Kazunori Morikawa

Lateral motion bias associated with reading direction

We found that when Americans view ambiguous lateral long-range apparent motion, they exhibit a robust bias to experience leftward movement. In successive experiments, right-handers and left-handers, and left-side drivers from Japan equally manifested this leftward bias. However, bilingual viewers whose first language reads from right to left exhibited no lateral bias. Furthermore, the bilingual sample produced a significant correlation between exposure to English and extent of leftward motion bias. The findings provide strong evidence that reading habits can influence directionality in motion perception.

Perceptual Bias for Forward-Facing Motion

When an occluded horizontal row of shapes is shifted laterally, apparent motion can he experienced in either the leftward or the rightward direction. Four experiments provide evidence for a motion bias in the direction that shapes appear to face. The bias tended to be largest when directionality was specified geometrically (e.g., triangles), next largest when it was specified biologically (e.g., mice), and absent when it was specified calligraphically (e.g., letter R). The bias increased parametrically as a function of triangle pointedness and was consistent with the directional interpretation of an ambiguous duck-rabbit. The results support the existence of a cognitively specified forward-facing attribute that can influence experienced direction of motion.

Symmetry and elongation of objects influence perceived direction of translational motion.

Five experiments were conducted to examine how perceived direction of motion is influenced by aspects of shape of a moving object such as symmetry and elongation. Random polygons moving obliquely were presented on a computer screen and perceived direction of motion was measured. Experiments 1 and 2 showed that a symmetric object moving off the axis of symmetry caused motion to be perceived as more aligned with the axis than it actually was. However, Experiment 3 showed that motion did not influence perceived orientation of symmetry axis. Experiment 4 revealed that symmetric shapes resulted in faster judgments on direction of motion than asymmetric shapes only when the motion is along the axis. Experiment 5 showed that elongation causes a bias in perceived direction of motion similar to effects of symmetry. Existence of such biases is consistent with the hypothesis that in the course of evolution, the visual system has been adapted to regularities of motion in the animate world.

Expression patterns of HNK-1 carbohydrate and serotonin in sea urchin, amphioxus, and lamprey, with reference to the possible evolutionaryorigin of the neural crest

We examined deuterostome invertebrates, the sea urchin and amphioxus, and an extant primitive vertebrate, the lamprey, for the presence of structures expressing the HNK-1 carbohydrate and serotonin. In sea urchin embryos and larvae, HNK-1 positive cells were localized in the ciliary bands and in their precursor ectoderm. Serotonergic cells were exclusively observed in the apical organs. In juvenile amphioxus, primary sensory neurons in the dorsal nerve cords were HNK-1 immunoreactive. The juvenile amphioxus nerve cords contained anti-serotonin immunoreactive nerve fibers that seem to be the Rohde axons extending from amphioxus interneurons, the Rohde cells. In lamprey embryos, migrating neural crest cells and primary sensory neurons, including Rohon-Beard cells, expressed the HNK-1 carbohydrate. Lamprey larvae (ammocoetes) contained cell aggregates expressing both the HNK-1 carbohydrate and serotonin in the pronephros and in the regions adjacent to the gut epithelium. Some of these cell aggregates were present in the anti-serotonin positive visceral motor nerve net. Motor neurons and Müller fibers were serotonergic in ammocoetes. Comparison of the expression patterns of HNK-1 carbohydrate among sea urchins, amphioxus and lampreys seem to suggest the possible evolutionary origin of the neural crest, that is, ciliary bands in dipleurula-type ancestors evolved into primary sensory neurons in chordate ancestors, as inferred from Garstangs auricularia hypothesis, and the neural crest originated from the primary sensory neurons.

Central performance drop in texture segmentation: the role of spatial and temporal factors.

Previous studies reported that performance in texture segmentation was lower near the fovea than in the periphery. However, the exact cause of this phenomenon had been unknown. Experiment 1 replicated the central performance drop (CPD). Experiments 2 and 3 demonstrated that the previously reported CPD was due to a temporal factor, i.e. slower neural processing in central vision, rather than a spatial factor. But Experiments 4 and 5 showed that certain textures can lead to a purely spatial form of CPD due to inhibition and/or interference from high spatial frequency mechanisms in central vision. This study showed that, depending on textures, CPD can arise from either temporal or spatial causes.

Adaptation to asymmetrically distorted faces and its lack of effect on mirror images.

Previous research showed that viewing symmetrically distorted faces for a few minutes causes undistorted faces to appear distorted in the opposite manner (face-distortion aftereffect, FDAE). Three experiments with 90 observers demonstrated that adaptation to an asymmetrically distorted face also causes FDAE, but does not affect perception of its mirror image. The results suggested the FDAE occurs at the level of visual processing where distinct neural populations respond to a non-frontal facial image and its mirror image. Unlike most aftereffects, this FDAE lasts at least 30 min. Spatial and temporal characteristics of the FDAE and its relevance to portrait drawing and painting are discussed.

A method to assess the relative contribution of lateral inhibition to the magnitude of visual-geometric illusions

Observer errors of judged length when viewing the Müller-Lyer illusion arise partially from distortions caused by lateral neural interactions in the retina. To assess the relative contribution of such lateral neural interactions to the total magnitude of the illusion, the Müller-Lyer figure was presented to observers under a form of intermittent-light stimulation that enhances lateral inhibitory activity. In Experiment 1, intermittent-light conditions produced the largest increase in illusion strength for the standard variant of the Müller-Lyer figure but not for a dot form in which contour interactions are minimized. The results of Experiment 2 showed that the hypothesized lateral inhibitory contribution varied as a function of wing-shaft angle. In addition to confirming the contribution of lateral neural interactions to illusion formation, these findings also suggest that exposure of illusion configurations under intermittent illumination may provide a method of determining the relative contribution of lateral inhibition to illusion configurations other than the Müller-Lyer.

A real-life illusion of assimilation in the human face: eye size illusion caused by eyebrows and eye shadow

Does an assimilative illusion like the Delboeuf illusion occur in the human face? We investigated factors that might influence the perceived size of the eyes in a realistic face. Experiment 1 manipulated the position of the eyebrows (high or low), the presence/absence of eye shadow, and the viewing distance (0.6 m or 5 m), then measured the perceived eye size using a psychophysical method. The results showed that low eyebrows (i.e., closer to the eyes) make the eyes appear larger, suggesting that the assimilation of eyes into the eyebrows is stronger when the eye-eyebrow distance is shorter. The results also demonstrated that the application of eye shadow also makes the eyes look larger. Moreover, the effect of eye shadow is more pronounced when viewed from a distance. In order to investigate the mechanism of the eye size illusion demonstrated in Experiment 1, Experiment 2 measured the magnitude of the Delboeuf illusion at a viewing distance of 0.6 m or 5 m, with or without gray gradation simulating the eye shadow that was used in Experiment 1. The experiment demonstrated that the Delboeuf illusion is modulated by viewing distance and gradation in the same way as the eye size illusion. These results suggest that the eye size illusion induced by the eyebrows and the Delboeuf illusion involve the same mechanism, and that eye shadow causes the assimilation of the eyes into itself and enhances assimilation between the eyes and the eyebrows.

Short report: The effect of expertise in hiking on recognition memory for mountain scenes

The nature of an expert memory advantage that does not depend on stimulus structure or chunking was examined, using more ecologically valid stimuli in the context of a more natural activity than previously studied domains. Do expert hikers and novice hikers see and remember mountain scenes differently? In the present experiment, 18 novice hikers and 17 expert hikers were presented with 60 photographs of scenes from hiking trails. These scenes differed in the degree of functional aspects that implied some action possibilities or dangers. The recognition test revealed that the memory performance of experts was significantly superior to that of novices for scenes with highly functional aspects. The memory performance for the scenes with few functional aspects did not differ between novices and experts. These results suggest that experts pay more attention to, and thus remember better, scenes with functional meanings than do novices.

Last but Not Least

Although most illusory figures published in scientific articles are very simple and abstract, visual illusions are not confined to vision laboratories. They also occur in nature and our daily life (Gregory and Gombrich 1973). The facet of human culture that takes advantage of visual illusions most actively is probably clothing. Clothes manufacturers and fashion magazines keep touting dresses that make you look slender, boots that make your legs look longer, jackets that make you look younger, and so on. One well-known flattering effect is the apparent lengthening of legs by high-cut bathing suits (see figure 1a). It is obvious that, when viewed from the side, a high-cut bathing suit exposes a larger area of the hip, which looks like an extension of the leg thus making the leg appear longer. However, there is a possibility that a high-cut bathing suit makes the legs look longer even when the actual length of the legs is clearly visible in a frontal view. The present study refers to this effect as the high-cut leg illusion. To the best of the authors knowledge, this possibility has not been scientifically tested. The first purpose of the present study is to demonstrate this illusion. Last but not least Perception, 2003, volume 32, pages 121 ^ 123