussed. A matrix of inter-behaviour correlations based on the frequency of behavioural events per various time units is presented and the finding that the duration of time units affects the correlations is discussed. In this context some correlation coefficients with non-maintenance behaviour are given and they support the idea that the comfort patterns may be related to a sleep syndrome. Matrices of auto-and cross-correlation functions and the related intensity functions support the view that frequency correlation matrices are not capable of imparting information on an important characteristic of interbehaviour relationships, the time dependent dynamic responses. Lastly, the transformation of the correlation function, the auto- and cross-spectra, are presented for comfort behaviour and flying. These support the notion that comfort behaviour is affected by rhythmical processes while flying is shown in an essentially random fashion. Little systematic relationship was found between comfort behaviour and flying as reflected by the transfer and coherence functions. In the discussion the various quantitative descriptive formats are briefly discussed and some of the objections to the use of advanced analytical techniques are dealt with. The implications of these techniques for models of behaviour are discussed and the complexity of interactions between the causal processes leading to behaviour are stressed. Finally some suggestions for future work are offered.

Visual Symmetry Recognition by Pigeons

SummaryPigeons learned to discriminate a large number of bilateral symmetric and asymmetric visual patterns successively projected on the pecking-key of an operant conditioning chamber. Responses to the positive stimuli were reinforced according to a variable interval schedule. Once acquisition was complete generalization trials, involving sets of new stimuli, were instituted under extinction. The birds classified these novel test stimuli with high accuracy throughout, according to their symmetry or asymmetry. Their performance was not disturbed by sets of test stimuli whose geometrical style differed considerably from the training stimuli. Pigeons were even able to discriminate when only allowed the use of one eye. The generalization series were partly designed to test some classical symmetry recognition theories. None was found to be adequate. Subsidiary experiments suggested that most pigeons have a slight spontaneous preference for asymmetric patterns and that symmetry/asymmetry differences can aid pattern discrimination learning at an early stage. It is concluded that pigeons, much like humans, can discriminate bilaterally symmetric from non-symmetric visual forms in a concept-like, generalizing way. The ontogenetic and phylogenetic development of this competence is considered. A novel symmetry recognition hypothesis based on spatial frequency analysis and neuronal feature-detector considerations is proposed.

Orientation invariance of shape recognition in forebrain-lesioned pigeons

Pigeons were trained to perform a visual orientation invariance task consisting of shape matching-to-sample or oddity-from-sample discriminations where the comparison forms differed in orientation from the sample forms, and the odd comparison forms were always a mirror image of the sample. They then received lesions affecting the visual projection area within the anterior hyperstriatum or the dorsal neostriatum, a control area with no known visual function. Both groups of birds evinced minor transient postoperative deficits of similar magnitude during the shape recognition task under orientation invariance conditions when the habitual training forms were used. When novel forms were introduced, the performance of hyperstriatal pigeons was significantly worse than that of the neostriatal pigeons, but still well above chance. The introduction of a delay between the offset of the sample and the onset of the habitual comparison stimuli did not yield any differential effect. It is concluded that orientation invariance of pattern recognition performance of birds, in contrast to that in mammals, is probably a midbrain, optic tectum function.

Transitive responding in animals and humans: Exaptation rather than adaptation?

In order to survive and reproduce, individual animals need to navigate through a multidimensional utility landscape in a near-optimal way. There is little doubt that the behaviourally more advanced species can bring cognitive competencies to bear on this difficult task. Among the cognitive abilities that are helpful in this context is transitive inference. This is typically the competency to derive the conclusion B>D from the premises A>B, B>C, C>D and D>E that imply the series A>B>C>D>E. In transitive inference tests used with humans, the letters stand for verbal items and the inequality symbols stand for a relational expression. To investigate analogous competencies in non-human animals a non-verbal form of the task is used. The premise pairs are converted into a multiple instrumental discrimination task A+B-, B+C-, C+D- and D+E-, where the letters stand for non-verbal stimuli and the plus and minus symbols indicate that choices of the corresponding stimuli either lead to a reward or to a penalty. When these training pairs are adequately discriminated, transitive responding is tested with intermittent presentations of the novel pair B∘D∘, where the circles indicate that responses to the stimuli are not reinforced. Using variants of this basic conditioning task it has been shown that pigeons, rats, squirrel-monkeys, macaques, chimpanzees, young children, older children and adult humans commonly reveal transitive preferences for B over D. Several theories have been proposed to explain this transitive behaviour. The evidence supporting these various models is reviewed. It is shown that the learning of the premises normally brings about a choice and reinforcement biasing and balancing process that can account for transitive responding. It is argued that a very simple algebraic learning model can satisfactorily simulate many of the results obtained in transitivity experiments, including some produced by human subjects who in principle, could have been applying rational logical rules. It is demonstrated that a value transfer mechanism also assumed to explain transitive responding, is in fact, a real phenomenon based on classical conditioning. However, it is argued that it mostly plays a minor role in transitive responding. It is shown that the algebraic learning model can be easily converted into a neural network model exhibiting an equivalent performance. The model can also be modified to cope with the surprising finding that a proportion of human individuals and a few animals subjects learn to discriminate the premise pairs, but nevertheless fail to respond transitively to the conclusion pair. This modification can simulate the results of experiments using non-linear, in particular circular, relational structures. The evolution of transitive responding is considered within the framework of ecosocial demands and neurobiological constraints. It is concluded that, in agreement with a preadaptation (exaptation) evolutionary origin, it seems to involve little beyond the capacity to learn multiple stimulus discriminations.

Pigeons (Columba livia) learn to link numerosities with symbols

After responding to each element in varying, successive numerosity displays, pigeons (Columba livia) had to choose, out of an array of symbols, the symbol designated to correspond to the preceding number of elements. After extensive training, 5 pigeons responded with significant accuracy to the numerosities 1 to 4, and 2 pigeons to the numerosities 1 to 5. Several tests showed that feedback tones accompanying element pecks, the familiarity of element configurations, and the shape of the elements were not crucial to this performance. One test, however, indicated that the number of pecks issued to the elements was important for numerosities above 2. An additional test confirmed that the birds chose the symbol that corresponded to a particular numerosity rather than the positions that the symbols had held during training.

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.

Categorical discrimination of objects and pictures by pigeons

With a three-choice instrumental discrimination procedure, pigeons were taught to distinguish small spherical objects from nonspherical objects. Spherical objects were defined as positive, nonspherical objects as negative. A device allowing an automatic presentation of the stimuli was employed. The subjects actually pecked the objects, and grain rewards were presented directly beside the correct objects. Acquisition was rapid, with the birds reaching a criterion of 80% correct choices within less than 150 trials. There was evidence that more than 200 objects were remembered individually over 3 months. Pigeons transferred the discrimination of spherical/nonspherical objects to novel objects. The criteria by which the birds judged the sphericity of objects seemed to be similar to those applied by humans. They could apply the categorization in a relational manner and generalize it to apply to photographs and drawings of objects. The categorization competence was retained for at least 3 months.