Gadi Geiger - Academia.edu (original) (raw)

Papers by Gadi Geiger

Research paper thumbnail of Preventing Dyslexia

The problem: Developmental dyslexia (dyslexia in short) also named severe reading disability (SRD... more The problem: Developmental dyslexia (dyslexia in short) also named severe reading disability (SRD) is the condition where a person is severely impaired in reading in spite of adequate intelligence, adequate tutoring and absence of obvious pathologies. Finding ways for the prevention of dyslexia is an important issue we address. Motivation: The prevalence of dyslexia among the student body is estimated to range from 3-5 % [14] to 20 % [12] depending on when the study was conducted, the criteria used to define dyslexia and the sociocultural background. In the USA, dyslexics constitute 80-85 % of learning disabled students [11,12]. The etiology and the remediation of dyslexia are widely researched. However, the interest in the prevention of dyslexia is less obvious. If there is a way for preventing or reducing the incidence of dyslexia it is important to find out how and then implement it. Previous work: Most commonly dyslexia is described as a language-based disorder of phonological p...

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Research paper thumbnail of Is the Human Visual System Invariant to Translation and Scale?

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Research paper thumbnail of Eye-Movements while observing "Parallel and Serial" Patterns

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Research paper thumbnail of A trainable videorealistic speech animation system

Audiovisual Speech Processing

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Research paper thumbnail of Dyslexic children learn a new visual strategy for reading: a controlled experiment

Vision Research, 1994

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Research paper thumbnail of Trainable Videorealistic Facial Animation

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Research paper thumbnail of Center for Biological and Computational Learning Department of Brain and Cognitive Sciences

We present a trainable system for detecting frontal and near-frontal views of faces in still gray... more We present a trainable system for detecting frontal and near-frontal views of faces in still gray images using Support Vector Machines (SVMs). We first consider the problem of detecting the whole face pattern by a sin-gle SVM classifier. In this context we compare different types ...

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Research paper thumbnail of Explicit and implicit perceptual discrimination of videorealistic speech

Journal of Vision, 2010

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Research paper thumbnail of Perceptual Evaluation of Video-Realistic Speech

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Research paper thumbnail of Wide and diffuse perceptual modes characterize dyslexics in vision and audition

Perception, 2008

We examined the performance of dyslexic and typically reading children on two analogous recogniti... more We examined the performance of dyslexic and typically reading children on two analogous recognition tasks: one visual and the other auditory. Both tasks required recognition of centrally and peripherally presented stimuli. Dyslexics recognized letters visually farther in the periphery and more diffuse near the center than typical readers did. Both groups performed comparably in recognizing centrally spoken stimuli presented without peripheral interference, but in the presence of a surrounding speech mask (the ‘cocktail-party effect’) dyslexics recognized the central stimuli significantly less well than typical readers. However, dyslexics had a higher ratio of the number of words recognized from the surrounding speech mask, relative to the ones from the center, than typical readers did. We suggest that the evidence of wide visual and auditory perceptual modes in dyslexics indicates wider multi-dimensional neural tuning of sensory processing interacting with wider spatial attention.

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Research paper thumbnail of Preventing Dyslexia

Motivation: The prevalence of dyslexia among the student body is estimated to range from 3-5% [14... more Motivation: The prevalence of dyslexia among the student body is estimated to range from 3-5% [14] to 20% [12] depending on when the study was conducted, the criteria used to define dyslexia and the sociocultural background. In the USA, dyslexics constitute 80-85% of learning disabled students [11,12]. The etiology and the remediation of dyslexia are widely researched. However, the interest in the prevention of dyslexia is less obvious. If there is a way for preventing or reducing the incidence of dyslexia, it is important to find out how and then implement it.

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Research paper thumbnail of Asymptotic oscillations in the tracking behaviour of the fly Musca domestica

Biological Cybernetics, 1981

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Research paper thumbnail of Task-determined strategies of visual process

Cognitive Brain Research, 1992

Lateral masking in the peripheral field of vision obscures letter recognition and is not accounte... more Lateral masking in the peripheral field of vision obscures letter recognition and is not accounted for by diminished acuity. In measuring lateral masking between letters in the peripheral visual field we accidentally discovered that ordinary readers and severe dyslexics differ markedly in tachistoscopic letter recognition tasks. Tests were devised to measure the differences accurately. Ordinary readers recognize letters best in and near the center of gaze. Recognition falls off rapidly with angular distance in the peripheral field. Severe dyslexics recognize letters farther in the periphery in the direction of reading (English-natives to the right, Hebrew-natives to the left). They have marked lateral masking in and near the center of the field when letters are presented in aggregates. With dyslexia as an example, we proposed that the distribution of lateral masking is a task-dependent strategy in visual perception. To test this notion we designed an active practise regimen for 4 severe adult dyslexics, who within a few months improved sharply in reading. At the same time their test results changed to those of ordinary readers. We conclude that there are switchable task-determined pre-cognitive strategies of vision that can be learned and that the distribution of lateral masking may be part of what is learned.

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Research paper thumbnail of Task-determined strategies of visual process

Cognitive Brain Research, 1992

Lateral masking in the peripheral field of vision obscures letter recognition and is not accounte... more Lateral masking in the peripheral field of vision obscures letter recognition and is not accounted for by diminished acuity. In measuring lateral masking between letters in the peripheral visual field we accidentally discovered that ordinary readers and severe dyslexics differ markedly in tachistoscopic letter recognition tasks. Tests were devised to measure the differences accurately. Ordinary readers recognize letters best in and near the center of gaze. Recognition falls off rapidly with angular distance in the peripheral field. Severe dyslexics recognize letters farther in the periphery in the direction of reading (English-natives to the right, Hebrew-natives to the left). They have marked lateral masking in and near the center of the field when letters are presented in aggregates. With dyslexia as an example, we proposed that the distribution of lateral masking is a task-dependent strategy in visual perception. To test this notion we designed an active practise regimen for 4 severe adult dyslexics, who within a few months improved sharply in reading. At the same time their test results changed to those of ordinary readers. We conclude that there are switchable task-determined pre-cognitive strategies of vision that can be learned and that the distribution of lateral masking may be part of what is learned.

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Research paper thumbnail of Enhancing the perception of form in peripheral vision

Perception, 1986

Experiments are reported which show that the tachistoscopic presentation of a figure at the point... more Experiments are reported which show that the tachistoscopic presentation of a figure at the point of fixation makes salient the same figure where it occurs elsewhere in the visual field during the same flash. This induced saliency operates in all directions from the axis of gaze. If the eccentric figure is alone on a blank field the phenomenon is termed ‘eccentric enhancement’. The induced saliency of figures that are laterally masked within horizontal strings of figures that lie off the fixation point is termed ‘demasking’.

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Research paper thumbnail of Peripheral vision in persons with dyslexia

New England Journal of Medicine, 1987

We compared persons with dyslexia and normal readers with respect to how well they identified let... more We compared persons with dyslexia and normal readers with respect to how well they identified letters and short strings of letters briefly presented in the peripheral visual field at the same time that a single letter was presented at the fixation point of gaze. We found that the dyslexic subjects had a markedly wider area in which correct identification occurred in the peripheral field than did the normal readers. However, the dyslexic subjects had a "masking" between letters in the foveal field and letters in the near periphery. It appears that dyslexic persons learn to read outside the foveal field and, more generally, that there are different learned strategies for task-directed vision. Among such strategies are different mutual interactions between foveal and peripheral vision.

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Research paper thumbnail of Preventing dyslexia? Early enhanced hand-eye coordination activities reduces reading difficulties

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Research paper thumbnail of The Müller-Lyer figure and the fly

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Research paper thumbnail of Wider recognition in peripheral vision common to different subtypes of dyslexia

Vision Research, 2004

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Research paper thumbnail of Werner Reichardt: the man and his scientific legacy

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Research paper thumbnail of Preventing Dyslexia

The problem: Developmental dyslexia (dyslexia in short) also named severe reading disability (SRD... more The problem: Developmental dyslexia (dyslexia in short) also named severe reading disability (SRD) is the condition where a person is severely impaired in reading in spite of adequate intelligence, adequate tutoring and absence of obvious pathologies. Finding ways for the prevention of dyslexia is an important issue we address. Motivation: The prevalence of dyslexia among the student body is estimated to range from 3-5 % [14] to 20 % [12] depending on when the study was conducted, the criteria used to define dyslexia and the sociocultural background. In the USA, dyslexics constitute 80-85 % of learning disabled students [11,12]. The etiology and the remediation of dyslexia are widely researched. However, the interest in the prevention of dyslexia is less obvious. If there is a way for preventing or reducing the incidence of dyslexia it is important to find out how and then implement it. Previous work: Most commonly dyslexia is described as a language-based disorder of phonological p...

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Research paper thumbnail of Is the Human Visual System Invariant to Translation and Scale?

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Eye-Movements while observing "Parallel and Serial" Patterns

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A trainable videorealistic speech animation system

Audiovisual Speech Processing

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Dyslexic children learn a new visual strategy for reading: a controlled experiment

Vision Research, 1994

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Research paper thumbnail of Trainable Videorealistic Facial Animation

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Center for Biological and Computational Learning Department of Brain and Cognitive Sciences

We present a trainable system for detecting frontal and near-frontal views of faces in still gray... more We present a trainable system for detecting frontal and near-frontal views of faces in still gray images using Support Vector Machines (SVMs). We first consider the problem of detecting the whole face pattern by a sin-gle SVM classifier. In this context we compare different types ...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Explicit and implicit perceptual discrimination of videorealistic speech

Journal of Vision, 2010

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Perceptual Evaluation of Video-Realistic Speech

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Wide and diffuse perceptual modes characterize dyslexics in vision and audition

Perception, 2008

We examined the performance of dyslexic and typically reading children on two analogous recogniti... more We examined the performance of dyslexic and typically reading children on two analogous recognition tasks: one visual and the other auditory. Both tasks required recognition of centrally and peripherally presented stimuli. Dyslexics recognized letters visually farther in the periphery and more diffuse near the center than typical readers did. Both groups performed comparably in recognizing centrally spoken stimuli presented without peripheral interference, but in the presence of a surrounding speech mask (the ‘cocktail-party effect’) dyslexics recognized the central stimuli significantly less well than typical readers. However, dyslexics had a higher ratio of the number of words recognized from the surrounding speech mask, relative to the ones from the center, than typical readers did. We suggest that the evidence of wide visual and auditory perceptual modes in dyslexics indicates wider multi-dimensional neural tuning of sensory processing interacting with wider spatial attention.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Preventing Dyslexia

Motivation: The prevalence of dyslexia among the student body is estimated to range from 3-5% [14... more Motivation: The prevalence of dyslexia among the student body is estimated to range from 3-5% [14] to 20% [12] depending on when the study was conducted, the criteria used to define dyslexia and the sociocultural background. In the USA, dyslexics constitute 80-85% of learning disabled students [11,12]. The etiology and the remediation of dyslexia are widely researched. However, the interest in the prevention of dyslexia is less obvious. If there is a way for preventing or reducing the incidence of dyslexia, it is important to find out how and then implement it.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Asymptotic oscillations in the tracking behaviour of the fly Musca domestica

Biological Cybernetics, 1981

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Task-determined strategies of visual process

Cognitive Brain Research, 1992

Lateral masking in the peripheral field of vision obscures letter recognition and is not accounte... more Lateral masking in the peripheral field of vision obscures letter recognition and is not accounted for by diminished acuity. In measuring lateral masking between letters in the peripheral visual field we accidentally discovered that ordinary readers and severe dyslexics differ markedly in tachistoscopic letter recognition tasks. Tests were devised to measure the differences accurately. Ordinary readers recognize letters best in and near the center of gaze. Recognition falls off rapidly with angular distance in the peripheral field. Severe dyslexics recognize letters farther in the periphery in the direction of reading (English-natives to the right, Hebrew-natives to the left). They have marked lateral masking in and near the center of the field when letters are presented in aggregates. With dyslexia as an example, we proposed that the distribution of lateral masking is a task-dependent strategy in visual perception. To test this notion we designed an active practise regimen for 4 severe adult dyslexics, who within a few months improved sharply in reading. At the same time their test results changed to those of ordinary readers. We conclude that there are switchable task-determined pre-cognitive strategies of vision that can be learned and that the distribution of lateral masking may be part of what is learned.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Task-determined strategies of visual process

Cognitive Brain Research, 1992

Lateral masking in the peripheral field of vision obscures letter recognition and is not accounte... more Lateral masking in the peripheral field of vision obscures letter recognition and is not accounted for by diminished acuity. In measuring lateral masking between letters in the peripheral visual field we accidentally discovered that ordinary readers and severe dyslexics differ markedly in tachistoscopic letter recognition tasks. Tests were devised to measure the differences accurately. Ordinary readers recognize letters best in and near the center of gaze. Recognition falls off rapidly with angular distance in the peripheral field. Severe dyslexics recognize letters farther in the periphery in the direction of reading (English-natives to the right, Hebrew-natives to the left). They have marked lateral masking in and near the center of the field when letters are presented in aggregates. With dyslexia as an example, we proposed that the distribution of lateral masking is a task-dependent strategy in visual perception. To test this notion we designed an active practise regimen for 4 severe adult dyslexics, who within a few months improved sharply in reading. At the same time their test results changed to those of ordinary readers. We conclude that there are switchable task-determined pre-cognitive strategies of vision that can be learned and that the distribution of lateral masking may be part of what is learned.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Enhancing the perception of form in peripheral vision

Perception, 1986

Experiments are reported which show that the tachistoscopic presentation of a figure at the point... more Experiments are reported which show that the tachistoscopic presentation of a figure at the point of fixation makes salient the same figure where it occurs elsewhere in the visual field during the same flash. This induced saliency operates in all directions from the axis of gaze. If the eccentric figure is alone on a blank field the phenomenon is termed ‘eccentric enhancement’. The induced saliency of figures that are laterally masked within horizontal strings of figures that lie off the fixation point is termed ‘demasking’.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Peripheral vision in persons with dyslexia

New England Journal of Medicine, 1987

We compared persons with dyslexia and normal readers with respect to how well they identified let... more We compared persons with dyslexia and normal readers with respect to how well they identified letters and short strings of letters briefly presented in the peripheral visual field at the same time that a single letter was presented at the fixation point of gaze. We found that the dyslexic subjects had a markedly wider area in which correct identification occurred in the peripheral field than did the normal readers. However, the dyslexic subjects had a "masking" between letters in the foveal field and letters in the near periphery. It appears that dyslexic persons learn to read outside the foveal field and, more generally, that there are different learned strategies for task-directed vision. Among such strategies are different mutual interactions between foveal and peripheral vision.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Preventing dyslexia? Early enhanced hand-eye coordination activities reduces reading difficulties

Bookmarks Related papers MentionsView impact

Research paper thumbnail of The Müller-Lyer figure and the fly

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Wider recognition in peripheral vision common to different subtypes of dyslexia

Vision Research, 2004

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Werner Reichardt: the man and his scientific legacy

Bookmarks Related papers MentionsView impact