Kent D. Bodily

On Discriminating between Geometric Strategies of Surface-Based Orientation.

Recently, a debate has manifested in the spatial learning literature regarding the shape parameters by which mobile organisms orient with respect to the environment. On one hand are principal-axis-based strategies which suggest that organisms extract the major and minor principal axes of space which pass through the centroid and approximate length and width of the entire space, respectively. On the other hand are medial-axis-based strategies which suggest that organisms extract a trunk-and-branch system similar to the skeleton of a shape. With competing explanations comes the necessity to devise experiments capable of producing divergent predictions. Here, we suggest that a recent experiment (i.e., Sturz and Bodily, 2011a) may be able to shed empirical light on this debate. Specifically, we suggest that a reevaluation of the design reveals that the enclosures used for training and testing appear to produce divergent predictions between these strategies. We suggest that the obtained data appear inconsistent with a medial-axis-based strategy and that the study may provide an example of the types of designs capable of discriminating between these geometric strategies of surface-based orientation. Such an approach appears critical to fundamental issues regarding the nature of space and spatial perception.

Matching-to-sample abstract-concept learning by pigeons.

Abstract concepts--rules that transcend training stimuli--have been argued to be unique to some species. Pigeons, a focus of much concept-learning research, were tested for learning a matching-to-sample abstract concept. Five pigeons were trained with three cartoon stimuli. Pigeons pecked a sample 10 times and then chose which of two simultaneously presented comparison stimuli matched the sample. After acquisition, abstract-concept learning was tested by presenting novel cartoons on 12 out of 96 trials for 4 consecutive sessions. A cycle of doubling the training set followed by retraining and novel-testing was repeated eight times, increasing the set size from 3 to 768 items. Transfer performance improved from chance (i.e., no abstract-concept learning) to a level equivalent to baseline performance (>80%) and was similar to an equivalent function for same/different abstract-concept learning. Analyses assessed the possibility that item-specific choice strategies accounted for acquisition and transfer performance. These analyses converged to rule out item-specific strategies at all but the smallest set-sizes (3-24 items). Ruling out these possibilities adds to the evidence that pigeons learned the relational abstract concept of matching-to-sample.

Orientation in trapezoid-shaped enclosures: implications for theoretical accounts of geometry learning.

Human participants learned to select 1 of 4 distinctively marked corners in a rectangular virtual enclosure. After training, control and test trials were interspersed with training trials. On control and test trials, all markers were equivalent in color, but only during test trials was the shape of the enclosure manipulated. Specifically, for each test trial, a single long wall or short wall of the enclosure increased twice as long as or decreased half as long as that present in the training enclosure. These manipulations produced 8 unique trapezoid-shaped enclosures. Participants were allowed to select 1 corner during control and test trials. Performance during control trials revealed that participants selected the correct and rotationally equivalent locations. Performance during test trials revealed that participants selected locations in trapezoid-shaped enclosures that were consistent with those predicted by global geometry (i.e., principal axis of space) but were inconsistent with those predicted by local geometry (i.e., proportion of rewarded training features present at a location). Results have implications for theoretical accounts of geometry learning.

Neither by global nor local cues alone: evidence for a unified orientation process

A substantial amount of empirical and theoretical debate remains concerning the extent to which an ability to orient with respect to the environment is determined by global (i.e., principal axis of space), local (i.e., wall lengths, angles), and/or view-based (i.e., stored representation) accounts. We developed an orientation task that allowed the manipulation of the reliability of the principal axis of space (i.e., searching at the egocentric left- and/or right-hand side of the principal axis) between groups while maintaining goal distance from the principal axis, local cues specifying the goal location (i.e., short wall left, short wall right, and obtuse angle), and visual aspects of the goal location consistent across groups. Control and test trials revealed that participants trained with a reliable principal axis of space utilized both global and local geometric cues, whereas those trained with an unreliable principal axis of space utilized only local geometric cues. Results suggest that both global and local geometric cues are utilized for reorientation and that the reliability of the principal axis of an enclosure differentially influences the use of geometric cues. Such results have implications for purely global-based, purely local-based, and purely view-based matching theoretical accounts of geometry learning and provide evidence for a unified orientation process.

Evidence against integration of spatial maps in humans

A dynamic 3-D virtual environment was constructed for humans as an open-field analogue of Blaisdell and Cooks (2005) pigeon foraging task to determine if humans, like pigeons, were capable of integrating separate spatial maps. Participants used keyboard keys and a mouse to search for a hidden goal in a 4×4 grid of raised cups. During Phase 1 training, a goal was consistently located between two landmarks (Map 1: blue T and red L). During Phase 2 training, a goal was consistently located down and left of a single landmark (Map 2: blue T). Transfer trials were then conducted in which participants were required to make choices in the presence of the red L alone. Cup choices during transfer assessed participants’ strategies: association (from Map 1), generalization (from Map 2), or integration (combining Map 1 and 2). During transfer, cup choices increased to a location which suggested an integration strategy and was consistent with results obtained with pigeons. However, additional analyses of the human data suggested participants initially used a generalization strategy followed by a progressive shift in search behavior away from the red L. This shift in search behavior during transfer was responsible for the changes in cup choices across transfer trials and was confirmed by a control condition. These new analyses offer an alternative explanation to the spatial integration account proposed for pigeons.

Learning strategies in matching to sample: If-then and configural learning by pigeons

Pigeons learned a matching-to-sample task with a split training-set design in which half of the stimulus displays were untrained and tested following acquisition. Transfer to the untrained displays along with no novel-stimulus transfer indicated that these pigeons learned the task (partially) via if-then rules. Comparisons to other performance measures indicated that they also partially learned the task via configural learning (learning the gestalt of the whole stimulus display). Differences in the FR-sample requirement (1 vs. 20) had no systematic effect on the type of learning or level of learning obtained. Differences from a previous study [Wright, A.A., 1997. Concept learning and learning strategies. Psychol. Sci. 8, 119-123] are discussed, including the effect of displaying the stimuli vertically (traditional display orientation) or horizontally from the floor.

Is Surface-based Orientation Influenced by a Proportional Relationship of Shape Parameters?

We investigated the extent to which parameters of environmental shape – namely the major and minor principal axes of space which pass through the centroid and approximate length and width of the entire space, respectively, were subject to similar psychophysical principles as those involved in distance discriminations. We developed an orientation task that allowed us to manipulate the ratio of the major to the minor principal axes of an enclosure during training and control for orientation by alternative cues other than principal axes such as wall lengths or corner angles during testing. Participants trained in an environment with a larger hypothetical discriminability ratio allocated more responses to locations specified by the principal axes of space across novel enclosure types compared to a group trained with a smaller hypothetical discriminability ratio. Results suggest that psychophysical principles may operate on the discrimination of environmental shape parameters and delineate a potential mechanism for experiential and developmental changes in orientation ability.

Enclosure size and the use of local and global geometric cues for reorientation

Multiple spatial cues are utilized to orient with respect to the environment, but it remains unclear why feature (i.e., objects in the environment) and geometric (i.e., shape of the environment) cues are differentially influenced by enclosure size, and the extent to which local (i.e., wall lengths and corner angles) and global (i.e., principal axis of space) geometric cues are influenced by enclosure size. In the present study, we investigated the extent to which environmental size influenced the use of corner angle (i.e., a local geometric cue) and the principal axis of space (i.e., a global geometric cue) for reorientation. We developed an orientation task that allowed the manipulation of enclosure size during training and the isolation of the use of the principal axis of space during testing. Participants were trained to respond to a location in either a small or a large trapezoid-shaped enclosure uniquely specified by both local (i.e., wall lengths and corner angles) and global (i.e., principal axis of space) geometric cues. During testing, we presented both groups with a small and large rectangle (to assess the use of principal axis of space) and a small and large parallelogram (to asses relative use of corner angles and the principal axis of space when in conflict). Enclosure size influenced the relative use of corner angles but not of the principal axis of space. Results suggest that corner angles function like features and that changes in the use of feature cues are the source of the relative reliance on feature and geometric cues during changes of enclosure size.

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.

Of global space or perceived place? Comment on Kelly et al.

Recently, Kelly et al . presented results of an orientation experiment with chicks and pigeons that involved training in a rectangular-shaped environment followed by testing in an L-shaped environment [[1][1]]. They interpreted the distribution of searches in the L-shaped environment as supporting a