Pupillary Responses Obey Emmert’s Law and Co-vary with Autistic Traits

We measured the pupil response to a light stimulus subject to a size illusion and found that stimuli perceived as larger evoke a stronger pupillary response. The size illusion depends on combining retinal signals with contextual 3D information; contextual processing is thought to vary across individuals, being weaker in individuals with stronger autistic traits. Consistent with this theory, autistic traits correlated negatively with the magnitude of pupil modulations in our sample of neurotypical adults; however, psychophysical measurements of the illusion did not correlate with autistic traits, or with the pupil modulations. This shows that pupillometry provides an accurate objective index of complex perceptual processes, particularly useful for quantifying interindividual differences, and potentially more informative than standard psychophysical measures.

Fixation Induced Blindness

This article reports how fixation could convey visual stimuli to the invisibility region whether the stimuli are presented centrally or peripherally regardless the textures of the background. It also reports the impossibility of conveying visual stimulus to the invisibility region when the stimulus is not fixated, namely, when the stimulus is in motion. We started in discussing how visual fixation could convey a centrally presented stimulus (pink horse) into the invisibility region under certain conditions, and why breaking the aforementioned invisibility by an intentional saccade away from the fixational point allows the stimulus to exert a ghostly horse but with complementary colours. Scientists had been hypothesizing that image aftereffect is caused by neural adaptation. In another word, the retinal photoreceptors & its corresponding neurological pathways to the visual awareness might be being idle, namely, the visual respective field might be idle. Idle visual receptive field seems to be the best explanation of the present illusion, namely, we see the light grayish background turned to greenish in the aforementioned desensitized receptive field. Important to mention, fixation greatly inhibits the spontaneous saccadic eye movements, and thus, it reduces the rooms of the receptive field remapping. Namely, every visual space will be possibly have unchangeable visual map in the brain. To arrest the aforementioned statements, we built a running stimulus to disallow the overlapping of the image and its aftereffect, and we found that the image cannot disappear. In another word, the visual awareness of the aforementioned stimulus would have ghostly & cloudy green balls in between the original materials (purple balls). The previously mentioned finding confirms the role of the spontaneous saccadic movement in promoting visibility & preventing the blindness, also see reference 1. We ended this research with asserting whether the claims against Emmert's law which raised doubts about the accurate compliance of the aforementioned law and size–distance invariance hypothesis. Weirdly enough, the claims are correct as if the image aftereffect projected against distant wall is following the dynamical visual angle but not the static one.

Constancy of Height and Speed in Three-Dimensional Information Displays

Pictorial cues to depth create a three-dimensional appearance in two-dimensional displays. With sufficient pictorial depth cues, a given physical size appears to be larger at a greater perceived distance (or the perceived size is constant at different perceived depths, despite changes in the retinal image – size constancy). Two experiments investigated the effects of perceived depth on the relation between the actual height of an object and the perceived height (Experiment 1) and the relation between the actual speed of the object the perceived speed (Experiment 2). Consistent with Emmert’s Law (Perceived Size = Retinal Image Size x Perceived Depth), perceived depth influenced both perceived height and perceived speed. These findings suggest that displays that use pictorial cues to depth could easily result in misperception of the height or speed of objects in the display.

Apparent Afterimage Size, Emmert's Law, and Oculomotor Adjustment

The apparent size of an afterimage viewed from distances between 5 cm and 580 cm was matched to that of a size-adjustable stimulus at a fixed distance (20, 30, 90, and 200 cm). The experiment was conducted under normal indoor illumination with a procedure that facilitated matching for angular size. The matched size was found to increase with focal distance within 1 m and very little beyond 1 m. Similar results were obtained with an equivalent series of real stimuli subtending a constant visual angle. These findings suggest a scaling in perceived angular size in proportion to the oculomotor adjustments for accommodation and convergence. The observations of perceived angular size of the afterimage complement what Emmert's law is meant to describe (perceived object size of the afterimage), even though as the focal distance decreases it may be increasingly difficult to tease out perceived object size and perceived angular size with the matching procedure.

An Empirical Test of Formal Equivalence between Emmert's Law and the Size-Distance Invariance Hypothesis

Emmert's law and the size-distance invariance hypothesis have been said to be formally equivalent, provided that Emmert's law means that the perceived size of an afterimage is proportional to the perceived distance of the projected surface of the afterimage. However, there have been very few studies that have attempted to verify this formal equivalence empirically. We measured both the perceived size and distance of afterimages and real objects with the same proximal size. Nineteen participants projected afterimages of 1 deg in visual angle on the wall located at distances of 1 to 23 meters from the participants. They also observed real objects, disc-shaped and made from a sheet of Styrofoam board, with the same proximal size as that of the afterimages, which were located at the same physical distances as those of the wall on which the afterimages were projected. Each participant reproduced the apparent sizes of the afterimages and real objects using the reproduction method and estimated the apparent distances using the magnitude estimation method. When the mean apparent sizes of the afterimages and real objects, represented as a function of apparent distance, were fitted to a linear function, the slopes for the afterimages and real objects did not differ significantly. These results are interpreted as evidence for the formal equivalence of Emmert's law and the size-distance invariance hypothesis.