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B W Tansley

Publications and source records attributed to B W Tansley.

7 recordsLinked to original sources
PubMed1979

Selective adaptation to frequency-modulated tones: evidence for an information-processing channel selectively sensitive to frequency changes.

Exposure to an FM tone elevates FM threshold but not AM threshold. This holds for a wide range of frequency deviations (delta F = +/- 0.4 Hz- +/- 30 Hz at least) provided that modulation frequency is low (fm = 2 Hz), but if fm is somewhat higher (e.g., 8 Hz) the finding only holds for small frequency deviations. FM threshold can rise with time up to an adapting duration of at least 1200 s, through this buildup depends on frequency deviation. Exposure to an AM tone elevates AM threshold, but not FM threshold, over a wide range of modulation depths (at least m = 5%--50%). Quasi-FM (QFM) adapting tones resemble FM adapting tones in their effects upon FM and AM sensitivities, even though QFM and AM adapting tones have identical power spectra. Exposure to a pure tone produces no difference between FM and AM threshold elevations. These data can be explained if the human auditory pathway contains separate information-processing channels for AM and FM signals whose sensitivities do not overlap even with suprathreshold stimuli. We suppose that the FM channel (but not the AM channel) is sensitive to changing differences (or ratios) between signals from different sites along the basilar membrane.

Adaptation, Psychological↗
PubMed1979

Chromatic border distinctness: not an index of hue or saturation differences.

Some investigators have suggested that the distinctness of chromatic borders (i.e., borders visible in photic arrays of uniform luminance) can be used as an index of hue and saturation differences between lights. However, recent evidence indicates that only two types of cones in the trichromatic eye contribute to chromatic border perception. A series of experiments are reported that were designed to discriminate between these alternatives, utilizing mainly the short-wavelength visible spectrum. The results support the notion that only R and G cones in the trichromatic eye mediate the perception of chromatic borders; thus the distinctness of such borders alone cannot be used as an index of either hue or saturation differences, because both of these aspects of color involve contributions from B cones.

Color Perception↗
PubMed1977

Tritanopic purity-difference function to describe the properties of minimally distinct borders.

Tansley and Boynton have recently demonstrated that color stimuli whose chromaticities all fall on a particular triptanopic confusion line in the CIE (x,y) diagram do not form distinct borders with each other. A tritanopic purity-difference function, involving only r- and g-cone contributions, is demonstrated to provide (i) a prediction of which chromatic stimuli have equivalent border-forming properties, and (ii) a description of the distinctness of minimally distinct borders (MDB) in terms of an equivalent luminance contrast. The tritanopic purity-difference concept is demonstrated to account for all available data on the assessment of the distinctness of borders at the MDB point.

Color Perception↗
PubMed1976

A line, not a space, represents visual distinctness of borders formed by different colors.

When observers are asked to rate the visual distinctness of borders formed by the junction of two photic stimuli, normal trichromatic subjects behave in a manner similar to that of tritanopes in a color mixture experiment. All stimuli that look the same to the tritanope produce the same border distinctness with any other stimulus. Sets of such stimuli, whose members do not form borders with each other, map as single points along a curved line, where the Euclidean distance between pairs of points representing the two stimuli is nearly proportional to the rated distinctness of the border formed between them. In the absence of luminance differences, the perception of contour apparently depends on the stimulation of only two cone types.

Color Perception↗