Masson disk

a device for measuring the threshold of brightness vision. The disk is white with a black segmented line along one radius. When it is rotated, varying shades of gray are seen, the darkest at the center. The point at which the disk becomes indistinguishable from the background provides the required measurement. [Antoine-Philibert Masson (1806–1860), French physicist]

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Psychology term of the day

November 21st 2024

equal rights amendment (ERA)

Sorry, "equal-rights-amendment-era" is not in the Dictionary of Psychology. Please report to APA if you believe this is an error.