The effect of texture relief on perception of slant from texture

Texture can be an effective source of information for perception of slant and curvature. A computational assumption required for some texture cues is that texture must be flat along a surface. There are many textures which violate this assumption, and have some sort of texture relief: variations perpendicular to the surface. Some examples include grass, which has vertical elements, or scattered rocks, which are volumetric elements with 3-D shapes. Previous studies of perception of slant from texture have not addressed the case of textures with relief. The experiments reported here test judgments of slant for textures with various types of relief, including textures composed of bumps, columns, and oriented elements. The presence of texture relief was found to affect judgments, indicating that perception of slant from texture is not robust to violations of the flat-texture assumption. For bumps and oriented elements, slant was underestimated relative to matching flat textures, while for columns textures, which had visible flat top faces, perceived slant was equal or greater than for flat textures. The differences can be explained by the way different types of texture relief affect the amount of optical compression in the projected image, which would be consistent with results from previous experiments using cue conflicts in flat textures. These results provide further evidence that compression contributes to perception of slant from texture.     

Stationary visual texture and the estimation of slant angle

Gibson (1950a) has suggested that a gradient of retinal stimulation from an irregularly textured surface is used in the estimation of slant. There are several measures that could form such a gradient. Eight pictures of slanting surfaces were constructed with the aid of a computer. These consisted only of texture elements: in this case, outline circles and ellipses. Subjects studied pairs of pictures and indicated which had the greater tilt. By varying separately the gradients of element size and element density, it was possible to show that only the former contributed appreciably to the impression of slant. Only some of the measures considered are consistent with this result.     

The effect of pattern and texture gradient on slant and shape judgments

The experiment reported was designed to explore the relationship between gradient of texture and monocular slantshape perception. The effects of instructional set and order of slant and shape judgments were studied in interaction with four patterns differing in regularity of texture. Judgments of slant and shape were made by the same Ss for all patterns at 20°, 45°, 60°slant for slant judgments and 0°, 20°, 45°, 60° for width judgments. There were three instructional groups. Within each group one half of the Ss made slant judgments first, the other half shape judgments first. For all patterns, accurate perception of the slant of patterned material resulted in increased compensation in width judgments. Apparent width was found to be a function of pattern and also subject to instructional manipulation.     

The perception of depth and slant from texture in three-dimensional scenes.

The perception of depth and slant in three-dimensional scenes specified by texture was investigated in five experiments. Subjects were presented with computer-generated scenes of a ground and ceiling plane receding in depth. Compression, convergence, and grid textures were examined. The effect of the presence or absence of a gap in the center of the display was also assessed. Under some conditions perceived slant and depth from compression were greater than those found with convergence. The relative effectiveness of compression in specifying surface slant was greater for surfaces closer to ground planes (80 degrees slant) than for surfaces closer to frontal parallel planes (40 degrees slant). The usefulness of compression was also observed with single-plane displays and with displays with surfaces oriented to reduce information regarding the horizon.     

Wrinkling and head shape as coordinated sources of age-level information

Changes in the shape of a human head and the development of facial wrinkles were examined as potential sources of information about age level. In Experiment 1, subjects estimated the ages of faces that had been produced by systematically manipulating characteristic head shapes and levels of wrinkles associated with ages 15, 30, 50, and 70 years. The results indicated that observers used both sources of craniofacial change in making age estimates; but the effect of either source of change on perceived age depended upon the level of the other source of change. In Experiment 2, subjects’ ratings of the apparent conflict between levels of head shape and wrinkles further substantiated the conclusion that observers are sensitive to the coordination of products of the two sources of change. These findings suggest that the information specifying perceived age level is a complexrelationship among different types of craniofacial change.     

Aging and the perception of slant from optical texture, motion parallax, and binocular disparity

The ability of younger and older observers to perceive surface slant was investigated in four experiments. The surfaces possessed slants of 20°, 35°, 50°, and 65°, relative to the frontoparallel plane. The observers judged the slants using either a palm board (Experiments 1, 3, and 4) or magnitude estimation (Experiment 2). In Experiments 1–3, physically slanted surfaces were used (the surfaces possessed marble, granite, pebble, and circle textures), whereas computer-generated 3-D surfaces (defined by motion parallax and binocular disparity) were utilized in Experiment 4. The results showed that the younger and older observers' performance was essentially identical with regard to accuracy. The younger and older age groups, however, differed in terms of precision in Experiments 1 and 2: The judgments of the older observers were more variable across repeated trials. When taken as a whole, the results demonstrate that older observers (at least through the age of 83 years) can effectively extract information about slant in depth from optical patterns containing texture, motion parallax, or binocular disparity.     

Social network profiles as information sources for adolescents' offline relations

This article presents the results of a study concerning the use of online profile pages by adolescents to know more about "offline" friends and acquaintances. Previous research has indicated that social networking sites (SNSs) are used to gather information on new online contacts. However, several studies have demonstrated a substantial overlap between offline and online social networks. Hence, we question whether online connections are meaningful in gathering information on offline friends and acquaintances. First, the results indicate that a combination of passive uncertainty reduction (monitoring a target's profile) and interactive uncertainty reduction (communication through the target's profile) explains a considerable amount of variance in the level of uncertainty about both friends and acquaintances. More specifically, adolescents generally get to know much more about their acquaintances. Second, the results of online uncertainty reduction positively affect the degree of self-disclosure, which is imperative in building a solid friend relation. Further, we find that uncertainty reduction strategies positively mediate the effect of social anxiety on the level of certainty about friends. This implies that socially anxious teenagers benefit from SNSs by getting the conditions right to build a more solid relation with their friends. Hence, we conclude that SNSs play a substantial role in today's adolescents' everyday interpersonal communication.     

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.     

Motion information in iconic memory

Motion perception was investigated in two experiments using Sperling's partial report procedure. In Experiment 1, subjects were presented with 8 moving squares; at array offset an arrow cued subjects to locate all squares moving in the direction of the arrow. The partial report was found to be superior to the whole report and this was taken as evidence for the existence, in iconic memory, of information about the direction of motion. The second experiment revealed only a minor decay in this superiority with the indicator delayed up to 1 sec. The importance of optical transformations in vision was stressed and it was argued that information processing models need pay greater attention to them.     

The role of the centre of projection in the estimation of slant from texture of planar surfaces

Displays were presented consisting of a perspective projection of a regular square grid, made up of vertical and horizontal equally spaced white lines, that was slanted in depth. The surface was viewed monocularly, through a circular aperture. A range of slants was shown (0 degree, 10 degrees, 20 degrees, 30 degrees, 40 degrees, 50 degrees, or 60 degrees) and the observers' task was to match the slant by means of a mouse-driven probe. The viewing distance (50, 75, or 100 cm) as well as the focal distance (25, 50, 75, 100, or 125 cm) were varied. We expected the estimation error to be smallest when the viewing distance and the focal distance coincided. This was not the case. Instead, subjects seemed to use the perspective deformation of the texture elements in the stimulus display to make a slant estimation, regardless of the specific combination of viewing distance and focal distance.     

An application of the optic sphere theory in discrimination of slant with minimal information

In Johansson and Börjesson (1989), a new theory of visual space perception—the optic sphere theory—was presented in which the hemispheric shape of the retina is utilized for determination of slant of plane surfaces in wide-angle perception. The process of the optic sphere mechanism can be described as the projection of a translating distal line on the optic sphere, and an extrapolation of this projection to a great circle. The determination of the 3-D slant of the distal line is made by identification of points of no change on the great circle during its rotation. The main objective of the present study was to investigate this process as applied to central stimulation of the retina with reduced and minimal information of slant or horizontal orientation. Each stimulus pattern consisted of either two continuous lines or two pairs of dots in motion presented on a computer screen. The pairwise lines and the pairs of dots defined simulated 3-D slants (or horizontal orientations) of different magnitude within each pair, and the subjects' task was to discriminate between these simulated slants. It was shown that the simulations evoke percepts of 3-D slants, and of horizontal orientations, and that it is possible to discriminate between them even from minimal information (pairs of dots). Further, the empirical findings of Börjesson (1994) indicated that longer extrapolations of the projected arc to a point of no change yield less accurate discriminations of slant. We failed to replicate this in Experiment 4, in which case stimulus variables that covaried with extrapolation length were eliminated or minimized. It is suggested that this raises some doubt about discrimination accuracy as dependent on extrapolation length per se. The overall conclusion, however, is that the optic sphere theory represents a possible explanation of, or analogy to, the process utilized by the visual system for determination of the simulated 3-D slants and horizontal orientations in the present study.     

Processing of haptic texture information over sequential exploration movements

Where textures are defined by repetitive small spatial structures, exploration covering a greater extent will lead to signal repetition. We investigated how sensory estimates derived from these signals are integrated. In Experiment 1, participants stroked with the index finger one to eight times across two virtual gratings. Half of the participants discriminated according to ridge amplitude, the other half according to ridge spatial period. In both tasks, just noticeable differences (JNDs) decreased with an increasing number of strokes. Those gains from additional exploration were more than three times smaller than predicted for optimal observers who have access to equally reliable, and therefore equally weighted, estimates for the entire exploration. We assume that the sequential nature of the exploration leads to memory decay of sensory estimates. Thus, participants compare an overall estimate of the first stimulus, which is affected by memory decay, to stroke-specific estimates during the exploration of the second stimulus. This was tested in Experiments 2 and 3. The spatial period of one stroke across either the first or second of two sequentially presented gratings was slightly discrepant from periods in all other strokes. This allowed calculating weights of stroke-specific estimates in the overall percept. As predicted, weights were approximately equal for all strokes in the first stimulus, while weights decreased during the exploration of the second stimulus. A quantitative Kalman filter model of our assumptions was consistent with the data. Hence, our results support an optimal integration model for sequential information given that memory decay affects comparison processes.     

Partial perceptual equivalence between vision and touch for texture information

The present study examined the extent to which vision and touch are perceptually equivalent for texture information in adults. Using Garbin's method, we selected two sets of textures having high versus low cross-modal dissimilarity values between vision and touch (Experiment 1). The two sets of textures were then used as material in a cross-modal matching task (Experiment 2). Results showed that asymmetries occurred in the performances when the stimuli had high cross-modal dissimilarity values, but not when the stimuli had low cross-modal dissimilarity values. These results extend Garbin's findings on shape information to the texture domain and support the idea that partial perceptual equivalence exists between vision and touch.