Orientation sensitivity in the peripheral visual field

Orientation sensitivity in the peripheral visual field has been tested in two tasks: (a) setting horizontal the orientation of a grating at various retinal eccentricities, and (b) matching the orientation of a peripherally viewed grating as close as possible to an oblique reference viewed foveally. Both performances fall off with increasing retinal eccentricity. Magnification of the stimulus optimizes peripheral performance. Peripheral performance, optimized by magnification, varies with retinal eccentricity. It approaches, but does not reach, the foveal value (tested by the same method) at 10 deg of eccentricity, and is much lower at 20 and 30 deg of eccentricity.     

Scaling extrafoveal detection of distortion in a face and grating

Peripheral performance involving simple visual tasks and stimuli can be equated with foveal performance by spatial scaling, whilst more complex tasks and stimuli seem to need additional scaling of image contrast. We therefore determined whether the contrast manipulation needed to compensate for eccentricity-dependent performance changes is due to an increase in stimulus or task difficulty. We measured contrast sensitivities to determine foveal and peripheral ability to discriminate between an original and a distorted version of a polar-circular sinusoidal grating and a face image. Contrast sensitivities as a function of image size were spatially scaleable across eccentricities for both the face and grating. Furthermore, irrespective of stimulus, performance could be scaled with the same individual E2 value. Thus task simplicity overrides the nature of the stimulus in determining scaling requirements, suggesting that it is the complexity of the task, not of the stimulus, that makes contrast scaling necessary in complex tasks.     

Visual resolution in the periphery

Visual acuity thresholds were determined for two Os with a 3-deg square grating target presented for 0.2 sec within a steadily illuminated surround field matched in luminance to the test field. Measurements were made in the fovea, and at 10, 20, and 30 deg along the horizontal meridian of the temporal retina, at luminances between ?3.5 and 3.0 log mL. The foveal acuity-luminance functions showed a large increase in acuity up to 1 or 2 log mL, but at peripheral locations very little increase occurred above 0 log mL. The maximum acuity reached at photopic luminances dropped sharply with increasing eccentricity. Visual acuities were two to four times higher than those previously reported for the periphery; methodological and target differences are presented to account for this result.     

Tunnel vision or general interference? Cognitive load and attentional bias are both important

Accuracy of identification of single letters presented in the near periphery (2.2 degrees, 3.3 degrees, or 4.4 degrees) was adversely affected when subjects were given a simultaneous foveal visual task as part of the same display. The level of processing required by the foveal task as well as the attentional allocation instructions were both found to be important. Tunnel vision as opposed to general interference can be induced by a combination of high foveal cognitive load, a focused attention strategy, and speed stress.     

Retinal location and its effect on the processing of target and distractor information

Two experiments were conducted to study the perceptual facilitation and inhibition that occurs between foveal and parafoveal or peripheral regions of the eye. Experiment 1 used a Stroop task to compare color detection latencies of foveal and parafoveal targets. The target and distractor components of the Stroop stimuli were separated and presented with varied stimulus onset asynchronies. Experiment 2 used a Stroop-like task to replicate and extend the findings into the visual periphery. Subjects were found to process foveally presented distractor information while attending to targets presented in parafoveal or peripheral regions of the eye. Distractor information that was incompatible was suppressed while compatible information was used to facilitate target processing. When the targets were presented foveally along with the distractor information, subjects appeared to automatically process the distractor information. The findings are discussed within the framework of past studies that presented subjects with competing tasks across retinal location. The implications of these findings to a two-process theory of attention are also considered.     

Primacy of emotional vs. semantic scene recognition in peripheral vision

Emotional scenes were presented peripherally (5.2° away from fixation) or foveally (at fixation) for 150 ms. In affective evaluation tasks viewers judged whether a scene was unpleasant or not, or whether it was pleasant or not. In semantic categorisation tasks viewers judged whether a scene involved animals or humans (superordinate-level task), or whether it portrayed females or males (subordinate-level task). The same stimuli were used for the affective and the semantic task. Results indicated that in peripheral vision affective evaluation was less accurate and slower than animal/human discrimination, and did not show any advantage over gender discrimination. In addition, performance impairment in the peripheral relative to the foveal condition was greater or equivalent for affective than for semantic categorisation. These findings cast doubts on the specialness and the primacy of affective over semantic recognition. The findings are also relevant when considering the role of the subcortical “low route” in emotional processing.     

Relative mislocalization of briefly presented stimuli in the retinal periphery

We studied the ability to localize flashed stimuli, using a relative judgment task. When observers are asked to localize the peripheral position of a probe with respect to the midposition of a spatially extended comparison stimulus, they tend to judge the probe as being more toward the periphery than is the midposition of the comparison stimulus. We report seven experiments in which this novel phenomenon was explored. They reveal that the mislocalization occurs only when the probe and the comparison stimulus are presented in succession, independent of whether the probe or the comparison stimulus comes first (Experiment 1). The size of the mislocalization is dependent on the stimulus onset asynchrony (Experiment 2) and on the eccentricity of presentation (Experiment 3). In addition, the illusion also occurs in an absolute judgment task, which links mislocalization with the general tendency to judge peripherally presented stimuli as being more foveal than they actually are (Experiment 4). The last three experiments reveal that relative mislocalization is affected by the amount of spatial extension of the comparison stimulus (Experiment 5) and by its structure (Experiments 6 and 7). This pattern of results allows us to evaluate possible explanations of the illusion and to relate it to comparable tendencies observed in eye movement behavior. It is concluded that the system in charge of the guidance of saccadic eye movements is also the system that provides the metric in perceived visual space.     

Reaction time reduction after parafoveal preview in a lexical decision task

Time and the accuracy of a lexical decision performed on a letter string (either a word or nonword), presented foveally after a parafoveal preview displayed at 5 degrees of eccentricity and 100 msec. duration were measured. Students of Padova University, 10 women and 7 men, ages 19 to 23 years were subjects. The hypothesis investigated was whether the facilitatory effect, a reduction in lexical decision time due to the parafoveal preview, was tied to global visual information acquired in the visual periphery during the preview presentation. In Exp. 1, eight subjects performed the task either with no preview (No Preview) or with a preview presented at 5 degrees eccentricity in two conditions, preview of the same foveal string (Preview-Letters) and preview of symbols ("x xx...") of the same length as the foveal string (Preview Symbols). In Exp. 2, 9 subjects performed the task with two preview conditions, No Preview and preview of the foveal string in uppercase letters at 5 degrees of eccentricity (Preview Uppercase). Analyses suggested the reduction in lexical decision time due to the Preview with respect to the No Preview condition is tied to global information extracted during parafoveal presentation. The reduction in lexical decision time depends on word texture, i.e., letters' identities and also word boundary, in addition to word length.     

The effect of feedback on luminance thresholds for peripherally presented stimuli

The effect of a central task on peripheral vision was determined by obtaining absolute luminance thresholds for peripherally presented stimuli. A competing central task was provided by interrupting the fixation light and requiring the S to reilluminate it. Data were obtained over five sessions, with feedback information provided on each trial. Thresholds were highest for the initial session and declined as a function of practice. The magnitude of the change depended upon the interruption rate. When central and peripheral stimuli compete for attention, priority is given initially to the central task, but, with practice, the differences are reduced.     

Primacy of emotional vs. semantic scene recognition in peripheral vision

Emotional scenes were presented peripherally (5.2° away from fixation) or foveally (at fixation) for 150 ms. In affective evaluation tasks viewers judged whether a scene was unpleasant or not, or whether it was pleasant or not. In semantic categorisation tasks viewers judged whether a scene involved animals or humans (superordinate-level task), or whether it portrayed females or males (subordinate-level task). The same stimuli were used for the affective and the semantic task. Results indicated that in peripheral vision affective evaluation was less accurate and slower than animal/human discrimination, and did not show any advantage over gender discrimination. In addition, performance impairment in the peripheral relative to the foveal condition was greater or equivalent for affective than for semantic categorisation. These findings cast doubts on the specialness and the primacy of affective over semantic recognition. The findings are also relevant when considering the role of the subcortical "low route" in emotional processing.     

Eye movements and a dynamic stimulus situation

Two experiments were conducted to investigate performance with and without voluntary eye movements in a dynamic stimulus situation. Experiment I used a combined tracking and prediction task. Level of training, complexity of the signal, and visual region sampled were the variables of interest. Experiment II manipulated the same variables in only the prediction task. Thus, the amount of attention allotted to the prediction task was varied between experiments. The d' measure indicated that under peripheral vision instructions accuracy on the prediction task was the same as under foveal vision instructions provided that: (1) the level of task complexity was low, (2) the subjects were well trained, and (3) only the prediction task was performed, or in the dual task situation only visual regions near the fovea were sampled. All other combinations of the variables resulted in a lower performance scores under peripheral vision instructions. Results are interpreted within the framework of current theories of the functional visual field.     

Increasing task complexity and ice hockey skills of youth athletes

The objective of this pilot study was to investigate the effects on cognitive performance of progressively adding tasks specific to ice hockey (skating, stick handling, and obstacle avoidance) during a visual interference task (Stroop Color Word Test-interference condition). In addition, the effects on locomotor performance of progressively adding tasks of stickhandling, visual interference, and obstacle avoidance related to maximal skating speed and minimal obstacle clearance were investigated in eight male athletes ages 10 to 12 years. Results revealed decreased performance on both cognitive and physical measures with increased task complexity, suggesting that adding complexity to an environment influences hockey skill performance.     

Contrast thresholds for identification of numeric characters in direct and eccentric view

Aubert and Foerster (1857) are frequently cited for having shown that the lower visual acuity of peripheral vision can be compensated for by increasing stimulus size. This result is seemingly consistent with the concept of cortical magnification, and it has been confirmed by many subsequent authors. Yet it is rarely noted that Aubert and Foerster also observed a loss of the "quality of form." We have studied the recognition of numeric characters in foveal and eccentric vision by determining the contrast required for 67% correct identification. At each eccentricity, the lowest contrast threshold is achieved with a specific stimulus size. But the contrast thresholds for these optimal stimuli are not independent of retinal eccentricity as cortical magnification scaling would predict. With high-contrast targets, however, threshold target sizes were consistent with cortical magnification out to 6 degrees eccentricity. Beyond 6 degrees, threshold target sizes were larger than cortical magnification predicted. We also investigated recognition performance in the presence of neighboring characters (crowding phenomenon). Target character size, distance of flanking characters, and precision of focusing of attention all affect recognition. The influence of these parameters is different in the fovea and in the periphery. Our findings confirm Aubert and Foester's original observation of a qualitative difference between foveal and peripheral vision.     

Blur detection is unaffected by cognitive load

Blur detection is affected by retinal eccentricity, but is it also affected by attentional resources? Research showing effects of selective attention on acuity and contrast sensitivity suggests that allocating attention should increase blur detection. However, research showing that blur affects selection of saccade targets suggests that blur detection may be pre-attentive. To investigate this question, we carried out experiments in which viewers detected blur in real-world scenes under varying levels of cognitive load manipulated by the N-back task. We used adaptive threshold estimation to measure blur detection thresholds at 0°, 3°, 6°, and 9° eccentricity. Participants carried out blur detection as a single task, a single task with to-be-ignored letters, or an N-back task with four levels of cognitive load (0, 1, 2, or 3-back). In Experiment 1, blur was presented gaze-contingently for occasional single eye fixations while participants viewed scenes in preparation for an easy picture recognition memory task, and the N-back stimuli were presented auditorily. The results for three participants showed a large effect of retinal eccentricity on blur thresholds, significant effects of N-back level on N-back performance, scene recognition memory, and gaze dispersion, but no effect of N-back level on blur thresholds. In Experiment 2, we replicated Experiment 1 but presented the images tachistoscopically for 200 ms (half with, half without blur), to determine whether gaze-contingent blur presentation in Experiment 1 had produced attentional capture by blur onset during a fixation, thus eliminating any effect of cognitive load on blur detection. The results with three new participants replicated those of Experiment 1, indicating that the use of gaze-contingent blur presentation could not explain the lack of effect of cognitive load on blur detection. Thus, apparently blur detection in real-world scene images is unaffected by attentional resources, as manipulated by the cognitive load produced by the N-back task.     

Deployment of spatial attention to words in central and peripheral vision

Four perceptual identification experiments examined the influence of spatial cues on the recognition of words presented in central vision (with fixation on either the first or last letter of the target word) and in peripheral vision (displaced left or right of a central fixation point). Stimulus location had a strong effect on word identification accuracy in both central and peripheral vision, showing a strong right visual field superiority that did not depend on eccentricity. Valid spatial cues improved word identification for peripherally presented targets but were largely ineffective for centrally presented targets. Effects of spatial cuing interacted with visual field effects in Experiment 1, with valid cues reducing the right visual field superiority for peripherally located targets, but this interaction was shown to depend on the type of neutral cue. These results provide further support for the role of attentional factors in visual field asymmetries obtained with targets in peripheral vision but not with centrally presented targets.     

Visual angle and apparent size of objects in peripheral vision

Measurements of apparent size were obtained by distance adjustment of a peripherally viewed stimulus to produce a match to a foveally viewed standard. As eccentricity increased, the peripheral stimulus was adjusted at distances of progressively greater visual angle, indicating that a continuous diminution in apparent size occurs with increased eccentricity. This effect was found to be stable for several conditions of illumination and for changes in the light adaptive state of S. Apparent size diminution and apparent distance increase were also found for familiar objects viewed in an open field.     

Visual attention in adolescents: Facilitating effects of sport expertise and acute physical exercise

ObjectivesThis study investigated visual attention of adolescent orienteers and physically active adolescents non-practising orienteering both at rest and under acute sub-maximal exercise. It was verified whether the practice of orienteering facilitates the development of visual attentional abilities and whether orienteers, who are used to simultaneously handle physiological and cognitive-attentional loads, may better profit than non-orienteers from the beneficial effects of sub-maximal physical load on processing speed.MethodsBoth the focusing of attention at foveal and parafoveal locations and the orienting of attention at peripheral locations were investigated. In two discriminative reaction time (RT) experiments, a cue of varying size was presented centrally or peripherally and followed by a compound stimulus with local and global target features. The stimulus-onset asynchrony (SOA) varied between a short and a long interval.ResultsIn both experiments, adolescent orienteers and non-practisers showed different patterns of attentional effects. Adolescent orienteers were more similar to young adults in the attentional performance, being better able than non-practisers to perform complex attentional operations involving the intentional zooming of attention in the central visual field and the orienting of the attentional focus in the peripheral visual field. Also, both orienteers and non-orienteers speeded up their performance during exercise, but this facilitation effect was more pronounced for orienteers, who are probably skilled in directing the available resources to task demands.ConclusionsOur results suggest that cognitive expertise represents a key factor in sports that accelerates the development of visual attention and enhances the facilitating effects of physical exercise on attentional performance.     

Peripheral target recognition and visual field narrowing in aviators and nonaviators

In the two experiments that examined recognition accuracy in the near visual periphery as a function of foveal cognitive load, aviators were shown to have larger effective functional visual fields than nonaviators. The aviators appeared to be far less susceptible to the visual field narrowing found in nonaviators. The narrowing found in nonaviators suggested a tunnel-vision-like pattern. The rather small effect of load increases on aviator performance was likely due to specialized training and experience. Student aviators who averaged only 70 flight hr were clearly superior to nonaviators on peripheral recognition with a concomitant foveal task.     

Orientation discrimination across the visual field: size estimates near contrast threshold

Performance in detection and discrimination tasks can often be made equal across the visual field through appropriate stimulus scaling. The parameter E2 is used to characterize the rate at which stimulus dimensions (e.g., size or contrast) must increase in order to achieve foveal levels of performance. We calculated both size and contrast E2 values for orientation discrimination using a spatial scaling procedure that involves measuring combination size and contrast thresholds for stimuli with constant size-to-contrast ratios. E2 values for size scaling were 5.77 degrees and 5.92 degrees. These values are three to four times larger than those recovered previously using similar stimuli at contrasts well above detection threshold (Sally & Gurnsey, 2003). E2 values for contrast scaling were 324.2 degrees and 44.3 degrees, indicating that for large stimuli little contrast scaling (.3% to 2.3% increase) was required in order to equate performance in the fovea and the largest eccentricity (10 degrees). A similar pattern of results was found using a spatial scaling method that involves measuring contrast thresholds for target identification as a function of size across eccentricities. We conclude that the size scaling for orientation discrimination at near-threshold stimulus contrasts is much larger than that required at suprathreshold contrasts. This may arise, at least in part, from contrast-dependent changes in mechanisms that subserve task performance.     

Processing of threat-related information outside the focus of visual attention

This study investigates whether threat-related words are especially likely to be perceived in unattended locations of the visual field. Threat-related, positive, and neutral words were presented at fixation as probes in a lexical decision task. The probe word was preceded by 2 simultaneous prime words (1 foveal, i.e., at fixation; 1 parafoveal, i.e., 2.2 deg. of visual angle from fixation), which were presented for 150 ms, one of which was either identical or unrelated to the probe. Results showed significant facilitation in lexical response times only for the probe threat words when primed parafoveally by an identical word presented in the right visual field. We conclude that threat-related words have privileged access to processing outside the focus of attention. This reveals a cognitive bias in the preferential, parallel processing of information that is important for adaptation.