What are the Uncurved Lines in Our Visual Field? A Fresh Look at Helmholtz's Checkerboard

Perception ◽  
10.1068/p6288 ◽  
2009 ◽  
Vol 38 (9) ◽  
pp. 1284-1294 ◽  
Author(s):  
Augustinus H J Oomes ◽  
Jan J Koenderink ◽  
Andrea J van Doorn ◽  
Huib de Ridder
Keyword(s):  
Individual Differences ◽  
Visual Field ◽  
Large Range ◽  
Geometrical Model ◽  
Checkerboard Pattern ◽  
Viewing Condition ◽  
Fixation Condition ◽  
Free Viewing ◽  
Close Range ◽  
Curvature Perception

What are the uncurved lines in our visual field? To answer this question, Helmholtz developed a geometrical model of line-curvature perception, and demonstrated it with his famous checkerboard pattern with pin-cushion distortion. He claimed it looked perfectly regular when viewed monocularly at close range while fixating the centre. Recently, doubts have been expressed whether this demonstration actually works. We tested twenty monocular, stationary observers who could adjust the distortion of a checkerboard pattern over a large range, from barrel-shaped to pin-cushion-shaped. Their task was to adjust the curvature of the edges of the checks such that the checkerboard looked straight and regular. In one condition they had to fixate the centre of the pattern, in another condition they were instructed to let their gaze wander. We found that most observers indeed perceived a pattern with pin-cushion distortion as undeformed, thereby seeing hyperbolic curves in the figure as uncurved lines in the visual field. They set a more strongly curved pattern in the fixation condition than in the free-viewing condition, as also described by Helmholtz. Interestingly, the effect is about half as strong as Helmholtz claimed. Furthermore, we found considerable inter-individual differences.

scholarly journals Cortical reorganization of the visual system in post-stroke hemianopia studied with fMRI

Stroke ◽  
2001 ◽  
Vol 32 (suppl_1) ◽  
pp. 334-334
Author(s):  
Gereon Nelles ◽  
Guido Widmann ◽  
Joachim Esser ◽  
Anette Meistrowitz ◽  
Johannes Weber ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Visual Field ◽  
Visual System ◽  
Primary Visual Cortex ◽  
Visual Stimuli ◽  
Checkerboard Pattern ◽  
Partial Recovery ◽  
Area 18 ◽  
Area 19 ◽  
Stimulation Of

102 Introduction: Restitution of unilateral visual field defects following occipital cortex lesions occurs rarely. Partial recovery, however, can be observed in patients with incomplete lesion of the visual cortex. Our objective was to study the neuroplastic changes in the visual system that underlie such recovery. Methods and Results: Six patients with a left PCA-territory cortical stroke and 6 healthy control subjects were studied during rest and during visual stimulation using a 1.5 T fMRI with a 40 mT gradient. Visual stimuli were projected with a laptop computer onto a 154 x 115 cm screen, placed 90 cm in front of the gantry. Subjects were asked to fixate a red point in the center of the screen during both conditions. During stimulation, a black-and-white checkerboard pattern reversal was presented in each hemifield. For each side, 120 volumes of 48 contiguous axial fMRI images were obtained during rest and during hemifield stimulation in alternating order (60 volumes for each condition). Significant differences of rCBF between stimulation and rest were assessed as group analyses using statistical parametric mapping (SPM 99; p<0.01, corrected for multiple comparison). In controls, strong increases of rCBF (Z=7.6) occurred in the contralateral primary visual cortex V1 (area 17) and in V3a (area 18) and V5 (area 19). No differences were found between the right and left side in controls. During stimulation of the unaffected (left) visual field in hemianopic patients, activation occurred in contralateral V1, but the strongest increases of rCBF (Z>10) were seen in contralateral V3a (area 18) and V5 (area 19). During stimulation of the hemianopic (right) visual field, no activation was found in the primary visual cortex of either hemisphere. The most significant activation (Z=9.2) was seen in the ipsilateral V3a and V5 areas, and contralateral (left) V3a. Conclusions: Partial recovery from hemianopia is associated with strong ipsilateral activation of the visual system. Processing of visual stimuli in the hemianopic side spares the primary visual cortex and may involve recruitment of neurons in ipsilateral (contralesional) areas V3a and V5.

Neural Correlates of Inter-Observer Visual Congruency in Free-Viewing Condition

2020 ◽  
pp. 1-1
Author(s):  
Huan Liu ◽  
Xintao Hu ◽  
Yudan Ren ◽  
Liting Wang ◽  
Lei Guo ◽  
...  
Keyword(s):  
Neural Correlates ◽  
Viewing Condition ◽  
Free Viewing

A Binocular Pinhole Device for Visual Field Constraint during Reading

1977 ◽  
Vol 44 (2) ◽  
pp. 677-678
Author(s):  
David Piggins ◽  
Robert Macerollo
Keyword(s):  
Individual Differences ◽  
Visual Field ◽  
Binocular Vision ◽  
Peripheral Vision ◽  
Head Movements

The Binocular Pinhole Device requires binocular vision, without constraints on head-movements, for viewing a group of letters at one fixation. It is simple and adjustable for individual differences. The role of peripheral vision can be explored in experimental settings.

Individual Differences in Responses to Induced Perceptual Conflict

1977 ◽  
Vol 44 (3) ◽  
pp. 991-998 ◽  
Author(s):  
John A. Cegalis ◽  
David Leen
Keyword(s):  
Individual Differences ◽  
Visual Field ◽  
Field Dependence ◽  
Major Change ◽  
Visual Condition ◽  
Tolerance Of Ambiguity ◽  
Personality Changes ◽  
Field Dependent ◽  
Rod And Frame Test ◽  
Rod And Frame

Examining reactions to experimentally induced perceptual conflict may be a useful method of studying perceptual/cognitive disorganization and adaptive features of personality. Changes in field-dependence (rod-and-frame test) were assessed in introverted and extraverted subjects (17–19 yr.) who were exposed to inversion of the visual field. Tolerance of ambiguity was also assessed. There were no significant differences between introverts ( n = 20) and extraverts ( n = 16) on preinversion measures of field-dependence. However, extraverts became more field-dependent on first exposure to inversion and maintained a generally higher level of field-dependence. Introverts became more field-dependent only after walking in the inverted visual condition and after a major change in exposure conditions. No significant differences in post-inversion levels of field-dependence were observed.

The nature of individual differences in EEG parameters during homogeneous visual field in 5- and 6-year-old twins: A pilot study

2009 ◽  
Vol 120 (8) ◽  
pp. 1492-1500 ◽  
Author(s):  
T. Stroganova ◽  
I. Posikera ◽  
E. Orekhova ◽  
M. Tsetlin ◽  
S. Novikova ◽  
...  
Keyword(s):  
Individual Differences ◽  
Pilot Study ◽  
Visual Field

scholarly journals Individual differences in the shape of the nasal visual field

2017 ◽  
Vol 141 ◽  
pp. 23-29 ◽  
Author(s):  
William H. Swanson ◽  
Mitchell W. Dul ◽  
Douglas G. Horner ◽  
Victor E. Malinovsky
Keyword(s):  
Individual Differences ◽  
Visual Field

scholarly journals Search strategies improve with practice, but not with time pressure or financial incentives

2020 ◽  
Author(s):  
Anna Nowakowska ◽  
Alasdair D F Clarke ◽  
Amelia R. Hunt ◽  
Jacqueline von Seth
Keyword(s):  
Individual Differences ◽  
Eye Movements ◽  
Financial Incentives ◽  
Time Pressure ◽  
Large Range ◽  
Financial Incentive ◽  
Search Strategies ◽  
Wide Range ◽  
Extensive Computation ◽  
The Cost

When searching for an object, do we minimize the number of eye movements we need to make? Under most circumstances, the cost of saccadic parsimony likely outweighs the benefit, given the cost is extensive computation and the benefit is a few hundred milliseconds of time saved. Previous research has measured the proportion of eye movements directed to locations where the target would have been visible in the periphery, as a way of quantifying the proportion of superfluous fixations. A surprisingly large range of individual differences has emerged from these studies, suggesting some people are highly efficient and others much less so. Our question in the current study is whether these individual differences can be explained by differences in motivation. In two experiments, we demonstrate that neither time pressure, nor financial incentive, led to improvements of visual search strategies; the majority of participants continued to make many superfluous fixations in both experiments. The wide range of individual differences in efficiency observed previously was replicated here. We observed small but consistent improvements in strategy over the course of the experiment (regardless of reward or time pressure) suggesting practice, not motivation, makes participants more efficient.

Field Dependence and the Role of Visual Frameworks in the Perception of Size

Perception ◽  
1977 ◽  
Vol 6 (6) ◽  
pp. 661-666 ◽  
Author(s):  
Eric Sigman ◽  
Philip K Oltman
Keyword(s):  
Individual Differences ◽  
Cognitive Style ◽  
Field Dependence ◽  
Large Range ◽  
Apparent Size ◽  
Target Figure ◽  
Field Independent ◽  
Field Dependent

The extent to which apparent size is relationally determined has been studied by Rock and Ebenholtz and by Wenderoth, who came to widely differing conclusions as to the magnitude of this phenomenon. In both studies, a large range of individual differences was observed. In the present study, an attempt was made to account for variations in the influence of visual contexts on the perception of size by relating them to the cognitive style dimension of field dependence/independence. In two situations, relatively field-dependent observers made size judgments which were influenced by a frame surrounding the target figure, while relatively field-independent observers tended to be less influenced by the frame, making their judgments approximate the retinal size of the target. The results suggest that assessment of the magnitude of the relational determination of apparent size must consider the cognitive style of the observers as well as situational variations.

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