Perceptual Span Research Articles

Music Rehearsal Increases the Perceptual Span for Notation

DESPITE EVIDENCE FOR IMPROVED VISUAL PROCESSING of the printed score among skilled musicians, the effect of music rehearsal on the effective visual field ("perceptual span") for a musical score has never been directly examined. Following 1–20 rehearsals, 11 skilled and 10 less skilled adult musicians reported whether a variant note appeared within a melodic sequence of 3–18 notes, presented onscreen for 200 ms in a tachistoscopic task designed to evaluate the perceptual span. Initially, skilled musicians showed a slightly larger perceptual span for challenging passages (5 notes vs. 4 notes for less skilled musicians). Perceptual spans increased incrementally in both groups, but skill differences in span size disappeared by 20 rehearsals (span of 11 notes). A correlation between improvements in visual perceptual span and performance speed suggests that perceptual learning could underlie early improvements in performance during music rehearsals.

Eye movements and the perceptual span in older and younger readers.

The size of the perceptual span (or the span of effective vision) in older readers was examined with the moving window paradigm (G. W. McConkie & K. Rayner, 1975). Two experiments demonstrated that older readers have a smaller and more symmetric span than that of younger readers. These 2 characteristics (smaller and more symmetric span) of older readers may be a consequence of their less efficient processing of nonfoveal information, which results in a riskier reading strategy.

Eye Movements and Music Reading: Where Do We Look Next?

IN CONTRAST TO SIMILAR RESEARCH IN TEXT reading, research in the eye movements used to read music is relatively undeveloped. Though simpler measures such as the eye-hand span and perceptual span have been evaluated by numerous scholars, more complex phenomena such as context effects have yet to receive proper attention; this is largely the result of a lack of both focus on fine-grained structural properties (i.e., interval size, tonal-harmonic expectation) and a pool of hypotheses and paradigms informed by current models of music perception and cognition. To encourage further, more sophisticated research in eye movements and music reading, the present review discusses recent developments in the field and uses relevant conclusions to build a conceptual springboard for future research.

Gender differences in remembering and inferring spatial distances

The abilities of males and females to make spatial inferences were compared. Spatial inference is concerned with the ability to work out new spatial information from memory. In two experiments, participants had to study line drawings depicting shapes linked either by straight or meandering lines. Afterwards, they had to remember the straight-line distances or to infer the straight-line distances. Several spatial abilities were also assessed: perceptual discrimination, mental rotation, and visuo-spatial working memory span. The results showed that males outperformed females in spatial inference and mental rotation. Experiment 2 extended the study to old people. The results replicated and clarified those obtained in Experiment 1. Spatial inference and mental rotation showed age-related and gender-related differences; in addition, age reduced the visuo-spatial memory span. Overall, the findings suggest that gender differences favouring males are maximised with tasks requiring active processing and strategic control of metric information.

The dependence of visual scanning performance on search direction and difficulty

Phillips and Edelman [Phillips, M. H., & Edelman, J. A. (2008). The dependence of visual scanning performance on saccade, fixation, and perceptual metrics. Vision Research, 48(7), 926–936] presented evidence that performance variability in a visual scanning task depends on oculomotor variables related to saccade amplitude rather than fixation duration, and that saccade-related metrics reflects perceptual span. Here, we extend these results by showing that even for extremely difficult searches trial-to-trial performance variability still depends on saccade-related metrics and not fixation duration. We also show that scanning speed is faster for horizontal than for vertical searches, and that these differences derive again from differences in saccade-based metrics and not from differences in fixation duration. We find perceptual span to be larger for horizontal than vertical searches, and approximately symmetric about the line of gaze.

The dependence of visual scanning performance on saccade, fixation, and perceptual metrics

We sought to understand the basis of performance variability and perceptual learning in saccadic visual search. Four subjects searched for a target based on its shape in a linear array of densely packed, regularly spaced items, a configuration used to simplify the analysis of performance and to minimize search strategy variability. We measured the dependence of performance—search speed—on the oculomotor variables of fixation duration and saccade amplitude, both within and across experimental sessions. We also measured perceptual span, the area in visual space in which subjects could identify the target above chance, with a modified version of the task using a gaze-contingent display with transiently appearing targets. The principal finding of this study was that both within and across sessions, saccade metrics accounted for much more of the variability and improvement in performance than did fixation duration. Increases in search speed were due primarily to subjects processing information from a greater area of the visual field, rather than processing information from a fixed area more quickly, though there was a small but consistent decrease in fixation duration across sessions. The increase in performance derived from an increase in perceptual span and not merely from an increase in subjects’ efficiency in ‘tiling’ the search array with regions of visibility.

Sensation Seeking and Visual Selective Attention in Adults with HIV/AIDS

The association between sensation seeking and visual selective attention was examined in 31 adults with the Human Immunodeficiency Virus (HIV). Sensation seeking was measured with Zuckerman's Sensation Seeking Scale Form V (SSS-V). Selective attention was assessed with a perceptual span task, where a target letter-character must be identified in a quickly presented array of nontarget letter-characters. As predicted, sensation seeking was strongly associated (R(2) = .229) with perceptual span performance in the array size 12 condition, where selective attention demands were greatest, but not in the easier conditions. The Disinhibition, Boredom Susceptibility, and Experience Seeking subscales of the SSS-V were associated with span performance. It is argued that personality factors such as sensation seeking may play a significant role in selective attention and related cognitive abilities in HIV positive adults. Furthermore, sensation seeking differences might explain certain inconsistencies in the HIV neuropsychology literature.

Preview benefit and parafoveal-on-foveal effects from word n + 2.

Using the gaze-contingent boundary paradigm with the boundary placed after word n, the experiment manipulated preview of word n + 2 for fixations on word n. There was no preview benefit for 1st-pass reading on word n + 2, replicating the results of K. Rayner, B. J. Juhasz, and S. J. Brown (2007), but there was a preview benefit on the 3-letter word n + 1, that is, after the boundary but before word n + 2. Additionally, both word n + 1 and word n + 2 exhibited parafoveal-on-foveal effects on word n. Thus, during a fixation on word n and given a short word n + 1, some information is extracted from word n + 2, supporting the hypothesis of distributed processing in the perceptual span.

Parafoveal preview benefit in reading is only obtained from the saccade goal

Previous research has demonstrated that reading is less efficient when parafoveal visual information about upcoming words is invalid or unavailable; the benefit from a valid preview is realised as reduced reading times on the subsequently foveated word, and has been explained with reference to the allocation of attentional resources to parafoveal word(s). This paper presents eyetracking evidence that preview benefit is obtained only for words that are selected as the saccade target. Using a gaze-contingent display change paradigm (Rayner, K. (1975). The perceptual span and peripheral cues in reading. Cognitive Psychology, 7, 65–81), the position of the triggering boundary was set near the middle of the pretarget word. When a refixation saccade took the eye across the boundary in the pretarget word, there was no reliable effect of the validity of the target word preview. However, when the triggering boundary was positioned just after the pretarget word, a robust preview benefit was observed, replicating previous research. The current results complement findings from studies of basic visual function, suggesting that for the case of preview benefit in reading, attentional and oculomotor processes are obligatorily coupled.

Visual search and eye movements in patients with chronic solvent-induced toxic encephalopathy

Various aspects of visual perception have been found to be impaired in patients with occupational chronic solvent-induced toxic encephalopathy (CSE). The purpose of the study was to characterise the changes in eye movements and visual search performance in CSE patients. We measured eye movements of 13 CSE patients and 22 healthy controls during dynamic visual search task by using a fast video eye tracker. The task was to search for and identify a target letter among numerals presented in a rectangular stimulus matrix (3 × 3–10 × 10 items). Threshold search time, i.e. the duration of stimulus presentation required for identifying the target with a given probability was determined by using a psychophysical staircase method. The visual search times of the CSE patients were clearly longer, and they needed considerably more eye fixations than healthy controls to find the target. Thus, their reduced performance in this task was mainly related to the reduction in the number of items which could be processed during a single eye fixation ( perceptual span). This reduction probably reflects a limited capacity of visual attention, since visual acuity, contrast sensitivity, and the oculomotor saccade velocity were found to be normal. The results suggest that motor slowness or low-level visual factors do not explain the poor performance of CSE patients in visual search tasks. The results are also discussed with respect to the effects of education, and compared to the performance in the widely used neuropsychological Trail Making Test, which uses similar stimuli and requires visual search.

Reading speed and the perceptual span in patients with macular disease

This presentation describes the results of a longitudinal assessment of the perceptual span, eye movements and reading speed in a group of patients with macular disease (MD). Eighteen patients with MD were recruited. All patients had developed a scotoma in their second affected eye in the 2 weeks prior to recruitment. Patients were assessed within 2 weeks of recruitment and again 3–12 months later. Eye movements were recorded whilst reading MN-Read style sentences using an infra-red gazetracker. Perceptual span was closely related to reading speed at the first (r2=0.53, p<0.001) and the second visit (r2=0.72, p<0.0001). In some patients the perceptual span changed by as much as two letters. Changes in the perceptual span were strongly related to change in reading speed (r2=0.43, p<0.005). These results lend support to the hypothesis that a reduced perceptual span is one cause of impaired reading in patients with macular disease. These results are relevant to the development of rehabilitation and training programs for patients with macular disease.

Eye movements and reading in macular disease: Further support for the shrinking perceptual span hypothesis

Reduced perceptual span is one factor which limits reading speed in patients with macular disease. This study measured the perceptual span and the number of saccades to locate a target in 18 patients with macular disease and seven control subjects on two occasions separated by up to 12 months. Perceptual span changed by up to two letters. Changes in perceptual span were significantly related to changes in reading speed ( r 2 = 0.43, p < 0.005), and were independent of changes in the number of saccades used to observe a target ( r 2 = 0.003, p = 0.62). These findings have important implications for the development of training programmes for patients with macular disease.

Parafoveal preview benefit in reading is not cumulative across multiple saccades

Two empirical predictions can be generated from recent parallel processing models of eye movement control in reading concerning the phenomenon of parafoveal preview benefit. These predictions derive from the assumption that lexical activation accumulates across more than one saccade. A large corpus of eye movement data was used to determine whether parafoveal preview benefit of a target word is modulated by (1) its distance from the penultimate fixation, and (2) the amount of time it spends in the ‘perceptual span’. There was an unexpected inverse relationship between first fixation duration and distance: fixations were longer the closer the penultimate fixation was to the target word, and a positive relationship between fixation duration and time: fixations were longer the greater the summed durations of the ultimate and penultimate fixations. These findings represent a challenge for computational models of eye movements in reading.

Detection of emotional faces: low perceptual threshold and wide attentional span

In two experiments, prime face stimuli with an emotional or a neutral expression were presented individually for 25 to 125 ms, either in foveal or parafoveal vision; following a mask, a probe face or a word label appeared for recognition. Accurate detection and sensitivity (A') were higher for angry, happy, and sad faces than for nonemotional (neutral) or novel (scheming) faces at short exposure times (25-75 ms), in both the foveal and the parafoveal field, and with both the probe face and the probe word. These results indicate that there is a low perceptual threshold for unambiguous emotional faces, which are especially likely to be detected both within and outside the focus of attention; and that this facilitated detection involves processing of the affective meaning of faces, not only discrimination of formal visual features.

Perceptual span deficits in adults with HIV.

Studies have found that infection with the Human Immunodeficiency Virus (HIV) leads to cognitive dysfunction. In fact, attention problems have been reported to be the most frequent cognitive symptom in HIV-infected adults. One question is how early in the course of information processing can attention impairment be detected? To address this issue, performance on a perceptual span task was examined in 54 HIV-infected adults and 19 seronegative controls. In this task a target had to be identified in a briefly presented (50 ms) array of 1, 4, or 12 letter-characters. Response accuracy was differentially worse in the HIV+ group relative to seronegative controls in the most difficult condition, the 12-item array, but not in the easier conditions. There was no evidence of a group difference in response strategy due to disinhibition or in psychomotor speed. These data suggest that HIV infection leads to a reduction in early visual processing capacity (or span of apprehension). The present results illustrate a new type of attentional deficit in HIV and show the impact of HIV on cognition at an earlier point in information processing than has been previously reported.

How many faces can be processed during a single eye fixation?

The purpose of our study was to estimate the perceptual span for facial information: how many faces can be processed during a single eye fixation. We used a visual-search task, in which the targets and distractors were facial photographs. The task of the observer was to search for and identify a target face in an array of faces. We measured the time needed for one search--threshold search time--by using a multiple-alternative staircase method. The threshold represents the duration of stimulus presentation at which the probability of correct responses was 79%. The array size was varied from 2 x 2 to 8 x 8 faces. Simultaneously with the performance measurements we measured eye movements with a video eye tracker. We found that threshold search time increased with increasing set size nearly linearly. The number of fixations also increased linearly from unity at the smallest set size to about fifteen at the largest set size. The result of 2 x 2 faces during a single fixation gave an estimate of 4 faces for the perceptual span. If, on average, only half of the elements had to be scanned for finding the target, 15 fixations at the largest set size (8 x 8) gave another estimate of 2.13 faces. The mean fixation duration was around 200 ms. Thus, the results suggest that 2-4 faces can be processed during one fixation of about 200 ms.

The effect of icon spacing and size on the speed of icon processing in the human visual system

Alphanumeric and graphical information needs to be presented in such a way that its perception is accurate, fast and as effortless as possible. This study investigated the effects of spacing and size of individual interface elements on their perception. Experiment 1 investigated the effect of icon spacing on the speed of visual search for a target icon and determined the perceptual span for icons, that is, the number of icons that can be processed by one eye fixation. Experiment 2 studied the effect of size, and experiment 3 the subjective preferences for levels of icon spacing. The results of experiment 1 showed that spacing does not have an effect on search times. On average the perceptual span for icons was found to be 25 arranged in a 5×5 array. The size of the interface elements, on the other hand, was found to have a great effect. Icons smaller than 0.7° resulted in significantly raised search times. Experiment 3 revealed that an inter-element spacing of one icon is to be preferred and a spacing of zero icons is to be avoided.

Restricting the field of view to investigate the perceptual spans of pianists

An experiment is reported, which was designed to determine how the perceptual span of pianists varies with developing skill and cognitive load. Eye-movements were recorded as musical phrases were presented through a gaze-contingent window, which contained one beat, two beats, or four beats. In a control condition, the music was presented without a window. The pianists were required to perform three tasks of varying cognitive load: An error-detection task (low load); a sight-reading task (medium load); and a transposition task (high load). Measures taken comprised fixation duration, fixation frequency, saccade length, fixation locations, performance duration, note duration, position of first error, number of errors, and eye-hand span. The results indicate that good and poor sight-readers do not differ in terms of perceptual span. However, good sight-readers were found to have larger eye-hand spans. Furthermore, the results show that increasing cognitive load decreases eye-hand span, but has little effect on perceptual span.

The inter‐relationship between magnification, field of view and contrast reserve: the effect on reading performance

SummaryFor the reading task, contrast reserve is defined as the ratio of the letter contrast of the printed letters, to the reader's contrast threshold. Acuity reserve is the ratio of the print size used for the reading task, to the reader's visual acuity. The effects of low contrast reserve on reading performance were investigated at various magnifications, ranging from 3 × to 7.5 ×, with the field of view systematically controlled. Eye movements were recorded whilst normally sighted subjects read using the magnifiers. It was shown that with adequate contrast reserve, increasing the field of view improved the reading rate because of the resulting increase in forward saccade length. Conversely, reducing the contrast reserve slowed the reading rate by decreasing the length of forward saccades and increasing the mean fixation duration, suggesting that the perceptual span is reduced at low contrast reserve. This study also shows that when the contrast reserve is low, providing magnification higher than that required for letter recognition (that is, increasing the acuity reserve) will not improve the reading performance. Furthermore, even when the contrast reserve was high, reading rates were lower for the magnifications of 5 × and higher, because increases in saccade length do not match those of the retinal image size at these magnifications.

The inter-relationship between magnification, field of view and contrast reserve: the effect on reading performance

For the reading task, contrast reserve is defined as the ratio of the letter contrast of the printed letters, to the reader's contrast threshold. Acuity reserve is the ratio of the print size used for the reading task, to the reader's visual acuity. The effects of low contrast reserve on reading performance were investigated at various magnifications, ranging from 3× to 7.5×, with the field of view systematically controlled. Eye movements were recorded whilst normally sighted subjects read using the magnifiers. It was shown that with adequate contrast reserve, increasing the field of view improved the reading rate because of the resulting increase in forward saccade length. Conversely, reducing the contrast reserve slowed the reading rate by decreasing the length of forward saccades and increasing the mean fixation duration, suggesting that the perceptual span is reduced at low contrast reserve. This study also shows that when the contrast reserve is low, providing magnification higher than that required for letter recognition (that is, increasing the acuity reserve) will not improve the reading performance. Furthermore, even when the contrast reserve was high, reading rates were lower for the magnifications of 5× and higher, because increases in saccade length do not match those of the retinal image size at these magnifications.