bluuebunny/crossref_metadata_2025 huggingface dataset:
The Microstructure of Dual-Task Interaction. 1. The Patterning of Main-Task Responses within Secondary-Task Intervals
Authors: Fisher Shirley
Published: January 2007

The patterning or microstructure of a situation where subjects were presented with two sets of information from two independent ‘high decision’ information processing tasks, was investigated. Thirty-two subjects worked at the five-choice serial-response task (designated by instructions to be the main task), whilst being presented with a transformation task which required that seven had to be added to a presented auditory digit (designated by instructions to be the secondary task). Results suggested that subjects were not able to process two streams of information in parallel, and that the way in which the attention process was ordered was partly a function of task instructions and partly a function of the random occurrence of each digit in relation to the on-going serial task. Results also gave support to the view that the locus of disruption was the production of the response to the secondary task. Explanations of this effect are considered.
Attention and the Perception of Duration during Encoding and Retrieval
Authors: Underwood Geoffrey
Published: January 2007

Separate groups of subjects spent 50 s encoding a list of nonsense syllables, or a list of unrelated words, or a list of related words, and then 50 s attempting to recall them. On a subsequent assessment of the durations of the encoding and retrieval intervals subjects judged that they had taken more time on retrieval than on encoding, and this difference increased as the meaningfulness of the material decreased. The data were interpreted in terms of an attentional model of time perception, with tasks which demand more attention being judged to occupy more time. By this model retrieval is seen as requiring more attention than does encoding, in accord with recent concurrent task investigations of mnemonic processes.
Derivation of a Hypothesis about Monocular Size and Depth Perception from a Simple General Perceptual Principle
Authors: Lambert Robert M
Published: January 2007

A viewer is assumed to look with one eye at a fixation point f and a reference point x of a surface in a frontal parallel plane. He can move his eye along its line of regard for f some distance Δ S; and we suppose that he can assess the ratio Δ R−1/Δ S, where R is the retinal separation between the images of f and x and Δ R−1 is the change in the reciprocal of R that attends his movement of a distance Δ S. A model is proposed that approximates the optical conditions of his stimulation, and that allows him to calculate the physical distance E between f and x and the distance S between f and the center of his eye in terms of Δ R−1/Δ S. His calculations of E and S are treated as perceptions of the linear extent and the distance of the surface on which the points f and x are located.
Perceptual Adaptation with Selective Reductions of Felt Sensation
Authors: Wallace Benjamin , Garrett James B
Published: January 2007

Hypnotic anesthesia was used to reduce sensation in the adapting arm during prism displacement. Magnitude of adaptation to displacement was assessed by negative aftereffects (NA), proprioceptive shifts (PS), and visual shifts (VS). Hypnotic anesthesia for the entire arm nearly eliminated adaptation as measured both by NA and PS. This was not the case when only portions of the arm (receptor joints) were selectively anesthetized. The sum of NA when different parts of the arm were left unanesthetized at different times equaled such adaptation produced when all those arm locations were left unanesthetized simultaneously. This was also the case for PS. VS, which involved no arm movements, was not affected by hypnotic anesthesia. Support for Wilkinson's component additive model (NA = PS + VS) was found only when the adapting arm was not anesthetized.
The Microstructure of Dual Task Interaction. 2. The Effect of Task Instructions on Attentional Allocation and a Model of Attention-Switching
Authors: Fisher Shirley
Published: January 2007

As an extension of an experimental design reported previously the microstructure of dual task interaction was investigated in a condition in which task instructions favoured the task which had previously been designated the secondary task.

In the situation explored in this paper subjects worked on the five-choice serial reaction task (designated secondary task) whilst at the same time they received single auditory digits at random time intervals, performed a transform operation (adding seven), and called the answer out into a voice key.

The nature of the interaction was investigated using fine analysis of data, and it is argued that the results give further support to the view that subjects were processing information sequentially. A change in the patterning of serial responses in the interval defined by the digit stimulus ( Ds) and the digit response ( Dr) under the changed-instructions condition suggested that individuals are able to play an active role in the ordering of the attention process in sequential processing situations. ‘Process theory’, in which the information processing state of the main task is considered to have a direct influence on the response to the secondary task signal, is argued to be of little use in explaining the data. Two types of explanations based on criterion theory are considered—one which involves criterion setting with respect to a direct time base and one which relies on information processing stage, as an indirect time base.

It is argued that the microstructure of dual task interaction should be investigated more closely and that the ordering of the time-sharing process is a skill.
Spatial Constraints on Focused Attention: Beyond the Right-Side Advantage
Authors: Hublet Claude , Morais José , Bertelson Paul
Published: January 2007

The subjects listened to one of two simultaneous synthetic speech syllables delivered independently over two loudspeakers. When the loudspeakers were situated at 90° to the left and to the right, right-side advantage was found. When one loudspeaker was situated in front of the subject in the median plane, and the other at one of several azimuthal positions around him, an advantage of the frontal position was observed in all cases. On the other hand, performance on the nonfrontal message was affected significantly by its position. The pattern of performance which is observed can be described in terms of three component factors: a right-side advantage, related presumably to cerebral dominance, an advantage of sources situated in front of the subject over those at his back, and possibly an advantage of sources near the median plane over more remote ones.
How Many Tastes are there for Low Concentration ‘Sweet’ and ‘Sour’ Stimuli?—Threshold Implications
Authors: O'Mahony Michael , Hobson Anita , Garvey John , Davies Mary , Birt Caroline
Published: January 2007

Ascending series of solutions of sucrose, glucose, and citric acid were tasted and detection and recognition thresholds were noted; subjects were also required to determine the number of taste sensations that occurred and their sequence of occurrence. It was found that subjects varied in their reports of the number of taste changes and hence potential criteria for detection and recognition. Even among those subjects who reported the same number of criteria there was little consistency as to which were actually chosen for detection and recognition. Some subjects even used an intensity change rather than a quality change to signal a threshold. The criterion can thus be seen to be a potential variable in threshold measurement, and criterion-free measures of sensitivity are recommended. Taste quality descriptions were also studied and a high proportion of novel descriptions was noted; it was hypothesised that this was due to the fact that subjects were not primed with traditional descriptive terms during the instructions.
Pulfrich Effect and the Filling in of Apparent Motion
Authors: Morgan Michael J
Published: January 2007

In the stroboscopic version of the Pulfrich effect a filter is able to induce depth shifts in a target as if the latter were moving continuously, rather than merely occupying a series of discrete positions. This was examined in a further series of experiments, in which a visual alignment technique was used to measure the perceived visual direction of an apparently moving target in intervals between its presentations. Results showed that the target has approximately the visual direction that it would have if it were moving continuously. This ‘filling in’ of apparent motion was shown to occur before the level of stereopsis. The possible influence of tracking eye movements is discussed.
A Possible Hybrid Mechanism for Modification of Visual Direction Associated with Eye Movements—The Paralyzed-Eye Experiment Reconsidered
Authors: Matin Leonard
Published: January 2007

Previous work on the paralyzed-eye experiment concerning visual direction can be interpreted by a hybrid mechanism: outflow control of gamma motor fibers determines whether or not muscle spindles respond to changes in muscle length.
The Role of Vision in the Perception of Speech
Authors: Dodd Barbara
Published: January 2007

The ability of hearing adolescents to use speech-read information in order to report lists of CVC words presented in white noise was investigated. The conditions of stimulus presentation included were auditory and visual information in synchrony, out of synchrony, auditory input alone, visual input alone, and a condition where the information presented in the auditory input conflicted with the visual input. The results indicated that the amount and type of information reported varied according to the condition of presentation, and that vision provided a complementary source of information for the perception of speech.
The Spatial Selectivity of Early and Late Waves within the Human Visual Evoked Response
Authors: Parker Denis M , Salzen Eric A
Published: January 2007

Two studies on the amplitude, latency, and waveform of human visual evoked responses to the onset of sine-wave grating patterns were made. Results indicated that the peak latencies of both early and late waves were a function of the spatial frequency of the stimulus. The amplitude of the early wave (N1−P1) was consistently greatest at low spatial frequencies while the late wave (N2−P2) showed consistent attenuation at low spatial frequencies. In addition the location of the peak amplitude response of the late, but not the early, wave depended on the location (macular versus extramacular) and area (small versus large stimulus field) of retina stimulated. These findings are discussed in the light of evidence for separate transient and sustained systems within the human visual system.
Shape Constancy: A Systematic Approach
Authors: Campione Francesco
Published: January 2007

This work contains the analysis of one experiment and its results. It was carried out to demonstrate that: (i) Shape is a shape-constancy ‘factor’. In other words, there must be a ‘shape-constancy scale’ where the various shapes can be arranged; (ii) when the shape factor is isolated, the shape constancy of a visual pattern is directly proportional to the strength of the ‘linear-perspective cue’ and inversely proportional to its degree of ‘simplicity’. A pattern such as the cross (which has many linear components and a high degree of complexity) should therefore exhibit a maximum of constancy. The results of the experiment have confirmed the above hypothesis except for an unexpected low degree of constancy of the cross. Another experiment is being performed to explain this last result.
Effect of Distance Information and Range on Two Indices of Visually Perceived Distance
Authors: Foley John M
Published: January 2007

Subjects made verbal reports of the perceived distance of near visual targets and indicated their distances by pointing at them with an unseen hand. The targets were presented under three stimulus conditions: monocular, binocular, and multicue. Two ranges of target distance were studied in separate experiments: 11–39 cm and 21–33 cm. When reciprocals of both response distance and target distance were plotted, all functions were approximately linear. The verbal and manual responses (distance indices) differed greatly, but were found to be related by a constant transform. The range of target distances had no effect on either index. The standard deviation of the manual response was about half that of the verbal response. Stimulus condition had a large effect, with the multicue condition producing the greatest change in indicated distance, and the monocular condition the least. The results are discussed with reference to the definition of perceived distance, and hypotheses concerning the integration of distance information.
Perceptual Grouping in Audition
Authors: Massaro Dominic W
Published: January 2007

The present experiments evaluated the effect of relative frequency as a determinant of the figure-ground organization of sequences of auditory tones. Observers counted sequences of 20 ms tones that were presented at the same frequency or that alternated between two different frequencies. The alternating tones differed in frequency by one whole tone, seven tones, or nineteen tones. Counting accuracy increased with increases in the silent interval between the tones. When the alternating tones differed by seven or nineteen tones, counting was disrupted at rates of presentation of eight tones per second or slower. In contrast to this decrement in the counting of tones that alternated by over an octave, very little decrement was observed when the tones alternated by just one whole tone. The best subjects counted these alternating tones more accurately than the tones presented at the same frequency. The poorest subjects showed a small decrement even when the tones alternated by just one whole tone. The results were discussed in terms of determinants of figure-ground organization in auditory information processing.
The Perception of Musical Rhythm and Metre
Authors: Steedman Mark J
Published: January 2007

The occurrence of relatively long notes, and the repetition of melodic phrases are important cues to the metre, or regular beat, of a piece of music. A model of how people use this information to infer the metre of unaccompanied melodies is described here. The model is in the form of a computer program, and involves a definition of melodic repetition which encompasses repetitions that include certain kinds of variation. The program has been applied to the task of analysing the metric structure of the forty-eight fugue subjects of the Well-Tempered Clavier by J S Bach. The program is discussed in relation to other models both of musical understanding and of sequential concept learning.
Perceived Bending Motions from a Quadrangle Changing Form
Authors: Jansson Gunnar , Runeson Sverker
Published: January 2007

In an earlier study by Jansson and Johansson it was found that rotation of a rigid object is perceptually preferred over bending motion, and that bending motion in turn is preferred over two-dimensional stretching. The aim of the present experiment was to study if the same preference order is retained also when the proximal stimuli are changing in a physically more complex way. The stimuli were quadrangular outline figures with two stationary and two moving corners; the figures differed in degree of phase lag between the motions of the two corners. The result was that the preference order found earlier was retained. It was also found that the relative frequency of two subcategories of bending motion, bending proper and folding, varied with phase lag. The relation of the result to a principle of minimum object change was discussed.
Pictorial Depth and Related Constancy Effects as a Function of Recognition
Authors: Rock Irvin , Shallo Josephine , Schwartz Fred
Published: January 2007

It is argued that while pictorial cues must be fundamental in the perception of an extended ground plane in daily life (and, by definition, in the perception of depth in pictures), the traditional pictorial cues such as perspective or texture gradients are neither a necessary nor a sufficient basis for it. That they are not necessary was shown by experiments in which such cues were eliminated from pictures representing a scene in depth. Illusory size perception based on localization of objects in depth in such pictures nonetheless occurred. That they are not sufficient was shown by experiments in which photographs of grassy fields did not yield impressions of depth or related size illusions when conditions were such that the scene was not recognized. Once recognized, however, these same pictures did yield such perceptions. It is suggested that a critical step in perceiving depth based on pictorial information is recognition of the scene.
Changes in the Apparent Lengths of Lines as a Function of Degree of Retinal Eccentricity
Authors: Schneider Bruce , Ehrlich Dan J , Stein Robert , Flaum Manning , Mangel Stuart
Published: January 2007

Magnitude estimates were obtained for the apparent lengths of (i) seven vertical lines of different lengths at eleven positions along the horizontal meridian and (ii) the same seven lines presented horizontally at ten different angles of elevation. In experiments 1 and 2 (experienced and naive subjects, respectively) the seven vertical lines were permutated randomly in the eleven azimuth positions within a session. In experiment 3, the seven vertical lines were all presented first at a single azimuth position before being presented at another azimuth position. In experiment 4, the same seven line lengths (presented in horizontal orientation) were permutated randomly within the ten angles of elevation. The results showed that the apparent length of a line decreases as the line was moved away from the midline position into the periphery. Power functions described the growth of line lengths at each azimuth position and each angle of elevation. The exponents of the power functions in experiments 1,2, and 4 were smallest at the midline position and became larger for the line lengths presented more peripherally. For lines presented vertically the exponents tended to decrease again at the more extreme azimuth positions. Equal-length contours were derived from the power functions of experiments 1, 2, and 4.
Generation of Synthetic Male and Female Walkers through Manipulation of a Biomechanical Invariant
Authors: Cutting James E
Published: January 2007

Synthetic versions of human walkers were generated by computer as point-light displays. Previously it had been determined that the natural gaits of males and females differ according to the extent of movement at the shoulder and the hip. These movements were measured and then used to synthesize the stimuli used in the present study. These stimuli are shown here to be identified by untrained viewers as male when the shoulder movement is greater than the hip movement, and female when the configuration is reversed. Because of the coherence of the display lights representing the shoulder and hip are not necessary for gender recognition, although they do increase performance level. Hypernormality and heavy-footedness in gait are also discussed. Finally, all results are linked to an underlying biomechanical invariant, the center of moment.
Form-Colour Aftereffects: Selectivity to Local Luminance Contrast
Authors: Stromeyer Charles F , Dawson Benjamin M
Published: January 2007

For long periods observers fixated low spatial frequency coloured gratings. Black and white test gratings of the same spatial frequency and orientation as the adapting gratings appeared coloured with the hue complementary to the adapting patterns when the dark test stripes fell on retinal areas previously occupied by the dark adapting stripes; no colour or very weak colour was seen when the test gratings were reversed in phase (contrast reversed). No colour aftereffects were produced with coloured gratings that lacked luminance contrast. This selectivity to the polarity of local luminance contrast can be explained by mechanisms that respond conjointly to colour and luminance contrast. The aftereffects are selective to spatial phase.
Contrast Sensitivity Function for Stereopsis
Authors: Frisby John P , Mayhew John E W
Published: January 2007

Contrast thresholds for stereopsis from narrow-band-filtered random-dot stereograms were compared with contrast thresholds for simple detection of similar narrow-band noise. Centre frequencies of filters were in the range 2·5–15 cycles deg−1. It was found that the contrast sensitivity function for stereopsis is similar in shape to that for detection, suggesting that as far as contrast requirements are concerned the mechanisms of global stereopsis do not show a bias in sensitivity to any particular spatial frequency but instead require a constant level of suprathreshold contrast regardless of spatial frequency.
The Use of Category Information in Perception
Authors: Humphreys Glyn W
Published: January 2007

Three tachistoscopic experiments are reported in which presentation of the target stimulus in a letter/digit categorization task was preceded by a briefly exposed priming stimulus (letter or digit). The primer was subject to backward masking from either the target or a pattern mask, and observers were unaware of its occurrence. With a primer duration of 25 ms, when masking was presumed to be at a central level, performance deteriorated when the two items were from different categories. This inhibition effect was reduced when the characters were physically similar. In contrast, there was little evidence of facilitated processing when primers validly cued targets. At shorter primer durations, when masking is presumed to be peripheral in origin, between-condition differences were less marked. An interpretation in terms of an active model of information processing, with utilization of both categorical and physical information extracted from the primer, is proposed.
A Comparison of Visual Tilt Illusions Measured by the Techniques of Vertical Setting, Parallel Matching, and Dot Alignment
Authors: Wenderoth Peter , Parkinson Alan , White Dennis
Published: January 2007

The tilt illusion (TI) was investigated by using both short (19 min) and long (2 deg 6 min) test lines, at three angles of test line-inducing line separation (15°, 45°, and 75°). Three groups of ten observers each provided data under one of three task conditions: vertical judgment, parallel matching, and dot alignment on a common visual display. The main result was that both the vertical judgment and the parallel matching task provided similar, classic TI angular functions with the means ordered 15° > 45° > 75° and with small attraction effects at 75° in three of the four relevant functions. The third task, dot alignment, yielded results different from the average of the other two: no attraction effects occurred and, with the short test line, the obtained mean illusion at 45° exceeded those at the other intersect angles. These results are consistent with alignment data reported by others. One explanation is that the inducing line produces an apparent bowing of the test line which would be reflected in dot alignments but not in vertical setting or in parallel matching. However, direct evidence does not support this hypothesis. An alternate hypothesis, for which independent evidence exists, is that alignment errors reflect perceptual mistracking but that the origin of these errors is not at the tip of the test line but within it. Although this does not explain dot alignment errors, it highlights their complexity and the need to interpret them with caution.
On the Limits of Fourier Decompositions in Visual Texture Perception
Authors: Julesz Bela , Caelli Terry
Published: January 2007

Recent discoveries of nonlinear perceptual analyzers in effortless texture discrimination cast serious doubt on the usefulness of Fourier image decompositions to describe suprathreshold visual-texture perception. We now explain the meaning of these results.
Bias-Free Improvement in Wine Discrimination
Authors: Owen Dean H , Machamer Peter K
Published: January 2007

Over three test sessions alternated with two training sessions, accuracy of ‘same’/‘different’ judgments of four dry, white wines improved 14%. Confidence ratings were obtained so that the area under the isosensitivity curve could be computed as a bias-free measure of accuracy while the wine used for same pairs was held constant. An initial bias for ‘different’ judgments persisted, rather than disappearing as Walk found. While perceptual learning did occur, the problem of attending to irrelevant differences was not overcome.
Are Black Circles Attentive Fields? A Reply to Bross, Blair, and Longtin
Authors: Pressey Alexander W
Published: January 2007

It is argued that the experiment carried out by Bross et al is not a valid test of assimilation theory because they confuse a graphic representation of a construct with the construct itself and assume that changing the former will alter the latter.
Figure-Ground Formation by Movement: Influences and Effects
Authors: Alwitt Linda F
Published: January 2007

A twelve-letter array was segmented into figure and ground by moving some of its letters. Moved letters were shifted one letter-width left or right, independently of each other, in apparent movement. Since the figure of a display attracts attention, identification of letters of the figure segment should show an advantage over letters of the background segment. Three results are of interest. First, moved letters were identified more accurately and faster than stationary letters when only one or two letters moved. Stationary letters showed the advantage when eight of the twelve letters moved. This result suggests that the segment seen as figure is determined by both rapidly encodable letter movement and by the number of moved letters within the display. Second, segmentation of the visual display aids identification of moved letters in less than 90 ms, or well before the eye can move to the selected letter position. Third, letters in the figure segment which are closer to fixation are more likely to be identified than more eccentric letters.
Decrease in Metacontrast Masking following Adaptation to Flicker
Authors: Petry Susan , Grigonis Antony , Reichert Bernard
Published: January 2007

Selective adaptation was used to explore the characteristics of a metacontrast masking stimulus which contribute to its effectiveness in masking the test stimulus. Subjects adapted for 10 s to a configuration like the masking stimulus that was either continuously on or flickering. Following this they viewed a metacontrast presentation and estimated the brightness of the test stimulus. Prior adaptation to a continuously present stimulus did not appreciably affect metacontrast masking; however, masking was greatly reduced following adaptation to flickering stimuli. These results are consistent with recent models of metacontrast masking based on transient and sustained visual channels.
Coloured Illusory Triangles Due to Assimilation
Authors: Ware Colin
Published: January 2007

A coloured addition by Varin to Kanizsa's triangle figure gives rise to a colour-tinted illusory triangle. Two theories for this effect are described, (i) a cognitive theory based on perceived transparency and (ii) a theory based on an assimilation mechanism. An experiment is reported which uses certain colour combinations incompatible with transparency and other combinations where the two theories predict different illusory colours. The results support the assimilation theory.
Human Vision Favors Centrifugal Motion
Authors: Ball Karlene , Sekuler Robert
Published: January 2007

Reaction times to motion onset were measured for targets in the peripheral field. Horizontal motion away from fixation evoked faster reactions than did motion toward fixation. The difference between motion toward fixation and motion away from fixation (i) increases with stimulus eccentricity, (ii) is not found when motion is along a vertical axis, and (iii) fails to affect contrast thresholds. The anisotropy between centrifugal and centripetal motion is correlated with differences in the apparent speed of targets moving in the two directions.
Orientation-Specific Adaptation: Effects of Checkerboards on the Detectability of Gratings
Authors: Green Marc
Published: January 2007

The predictive values of Fourier analysis and local-feature analysis of spatial stimuli were compared in an orientation-specific adaptation experiment. Observers adapted to checkerboard patterns, which have fundamental Fourier components oriented 45° away from the edges. Detection of gratings was found to be maximally impaired when fundamental Fourier components of adaptation and test patterns were in the same orientation and minimal when edges were aligned. The orientation spread and amount of adaptation effect were similar to that found in previous experiments which employed sinusoids as adaptation and test stimuli.
The Movement Aftereffect and a Distribution-Shift Model for Coding the Direction of Visual Movement
Authors: Mather George
Published: January 2007

At present the only widely accepted explanation for the movement aftereffect is Sutherland's so-called ratio model, which states that motion is coded by taking the ratio between the outputs of detectors tuned to opposite directions. However, as yet there have been few attempts to derive predictions from the model in the context of movement aftereffects and test them experimentally. This paper reports experiments which attempt to determine whether such a simple model is sufficient, or requires additional assumptions which recast it in a form more akin to the distribution-shift models used in other domains (which assume comparisons between outputs in the whole population of direction detectors, rather than just those tuned to opposite directions). These experiments examined the interactive effects of two simultaneous directions on subsequent aftereffect durations and directions. The results obtained are difficult to explain in terms of a simple ratio model but can be incorporated into a more complex distribution-shift type model.
The Dominance of Touch by Vision: Sometimes Incomplete
Authors: Power Roderick P
Published: January 2007

It is generally agreed that, when the two senses are in conflict, vision dominates touch. In the series of experiments reported here the discrepancy between the visual and the haptic images was progressively increased. In each experiment half of the observers were adults and half children, and half of each group wore a glove which concealed the distortion produced by the lens. In experiment 1 the visual image of a haptic square was transformed by a weak or strong cylindrical lens so that the sides were in the ratio 1:1·5 or 1:1·8. Gloved observers selected a comparison image close to the visual image. Bare-handed observers gave compromise judgements with the strong lens, but judgements similar to those of the gloved observers with the weak lens. In experiment 2 the square had a visual image which was either a diamond or a parallelogram, the parallelogram having angles of 70° and 110°. Observers described and drew their percepts, which were generally in accord with the visual image. There were no significant differences due to age, a finding contrary to that of Page and Locke, nor were there differences in experiment 2 due to the gloved-hand–bare-hand dimension. It is concluded (i) that repeated observations do not destroy the effect, (ii) that considerable discrepancies between the visual and haptic images do not destroy the effect, but (iii) that feedback from a bare hand can reduce the effect when it is of considerable magnitude.
Modifications of the Classical Notion of Panum's Fusional Area
Authors: Burt Peter , Julesz Bela
Published: January 2007

It is generally believed that there is an absolute disparity limit for binocular fusion; objects with disparities within this limit, known as Panum's fusional area, will appear fused and single, while objects with disparities outside the limit appear double. It is demonstrated, however, that the disparity gradient, rather than the disparity magnitude, dictates binocular fusion when several objects occur near one another in the visual field. The disparity gradient is defined as the difference between the disparities of neighboring objects divided by their angular separation. If this ratio exceeds a critical value (∼1) then fusion does not occur, even though the absolute disparities of the individual objects may be well within the classical Panum's area. This discovery leads to the reinterpretation of several enigmatic phenomena in stereopsis, including Panum's limiting case.
Control and Sense of Eye Movement behind Closed Eyelids
Authors: Allik Jüri , Rauk Marika , Luuk Aavo
Published: January 2007

To investigate the question of what happens with regard to position sense and control of the human eyes when the eyelids are closed, the contact-wire-free electromagnetic eye movement recording method was developed. It was shown that after the start of blinking or eyelid closure, the eyball moves up as the upper eyelids come down. Experimental data show human inability to maintain a given position of the eyes in the head under the closed eyelids. When the subject was asked to follow a simple geometrical path, a very weak metrical and topological correspondence between desired and actual paths occurred with closed eyes. It is proposed that the poor control of eye movements behind closed eyelids is due to the lack of available information about eye position in the head. The assumption was confirmed by providing artificial auditory feedback about eyeball position to the subject, which can be effectively used for gaze stabilization by the subject. It is suggested that visual information is the only useful basis for eye movement regulation under normal conditions.
Vergence Eye Movements Made in Response to Spatial-Frequency-Filtered Random-Dot Stereograms
Authors: Mowforth Peter , Mayhew John E W , Frisby John P
Published: January 2007

Vergence responses were recorded from practised observers viewing narrow-band spatial-frequency-filtered planar random-dot stereograms. It was found that low spatial frequencies of 1·75–3·5 cycles deg−1 could trigger appropriate vergence responses to larger disparities than could the relatively high spatial frequency of 7·0 cycles deg−1. Nevertheless, appropriate vergence shifts were observed reliably for spatial-frequency/disparity combinations well outside the range predicted by Marr and Poggio's (1979) model of stereo vision. It was also found that for large-disparity/high-spatial-frequency combinations which the subjects could not fuse, the vergence system went into oscillation with the eyes diverging and converging at a frequency of about 1·5 Hz and with an amplitude of about 10–20 min arc. Finally, it was demonstrated that when a prominent monocular cue was superimposed upon a large-disparity/high-spatial-frequency stereogram then a speedy vergence response occurred which resulted in successful fusion. This latter finding supports the hypothesis advanced earlier that monocular cues can facilitate stereopsis by triggering appropriate vergence shifts.
Adaptation to Incomplete Flow Patterns: No Evidence for ‘Filling-In’ the Perception of Flow Patterns
Authors: Beverley Kenneth I , Regan David
Published: January 2007

Inspecting a radial flow pattern reduced visual sensitivity to changes in the size of a test square of 0·5 deg side length when the square was accurately located at the point previously occupied by the focus of the adapting flow pattern. The effect was reduced by a third when there was a 1·0 deg diameter hole at the centre of the flow pattern, and abolished when the hole was 1·5 or 2·0 deg in diameter. These findings support the idea that any depression of sensitivity in the hole is entirely due to spread of adaptation from the stimulated region, and provide no evidence for ‘filling-in’ or ‘visual-phantom’ phenomena in flow patterns.
Salt Taste Sensitivity and Stimulus Volume: Effect of Stimulus Residuals
Authors: O'Mahony Michael , Klapman Karen , Wong Joanne , Atassi Sanah
Published: January 2007

Sodium chloride (NaCl) stimulus residuals were seen to be greater after a large-volume NaCl rinse than after a small-volume rinse. Predicted changes in sensitivity dependent on adapting concentrations determined by residual levels were confirmed by signal detection R-index measures of sensitivity. R-index values were seen to be independent of the volume of the test water and NaCl stimuli used in their determination.
Anomalous Perception of Extrafoveal Motion
Authors: MacKay Donald M
Published: January 2007

Experiments are reported in which the perceived motion of an extrafoveal grating slowed down to zero and that of an extrafoveal sector disc became fragmented upon prolonged fixation.
Transfer of Learning in Transformed Random-Dot Stereostimuli
Authors: Long Nigel R
Published: January 2007

The transfer of learning between normal and monocularly-transformed small-disparity, random-dot stereostimuli has been examined under extended viewing conditions. When the disparity value was constant, transfer of learning between normal and monocularly-transformed stereostimuli was disrupted by both low-frequency and high-frequency transformations. These results suggest that stereolearning is restricted to disparity units that are selective to the same spatial-frequency characteristics.
Motion Perception in the Peripheral Visual Field
Authors: Finlay David
Published: January 2007

Literature dealing with the peripheral retina and its ‘specialization for motion detection’ is reviewed. The data at hand seem to indicate that the central retina is more ‘specialized’ for motion perception than the peripheral retina. It is clear that motion improves vision for stimuli presented peripherally.
Autokinesis and Peripheral Stimuli: Implications for Fixational Stability
Authors: Post Robert B , Leibowitz Herschel W , Shupert Charlotte L
Published: January 2007

The reduction in autokinesis of a fixated stimulus was determined as a function of the eccentricity of an identical second stimulus. When the stimuli were separated by 1 deg, autokinesis was reduced by approximately 50% but with increasing separation the attenuation was diminished. The results are interpreted in terms of fixational stability models of autokinesis. It is suggested that autokinesis as well as other examples of apparent movement result from fixational instability.
A Possible Analogy between Contours in Mathematics—As Exemplified by Cauchy's Integral Formula—And Contours in the Arts
Authors: Gerr Stanley
Published: January 2007

An attempt is made to draw an analogy between contour drawing and a particular mathematical theorem. The analogy is seen to depend on the fact that both methods use definite values along a contour to imply a totality of values within the contour; thus, the use of a part to suggest the whole, by way of a hypothetical ‘gestalt-like integration’ in the case of the art contour, and the usual process of mathematical integration in the case of Cauchy's formula. Examples illustrating the analogy are drawn from a wide range of artistic work: a modern American drawing, a Cro-Magnon cave painting, and two Chinese works. The traditional Chinese philosophy of painting is invoked in support of the analogy because of its explicit emphasis on the primacy of outline drawing in Chinese painting. Some speculations are offered on further development and application of the analogy.
Interpolation during Apparent Motion
Authors: Shaw Gordon L , Ramachandran Vilayanur S
Published: January 2007

A simple experiment was performed to demonstrate a spatiotemporal filling-in process in apparent motion. A vertical column consisting of seven closely spaced dots was presented in a sequence of eight discrete positions, except for the fifth position in which only part of the column (upper two dots) was shown. At an appropriate timing of this repeated sequence no partial gap could be discerned. A sequence of at least two complete columns on either side of the partial column is necessary for this filling-in to occur. This implies that the visual system must be integrating information over several frames and that the result of this computation influences the perception of subsequent spatially adjacent frames.
Metaphor in Pictures
Authors: Kennedy John M
Published: January 2007

Pictures can be literal or metaphoric. Metaphoric pictures involve intended violations of standard modes of depiction that are universally recognizable. The types of metaphoric pictures correspond to major groups of verbal metaphors, with the addition of a class of pictorial runes. Often the correspondence between verbal and pictorial metaphors depends on individual features of objects and such physical parameters as change of scale. A more sophisticated analysis is required for some pictorial metaphors, involving juxtapositions of well-known objects and indirect reference.
Configurational Differences in Stereovision
Authors: Bacon Joshua , Wallach Hans
Published: January 2007

Retinal disparities which produce perceived depth in stereoscopic vision result from configurational differences in the retinal images in the two eyes of objective three-dimensional arrangements. Experiments reported earlier demonstrated special effectiveness of differences in the alignment in the vertical dimensions of the images of points that are at different depth. Here a stereoscopic experiment is reported where alignment differences were increased without altering disparity. An increase in perceived depth resulted and was measured by estimation and by matching. The reason for the special effectiveness of binocular alignment differences is discussed.
The Multiple Determination of Illusory Contours: 2. An Empirical Investigation
Authors: Halpern Diane F , Salzman Billie , Harrison Wayne , Widaman Keith
Published: January 2007

Judgments of contour strength or saliency for twenty-four illusory-contour configurations were subjected to a confirmatory factor analysis. A four-factor model that posited the involvement of simultaneous contrast, linear effects (assimilation and dissimilation), depth/completion cues, and feature analyzers accounted for a substantial proportion of the variance in judgments of illusory-contour strength. The hierarchical addition of a fifth factor, diffuse illusory contours, significantly improved the overall fit of the model, but added little to the proportion of explained variance. The taxonomic approach adopted provides support for a multiprocess model of illusory-contour perception.
Haptic Dominance in Form Perception with Blurred Vision
Authors: Heller Morton A
Published: January 2007

Three experiments are reported in which subjects were exposed to discrepant visual and haptic form information. Stained glass was used to blur vision and lower its accuracy close to the level of touch. Haptic dominance occurred with the large intersensory conflicts under study. It is proposed that touch may be dominant in form perception when vision is peripheral and blurry.
Perception of Lightness and Illumination in a World of One Reflectance
Authors: Gilchrist Alan , Jacobsen Alan
Published: January 2007

Observers looked into a miniature room in which everything was painted matte white, or—in another room—matte black. They made both reflectance and illumination judgments for eight test spots. The test spots (which varied in luminance) were perceived as approximately equal in reflectance—not different, as conventional contrast theories would seem to require. The illumination matches made to the same points, however, closely paralleled the pattern of actual illumination levels, and this result is discussed as evidence that edges are classified as changes in either reflectance or illumination. The white room was correctly perceived as white, and the black room was perceived as middle gray; similar results were obtained even when the luminances in the black room were higher (owing to higher illumination) than the corresponding luminances in the white room. An explanation in terms of differences in gradient patterns is presented and supported with luminance profiles.
A Counterexample to the Rigidity Assumption in the Visual Perception of Structure from Motion
Authors: Braunstein Myron L , Andersen George J
Published: January 2007

It has been proposed that the human visual system prefers perceptions of objects that are rigid or undergo minimum form change. A counterexample is presented in which a rigid two-dimensional figure rotating in the frontal plane is perceived as a distorting three-dimensional shape. It is argued that this perception results from the stimulation of automatic processes for perceiving size change, and that these processes are not subject to a general rigidity assumption.
The Waggon-Wheel Effect
Authors: Finlay David , Dodwell Peter , Caelli Terry
Published: January 2007

The waggon-wheel effect was studied by use of three wheels with different numbers of spokes (4, 8, 16) and a wide range of strobe temporal frequencies. The results obtained are discussed in terms of a model in which: (i) nearest-neighbour relationships predict the direction and speed of movement, (ii) persistence and masking occur over ranges consistent with values reported in the literature, (iii) apparent motion is generated between currently illuminated spokes and persisting images of spokes, (iv) duration of spoke illumination (sweep) is a determining factor and, (v) a top-down process finds the best fit (a sort of ‘simple structure’) for the complex spatiotemporal display.
Discrimination of Velocities and Mechanisms of Motion Perception
Authors: Bonnet Claude
Published: January 2007

In a first experiment, velocity discrimination thresholds were measured in twenty-one experimental conditions by presentation of successive pairs of standard/comparison motions of a single spot target. Exposure times between 300 to 900 ms did not affect velocity discrimination. However, very slow velocity increased discrimination thresholds. Velocity discrimination is improved by the presence of stationary references and decreased by eccentricity. At slow velocities, in the absence of a motion phase, a discrete mode of presentation of the translation leads to higher discrimination thresholds than those observed with the continuous and stop-go-stop modes of the same translation. In a second experiment, it was shown that for shorter exposure time (100 ms), discrimination thresholds are much higher for the discrete mode. It is concluded that at long exposure time, velocity discrimination thresholds are essentially independent of the presence of a motion phase.
Piagetian Stage IV Search Errors with an Object That is Directly Accessible Both Visually and Manually
Authors: Bremner J Gavin , Knowles Linda S
Published: January 2007

Previous work has shown that infants make the Piagetian stage IV error when the object is covered by a transparent occluder. However, it is not clear whether this happens because nine-month-old infants' failure to understand the identity of hidden objects extends to visible objects, or whether they are puzzled by object relationships involving transparency. Nine-month-old infants were presented with one of three different stage IV tasks in which the object was visible and uncovered at the second location. Stage IV errors were obtained with the object visible, but only when a covered place was provided at the first location. It is concluded that this result is stronger evidence that the stage IV error is not simply a hidden-object phenomenon, and that it may be best explained by taking account of infants' functional place knowledge, as well as their knowledge of object identity.