Adaptation in the constancy of visual direction tested by measuring the constancy of auditory direction

Modification of the constancy of visual direction was produced by partially adapting Ss to the displacements of the visual field caused by magnifying lenses during 1 h of continuous head turning. The adaptation effects were measured by determining the range of perceived target immobility before and after this adaptation period. A method for measuring the range of apparent immobility of an auditory signal during head movements was developed and employed to test whether a modification of the constancy of visual direction transfers to the constancy of auditory direction. No such transfer was found, and it was concluded that a modification of the constancy of visual direction does not consist in an altered evaluation of kinesthetic cues for head turning. The method and the equipment used in the investigation of the constancy of visual direction are described; knowledge of the previous brief publications on this topic is not needed.     

Two kinds of adaptation in the constancy of visual direction

Adaptation in the constancy of visual direction had previously been obtained by causing a large or a small visible area representing the environment to be objectively displaced in dependence on head movements. No stationary objects were permitted to be visible. Now experiments are reported in which displacements of a large patterned field, with the subject fixating a stationary mark in its center, led to adaptation. In these experiments, objective displacements of the environment were given by image displacements on the retina. Adaptation also resulted when the large field was stationary and only the fixation mark was displaced. Here the objective displacement was given by the rate of pursuit eye movements.     

Visual tracking and existence constancy in 5-month-old infants

Visual fixation and cardiac deceleration for 36 infants 20–24 weeks old were recorded during three kinds of events in which objects moving on a linear trajectory were temporarily occluded by a screen: (1) a familiar object appeared on both sides of the screen; (2) a novel object appeared on both sides of the screen; and (3) a novel object appeared to change to a familiar one behind the screen. Infant attention was related to novelty and familiarity of objects and there was no evidence of behavior reflecting the expectancy that a stable object continued to exist behind the screen. These findings are in conflict with those of previous tracking studies and the discussion focuses upon explanations for this discrepancy.     

Adaptation in the constancy of visual direction measured by a one-trial method

Adaptation to field displacement during head movements in the direction with the head rotation and in the direction against it was produced under otherwise identical conditions and compared; the field displacement rate was also varied. A rapid training procedure was used, and a novel one-trial test was employed that could measure the adaptation well enough to compare the effects of various training conditions. The one-trial test measured the magnitude of one of the manifestations of adaptation, the apparent displacement of a stationary target during head movements. This apparent horizontal target displacement was transformed into an oblique one by having the head movements that brought forth the apparent target displacement simultaneously cause an objective vertical target displacement. The slant of the resultant apparent motion path varied with the magnitude of the apparent horizontal target displacement. It was measured by having S reproduce its slant angle. It was found that adaptation to field displacement in the direction with the head rotation was consistently greater than adaptation to the opposite displacement conditions. An explanation for this result is offered.     

Visual search asymmetry for viewing direction

In visual search experiments, we examined the existence of a search asymmetry for the direction with which three-dimensional objects are viewed. It was found that an upward-tilted target object among downward-tilted distracting objects was detected faster than when the orientation of target and distractors was reversed. This indicates that the early visual process regards objects tilted downward with respect to the observer as the situation that is more likely to be encountered. That is, the system is set up to expect to see the tops of these objects. We also found a visual field anisotropy, in that the asymmetry was more pronounced in the lower visual field. These findings are consistent with the idea that the tops of objects are usually situated in the lower visual field and less often in the upper field. Examination of the conditions under which the asymmetry and the anisotropy occur demonstrated the importance of the three-dimensional nature of the stimulus objects. Early visual processing thus makes use of heuristics that take into account specific relationships between the relative locations in space of the observer and 3-D objects.     

Achieving visual object constancy across plane rotation and depth rotation.

Visual object constancy is the ability to recognise an object from its image despite variation in the image when the object is viewed from different angles. I describe research which probes the human visual system's ability to achieve object constancy across plane rotation and depth rotation. I focus on the ecologically important case of recognising familiar objects, although the recognition of novel objects is also discussed. Cognitive neuropsychological studies of patients with specific deficits in achieving object constancy are reviewed, in addition to studies which test neurally intact subjects. In certain cases, the recognition of invariant features allows objects to be recognised irrespective of the view depicted, particularly if small, distinctive sets of objects are presented repeatedly. In contrast, in most situations, recognition is sensitive to both the view in-plane and in-depth from which an object is depicted. This result suggests that multiple, view-specific, stored representations of familiar objects are accessed in everyday, entry-level visual recognition, or that transformations such as mental rotation or interpolation are used to transform between retinal images of objects and view-specific, stored representations.     

Visual recognition memory across contexts

In two experiments, we investigated the development of representational flexibility in visual recognition memory during infancy using the Visual Paired Comparison (VPC) task. In Experiment 1, 6- and 9-month-old infants exhibited recognition when familiarization and test occurred in the same room, but showed no evidence of recognition when familiarization and test occurred in different rooms. In contrast, 12- and 18-month-old infants exhibited recognition irrespective of testing room. Thus, flexibility across a change of room was observed at a younger age than flexibility across a change of background that has previously been seen with the VPC procedure (Robinson & Pascalis, 2004). To determine if limitations in representational flexibility across a change of background could be overcome by experiences during encoding, in Experiment 2, 6-, 9-, 12- and 18-month-old infants were familiarized with a picture on multiple backgrounds. At all ages, infants showed recognition across a change in background at test. These findings indicate that dissociating an item from its context during encoding may be an important factor in understanding the representational flexibility of visual recognition memory in infancy. Developmental changes in representational flexibility are likely driven by changes in the functional maturity of the hippocampal formation, and experience.     

Target distance and adaptation in distance perception in the constancy of visual direction

Hay and Sawyer recently demonstrated that the constancy of visual direction (CVD) also operates for near targets. A luminous spot in the dark, 40 cm from the eyes, was perceived as stationary when S nodded his head. This implies that CVD takes target distance, as well as head rotation, into account as a stationary environment is perceived during head movements. Distance is a variable in CVD because, during a turning or nodding of the head, the eyes become displaced relative to the main target direction, the line between the target and the rotation axis of the head. This displacement of the eyes during head rotation causes an additional change in the target direction, i.e., a total angular change greater than the angle of the head rotation. The extent of this additional angular displacement is greater the nearer the target. We demonstrated that the natural combination of accommodation and convergence can supply the information needed by the nervous system to compensate for this additional target displacement. We also found that wearing glasses that alter the relation between these oculomotor adjustments and target distance produces an adaptation in CVD. An adaptation period of 1.5 h produced a large adaptation effect. This effect was not entirely accounted for by an adaptation in distance perception. Measurements of the alteration between oculomotor cues and registered distance with two kinds of tests for distance perception yielded effects significantly smaller than the effect measured with the CVD test. We concluded that the wearing of the glasses had also produced an adaptation within CVD.     

Visual marking across eye blinks

Visual search for a conjunction target can be made efficient by presenting one initial set of distractors as a preview, prior to the onset of the other items in the search display Watson & Humphreys (Psychological Review 104:90–122, 1997). However, this “preview advantage” is lost if the initial items are offset for a brief period before onsetting again with the search display Kunar, Humphreys, & Smith (Psychological Science 14:181–185, 2003). Researchers have long disputed whether the preview advantage reflects a process of internally coding and suppressing the old items or of the onset of the new items capturing attention Donk & Theeuwes (Perception & Psychophysics 63:891–900, 2001). In this study, we assessed whether an internally driven blink (in which participants close their eyes) acts in the same manner as an external blink produced by offsetting and then onsetting the preview. In the novel blink conditions, participants searched feature, conjunction, and preview displays after being cued to blink their eyes. The search displays were presented during the eye blink, and so were immediately available once participants opened their eyes. Having participants make an eye blink generally slowed search but had no effect on the search slopes. In contrast, imposing an externally driven blink disrupted preview search. The data indicated that visual attention can compensate for internally driven blinks, and this does not lead to the loss of the representations of distractors across time. Moreover, efficient preview search occurred when the search items had no abrupt onsets, demonstrating that onsets of new search items are not critical for the preview benefit.     

Reflex eyeblinks and visual suppression

Voluntary blinks are known to be accompanied by visual suppression that arises, at least in part, through nonretinal processes. We wanted to test the hypothesis that this suppression must arise as a corollary to the voluntary command to blink. We therefore examined visual sensitivity at the time of a blink that does not involve a voluntary command, namely the corneal reflex elicited by a puff of air. We found that sensitivity was reduced during these reflex blinks; the magnitude and time course of suppression were similar to those of voluntary blinks. We therefore adopt the view that visual suppression stems from signals from the common, efferent, blink pathway.     

Voluntary eyeblinks disrupt iconic memory

In the present research, we investigated whether eyeblinks interfere with cognitive processing. In Experiment 1, the participants performed a partial-report iconic memory task in which a letter array was presented for 106 msec, followed 50, 150, or 750 msec later by a tone that cued recall of onerow of the array. At a cue delay of 50 msec between array offset and cue onset, letter report accuracy was lower when the participants blinked following array presentation than under no-blink conditions; the participants made more mislocation errors under blink conditions. This result suggests that blinking interferes with the binding of object identity and object position in iconic memory. Experiment 2 demonstrated that interference due to blinks was not due merely to changes in light intensity. Experiments 3 and 4 demonstrated that other motor responses did not interfere with iconic memory. We propose a new phenomenon, cognitive blink suppression, in which blinking inhibits cognitive processing. This phenomenon may be due to neural interference. Blinks reduce activation in area V1, which may interfere with the representation of information in iconic memory.     

Adaptation to field displacement during head movement unrelated to the constancy of visual direction

Adaptation to vertical field displacements dependent on head turning about a vertical axis was demonstrated under two conditions, rapid training with 100 head movements and 1-h-long training with continuous head turning. The effect of rapid training was measured with the slant estimation method. Adaptation after the longer training was ascertained by comparing the uncertainty ranges for apparent target immobility before and after the adaptation period. Adaptation to field displacements in directions parallel to the plane of the head rotation obtained under corresponding conditions was also measured and found to be somewhat greater than adaptation to vertical field displacements. The result of work by Wallach and Frey that adaptation to field displacement in the direction with the head rotation is greater than to displacement against it was corroborated. While the previous result had, been obtained with rapid adaptation and with the slant estimation method, we confirmed it with 1-h training and by measuring the uncertainty ranges before and after the adaptation period.     

Visual search across the life span

Gains and losses in visual search were studied across the life span in a representative sample of 298 individuals from 6 to 89 years of age. Participants searched for single-feature and conjunction targets of high or low eccentricity. Search was substantially slowed early and late in life, age gradients were more pronounced in conjunction than in feature search, and all age groups were uniformly affected by eccentricity manipulations. However, developmental and aging trends were distinctly asymmetrical: Children's performance was particularly affected by the mere presence of distractors; whereas in late life, performance was particularly impaired on target-absent trials and with increasing numbers of distractors. The implications for life span theories of cognitive and attentional development and for cognitive-speed and inhibitory-control accounts are discussed.     

Two kinds of adaptation in the constancy of visual direction and their different effects on the perception of shape and visual direction

Adaptation in the constancy of visual direction can be obtained under two radically different conditions, called eye-movement adaptation and field adaptation. Adaptation resulting from these conditions and from a “normal” condition was measured with a newly developed estimation test. Eye-movement adaptation was found to cause an alteration of compensatory eye movements. It apparently consists of a changed evaluation of eye movements, as demonstrated by two different pointing tests. A form test where the shape of a large oblong is set to look square also confirmed this interpretation. After field adaptation, a pointing test did not register a change, but an adaptation effect could be measured with a forward direction test. This test and a square test where no eye movements were permitted proved to be specific to field adaptation; they measured no effect after eye-movementadaptation. The normal adaptation condition Was apparently equivalent to the eye-movement adaptation condition. Its effect could be measured only with a pointing test. When we changed the normal adaptation condition so that frequent saccades were made during head turning, strong effects were measured with the two tests that were specific to field adaptation.     

Auditory color constancy: Calibration to reliable spectral properties across nonspeech context and targets

Brief experience with reliable spectral characteristics of a listening context can markedly alter perception of subsequent speech sounds, and parallels have been drawn between auditory compensation for listening context and visual color constancy. In order to better evaluate such an analogy, the generality of acoustic context effects for sounds with spectral-temporal compositions distinct from speech was investigated. Listeners identified nonspeech sounds—extensively edited samples produced by a French horn and a tenor saxophone—following either resynthesized speech or a short passage of music. Preceding contexts were “colored” by spectral envelope difference filters, which were created to emphasize differences between French horn and saxophone spectra. Listeners were more likely to report hearing a saxophone when the stimulus followed a context filtered to emphasize spectral characteristics of the French horn, and vice versa. Despite clear changes in apparent acoustic source, the auditory system calibrated to relatively predictable spectral characteristics of filtered context, differentially affecting perception of subsequent target nonspeech sounds. This calibration to listening context and relative indifference to acoustic sources operates much like visual color constancy, for which reliable properties of the spectrum of illumination are factored out of perception of color.     

Spontaneous eyeblinks elicited by vertical eye movements

Two experiments were carried out to examine the relationship between eyeblinks and eye movements under a visual search task. Exp. I showed that the vertical eye movements brought about slightly more eyeblinks than the horizontal ones. In Exp. II, the vertical eye movements were accompanied with significantly more frequent eyeblinks than the horizontal ones. Upward saccadic eye movements especially were associated with the more frequent eyeblinks than the downward ones. These results suggested a possible relationship between the eyeblinks and Bell's phenomenon. However, the comparison of eyeblink rates between eye-movement and the no-eye-movement conditions in Exp. II indicated that in the latter condition eyeblinks were significantly more frequent than in the former condition. Some psychological factors were suggested as likely important determinants of the frequency of eyeblinks.     

Expectancy for airpuff and conditioned eyeblinks in humans

Three experiments were designed to test the hypothesis that expectancy for an unconditioned stimulus (US) serves as an intervening variable in the well-documented empirical relationship between the awareness of stimulus contingencies and the occurrence of conditioned reactions (CR) in human classical conditioning. Experiment 1 showed that, when subjects are instructed to respond by keypressing to US in a conditioning-like procedure, reaction (RT) provides the same kind of information as a direct rating of expectancy. In experiment 2, the RT task was superimposed on an otherwise standard eyeblink conditioning procedure. Reliable discriminative conditioning failed to occur, although changes in RT give evidence of increasing expectancy for US. Experiment 3 aimed to repeat experiment 2 with several modifications in procedure, intended to facilitate conditioning. The between-subjects correlation between RT to US and frequency of eyeblink CRs was reasonably high (-0.52). However, when consecutive trials were considered, a shift was apparent between the two variables: RT changes occurred earlier than CR development. The implications of these results with respect to the expectancy theory of conditioning are discussed.     

Simultaneity constancy

Sound and light take different amounts of time to reach their respective receptors, to be transduced, and to be transmitted to the cortex. Their processing times also vary with factors such as intensity and retinal eccentricity. We assessed the capability of subjects to perceive simultaneity correctly despite these variations. Temporal asynchronies of up to 200 ms were introduced between the components of sound/light pairs. Using the method of constant stimuli, seven subjects judged which came first. Distance, and hence the times of arrival of paired visual and auditory targets, was varied from 1 to 32 m. Visual intensity was varied by viewing the target through 1.8 dB attenuating glasses, and a retinal eccentricity of 20 degrees was compared to central presentation. Despite large differences in reaction times, which varied in a predictable way with the stimulus parameters, the timing of sound/light pairings judged as simultaneous corresponded to when the light and sound left the source simultaneously. Almost complete compensation was found in all conditions tested, showing that these substantial but predictable variations in timing can be taken into account in creating simultaneity constancy.     

On the relation of adaptation to field displacement during head movements to the constancy of visual direction

When the normal constancy process on which the apparent immobility of the visualfield during head movements is based was strengthened by the same method that produces adaptation to abnormal conditions in the constancy of visual direction, and when this training of the normal constancy process immediately preceded experimental adaptation, the effectiveness of the latter was diminished. This result applied not only to adaptation to horizontal field displacement and to vertical field displacement during turning of the head, but also to vertical field displacement during nodding of the head, a condition to which adaptation was here demonstrated for the first time.