Foveal Information Research Articles

Cell phone-induced failures of visual attention during simulated driving.

This research examined the effects of hands-free cell phone conversations on simulated driving. The authors found that these conversations impaired driver's reactions to vehicles braking in front of them. The authors assessed whether this impairment could be attributed to a withdrawal of attention from the visual scene, yielding a form of inattention blindness. Cell phone conversations impaired explicit recognition memory for roadside billboards. Eye-tracking data indicated that this was due to reduced attention to foveal information. This interpretation was bolstered by data showing that cell phone conversations impaired implicit perceptual memory for items presented at fixation. The data suggest that the impairment of driving performance produced by cell phone conversations is mediated, at least in part, by reduced attention to visual inputs.

Brief foveal masking during scene perception

In the present experiment, participants were exploring line drawings of scenes in the context of an object-decision task, while eye-contingent display changes manipulated the appearance of the foveal part of the image. Foveal information was replaced by an ovoid noise mask for 83 ms, after a preset delay of 15, 35, 60, or 85 ms following the onset of fixations. In control conditions, a red ellipse appeared for 83 ms, centered around the fixation position, after the same delays as in the noise-mask conditions. It was found that scene exploration was hampered especially when foveal masking occurred early during fixations, replicating earlier findings. Furthermore, fixation durations were shown to increase linearly as the mask delay decreased, which validates the fixation duration as a measure of perceptual processing speed.

Recollective Experience Following Suppression of Focal Attention

Studies that have adopted an experiential approach to memory and awareness have shown that several variables produce dissociations between "remember" and "know" responses, although judgements of recollective experience are made in explicit memory tasks. However, there have been few studies in which a given variable has been found to affect knowing but not remembering, although a number of studies have shown the opposite pattern of results. The present study increases the generality of these findings by showing that dividing attention (by suppressing the processing of foveal information) facilitates knowing, but not remembering. The results support the notion that know judgements are dissociable from remember judgements, and that recognition in the absence of recollective experience is influenced by manipulations that emphasise perceptual processing.

Detection of the sign of expansion as a function of field size and eccentricity.

Small optical flow fields are involved in object and shape recognition. These tasks depend on high resolution and low speed of the flow-field elements. Large optical flow fields are involved in tasks such as orientation and navigation, which require flow-field elements to move at high speed. From the above, we would expect to find different behavior of subjects for different parameter ranges of field size and speed of the elements. In this paper, we address the question of whether such different behavior exists for a task that is associated neither with object recognition nor with navigation. We obtained detection thresholds for expansion in the presence of translation for a wide range of field sizes. The same paradigm was used to investigate whether subjects made efficient use of peripheral information. We found viewing-distance invariance, meaning that subjects' performance scaled with stimulus size. Subjects performed very similarly with and without foveal information.

Eye movements and fixation characteristics in perception of stationary scenes: normal subjects as compared to patients with visual neglect or hemianopia

Saccade amplitudes, fixation times, and the spatial distribution of fixation points were comparatively studied in patients with visual hemineglect and/or homonymous hemianopia, as well as in normals (each group, n = 8). Two types of picture slides were presented (with and without search task) while eye movements were recorded with the infrared reflection technique. Self-developed software served to detect fixations, and to document their spatio-temporal parameters. Spectra of saccade amplitudes and fixation times were characteristic of each slide, while exhibiting notable similarities across subject groups. It is concluded that foveal information processing may not be much different in patients and in normals. Average saccade amplitudes and total scanpath lengths across all pictures were significantly smaller in the patients than in normals with both types of slides. In the neglect patients, saccades starting and terminating in the unaffected visual hemifield were larger, on an average, than those entirely located in the affected hemifield. The same was true for many of the hemianopic patients. Nevertheless, during free exploration, mean amplitudes of saccades restricted to the unaffected hemifield of the patients were apparently still smaller than those of normal controls within the corresponding hemifield. Average dwell time of fixations, total fixation time, as well as the total number of fixations did not vary significantly between groups. However, in the patient groups, average fixation times were shorter after large as compared to small saccades. This finding is discussed in the context of saccadic programming on the background of the sequential attention model of eye movement control. In subsamples of five hemianopic and six neglect patients, asymmetry in the distribution of fixation points was compared before and after a 4-week period of comprehensive rehabilitation that Included computerized scanning and attentional training. Only patients with pure hemianopia (who were less severely impaired from the beginning) improved according to this criterion, while neglect patients remained unchanged or deteriorated slightly. Total scanpath lengths, however, were not significantly different before and after therapy in any of the two groups of patients, indicating a persisting disturbance in scanning performance also in the hemianopic group.

Alternative models for fish-eye lenses

The human visual system can be characterized as a variable-resolution system: foveal information is processed at very high spatial resolution whereas peripheral information is processed at low spatial resolution. Various transforms have been proposed to model spatially varying resolution. Unfortunately, special sensors need to be designed to acquire images according to existing transforms. In this work, two models of the fish-eye transform are presented. The validity of the transformations is demonstrated by fitting the alternative models to a real fish-eye lens.

When shape information from a foveal nontarget affects gap detection accuracy in a parafoveal target.

Effects on gap detection accuracy of information at fixation concerning a parafoveally presented target form's global shape were determined in three experiments. Shape information was not directly relevant to the correct response regarding the presence of the gap. Tests were conducted to determine whether costs and benefits were associated with shape information, whether the effectiveness of shape information was sensitive to spatial attention, and whether subjects could volitionally suppress the nontarget information if it became apparent from preattentive analysis that it would not be helpful. Results were positive in all instances. Conclusions were that the foveal information was subject to early selection and that therefore it was not processed automatically.

The Span of Letter Recognition of Good and Poor Readers

THIS STUDY investigated the span of letter recognition for good and poor readers during a reading task. Sixteen fifth-grade children read passages from a cathode-ray tube as their eye movements were monitored. On selected fixations during reading, letters in certain regions of the display were replaced by other letters. This manipulation provided erroneous text in specific regions of the visual field. The results of the study indicate that both groups acquire letter information from a region of text extending from two letters to the left of the center of the fixation through to about six or seven letters to the right. There was no evidence to suggest that skilled readers utilize letter information from a wider region of text than do less able readers. The findings have significant implications for theories of information processing and theories of eye guidance in reading, especially as the present investigation is the first to compare the performance of good and poor readers when peripheral information is disrupted but foveal information remains intact.

Parafoveal attention in congenitally deaf and hearing young adults

This reaction-time study compared the performance of 20 congenitally and profoundly deaf, and 20 hearing college students on a parafoveal stimulus detection task in which centrally presented prior cues varied in their informativeness about stimulus location. In one condition, subjects detected a parafoveally presented circle with no other information being present in the visual field. In another condition, spatially complex and task-irrelevant foveal information was present which the subjects were instructed to ignore. The results showed that although both deaf and hearing people utilized cues to direct attention to specific locations and had difficulty in ignoring foveal information, deaf people were more proficient in redirecting attention from one spatial location to another in the presence of irrelevant foveal information. These results suggest that differences exist in the development of attentional mechanisms in deaf and hearing people. Both groups showed an overall right visual-field advantage in stimulus detection which was attenuated when the irrelevant foveal information was present. These results suggest a left-hemisphere superiority for detection of parafoveally presented stimuli independent of cue informativeness for both groups.

Peripheral Visual Processing in Human Performance

Information processing in the visual periphery plays a significant role in many everyday perceptual experiences. The importance of peripheral visual processing has often been examined by either restricting the availability of peripheral input or varying foveal demands. In contrast, the research reported in this paper focuses upon how information detected in the visual periphery is actually processed and used to guide visual search. Data regarding the dual processing of foveal and peripheral information during a brief exposure of a stimulus display as well as during extended search for a target will be presented. Since the subject population included young children, college adults, and professional athletes, the results are discussed in relation to both age and skill.

Integrating information across eye movements

A series of experiments was conducted in which a word initially appeared in parafoveal vision, followed by the subject's eye movement to the stimulus. During the eye movement, the initially displayed word was replaced by a word which the subject read. Under certain conditions, the prior parafoveal word facilitated naming the foveal word. Three alternative hypotheses were explored concerning the nature of the facilitation. The verbalization hypothesis suggests that information acquired from the parafoveal word permits the subject to begin to form the speech musculature properly for saying the word. The visual features integration hypothesis suggests that visual information obtained from the parafoveal word is integrated with foveal information after the saccade. The preliminary letter identification hypothesis suggests that some abstract code about the letters of the parafoveal word is stored and integrated with information available in the fovea after the saccade. The results of the experiments supported the latter hypothesis in that information about the beginning letters of words was facilitatory in the task. The other two hypotheses were disconfirmed by the results of the experiments.

Influence of foveal load on the functional visual field

The functional visual field defined in terms of a discrimination task of a target presented peripherally among ambiguous background patterns was investigated for various foveal loads which were to be recognized at the central retina. Foveal loads were numbers, letters, place names, traffic signs, and other figures to simulate commonplace situations for foveal information processing, and grouped into three in order of recognition difficulty based on daily experience. Boundaries of the functional visual field were obtained for simple fixation and for certain foveal loads. Comparison of these boundaries clearly showed shrinkage of the functional visual field size with the foveal loads of greater recognition difficulty.

Foveal information processing at photopic luminances.

A tentative model of information processing in the human fovea at photopic luminances is described, that handles both luminosity and chromaticity signals. The model consists of a “scaling-ensemble”, a group of sealers with common scaling-factor that provide an effective compression of the dynamic range of the input signals. The scaling factor adapts in such a way that the model conforms to Weber's law for the detection of short, small flashes on a bright background. The dynamics of the adaptation is such that the model effectively computes the logarithmic time derivative of the input signal. The model predicts the outcome of several psychophysical experiments. The predictions include Weber's law, Bloch's law, the apparent brightness of suprathreshold flashes as a function of adaptation level, the influence of spatial inhomogeneities on the perception of flicker, and the transfer function for moving sinusoidal bar patterns for both luminosity and chromaticity modulations. The influence of involuntary eye-movements on the perception of spatial patterns is also discussed. Finally an attempt is made to locate the components of the model in the anatomical structure of the retina. A tentative scheme of neural connections in the human fovea is presented.

SEARCH BEHAVIOR

The search of a roentgenogram is the first phase in the detection of a lesion. It is a skilled psychomotor task, largely outside conscious control, which includes psychological and motor components, shifting of selective attention, and movement of the eyes. It is affected by many factors, including the nature of the target and the display, the characteristics of the human visual-perceptual system, the skill and knowledge of the radiologist, and the information he has about the patient. Both the roentgenogram and the radiologist are elements in an information processing system, and the importance of the interface between them for successful detection has not always been realized. One reason is the common misconception that the search process is under voluntary control. That this is not entirely true is demonstrated by phenomena such as the oculomotor reflex which attracts the eye to objects seen indistinctly by peripheral vision. In fact, there is a continuous interplay between foveal information, information from the peripheral retina, and perceptions from previous visual fixations. Experimental results suggest that “free search” usually gives incomplete coverage, without the searcher being aware that he has not examined the whole display in the detail needed to detect less obvious targets. Some suggestions are made as to how search might be improved. These are based on the way radiologists search roentgenograms as well as the manner in which other search tasks are performed, such as the photointerpreter's. It seems that some form of guided search is necessary to insure complete coverage and that clinical and other information affects search patterns to the extent that it would seem wise to make the initial search in ignorance and later repeat it after studying clinical information. Various new techniques, such as television viewing, may be useful in improving search. It is also suggested that the radiologist may be able to improve his search and detection by knowledge of what may affect it and of his own personal strengths and weaknesses.