Differences In Fixation Duration Research Articles

The influence of image characteristics on image recognition: a comparison of photographs and line drawings

Background: Photographs provide more information including colour, luminance, texture, and shading cues compared to line drawings. There is evidence that these additional cues facilitate image recognition in individuals with and without neurological deficits. Black-and-white line drawings and colour photographs are commonly used with individuals with aphasia in evaluation and treatment. Eye tracking provides an opportunity to assess the influence of these different image types on object recognition processes without relying on verbal responses.Aims: The purpose of this study was to determine whether differences in object recognition of photographs and line drawings were observed using eye-tracking measures. Specific goals were to compare the influence of (a) image type of the same target image presented as colour photograph and black-and-white line drawing and (b) degree of colour diagnosticity (high-colour diagnostic natural objects and low-colour diagnostic human-made objects) in multiple-choice image displays on language-mediated eye movements in language-normal adults.Methods & Procedures: Eye movements of 19 participants were recorded while they viewed 66 multiple-choice image displays of colour photographs and black-and-white line drawings presented with a verbal stimulus. Target images included high-colour diagnostic natural objects and low-colour diagnostic human-made objects.Outcomes & Results: Participants allocated significantly greater proportions of fixation duration and first-pass gaze duration to the photographs compared to line drawings. No significant differences were observed for colour diagnosticity differences within the colour or the black-and-white line drawing displays.Conclusions: Eye tracking indexed significant differences in fixation duration allocated to target images in displays that only differed with respect to image type and colour, and were otherwise carefully controlled for shape, size, orientation, and content conveyed. Results suggest that language-normal participants’ object recognition was facilitated by colour photographs compared to line drawings, highlighting the clinical relevance and the need for research of image design for clinical use with individuals with neurological impairments.

Morphology of primary visual cortex predicts individual differences in fixation duration during text reading.

In skilled reading, fixations are brief periods of time in which the eyes settle on words. E-Z Reader, a computational model of dynamic reading, posits that fixation durations are under real-time control of lexical processing. Lexical processing, in turn, requires efficient visual encoding. Here we tested the hypothesis that individual differences in fixation durations are related to individual differences in the efficiency of early visual encoding. To test this hypothesis, we recorded participants' eye movements during reading. We then examined individual differences in fixation duration distributions as a function of individual differences in the morphology of primary visual cortex measured from MRI scans. The results showed that greater gray matter surface area and volume in visual cortex predicted shorter and less variable fixation durations in reading. These results suggest that individual differences in eye movements during skilled reading are related to initial visual encoding, consistent with models such as E-Z Reader that emphasize lexical control over fixation time.

Individual Differences in Infant Fixation Duration Relate to Attention and Behavioral Control in Childhood

Individual differences in fixation duration are considered a reliable measure of attentional control in adults. However, the degree to which individual differences in fixation duration in infancy (0–12 months) relate to temperament and behavior in childhood is largely unknown. In the present study, data were examined from 120 infants (mean age = 7.69 months, SD = 1.90) who previously participated in an eye-tracking study. At follow-up, parents completed age-appropriate questionnaires about their child’s temperament and behavior (mean age of children = 41.59 months, SD = 9.83). Mean fixation duration in infancy was positively associated with effortful control (β = 0.20, R2 = .02, p = .04) and negatively with surgency (β = −0.37, R2 = .07, p = .003) and hyperactivity-inattention (β = −0.35, R2 = .06, p = .005) in childhood. These findings suggest that individual differences in mean fixation duration in infancy are linked to attentional and behavioral control in childhood.

Not fixating at the line of text comes at a cost

Previous research on eye guidance in reading has investigated systematic tendencies with respect to horizontal fixation locations on letters within words and the relationship between fixation location in a word and the duration of the fixation. The present study investigates where readers place their eyes vertically on the line of text and how vertical fixation location is related to fixation duration. Analyses were based on a large corpus of eye movement recordings from single-sentence reading. The vertical preferred viewing location was found to be within the vertical extent of the font, but fixations beyond the vertical boundaries of the text also frequently occurred. Analyzing fixation duration as a function of vertical fixation location revealed a vertical optimal viewing position (vOVP) effect: Fixations were shortest when placed optimally on the line of text, and fixation duration gradually increased for fixations that fell above or below the line of text. The vOVP effect can be explained by the limits of visual resolution along the vertical meridian. It is concluded that vertical and horizontal landing positions in single-sentence reading are associated with differences in fixation durations in opposite ways.

Individuals exhibit idiosyncratic eye-movement behavior profiles across tasks

The purpose of this study was to examine individual differences in eye-movement behavior. Six metrics (Fixation Rate, Duration, and Size; Saccade Amplitude; Micro-Saccade Rate and Amplitude) were used to measure individuals' eye-movement behavior profiles (EmBP). We replicate previous research (Andrews & Coppola, 1999; Castelhano & Henderson, 2008) by finding consistent individual differences in fixation duration and saccade amplitude across tasks, and present new findings of stable idiosyncrasies in measures of fixational eye-movement (Fixation Size, Micro-Saccade Rate and Amplitude). Moreover, we observed consistent inter-metric correlations across tasks (e.g., individuals that exhibited relatively high Fixation Rates also presented relative low Micro-Saccade Rates and relatively high Micro-Saccade Amplitudes). Factor Analysis linked the six EmBP metrics together with a single factor, which we speculate might be related to the operational effectiveness of the attentional system, given that individual factor scores were correlated with scores on a self-report measure of attentional function. Normal subjects with relatively high scores on this attention-deficit measure exhibited relatively frequent fixations of short duration and large spatial extent, and relatively infrequent micro-saccades of large amplitude. This EmBP is similar to a general pattern of eye-movement behavior observed with ADHD individuals - difficulty controlling eye movements, maintaining fixation, and inhibiting intrusive saccades. Results of this study indicate that normal individuals exhibit idiosyncratic EmBPs that are quite stable across tasks and are related to attentional ability.

Kinematics matters: A new eye-tracking investigation of animated triangles

Eye movements have been recently recorded in participants watching animated triangles in short movies that normally evoke mentalizing (Frith-Happé animations). Authors have found systematic differences in oculomotor behaviour according to the degree of mental state attribution to these triangles: Participants made longer fixations and looked longer at intentional triangles than at triangles moving randomly. However, no study has yet explored kinematic characteristics of Frith-Happé animations and their influence on eye movements. In a first experiment, we have run a quantitative kinematic analysis of Frith-Happé animations and found that the time triangles spent moving and the distance between them decreased with the mentalistic complexity of their movements. In a second experiment, we have recorded eye movements in 17 participants watching Frith-Happé animations and found that some differences in fixation durations and in the proportion of gaze allocated to triangles between the different kinds of animations were entirely explained by low-level kinematic confounds. We finally present a new eye-tracking measure of visual attention, triangle pursuit duration, which does differentiate the different types of animations even after taking into account kinematic cofounds. However, some idiosyncratic kinematic properties of the Frith-Happé animations prevent an entirely satisfactory interpretation of these results. The different eye-tracking measures are interpreted as implicit and line measures of the processing of animate movements.

LCD vs. E-ink: An Analysis of the Reading Behavior

Electronic books (e-book) are an interesting option compared to classic paper books. Most e-reading devices of the first generation were based on e-ink technology. With the appearance of the Apple iPad on the market, TFT-LCDs became important in the field of e-reading. Both technologies have advantages and disadvantages but the question remains whether one or the other technology is better for reading. In the present study we analyzed and compared reading behavior when reading on e-inkreader (e-ink displays) and on tablets (TFT-LCDs) as measured by eye-tracking. The results suggest that the reading behavior on tablets is indeed very similar to the reading behavior on e-ink-reader. Participants showed no difference in fixation duration. Significant differences in reading speed and in the proportion of regressive saccades suggest that tablets, under special artificial light conditions, may even provide better legibility.

Comparing reading processes on e-ink displays and print

E-book reading devices open new possibilities in the field of reading. More activities than just reading a book can be performed with a single electronic device. For a long time, electronic reading devices have not been favored because their active LCD displays used to have a relatively low contrast. The new generation of electronic reading devices differs from earlier ones in the nature of the display: active LCD displays have been replaced with displays based on e-ink technology, which has display properties closer to that of printed paper. Moreover, e-ink technology has higher power efficiency, thereby increasing battery life and reducing weight. At first sight, the display looks similar to paper print, but the question remains whether the reading behavior also is equal to that of reading a printed book. In the present study, we analyzed and compared reading behavior on e-reader displays and on printed paper. The results suggest that the reading behavior on e-readers is indeed very similar to the reading behavior on print. Participants shared similar proportions of regressive saccades while reading on e-readers and print. Significant differences in fixation duration suggest that e-readers, in some situations, may even provide better legibility.

When attractiveness demands longer looks: The effects of situation and gender

We investigated how aesthetics guides our exploration of the environment. We embedded attractive and nonattractive faces into complex, real-world scenes and measured eye movements during scene viewing. We examined whether attractive faces would elicit longer looks, which would suggest that the aesthetic response orients people toward the rewarding and pleasing aspects of the environment. Experiment 1 showed that mean fixation, mean first fixation, and total fixation durations were longer to attractive faces, and fixations were longest to female faces and by female perceivers. In Experiment 2, we examined whether these effects of attractiveness are sensitive to situational factors. When perceivers were subjected to a threat or social approach manipulation prior to viewing the scenes, we confirmed specific hypotheses concerning the two manipulations. In accordance with the hypothesis that males have higher aggression potential than females, there were no differences in fixation durations between attractive and nonattractive male faces in the threat condition. On the other hand, in the social approach condition, both female and male attractive faces received longer looks. These results suggest that the aesthetic response orients people not only to the pleasing aspects of their environment, but also to those features that are adaptively relevant.

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 perceptual aspect of skilled performance in chess: evidence from eye movements.

Expert and intermediate chess players attempted to choose the best move in five chess positions while their eye movements were monitored. Experts were faster and more accurate than intermediates in choosing the best move. Experts made fewer fixations per trial and greater amplitude saccades than did intermediates, but there was no difference in fixation duration across skill groups. Examining the spatial distribution of the first five fixations for each position by skill group revealed that experts produced more fixations on empty squares than did intermediates. When fixating pieces, experts produced a greater proportion of fixations on relevant pieces than did intermediates. It is argued that expert chess players perceptually encode chess configurations, rather than individual pieces, and, consequently, parafoveal or peripheral processing guides their eye movements, producing a pattern of saccadic selectivity by piece saliency.

Individual Differences in Infant Visual Attention: Recognition of Degraded Visual Forms by Four-Month-Olds

In 5 experiments, 4-month-old infants were tested for their ability to recognize degraded visual targets as a function of individual differences in fixation duration. Targets were degraded by removing 10% of the total contour either from vertices (vertex-absent) or from midsegments (vertex-present). Both qualitative and quantitative differences were found in long and short lookers' ability to recognize the degraded forms. Short-looking infants were able to recognize degraded forms in both vertex-absent and vertex-present conditions, but the vertex-absent discrimination was more difficult. Long-looking infants required longer familiarization times before showing evidence of recognition in the vertex-present condition, and were unable to recognize targets in which contour was removed at vertices. The findings are discussed within the framework of the persistence of early visual processing strategies, and reliance of long-looking infants on particular local elements in visual analysis.

Four-month-olds' recognition of complementary-contour forms

Four-month-old long- and Short-looking infants were habituated to a visual form from which 50% of the contour was removed. Infants were then tested for recognition of the visual form with paired comparison trials in which two other 50%-degraded visual forms were simultaneously presented. One of the two degraded forms presented in the test trials was a novel form, and the other form was comprised of the “complementary contour” (e.i., the contour not previously shown) of the degraded habituation stimulus. Thus, the task involved a testof infants' recognition of a form across stimuli that shared no common contour. Only infants with attentional profiles characterized by shorter fixation durations recognized forms when tested inthis way. These results suggest that some infants are in fact capable of generalizing from one coplementary image to another; the observation of this ability short-looking infants is consistent with previous suggestions of differences in visual encoding as a function of individual differences in fixation duration.

On the Neural Mechanisms Underlying Developmental and Individual Differences in Visual Fixation in Infancy: Two Hypotheses

Both developmental and individual differences in fixation duration during the first year of life suggest that the duration of visual fixations is correlated with the rapidity of visual encoding: fixation durations decrease significantly over the first year, and individual differences in infant fixation duration within ages are reliable characteristics that correlate with measures of cognitive performance in infancy and in later childhood. The mechanism(s) responsible for these apparent individual and developmental differences in fixation (and thus, visual encoding) has yet to be determined. This review presents hypotheses concerning two specific CNS systems and how they might contribute to such individual and developmental differences in infancy. One system is the "transient" and "sustained" pathways of visual processing within the primary geniculostriate visual system (the magnocellular and parvocellular layers of the lateral geneculate). The other system is a "posterior attentional system" that has been identified with the engagement and disengagement of visuospatial orienting. Evidence is reviewed regarding how each subsystem might account for developmental and individual differences in infant visual fixation.

Individual differences in infant fixation duration: Dominance of global versus local stimulus properties

In three experiments, the dominance of global versus local visual properties was investigated in 4-month-old infants as a function of individual differences in fixation duration (i.e., “long-” versus “short-looking” infants). Dominance was assessed through paired-comparison discrimination tasks in which global and local visual properties were placed in competition with one another for infants' attention. Familiarization time was varied parametrically across experiments. Short-looking infants showed responses consistent with a global-to-local sequence of processing: dominance for the global attribute was supplanted by dominance for the local attribute as familiarization was extended. Long-looking infants, however, did not show dominance for either visual property until after considerable familiarization. When dominance was observed for this group, it was for the local visual attribute. These findings are in accord with previous observations that long-looking infants process visual information more slowly than short-looking infants, but further suggest that there may be qualitative differences in the manner in which the two groups of infants attend to the properties of visual stimuli. Links between this finding and the long-term predictive validity of fixation duration are discussed.