The influence of texture on judgments of slant and relative distance in a picture with suggested depth

Six surfaces from natural environments with different visual textures were photographed at angles of 60, 65, and 70 deg from perpendicular. Measurements were taken of 24 Ss’ judgments of the inferred angles of slant and inferred midpoints of the six textured surfaces represented in the photographs which were viewed in the frontoparallel plane. Judgments of both slant and relative distance within the photographs were influenced by represented angle of slant and by variations in surface texture.     

Sequential dependencies and regression in psychophysical judgments

A tendency for judgments of stimulus magnitude to be biased in the direction of the value of the immediately preceding stimulus is found in magnitude estimations of loudness. This produces a bias in the empirical psychophysical function that results in underestimation of the exponent of the unbiased function presumed to relate number and stimulus intensity, N = aSⁿ. The biased judgment can be represented as a power product of focal and preceding stimulus intensity, N_ij= aS ^m S_j ^b. A bias-free estimate of the correct exponent, n, can be obtained from the relation n = m + b.     

Variations in size judgements as a function of surface texture

Adult subjects made monocular size judgements in two experiments in which the independent variables of surface texture and restrictions on viewing conditions were manipulated. Texture density gradients of stimulation had a significant influence of size judgements only under the less reduced conditions of observation when subjects could see other textured surfaces beyond the surfaces over which judgements were made. Identical manipulations of surface texture had earlier been found to have a highly significant influence on relative distance judgements (Newman, 1971). The principally negative results were thus taken to imply that subjects extract different information from the texture density gradient when judging size from that extracted when judging relative distance.     

SCV-A general subroutine for the selection of combinations of variables

SCV is a FORTRAN IV subroutine for sequencing combinations of variables. Selection of the combinations can be random with or without replacement and with equal or unequal frequencies of occurrence. Application is illustrated in terms of an interactive process-control experiment, but the subroutine is applicable to any problem requiring the generation of multidimensional sequences or the permutation of a set of numbers.     

TESTS OF THE “CARPENTERED WORLD” HYPOTHESIS BY RACE AND ENVIRONNEMENT IN AMERICA AND ZAMBIA1

La sensibilité aux illusions optico-géométriques est-elle un trait héréditaire ou dérive-t-elle de facteurs d'environnement ? Ces deux hypothèses — hypothèse physiologique de Pollack et hypothèse écologique de Segall et al. — ont été examinées à l'aide des illusions de Muller-Lyer et de Sander appliquées à un échantillon américain et cinq échantillons zambiens. Dans le premier cas, on a étudié l'effet des variations de pigmentation rétinienne en milieu constant; en Zambie, au contraire, la variable raciale étant contrôlée, on a observé l'influence de différentes écologies (degré de “charpentisation” du milieu). Les résultats ne révèlent aucun effet significatif dû à la pigmentation rétinienne et appuient l'hypothèse de l'influence écologique. l'effet de la variable âge est aussi confirmé, la suggestibilité diminuant avec l'âge, tandis qu'apparaît un effet peu remarqué jusqu'ici, celui du sexe, les femmes se montrant moins sensibles à l'illusion.