Perceptual Rescaling Research Articles

Linear perspective cues have a greater effect on the perceptual rescaling of distant stimuli than textures in the virtual environment.

The presence of pictorial depth cues in virtual environments is important for minimising distortions driven by unnatural viewing conditions (e.g., vergence-accommodation conflict). Our aim was to determine how different pictorial depth cues affect size constancy in virtual environments under binocular and monocular viewing conditions. We systematically removed linear perspective cues and textures of a hallway in a virtual environment. The experiment was performed using the method of constant stimuli. The task required participants to compare the size of 'far' (10 m) and 'near' (5 m) circles displayed inside a virtual environment with one or both or none of the pictorial depth cues. Participants performed the experiment under binocular and monocular viewing conditions while wearing a virtual reality headset. ANOVA revealed that size constancy was greater for both the far and the near circles in the virtual environment with pictorial depth cues compared to the one without cues. However, the effect of linear perspective cues was stronger than textures, especially for the far circle. We found no difference between the binocular and monocular viewing conditions across the different virtual environments. We conclude that linear perspective cues exert a stronger effect than textures on the perceptual rescaling of far stimuli placed in the virtual environment, and that this effect does not vary between binocular and monocular viewing conditions.

Interocular transfer effects of linear perspective cues and texture gradients in the perceptual rescaling of size

Our objective was to determine whether the influence of linear perspective cues and texture gradients in the perceptual rescaling of stimulus size transfers from one eye to the other. In experiment 1, we systematically added linear perspective cues and texture gradients in a background image of the corridor illusion. To determine whether perceptual size rescaling takes place at earlier or later stages, we tested how the perceived size of top and bottom rings changed under binocular (rings and background presented to both eyes), monocular (rings and background presented to the dominant eye only), and dichoptic (rings and background presented separately to the dominant and nondominant eyes, respectively) viewing conditions. We found differences between viewing conditions in the perceived size of the rings when linear perspective cues, but not texture gradients, were presented. Specifically, linear perspective cues produced a stronger illusion under the monocular compared to the dichoptic viewing condition. Hence, there was partial interocular transfer from the linear perspective cues, suggesting a dominant role of monocular neural populations in mediating the corridor illusion. In experiment 2, we repeated similar procedures with a more traditional Ponzo illusion background. Contrary to findings from experiment 1, there was a full interocular transfer with the presence of the converging lines, suggesting a dominant role of binocular neural populations. We conclude that higher order visual areas, which contain binocular neural populations, are more involved in the perceptual rescaling of size evoked by linear perspective cues in the Ponzo compared to the corridor illusion.

The contribution of linear perspective cues and texture gradients in the perceptual rescaling of stimuli inside a Ponzo illusion corridor.

We examined the influence of linear perspective cues and texture gradients in the perceptual rescaling of stimuli over a highly-salient Ponzo illusion of a corridor. We performed two experiments using the Method of Constant Stimuli where participants judged the size of one of two rings. In experiment 1, one ring was presented in the upper visual-field at the end of the corridor and the other in the lower visual-field at the front of the corridor. The perceived size of the top and bottom rings changed as a function of the availability of linear perspective and textures. In experiment 2, only one ring was presented either at the top or the bottom of the image. The perceived size of the top but not the bottom ring changed as a function of the availability of linear perspective and textures. In both experiments, the effects of the cues were additive. Perceptual rescaling was also stronger for the top compared to the bottom ring. Additional eye-tracking revealed that participants tended to gaze more in the upper than the lower visual-field. These findings indicate that top-down mechanisms provide an important contribution to the Ponzo illusion. Nonetheless, additional maximum likelihood estimation analyses revealed that linear perspective fulfilled a greater contribution in experiment 2, which is suggestive of a bottom-up mechanism. We conclude that both top-down and bottom-up mechanisms play important roles. However, the former seems to fulfil a more prominent role when both stimuli are presented in the image.

Life among the Vermin: Nineveh and Ecological Relocation

Henrietta Rose-Innes's novel Nineveh (2011) catalogs the activities of a humane pest expert as she discovers, on an estate under construction outside Cape Town, how human and insect actors undermine the spatial expectations of post-apartheid South Africa. Rose-Innes advances a vision of interspecies connection by recasting controversial themes drawn from South Africa's history to address ecological concerns. Rose-Innes transforms South African literature's "vermin" imaginary to collapse figurative boundaries among humans and nonhumans, and repurposes the fraught concept of "relocation" to spotlight creaturely entanglements in the post-apartheid city. These gestures of reclamation produce a representational tension, reframing immediate political matters to focus on more durable ecological concerns. Yet Nineveh further tilts these discourses into an "ethics of transience" attentive to ecological scale but still cognizant of historical and ongoing injustices. The novel thus undertakes an "ecological relocation," understood along the lines of the essay's three movements as figurative interchange, spatial transit, and perceptual rescaling.

Body-Based Perceptual Rescaling Revealed through the Size — Weight Illusion

An embodied approach to the perception of spatial layout contends that the body is used as a 'perceptual ruler' with which individuals scale the perceived environmental layout. In support of this notion, previous research has shown that the perceived size of objects can be influenced by changes in the apparent size of hand. The size-weight illusion is a well known phenomenon, which occurs when people lift two objects of equal weight but differing sizes and perceive that the larger object feels lighter. Therefore, if apparent hand size influences perceived object size, it should also influence the object's perceived weight. In this study, we investigated this possibility by using perceived weight as a measure and found that changes in the apparent size of the hand influence objects' perceived weight.

Categorical perception occurs in newly learned faces, other-race faces, and inverted faces.

On the basis of findings that categorical perception (CP) is possible in complex visual stimuli such as faces, the present study tested for CP on continua between unfamiliar face pairs. Results indicate that CP can be observed for unfamiliar faces, in both familiar (same-race) and unfamiliar (other-race) groups. In addition, significant CP effects were observed in inverted faces. Finally, half-continua were tested where midpoint stimuli became endpoints. This was done to ensure that stimulus artifacts did not account for the observed CP effects. Consistent with the perceptual rescaling associated with CP, half-continua showed a rescaled CP effect. We argue that these CP effects are based on the rapid acquisition of perceptual equivalence classes.

Visual processing of depth information in stereoscopic displays

This paper discusses the perception of depth in stereoscopic displays, with an emphasis on the validity of depth perception. The paper presents the idea that stereoscopic depth perception involves a number of processing steps such as detecting disparity and perceptual rescaling of disparity for different viewing distances to yield perceived depth. The paper concludes with several ideas relating to the design of stereoscopic displays.

GROUP AND INDIVIDUAL VARIATIONS IN JUDGMENT AND THEIR RELEVANCE TO THE SCALING OF GRADUATED CIRCLES

Widely disparate opinions have been expressed about the need for and value of the perceptual scaling of graduated (proportional) circles. This continuing debate has concentrated on the measurement of the power law exponent derived from the average estimates of subject groups, with the implicit assumption that the identification of the 'correct' value for this exponent would ensure effective cartographic communication. Average exponents derived from a range of experiments have exhibited wide variety. The analysis of experimental data indicates that this variation is also a characteristic of individual subjects. The character and dimension of inter-subject and intra-subject variation are such that the employment of perceptual rescaling for graduated circles appears to provide little overall benefit. Indeed, it appears to prejudice the performance of the most consistent judges.