Memory for urban geography

Consistent patterns of errors are found in estimations of distances and angles along urban routes, even among subjects who know the areas well. These patterns can be used to discover the organization of the knowledge we use to find our way around in everyday life.

In the first experiment, 80 undergraduates estimated by ratio scaling the walking distances between pairs of locations in St. Andrews. Routes varied independently in their location, number of major bends, and length. Relative overestimation of length was found with routes in the town centre, with routes having several major bends, and (perhaps as an experimental artifact) with short routes. In the second experiment, 30 Cambridge residents estimated the angles between pairs of roads, by drawing the configuration of roads at their junctions. The real angles were either in the range 60-70° or 110-120°. All the estimates differed little from 90°, regardless of the true magnitude of the angle.

The implications of these findings for theories of mental representation of largescale space are discussed. A model is supported in which a spatial area is represented as a “network-map”, consisting of strings of locations forming a net of paths known to be traversable, but vector distance is not preserved.     

Effect of effort and latent extinction on resistance to extinction

Sixty-four male Wistar rats were given acquisition training in an enclosed straight-alley runway which could be adjusted for angles of inclination. The 2×2×2 design involved two angles of inclination in acquisition (0° and 40°) and two angles of inclination in extinction (0° and 40°). Between acquisition and extinction, half the subjects were exposed to a latent extinction procedure and half served as controls. Number of responses in a 30-min extinction session was an inverse function of effort required in extinction. Additionally, latent extinction procedures resulted in reduced resistance to extinction, but only when the effort conditions of acquisition and extinction were constant. When the effort conditions of acquisition and extinction were dissimilar, latent extinction procedures resulted in increased resistance to extinction. The results raise questions about the nature of the learning which occurs during latent extinction training.     

The threshold for sudden changes in the velocity of a seen object

The difference threshold for the velocity of a seen object was measured by the method of constant stimuli, using two categories. An approximate correspondence with Weber's law was found, the divergence from it appearing, in general, as an increase of the threshold at both ends of the range of initial velocities. The Mean Threshold (0-5 probability of perception, corrected for guessing) was, in favourable conditions, about 12 per cent, of the initial velocity. Whether the stimulus was an increase or a decrease of velocity made no marked difference. With two moving objects, which converged, crossed, and then diverged, both suffering the same change of velocity, the threshold was higher.

Velocity changes as low as 2 ± 5 per cent, elicited a significant proportion of correct responses. Some theoretical points in connection with this are discussed. Responses to blank stimuli showed a strong tendency to guess “slower,” which tendency differed significantly in degree between most of the experimental conditions. Tests with reduced exposure times showed that exposures could be as short as 0 ± 5 second (the velocity change occurring in the middle of the exposure) without appreciable detriment.     

Angular subtense effects on perception of polar and parallel projections of cubes

Many authors contend that the perception of 2-D drawings of a 3-D object is governed by polar projective geometry. A problem for this position is that observers accept parallel projections, which are not produced with polar projective geometry, as accurate representations of 3-D objects. In Experiments 1 and 2, we used two different standards of comparison to study the perceptions of three line drawings of cubes—correct polar projections of cubes with subtenses of 15° and 35°, and a parallel projection—at five different angular subtenses. In Experiment 1, 14 observers judged each drawing when it subtended about 35°, 15°, 5°, 4°, and 2° in width. Subjects used an 8-point rating scale to compare each drawing with a correct polar projection of a cube subtending 35°, viewed with the drawing subtending 15°. As predicted, both polar projections had their highest ratings at their correct vantage points. Ratings for the parallel projection were highest at small angular subtenses and decreased when it subtended 35°. These findings were supported by a second experiment in which the 15° polar projection was set at a 5° viewing angle as a standard. In Experiment 3, 15 observers compared the three drawings, viewed at a second set of angular subtenses (30°, 35°, 40°, 45°, and 50°), with a standard, the 35° polar set at 45°. Ratings fell with increases in viewing angle, and the parallel projection was rated lowest. The results indicate that parallel projections are assessed as polar projections that are correct for objects at a small angular subtense. Furthermore, projections at a small angular subtense are robust; that is, they are acceptable over a wide range of angular subtenses. We suggest that robustness can be explained by the modest variability in the proportions of pictures of cubes subtending small angles.     

Visual factors in auditory localization

Previous experiments showing the importance of visual factors in auditory localization are shown to have been insufficiently quantitative.

In the first Experiment, bells were rung and lights shone on the same or different vectors, eleven subjects indicating which bell had rung. In the second Experiment, a puff of steam was seen to issue from a kettle whistle with no whistling sound, while similar whistles were sounded by compressed air on that or another vector. Twenty-one subjects cooperated.

The addition of a visual stimulus at 0° deviation increased the percentage of correct responses significantly in the second, and insignificantly in the first experiment. At 20°-30° deviation the proportion of naive responses to the visual cue was 43 per cent. in the first and 97 per cent, in the second experiment. At greater angular deviations, the proportion of naive responses fell to chance level in the first, but remained significant in the second experiment, even at 90°. The “visuo-auditory threshold” was found to be 20°-30°, but might be much larger if there were more grounds for supposing the two stimuli to be from the same source in space.     

On varying the span of visual attention: Evidence for two modes of spatial attention

Three experiments investigated whether subjects could selectively attend to a target item presented in close spatial proximity to a distractor element. Typically, the display consisted of two curved lines, one a target and the other a distractor. The task was to judge the direction of curvature of the target. When subjects attended to a target away from fixation, performance was affected by the presence of a distractor within an area of 1° around the target. In contrast, the distractor did not influence target processing when subjects fixated on the target location. Two modes of visual attention are proposed. When a target is located away from fixation, a “wide” attentional span is employed. With the present stimuli, this led to the detailed processing of items within 1° of the attended position. However, when targets are at fixation a “narrow” span can be adopted, with the result that there is differential processing of attended items even within the formerly critical area.     

Contribution of extraretinal signals to the scaling of object distance during self-motion

We investigated the role of extraretinal information in the perception of absolute distance. In a computer-simulated environment, monocular observers judged the distance of objects positioned at different locations in depth while performing frontoparallel movements of the head. The objects were spheres covered with random dots subtending three different visual angles. Observers viewed the objects ateye level, either in isolation or superimposed on a ground floor. The distance and size of the spheres were covaried to suppress relative size information. Hence, the main cues to distance were the motion parallax and the extraretinal signals. In three experiments, we found evidence that (1) perceived distance is correlated with simulated distance in terms of precision and accuracy, (2) the accuracy in the distance estimate is slightly improved by the presence of a ground-floor surface, (3) the perceived distance is not altered significantly when the visual field size increases, and (4) the absolute distance is estimated correctly during self-motion. Conversely, stationary subjects failed to report absolute distance when they passively observed a moving object producing the same retinal stimulation, unless they could rely on knowledge of the three-dimensional movements.     

Effect of prolonged tilt on visual orientation

Visual orientation during lateral tilt is viewed in terms of orientation constancy. The postural systems involved in the maintenance of constancy are considered to be those of the otolith, neck and trunk. The relative contribution of these systems was investigated by obtaining visual verticality judgments immediately upon and several minutes after head, body, and trunk tilts. Due to the apparent non-adaptation of the otolith system any changes in visual orientation resulting from prolonged tilt would be attributed to adaptation of the proprioceptive system stimulated. For 30° head tilt visual orientation over-constancy was reduced by about 2°, reflecting the influence of the neck system. Prolonged body tilts of 30°, 60° and 90° reduced the constancy operating by approximately 1°, 3° and 8°, respectively. This was taken to indicate the contribution of the trunk system, which increased with increasing degrees of body tilt. The above interpretations received strong support from experiments involving trunk tilt, which stimulates only the neck and trunk systems.     

The Poggendorff illusion: Apparent misalignment which is not attributable to apparent orientation of the transversals

Subjects while looking down were required to adjust a horizontal field of parallel lines (Experiment I) or a single line (Experiment II) to the apparent sagittal direction with and without a superimposed rectangle in the centre of a circular field. The rectangle was tilted at 20, 30 or 40° to the parallels and at 20° to the line. For the 20° condition the parallel lines were apparently oriented at about half a degree compared with the field without a rectangle but in the direction opposite to that necessary to account for the Poggendorff misalignment effect. For the 30 and 40° conditions the lines did not change in apparent orientation. The orientation of the single line did not change. Almost all subjects readily reported an apparent misalignment between the collinear parallels and line separated by the oblique rectangle. It is concluded that the Poggendorff misalignment illusion occurs without apparent regression of the lines to right angles with the figure.     

Perceptual Anticipation and Reaction Time

To determine the effect of perceptual anticipation upon reaction time, two different types of experiment were carried out. In the first a skilled response had occasionally to be altered at a given point after a variable warning period. In the second the subject had to react to two auditory signals separated by a short time interval which was systematically varied, the second signal being expected or unexpected.

It was found that lack of readiness to respond to a signal, as revealed by a lengthened reaction time, may be due either to the subject not having prepared himself, as he was not expecting the signal; or to the subject not being able to prepare himself in time. Preparation for reacting to the second of the two signals, when both are expected and have to be reacted to, never appears to take more than between 0·2 and 0·4 seconds, as judged by reaction time. On the majority of occasions it appears to be complete in 0·2 seconds. These times are shorter than those usually given, because the extra delay due to incorrect anticipation has been excluded. With intervals of 0·1 seconds or less, delay in the second reaction may be due to the mechanical difficulty of responding quickly enough, especially when the two reactions have to be made in opposite directions.

The finding that lack of readiness might be due to the subject not expecting the signal, and the further finding that preparation took longer when a skilled response had to be extended than when it had to be stopped, both suggest that so-called Psychological refractoriness is due to lack of fore period in which to prepare for the response, rather than to a “Psychological refractory phase” comparable to the refractory phase of nerves. If, by dividing his attention, the subject was able to prepare for his next response while making his previous one, so-called Psychological refractoriness could be completely absent.     

The restriction of peripheral vision during exposure to hot and humid conditions

Eighteen, heat-acclimatized subjects were exposed to temperatures of 70/60° F. and 105/95° F. (air velocity 120 ft./min.) in three experiments requiring them to respond to a peripheral task concurrently with a continuous central pursuitmeter task. The peripheral signals were presented randomly in order and time at six positions, 20°, 50°, and 80° left and right to the point of fixation. The experimental findings suggest that when, while being subjected to high thermal conditions, operators are engaged in a central task consistently demanding their attention, there is a tendency for the field of awareness to be funnelled towards the centre. Signals presented at greater eccentric angles have a higher probability of being missed in the hotter condition. The longer the previous exposure to heat, the greater is the tendency to miss signals—but the effect does not always appear to be progressive during the actual performance. Operationally, the funnelling is defined by the proportional increase in the number of signals missed as the eccentric angle of the stimulus increases relative to the point of fixation. The phenomena does not occur when the perceptual load on the central task is reduced. Central attentional processes rather than mechanisms peripheral to the CNS are therefore implicated.     

Spontaneous fixation tendencies for visual forms

Haidinger’s brush was used as a method of locating fixation positions on a display. The various experimental patterns studied showed: (1) It is the already organized cortical representation of shape which governs fixation, rather than the peripheral input per se; (2) Acute angles near 20 deg are the most effective angular stimuli: (3) For figures subtending angles less than 5 deg, the eye is directed toward the center of the figure. and not toward its edge; and (4) Removing one segment from a completely enclosed figure may not alter the mean fixation position.     

A further investigation of apparent size and retinal size as determinants of the figural after-effect

A figure which is more distant from the eye than another but subtends the same visual angle is usually seen as the larger. This phenomenon is called perceptual size constancy. Experiments have been reported which show that sometimes the apparent and sometimes the retinal sizes of the stimulus figures determine the direction of the figural after-effect. These experiments are reviewed and two further experiments are reported. In the first experiment two types of stimulus figure (discs and annuli) which subtended a visual angle of 1° 36' resulted in figural after-effects, the direction of which would have been predicted by the retinal sizes of the figures. In the second experiment larger figures were used which subtended a visual angle of about 4° and which were the same as those used by Sutherland (1954). In this experiment the after-effects were generally in a direction which would have been expected if apparent size determined the direction of the after-effect. In the interpretation of the results attention is drawn to the “Central Tendency Effect” which has been observed in size judgements of stimulus figures of varying size. Two hypotheses are suggested; one is that the true figural aftereffect has been obscured by the “Central Tendency Effect” in successive judgements, and the other is that time error in successive judgements of size is essentially a figural aftereffect. Some supportive evidence for the latter hypothesis is reported. It is concluded that apparent size is not a critical determinant of the figural after-effect.     

Orientational Effects and Component Processes in Symmetry Detection

In previous research on symmetry detection, factors contributing to orientational effects (axis and virtual lines connecting symmetrically positioned dots) and component processes (axis selection and pointwise evaluation) have always been confounded. The reason is the restriction to bilateral symmetry (BS), with pointwise correspondences being orthogonal to the axis of symmetry. In our experiments, subjects had to discriminate random dot patterns from symmetries defined by combining 12 axis orientations (every 15°) with seven reflection angles (0°, yielding BS, and three clockwise and counterclockwise 15° steps, yielding skewed symmetry, SS). In Experiment 1, with completely randomized trial order, a significant interaction between axis and skewing angle was obtained, indicating that classically observed orientational effects are restricted to BS and that the orientation of the pointwise correspondences is important. These basic findings were replicated in three subsequent experiments, which differed in that they used blocks containing patterns with the same axis (Experiment 2), virtual lines orientation (Experiment 3), or their combination (Experiment 4). Based on a comparison between the results obtained by these manipulations, we suggest a possible reason for the failure of preattentive symmetry detection in the case of dot patterns with SS.     

Visual comparison of rotated and reflected random-dot patterns as a function of their positional symmetry and separation in the field

Subjects viewed pairs of random-dot patterns which were presented in a number of arrangements varying in the transformations applied to the patterns, in the distance between the patterns, and in the symmetry of the pattern positions with respect to the point of fixation. The task was to judge whether the patterns were “the same” taking into account possible rotations or reflections, or “different”. It was found that correct judgements for identical patterns were most affected by the distance between the two patterns, whereas correct judgements for patterns where one had been rotated through 180° or reflected were most affected by the symmetry of the pattern positions. A scheme modelling the visual recognition of transformed patterns, sufficient to explain the results, is presented.     

A comparison of body perceptions in relation to measured body composition in young Japanese males and females

The body composition of 139 Japanese females and 84 Japanese males (aged 18–30 years) was measured using anthropometry to assess gender differences in body perceptions in relation to their measured values. Participants were asked to rate perceptions of their own “heaviness” and “fatness” and these were compared to their BMI and percent body fat (%BF). Japanese females showed a significantly greater desire to lose body weight (−4.20 ± 0.6 kg) compared to males (0.27 ± 1.4 kg). Females also showed poor understanding of their “heaviness” and “fatness” in relation to actual body composition compared to males. The results confirmed distinct gender differences in body perception in relation to actual body composition and attitudes to weight management. Further promotion of “healthy” body image is recommended for the Japanese population.     

The apparent length of a line as a function of its inclination

In the first of two experiments reported here, subjects adjusted the length of a variable line until it appeared to be as long as a standard line. There were two sizes of standard line, 3 and 6 inches, and each was shown vertically for some trials and horizontally for others. The variable line was presented in each of the 10° positions from 0° (horizontal), through 90° (vertical), to 170°. The principal results of the first experiment are:

(1) Vertical lines look longer than horizontal lines of the same length, but lines tilted 20°-30° to the left of vertical look longer than lines in any other orientation. The results are asymmetrical, because lines tilted to the right of vertical do not look as long as those tilted to the left of vertical.

(2) The variability of the settings increases as the angle increases between the standard and variable lines.

(3) When they are expressed in percentage terms, the data obtained with the 3-and 6-inch standards are virtually identical, i.e. the data for the 3-inch standard can be made to match those for the 6-inch standard simply by doubling the former.

(4) There are enormous differences among subjects in the patterns of settings made at the various angles. A few subjects apparently experienced no illusory effects since they adjusted the variable line to about the same physical length irrespective of its orientation. Other subjects showed exaggerated overestimations of the variable line for vertical and near-vertical positions.

In the first experiment, the variable line was always to the left of the standard, and it was natural to assume that this position effect had somehow produced the asymmetry noted in paragraph 1 above. This hypothesis was tested in the second experiment which alternatively showed the variable line above, below, to the right of, and to the left of the standard line. The results of this experiment generally confirm the data of the first experiment in showing that lines tilted 20°-30° to the left of vertical look longer than lines tilted to any other position. In addition, the second experiment shows that this asymmetry in the results is not a function of the relative positions of the variable and standard lines. In general, however, overestimations of length are smaller when the two lines are one above the other, greater when the two lines are side by side.     

Remembering, Familiarity, and Source Monitoring

Two experiments investigated recollective experience in a source monitoring task. Subjects saw an array of objects and performed, watched, or imagined actions involving pairs of objects. In a subsequent recognition test, subjects indicated whether their recognition judgements were made on the basis of conscious recollective experience (“remember” responses), or on some other basis such as familiarity (“know” responses). The proportions of correct “remember” responses for both objects and actions decreased from performed, through watched, to imagined actions, whereas the proportions of correct “know” responses were uninfluenced by the source of the memories. In addition, the relationship between recollective experience and accuracy of source judgement varied across sources. Source accuracy for performed actions was obtained only in “remember” responses, whereas source accuracy for imagined actions was obtained only in “know” responses. Source accuracy for watched actions was obtained in both “remember” and “know” responses. The findings suggest that the types of memory attributes available at retrieval determine the quality of subsequent memory experience, and it is proposed that memories with strongly self-referential attributes (arising from performed actions) powerfully cue recollective experience during retrieval.     

An examination of the effects of axis foreshortening, monocular depth cues, and visual field on object identification

Four experiments are reported on the identification of line drawings of common objects. In each experiment, performance on “unconventional” views of the objects, in which the major axis of the object was foreshortened, was compared to performance on more “conventional” views without appreciable foreshortening. In each experiment, except Experiment 2, where performance on the two views was experimentally equated, the foreshortened views were more difficult to identify than were the conventional views. Experiments 1 and 2 showed that if the foreshortened views were presented on a background with strong monocular depth cues, object identification was improved. This result suggests that part of the difficulty in identifying objects depicted from such a view stems from an improper depth interpretation of the object depictions. Experiments 3 and 4 examined visual field differences in the identification of the two types of object view. Results reported in the neuropsychological literature have shown that people with right-hemisphere damage have particular difficulty with the identification of unconventional views of objects that foreshorten major axes. Accordingly, it was expected that there would be a left visual field advantage for the foreshortened views. Neither experiment yielded any visual field effects consistent with this expectation. Possible reasons for the lack of a field effect are discussed.