A study of sine-wave contrast sensitivity by two psychophysical methods

Kelly, D. H.; Savoie, R. E.

doi:10.3758/bf03212397

Cited by 79 publications

(25 citation statements)

References 12 publications

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“…Such work had been performed before (Kelly & Savoie, 1973), and my work essentially replicated those results. In the present paper, however, I am not concerned with the psychophysical data itself (which indicated that the forced-choice technique gave slightly lower thresholds for vastly greater effort, while not changing the relative shapes of any curves), but rather with the technical problems that arose in using computer-generated raster images to do the vision experiments.…”

Section: Case 1: Changing Color Interactively While Maintaining Luminsupporting

confidence: 74%

Making quantized images appear smooth: Tricks of the trade in vision research

Savoy

1986

Behavior Research Methods, Instruments, & Computers

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Digital image-processing systems combined with color raster television technology are opening new worlds for the visual psychophysicist. Some of the inherent limitations and practical hazards of these technologies are explored. Techniques for circumventing some of the current limitations are presented, especially with regard to the issue of real-time variation of visual images. This paper is divided into two parts. In the first part, I examine the question: To what extent can we generate arbitrary visual stimuli using current computer imageprocessing systems? Thisquestion can bestbe approached by making analogies between vision and audition. For both vision and audition, the problem is divided (somewhat idiosyncratically) into four issues: (1) abstract representation of the stimulus (e.g., an equation or algorithm); (2) explicit representation of the stimulus (e.g., pixelvalues); (3) communication of the explicit representation to a physical transducer; and (4) physical transduction. Limitations of current theory or hardware are pointed out for each issue.In the second part of the paper, I describe several instances (fromactual practice) in which varioustechniques wereusedto generate stimuli thatwerenot whattheunderlying hardware devices were designed to generate; in short, I will document various tricks used to get around some of the limitations. Attention will be focused on a specific image-processing computer system, but the ideas are of wide applicability, given the current generationof imageprocessors. At somepoint in the future, there may be image processors and displays that are designed explicitly for use in psychophysical vision research; in the meantime, however, the experimenter can generate a surprisingly general collection of stimuli despite hardware constraints. The Dream of Psychophysical OmnipotenceWhat is needed to be able to create, in a laboratory, any visual stimulus? What information rate is required? How can the information be stored, communicated, and transformed into light? In addressing these questions, it is helpful to first considerthe analogous questions for audition, using data summarized by Green (1976 An arbitrary auditory stimulus has two dimensions: intensity and time. For most purposes in psychophysics (i.e., ignoring such things as bone conduction), if we specify intensity as a function of time at two points in space (one for each ear), we have specifiedthe auditory stimulus completely. Furthermore, the required bandwidth for an auditory stimulus is 20 kHz. If we were to specify an auditory stimulusat discrete points in time separated by, for example, %0,000 sec (twice the maximum frequency), then any errors introducedby temporal quantization would be irrelevant, because the auditory system cannot respond to them. (This is not the whole story, as temporal differences in phase between the two ears can be detectedat finer temporal resolution.) Audible sound pressurescover a range of 10 log units, and intensity discrimination is on the order of I %. Ifwe were to represent intensit...

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Section: Case 1: Changing Color Interactively While Maintaining Luminsupporting

confidence: 74%

Making quantized images appear smooth: Tricks of the trade in vision research

Savoy

1986

Behavior Research Methods, Instruments, & Computers

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“…CSFs do not have a ceiling effect, but could have a floor effect because threshold can never be greater than 100% contrast (i.e., contrast sensitivity of 1 is a lower limit in performance). Practice effects are negligible with the 2-alternative forced choice tracking method37. In addition, there is good agreement in observers in the shape of the function and absolute values of contrast sensitivity.…”

Section: Steady-state Visual Evoked Potentials and Contrast Sensitivimentioning

confidence: 68%

“…Spatial frequency refers to the number of pairs of light and dark bars in a degree of visual angle such that lower spatial frequencies indicate wider bars and higher spatial frequencies indicate thinner bars. Different psychophysical methods have been used to measure contrast sensitivity functions (CSF)37. A preferred method is two-alternative forced-choice tracking in which, for instance, gratings are presented randomly to one half of a visual display, while the other half has a uniform field33.…”

Section: Steady-state Visual Evoked Potentials and Contrast Sensitivimentioning

confidence: 99%

Perception Measurement in Clinical Trials of Schizophrenia: Promising Paradigms From CNTRICS

Green

Butler

Chen

et al. 2009

Schizophrenia Bulletin

112

111

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The third meeting of the Cognitive Neuroscience Treatment Research to Improve Cognition in Schizophrenia (CNTRICS) focused on selecting promising measures for each of the cognitive constructs selected in the first CNTRICS meeting. In the domain of perception, the two constructs of interest were Gain Control and Visual Integration. CNTRICS received five task nominations for Gain Control and three task nominations for Visual Integration. The breakout group for perception evaluated the degree to which each of these tasks met pre-specified criteria. For Gain Control, the breakout group for perception believed that two of the tasks (Prepulse Inhibition of Startle and Mismatch Negativity) were already mature and in the process of being incorporated into multisite clinical trials. However, the breakout group recommended that Steady State Visual Evoked Potentials be combined with contrast sensitivity to magnocellular vs. parvocellular biased stimuli, and that this combined task and the Contrast-Contrast Effect Task be recommended for translation for use in clinical trial contexts in schizophrenia research. For Visual Integration, the breakout group recommended the Contour Integration and Coherent Motion tasks for translation for use in clinical trials. This manuscript describes the ways in which each of these tasks met the criteria used by the breakout group to evaluate and recommend tasks for further development.

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“…Legge 1981). Although quantitative differences may be introduced by the use of different procedures, the relationships between the measured thresholds is generally found to be quite stable (Kelly & Savoie 1973;Graham 1989). At any rate, experiments ofthe kind reported here, where a great amount of data needs to be collected from individual observers, are largely impractical using other, more time-consuming methods.…”

Section: Experimental Designmentioning

confidence: 99%