Sensorimotor expectations and the visual field

Sensorimotor expectations concern how visual experience covaries with bodily movement. Sensorimotor theorists argue from such expectations to the conclusion that the phenomenology of vision is constitutively embodied: objects within the visual field are experienced as 3-D because sensorimotor expectations partially constitute our experience of such objects. Critics argue that there are (at least) two ways to block the above inference: to explain how we visually experience objects as 3-D, one may appeal to such non-bodily factors as (1) expectations about movements of objects, not the perceiver, or to (2) the role of mental imagery in visual experience. But instead of using sensorimotor expectations to explain how objects are experienced within the visual field, we can instead use them to explain our experience of the visual field itself and, in particular, our experience of its limits; that is, our ever-present visual sense of there being more to see, beyond what’s currently within the visual field. Crucially, this inference from sensorimotor expectations to the constitutive embodiment of visual phenomenology is not threatened by the above two challenges. I thus present here a sensorimotor theory of the phenomenology of the visual field, that is, our experience of our visual fields as such.

     

Functional visual field in a rapid serial visual presentation task

Dynamic temporal change in the size of functional visual field was measured using a dual task: a peripheral task in which one square in a background pattern of squares was changed in shape to a dot; and a central task involving the rapid serial visual presentation of a sequence of letters (RSVP task). The temporal lag between the occurrences of the dot and the RSVP target was manipulated. University students were asked to detect the dot and to depress a mouse button as quickly as possible while searching for the RSVP target among a sequence of distracter letters. The abrupt change in the shape of a background square in the peripheral task caused a processing deficit in the RSVP task at relative lags from –3 to –1 (255 ms to 85 ms before presentation of the RSVP target), but the encoding and retaining processes involved in identifying the RSVP target did not impair the detection of the peripheral dot. The functional visual field was found to expand while participants were performing the dual task, suggesting that preattentive detection is affected by general attentional activity.     

Dynamic visual capture: apparent auditory motion induced by a moving visual target

Apparent motion of a sound source can be induced by a moving visual target. The direction of the perceived motion of the sound source is the same as that of the visual target, but the subjective velocity of the sound source is 25-50% of that of the visual target measured under the same conditions. Eye tracking of the light target tends to enhance the apparent motion of the sound, but is not a prerequisite for its occurrence. The findings are discussed in connection with the 'visual capture' or 'ventriloquism' effect.     

Measurement of the visual field

There is increasing evidence that concurrent visual and nonvisual tasks not only reduce the size but also result in systematic deformation of the visual field. Given such complex changes in the visual field, appropriate representation and measurement of its shape is all important. Shape measures utilized by researchers and reported in the literature should also be sufficiently standardized to allow comparison of results across experiments.     

Visual field asymmetries and allocation of attention in visual scenes

Single items such as objects, letters or words are often presented in the right or left visual field to examine hemispheric differences in cognitive processing. However, in everyday life, such items appear within a visual context or scene that affects how they are represented and selected for attention. Here we examine processing asymmetries for a visual target within a frame of other elements (scene). We are especially interested in whether the allocation of visual attention affects the asymmetries, and in whether attention-related asymmetries occur in scenes oriented out of alignment with the viewer. In Experiment 1, visual field asymmetries were affected by the validity of a spatial precue in an upright frame. In Experiment 2, the same pattern of asymmetries occurred within frames rotated 90 degrees on the screen. In Experiment 3, additional sources of the spatial asymmetries were explored. We conclude that several left/right processing asymmetries, including some associated with the deployment of spatial attention, can be organized within scenes, in the absence of differential direct access to the two hemispheres.     

The vista paradox: a natural visual illusion

Suppose an observer views a distant object through a window in the far wall of a room or corridor--a visual scene constituting a vista. If the observer moves toward the window, then the distant object will shrink in apparent size and appear farther away. These effects are paradoxical, because the distant object appears smaller as its visual angle increases. The vista paradox occurs under many other real-world conditions, such as viewing a distant object while moving out of the mouth of a valley, or driving across a topographic crest. In the present study, framing effects and the equidistance tendency are considered as possible factors. However, an explanation based on the dynamic relationship between the visual angle of the framing portion of a vista and the visual angle of a distant object appears more promising.     

The differential contributions of visual imagery constructs on autobiographical thinking

There is a growing theoretical and empirical consensus on the central role of visual imagery in autobiographical memory. However, findings from studies that explore how individual differences in visual imagery are reflected on autobiographical thinking do not present a coherent story. One reason for the mixed findings was suggested to be the treatment of visual imagery as an undifferentiated construct while evidence shows that there is more than one type of visual imagery. The present study investigates the relative contributions of different imagery constructs; namely, object and spatial imagery, on autobiographical memory processes. Additionally, it explores whether a similar relation extends to imagining the future. The results indicate that while object imagery was significantly correlated with several phenomenological characteristics, such as the level of sensory and perceptual details for past events – but not for future events – spatial imagery predicted the level of episodic specificity for both past and future events. We interpret these findings as object imagery being recruited in tasks of autobiographical memory that employ reflective processes while spatial imagery is engaged during direct retrieval of event details. Implications for the role of visual imagery in autobiographical thinking processes are discussed.     

Name and face matching in one or two visual fields: a test of models of hemispheric specialization

In two experiments a name and a face (each male or female) were simultaneously flashed to either the same or opposite visual fields (left or right), for matching congruent (same sex) or incongruent (opposite sex), to test the predictions of various models of hemispheric specialization. While overall best performance occurred with a face in the left visual field (LVF) and a name in the right visual field (RVF), and worst with the opposite configuration, the general pattern of results was incompatible with either a direct access model or an activational/attentional account. The results were, however, most compatible with the predictions of a semispecialized hemispheres account, whereby cerebral asymmetries are seen as relative rather than absolute, either hemisphere being capable of processing either kind of material (verbal or visuospatial), but to different levels of efficiency. However, despite the fact that the stimulus materials had previously been shown to produce stable and consistent lateral asymmetries in the predicted directions when presented in isolation, in the composite, integrative matching task the position of the name seemed to be the major determinant of the resultant asymmetries. It would seem therefore that when such stimuli are to be cross matched, either left hemisphere (language) processes somehow dominate right hemisphere (visuospatial) processing (though not in the way that would be predicted by a simple activational/attentional account) or the left hemisphere's greater capacity predominates.     

A device for inverting the visual field of animals

A device for inverting the visual field of small animals is described. Binocular lenses are mounted in a lightweight, aluminum frame which, in turn, is secured to a surgically attached, dental acrylic skull cap. The construction of the device, and its usefulness when simultaneous electrophysiological recordings are desired, is described by illustrating the details of fabricating such a device for a cat.     

Evaluating a split processing model of visual word recognition: effects of orthographic neighborhood size

The split fovea theory proposes that visual word recognition of centrally presented words is mediated by the splitting of the foveal image, with letters to the left of fixation being projected to the right hemisphere (RH) and letters to the right of fixation being projected to the left hemisphere (LH). Two lexical decision experiments aimed to elucidate word recognition processes under the split fovea theory are described. The first experiment showed that when words were presented centrally, such that the initial letters were in the left visual field (LVF/RH), there were effects of orthographic neighborhood, i.e., there were faster responses to words with high rather than low orthographic neighborhoods for the initial letters ('lead neighbors'). This effect was limited to lead-neighbors but not end-neighbors (orthographic neighbors sharing the same final letters). When the same words were fully presented in the LVF/RH or right visual field (RVF/LH, Experiment 2), there was no effect of orthographic neighborhood size. We argue that the lack of an effect in Experiment 2 was due to exposure to all of the letters of the words, the words being matched for overall orthographic neighborhood count and the sub-parts no longer having a unique effect. We concluded that the orthographic activation found in Experiment 1 occurred because the initial letters of centrally presented words were projected to the RH. The results support the split fovea theory, where the RH has primacy in representing lead neighbors of a written word.     

Immediate spatial distortions of pointing movements induced by visual landmarks

We tested the influence of two horizontally aligned visual landmarks on pointing movements to memorized targets, to investigate whether the visuomotor system can make use of an egocentric representation unaffected by visual context. The endpoints of pointing movements were systematically distorted toward the nearest visual landmark, indicating that spatial representations included both target and nontarget information. These distortions were not due to the presence of the landmarks during the movement but, rather, to their presence in the encoding phase. Qualitatively similar distortions were present even with the shortest possible retention phase, when the target was extinguished at movement onset. Finally, we found the same pattern of distortion when participants were forced to remember the target within an allocentric frame of reference. We argue that even early memory representations for pointing movements are influenced by visual information in the surrounding visual field.     

Cueing attention by relative motion in the periphery of the visual field

Sudden changes of visual stimulation attract attention. The observer's body motion generates retinal-flow field patterns containing information about his/her own speed and trajectory and relative motion of other objects. We investigated the effectiveness of relative motion as an attentional cue and compared it with conventional cueing by appearance of a frame in the far periphery of the visual field. In a group of ten subjects, contrast thresholds for the perception of static Gabor grating orientation [four alternative non-forced-choice (4ANFC)] task were determined at 20 degrees, 30 degrees, 40 degrees, and 60 degrees eccentricity. Subsequently, near-threshold discrimination performance of Gabor pattern orientation without versus with a ring-shaped cue was measured at the same positions. The same Gabor patterns were then presented embedded in a random-dot flow field, and uncued discrimination performance was compared with performance after presentation of a relative-motion cue (RMC), ie a small random-dot field with motion in the opposite direction of the flow field. Both the conventional ring cue and the RMC induced significantly increased discrimination performance at all test locations. With the parameters chosen for this study, the RMC was slightly less effective than the conventional cue, but its effects were somewhat more pronounced in the far periphery of the visual field. Thus, relative motion is a powerful cue to attract attention to peripheral visual objects and improves performance as effectively as a conventional ring cue. The findings have practical relevance for everyday life, in particular for tasks like driving and navigation.     

The interplay between nonsymbolic number and its continuous visual properties

To date, researchers investigating nonsymbolic number processes devoted little attention to the visual properties of their stimuli. This is unexpected, as nonsymbolic number is defined by its visual characteristics. When number changes, its visual properties change accordingly. In this study, we investigated the influence of different visual properties on nonsymbolic number processes and show that the current assumptions about the relation between number and its visual characteristics are incorrect. Similar to previous studies, we controlled the visual cues: Each visual cue was not predictive of number. Nevertheless, participants showed congruency effects induced by the visual properties of the stimuli. These congruency effects scaled with the number of visual cues manipulated, implicating that people do not extract number from a visual scene independent of its visual cues. Instead, number judgments are based on the integration of information from multiple visual cues. Consequently, current ways to control the visual cues of the number stimuli are insufficient, as they control only a single variable at the time. And, more important, the existence of an approximate number system that can extract number independent of the visual cues appears unlikely. We therefore propose that number judgment is the result of the weighing of several distinct visual cues. (PsycINFO Database Record (c) 2012 APA, all rights reserved).     

The potentiation of grasp types during visual object categorization

The close integration between visual and motor processes suggests that some visuomotor transformations may proceed automatically and to an extent that permits observable effects on subsequent actions. A series of experiments investigated the effects of visual objects on motor responses during a categorisation task. In Experiment 1 participants responded according to an object's natural or manufactured category. The responses consisted in uni-manual precision or power grasps that could be compatible or incompatible with the viewed object. The data indicate that object grasp compatibility significantly affected participant response times and that this did not depend upon the object being viewed within the reaching space. The time course of this effect was investigated in Experiments 2–4b by using a go-nogo paradigm with responses cued by tones and go-nogo trials cued by object category. The compatibility effect was not present under advance response cueing and rapidly diminished following object extinction. A final experiment established that the compatibility effect did not depend on a within-hand response choice, but was at least as great with bi-manual responses where a full power grasp could be used. Distributional analyses suggest that the effect is not subject to rapid decay but increases linearly with RT whilst the object remains visible. The data are consistent with the view that components of the actions an object affords are integral to its representation.     

Changes of visual fields in intracranial tumors outside the cerebral hemispheres]

Based on neurosurgical material of 1,746 brain tumours, the changes of the visual field determined by isopteric perimetry are discussed with their significe with regard to tumours of corpus callosum, lateral ventricles, brain stem ganglia, IIIrd ventricle, region of the sella and adjacent areas as well as posterior fossa. The proportion of unilateral blindness with primary opticus atrophy and of skotomas is strinkingly high, so that in cases of loss of vision, not readily explicable by ophthalmology, as well as in unilateral defects of the visual field, intracranial processes must be thought of.     

Position in the visual field and spatial expansion

Measurements of the tilt illusion by parallelism matches have taken as their baseline data estimates of parallelism between two lines. This is because Carpenter and Blakemore and others found in this situation that parallel lines appeared to diverge at their upper ends. It was hypothesised that this effect was due to inappropriate constancy scaling-the parallel lines being interpreted as being located in a receding plane-and that consequently it was inappropriate to take this effect into account in assessing the degree of the tilt illusion. To test the theory, a horizontal line was compared with other horizontal and vertical lines lower down in the visual field. A tendency to underestimate the length of lines lower down in the visual field was found but this varied inversely with distance from the standard. The findings were accounted for on the assumption that the occurrence of inappropriate constancy scaling depended upon prior organization by contiguity which determined whether the two lines were taken as a group or not.     

Interaction of cognitive and sensorimotor maps of visual space

Studies of saccadic suppression and induced motion have suggested separate representations of visual space for perception and visually guided behavior. Because these methods required stimulus motion, subjects might have confounded motion and position. We separated cognitive and sensorimotor maps without motion of target, background, or eye, with an “induced Roelofs effect”: a target inside an off-center frame appears biased opposite the direction of the frame. A frame displayed to the left of a subject’s center line, for example, will make a target inside the frame appear farther to the right than its actual position. The effect always influences perception, but in half of our subjects it did not influence pointing. Cognitive and sensorimotor maps interacted when the motor response was delayed; all subjects now showed a Roelofs effect for pointing, suggesting that the motor system was being fed from the biased cognitive map. A second experiment showed similar results when subjects made an open-ended cognitive response instead of a five-alternative forced choice. Experiment 3 showed that the results were not due to shifts in subjects’ perception of the felt straight-ahead position. In Experiment 4, subjects pointed to the target and judged its location on the same trial. Both measures showed a Roelofs effect, indicating that each trial was treated as a single event and that the cognitive representation was accessed to localize this event in both response modes.     

Reexamining the possible benefits of visual crowding: dissociating crowding from ensemble percepts

Peripheral objects and their features become indistinct when closely surrounding but nonoverlapping objects are present. Most models suggest that this phenomenon, called crowding, reflects limitations of visual processing, but an intriguing idea is that it may be, in part, adaptive. Specifically, the mechanism generating crowding may simultaneously facilitate ensemble representations of features, leaving meaningful information about clusters of objects. In two experiments, we tested whether visual crowding and the perception of ensemble features share a common mechanism. Observers judged the orientation of a crowded bar, or the ensemble orientation of all bars in the upper and lower visual fields. While crowding was predictably stronger in the upper relative to the lower visual field, the ensemble percept did not vary between the visual fields. Featural averaging within the crowded region does not always scale with the resolution limit defined by crowding, suggesting that dissociable processes contribute to visual crowding and ensemble percepts.     

Cross-modal correlation of auditory and visual language laterality tasks: a serendipitous finding

Two experiments were conducted to investigate whether auditory and visual language laterality tasks test the same brain processes for verbal functions. In the first experiment, 48 undergraduate students (24 males, 24 females) completed both an auditory monitoring task and a visual monitoring task, with the Waterloo Handedness Questionnaire administered between the two tasks. The visual task was an analogue of the dichotic listening task used. It was hypothesized that a significant cross-modal correlation would be found, indicating that the dichotic listening task and the visual analogue task do, in fact, test the same brain processes for verbal functions. Results revealed a right ear advantage in the auditory task, a left visual field advantage (LVFA) in the visual task, and a cross-modal correlation of asymmetries of -.09. The LVFA observed in the visual task was replicated in Experiment 2, thus establishing its legitimacy. Results are discussed in relation with the type of processing that might produce such an unexpected finding on the visual task.     

The perception of verticality and the frame of reference of the visual tilt aftereffect

Previous research has suggested that the visual tilt aftereffect operates according to a gravitational frame of reference. Three experiments were conducted to test this conclusion further. In each experiment, observers (with head upright) adjusted an illuminated bar to apparent vertical following various adaptation conditions. In Experiment 1, observers were given clear visual cues for objective vertical while adjusting the bar. In Experiment 2, they were not given visual cues for vertical. The adaptation conditions in Experiments 1 and 2 consisted of various combinations of head and stimulus tilt. Experiment 3 investigated the effects of head tilt alone. The results indicated that the tilt aftereffect follows a retinal frame of reference under some conditions (Experiment 1) and appears to follow a gravitational frame under others (Experiment 2). These results can be predicted by a simple model involving two factors, a purely visual aftereffect that follows a retinal frame and an extravisual aftereffect that appears to follow a gravitational frame.