Ken Cheng

A purely geometric module in the rat's spatial representation*

Abstract Rats were tested in place finding tasks in a rectangular environment with distinct featural panels in the corners, such as the example in Figure 1A. When given a target place to seek, they made a systematic error both in a working memory paradigm and in a reference memory paradigm: they sometimes searched at the point located at 180° rotation from the target through the centre. In a working memory paradigm, these rotational errors were almost as numerous as correct searches. The target and its rotational equivalent have the same geometric relations to the arrangement of surfaces as surfaces, or the shape of the environment, but differ in their relations to non-geometric properties such as the brightness or texture of a surface. In making systematic rotational errors, the animal must have been using some record specifying only the targets geometric relations to the shape of the environment, and not its relations to the arrangement of non-geometric information. Further tests showed that rats could use the non-geometric information, but that they primarily checked features near a geometrically specified target address, that is, an address specified by its geometric relations to the shape of the environment alone. They did not seem to use the overall arrangement of non-geometric features. It is theorized that in orienting in space by using landmarks, the rat uses primarily a purely geometric module, which also serves as a basis for coordinating the locations of non-geometric data.

Is there a geometric module for spatial orientation? squaring theory and evidence

There is evidence, beginning with Cheng (1986), that mobile animals may use the geometry of surrounding areas to reorient following disorientation. Gallistel (1990) proposed that geometry is used to compute the major or minor axes of space and suggested that such information might form an encapsulated cognitive module. Research reviewed here, conducted on a wide variety of species since the initial discovery of the use of geometry and the formulation of the modularity claim, has supported some aspects of the approach, while casting doubt on others. Three possible processing models are presented that vary in the way in which (and the extent to which) they instantiate the modularity claim. The extant data do not permit us to discriminate among them. We propose a modified concept of modularity for which an empirical program of research is more tractable.

Longitudinal gains in self-regulation from regular physical exercise.

OBJECTIVES The purpose of the present study was to test whether the repeated practice of self-regulation could improve regulatory strength over time. METHOD Regulatory performance was assessed at baseline, then at monthly intervals for a period of 4 months using a visual tracking task. Perceived stress, emotional distress, self-efficacy and general regulatory behaviour were assessed by questionnaire. Following a 2-month control phase, participants entered a 2-month self-regulation programme designed to increase regulatory strength: a programme of regular physical exercise. RESULTS Relative to the control phase, participants who exercised showed significant improvement in self-regulatory capacity as measured by an enhanced performance on the visual tracking task following a thought-suppression task. During the regulatory exercise phase, participants also reported significant decreases in perceived stress, emotional distress, smoking, alcohol and caffeine consumption, and an increase in healthy eating, emotional control, maintenance of household chores, attendance to commitments, monitoring of spending and an improvement in study habits. The control phase showed no systematic changes in performance on the visual tracking task across sessions. Reports of perceived stress, emotional distress and regulatory behaviours were also stable across sessions. CONCLUSIONS The uptake and maintenance of an exercise programme over a 2-month period produced significant improvements in a wide range of regulatory behaviours. Nearly every major personal and social problem has some degree of regulatory failure. The idea that the capacity for self-regulation can be improved is therefore of vast practical importance.

Bayesian integration of spatial information.

Spatial judgments and actions are often based on multiple cues. The authors review a multitude of phenomena on the integration of spatial cues in diverse species to consider how nearly optimally animals combine the cues. Under the banner of Bayesian perception, cues are sometimes combined and weighted in a near optimal fashion. In other instances when cues are combined, how optimal the integration is might be unclear. Only 1 cue may be relied on, or cues may seem to compete with one another. The authors attempt to bring some order to the diversity by taking into account the subjective discrepancy in the dictates of multiple cues. When cues are too discrepant, it may be best to rely on 1 cue source. When cues are not too discrepant, it may be advantageous to combine cues. Such a dual principle provides an extended Bayesian framework for understanding the functional reasons for the integration of spatial cues.

Improved Self-Control: The Benefits of a Regular Program of Academic Study

Academic examination stress impairs regulatory behavior by consuming self-control strength (Oaten & Cheng, 2005). In this study, we tested whether a study intervention program, a form of repeated practice of self-control, could improve regulatory strength and dampen the debilitating effects of exam stress. We assessed 2 cohorts at baseline and again at the commencement of exams. Without any intervention, we replicated our previous findings of deteriorations in regulatory behaviors at exam time. Students receiving the study program, however, showed significant improvement in self-regulatory capacity as shown by an enhanced performance on a visual tracking task following a thought-suppression task. During examinations, these participants also reported significant decreases in smoking, alcohol, and caffeine consumption and an increase in healthy eating, emotional control, maintenance of household chores, attendance to commitments, monitoring of spending, and an improvement in study habits. Hence, the study program not only overcame deficits caused by exam stress but actually led to improvements in self-control even during exam time.

Whither geometry? Troubles of the geometric module

In rectangular arenas, rats often confuse diagonally opposite corners, even when distinctive cues differentiate them. This led to the postulation that rats rely preferentially on the geometry of space, encoded in a dedicated geometric module. Recent research casts doubt on this idea. Distinctive featural cues such as entire walls of a distinct color can hinder or aid the learning of geometry. In one situation in which using geometry would help greatly, rats had trouble learning the task. An associative model has been developed to capture these different learning processes, and view-based matching has been proposed as an alternative to the explicit coding of geometric cues. Considerations about how cues interact in learning are crucial in a recent theory of human spatial cognition.

Ants use the panoramic skyline as a visual cue during navigation.

Foragers of many ant species learn long, visually guided routes between their nest and profitable feeding grounds [1], [2] and [3]. The sensorimotor mechanisms underpinning the use of visual landmarks are much studied [3], but much less is known about how ants extract reliable visual landmark information from a complex visual scene. For navigation, useful visual information should be reliably identifiable across multiple journeys in differing lighting conditions, and one such robust source of information is provided by the skyline profile generated where terrestrial objects contrast against the sky. Experiments with ants and bees [4], [5] and [6] suggest that insects might use directional information derived from the skyline, and in the work reported here, we explicitly tested this hypothesis. Ants were trained to shuttle between their nest and a feeder. We then recreated the skyline profile as seen from the feeder using an artificial arena with variable-height walls. Ants returning from the feeder were captured near their nest entrance and released in the arena. Ants followed the direction given by the artificial skyline when it was aligned with their habitual homeward compass direction or rotated by 150. This result indicates that a crude facsimilie of a skyline can functionally mimic the natural panoramic scene.

Some psychophysics of the pigeon's use of landmarks

Summary1.Three pigeons (Columba livid) were trained to find hidden food in a sunken well (3.3 cm in diameter) at a constant place within an (160 cm×160 cm) experimental box (Fig. 1). After learning the location, the animals were tested occasionally with the well and food absent. Landmarks in the experimental box might be transformed on such tests.2.Changing the height or width of a nearby landmark had no systematic influence on the position of peak search. Translating a nearby landmark, however, led to a shift in peak search position. All three birds then searched most somewhere between the original goal location, as defined by the unmoved landmarks, and the goal location as defined by the shifted landmark. Within a limited range of landmark shift, the peak shift as a function of landmark shift is linear (Fig. 3).3.To explain the data (Fig. 7), the pigeon records at the location of the goal the algebraic vectors from a number of landmarks to the goal. These vectors have both a direction and a distance component. When searching for the goal again in the experimental box, it computes independently for each landmark a navigation vector. This is arrived at by vector-adding the algebraic vector from the birds current position to the landmark in question, supplied by perception, to the corresponding landmark-goal vector in its record. The pigeon moves in the direction and distance specified by a weighted average of the independently calculated navigation vectors. For positive vector weights, vector geometry guarantees that the bird would search somewhere between the original goal and the goal according to the shifted landmark. The extent to which it shifts toward the shifted goal reflects the vector weight given to the shifted landmark.

Use of Landmark Configuration in Pigeons and Humans: II. Generality Across Search Tasks

Pigeons and humans searched for a goal that was hidden in varied locations within a search space. The goal location was fixed relative to an array of identical landmarks. Pigeons searched on the laboratory floor, and humans searched on a table top or an outdoor field. In Experiment 1, the goal was centered in a square array of 4 landmarks. When the spacing between landmarks was increased, humans searched in the middle of the expanded array, whereas pigeons searched in locations that preserved distance and direction to an individual landmark. In Experiment 2, the goal was centered between and a perpendicular distance away from 2 landmarks aligned in the left-fight dimension. When landmark spacing was increased, humans, but not pigeons, shifted their searching away from the landmarks along the perpendicular axis. These results parallel those obtained in touch-screen tasks. Thus, pigeons and humans differ in how they use landmark configuration.

Learning the Configuration of a Landmark Array: I. Touch-Screen Studies With Pigeons and Humans

Pigeons and humans searched on a touch-screen monitor for an unmarked goal located relative to an array of landmarks presented in varied screen locations. After training with the goal centered in various square arrays of 4 landmarks, humans, but not pigeons, transferred accurately to arrays with novel elements. Humans searched in the middle of expanded arrays, whereas pigeons preserved the distance and direction to a single landmark. When trained with the goal centered below 2 identical horizontally aligned landmarks, humans responded to horizontal expansions or contractions of the array by shifting their search vertically, preserving angles from landmarks to goal. Pigeons did not adjust their search vertically. Humans trained with a single landmark adjusted search distance when landmark size was changed. Both pigeons and humans use the configuration of a landmark array, but the underlying processes seem to differ.