Border locking and the Café Wall illusion

The Café Wall illusion (seen on the tiles of a local café) is a Münsterberg chequerboard figure, but with horizontal parallel lines which may have any luminance separating the rows of displaced squares. These (the 'mortar' lines) display marked wedge distortion which is especially affected by: contrast of the squares ('tiles'); width of the 'mortar' lines, and their luminance which must not be significantly higher than that of the light squares or lower than that of the dark squares for distortion to occur. An experiment is described from which quantitative data have been obtained by varying these parameters. It is suggested that contiguous regions of different luminance (and contiguous colour regions) are normally held in spatial register by locking from common luminance boundaries. The Café Wall illusion is attributed to this border locking producing inappropriate contour shifts from neighbouring regions of contrasting luminance when separated by narrow gaps of neutral luminance. Further implications on the border-locking notion are discussed.     

Random-dot picture sampling by optical projection

An optical projection technique for controllable and quantifiable degradation of any two-dimensional test slide is described. The technique provides many of the features of electronic methods at low cost.     

Psychometric evaluation of the Menstrual Joy Questionnaire

Analysis of 10 terms in the Menstrual Joy Questionnaire of Delaney, Lupton, and Toth indicated that the 34 undergraduate students did not agree on the definitions of scale items. The authors discuss the use of this questionnaire as a stimulus in experimental research and as a measure of positive perimenstrual experience.     

Vision with equiluminant colour contrast: 2. A large-scale technique and observations.

A simple technique is described for producing large-scale, tritanopic displays. The technique reproduces the various phenomena of vision with equiluminous-colour contrast that have previously been reported with red/green stimuli. It is, however, much less demanding technically, robust against artifacts, and can be used on large-scale scenes. One advantage of the technique is that a piece of blue filter can be used individually by each observer to compare quickly tritanopic and luminance conditions.