Book 1 of Aristotle’s De Anima extensively discusses two characteristics of the soul: the soul as the source of motion of the living being, and the soul as the seat of perception and cognition. The following conclusions are drawn on the nature and function of the soul. The soul is not a magnitude and not material; it is a substance and not an attribute; it is a unity, and the principle of unity is not material continuity. The soul is (...) the origin of perception and motion, and of psychological processes such as emotions and desires. An adequate account of how the soul causes perception, motion, and the like must not attribute motion to the soul. (shrink)

Self-motion through space generates a visual pattern called optic flow. It can be used to determine one’s direction of self-motion (heading). Previous studies have already shown thatthis perceptual ability, which is of critical importance during everyday life, changes with age. In most of these studies subjects were asked to judge whether they appeared to be heading to the left or right of a target. Thresholds were found to increase continuously with age. In our current study, we were interested (...) in absolute rather than relative heading judgements and in the question about a potential neural correlate of an age-related deterioration of heading perception. Two groups, older test subjects and younger controls, were shown optic flow stimuli in a virtual-reality setup. Visual stimuli simulated self-motion through a 3-D cloud of dots and subjects had to indicate their perceived heading direction after each trial. In different subsets of experiments we varied individuallyrelevant stimulus parameters: presentation time, number of dots in the display, stereoscopic vs. non-stereoscopic stimulation, and motion coherence. We found decrements in heading performance with agefor each stimulus parameter. In a final step we aimed to determine a putative neural basis of this behavioural decline. To this end we modified a neural network model which previously has proven to be capable of reproduce and predict certain aspects of heading perception. We show that the observed data can be modeled by implementing an age related neuronal cell loss in this neural network. We conclude that a continuous decline of certain aspects of motion perception, among them heading, might directly be based on anage-related progressive loss of groups of neurons being activated by visual motion. (shrink)

This paper defends a 'punctivist' conception of consciousness from recent attacks by Ian Phillips and Matthew Soteriou. As we intend it, 'punctivism' is the view that a subject's experience over some interval is determined by their experiential states at each instant during it. Phillips and Soteriou both offer ingenious arguments purporting to show that the punctivist is unable to make sense of motion perception; and that only by adopting an 'holistic' conception -- whereby a subject's instantaneous experiences are determined (...) by their experience over the interval -- can we make sense of the puzzles such phenomena pose. We contend that both arguments invoke dubious claims, their proffered solutions come with highly controversial commitments, and, if we take punctivism seriously, it is difficult to see why the so-called puzzles should be puzzling in the first place. A punctivist model of motion perception is proposed in response, and objections anticipated. (shrink)

According to the traditional inferential theory of perception, percepts of object motion or stationarity stem from an evaluation of afferent retinal signals (which encode image motion) with the help of extraretinal signals (which encode eye movements). According to direct perception theory, on the other hand, the percepts derive from retinally conveyed information only. Neither view is compatible with a perceptual phenomenon that occurs during visually induced sensations of ego motion (vection). A modified version of inferential theory yields (...) a model in which the concept of extraretinal signals is replaced by that of reference signals, which do not encode how the eyes move in their orbits but how they move in space. Hence reference signals are produced not only during eye movements but also during ego motion (i.e., in response to vestibular stimulation and to retinal image flow, which may induce vection). The present theory describes the interface between self-motion and object-motion percepts. An experimental paradigm that allows quantitative measurement of the magnitude and gain of reference signals and the size of the just noticeable difference (JND) between retinal and reference signals reveals that the distinction between direct and inferential theories largely depends on: (1) a mistaken belief that perceptual veridicality is evidence that extraretinal information is not involved, and (2) a failure to distinguish between (the perception of) absolute object motion in space and relative motion of objects with respect to each other. The model corrects these errors, and provides a new, unified framework for interpreting many phenomena in the field of motion perception. (shrink)

Although much evidence indicates that young infants perceive unitary objects by analyzing patterns of motion, infantsÕ abilities to perceive object unity by analyzing Gestalt properties and by integrating distinct views of an object over time are in dispute. To address these controversies, four experiments investigated adultsÕ and infantsÕ perception of the unity of a center-occluded, moving rod with misaligned visible edges. Both alignment information and depth information affected adultsÕ and infantsÕ perception of object unity in similar ways, and infants (...) perceived object unity by integrating information about object features over time. However, infants perceived a moving, misaligned, three-dimensional object as indeterminate in its connectedness, whereas adults perceived it as connected behind the occluder. These findings indicate that the effectiveness of common motion in specifying unified surfaces across an occluder is reduced by misalignment of edges. Alignment information enhances perception of object unity either by serving directly as information for unity or by optimizing the detectability of motion-carried information for unity. In addition, young infants are able to retain information about edge orientation over short intervals in determining connectedness via a process of spatiotemporal integration. Ó 2003 Elsevier Science (USA). All rights reserved. (shrink)

This chapter considers Aristotle's requirements for perceptible objects qua movable, changeable, and perceptible, namely that they must be extended in three dimensions, movable in space, and capable of physical contact with other extended bodies.

People are adept at perceiving interactions from movements of simple shapes, but the underlying mechanism remains unknown. Previous studies have often used object movements defined by experimenters. The present study used aerial videos recorded by drones in a real-life environment to generate decontextualized motion stimuli. Motion trajectories of displayed elements were the only visual input. We measured human judgments of interactiveness between two moving elements and the dynamic change in such judgments over time. A hierarchical model was developed (...) to account for human performance in this task. The model represents interactivity using latent variables and learns the distribution of critical movement features that signal potential interactivity. The model provides a good fit to human judgments and can also be generalized to the original Heider–Simmel animations. The model can also synthesize decontextualized animations with a controlled degree of interactiveness, providing a viable tool for studying animacy and social perception. (shrink)

Atypical sensorimotor developmental trajectories greatly contribute to the profound heterogeneity that characterizes Autism Spectrum Disorders. Individuals with ASD manifest deviations in sensorimotor processing with early markers in the use of sensory information coming from both the external world and the body, as well as motor difficulties. The cascading effect of these impairments on the later development of higher-order abilities underlines the need for interventions that focus on the remediation of sensorimotor integration skills. One of the promising technologies for such stimulation (...) is Immersive Virtual Reality. In particular, head-mounted displays have unique features that fully immerse the user in virtual realities which disintegrate and otherwise manipulate multimodal information. The contribution of each individual sensory input and of multisensory integration to perception and motion can be evaluated and addressed according to a user’s clinical needs. HMDs can therefore be used to create virtual environments aimed at improving people’s sensorimotor functioning, with strong potential for individualization for users. Here we provide a narrative review of the sensorimotor atypicalities evidenced by children and adults with ASD, alongside some specific relevant features of IVR technology. We discuss how individuals with ASD may interact differently with IVR versus real environments on the basis of their specific atypical sensorimotor profiles and describe the unique potential of HMD-delivered immersive virtual environments to this end. (shrink)

In line with my model of object motion perception (Wertheim 1994) and in contradistinction to what Stoffregen (1994) states, Sauvan's data suggest that percepts of motion are not sense specific. It is here argued that percepts of object- or self-motion are neither sense specific nor do they necessarily stem from what Stoffregen calls “kinematic events.” Stoffregen's error is in believing that we can only perceive object- or self-motion relative to other objects, which implies a failure to (...) realise that percepts of absolute object- or self-motion in space (relative to the earth's surface) do exist as well, even when the earth's surface itself is not perceived. (shrink)

This paper offers an inconsistent model of motion perception. It was prompted by work on inconsistent motion due to Hegel and, following him, Priest. But the paper skirts Hegel's full scale idealism, by proposing that the inconsistency is with the cognitive contents of motion perception. The paper draws on work in the psychology of perception, and in the theory of inconsistency. I begin by noting the prima facie argument that temporal change threatens inconsistency, and canvassing ways in (...) which this might be avoided. The orthodox reply to the prima facie argument is that one and the same thing can have different incompatible properties at different times. This is plausible when applied to motion in the physical world. However, applied to cognition, it can be seen that the phenomenon of phi or beta, combined with the mechanism of a Reichardt detector, lends support to one key step in the prima facie argument, namely re-identification over time. The inconsistency of the model is then seen to follow from application of the Fade Principle. Advantages of the model are stressed: including a simple explanation of the debilitating condition of akinetopsia, that is, motion blindness; and a suggestion as to how to account for the “moving now.”. (shrink)

Human infants begin very early in life to take advantage of multisensory information by extracting the invariant amodal information that is conveyed redundantly by multiple senses. Here we addressed the question as to whether infants can bind multisensory moving stimuli, and whether this occurs even if the motion produced by the stimuli is only illusory. Three- to four-month-old infants were presented with two bimodal pairings: visuo-tactile and audio-visual. Visuo-tactile pairings consisted of apparently vertically moving bars (the Barber Pole illusion) (...) moving in either the same or opposite direction with a concurrent tactile stimulus consisting of strokes given on the infant’s back. Audio-visual pairings consisted of the Barber Pole illusion in its visual and auditory version, the latter giving the impression of a continuous rising or ascending pitch. We found that infants were able to discriminate congruently (same direction) vs. incongruently moving (opposite direction) pairs irrespective of modality (Experiment 1). Importantly, we also found that congruently moving visuo-tactile and audio-visual stimuli were preferred over incongruently moving bimodal stimuli (Experiment 2). Our findings suggest that very young infants are able to extract motion as amodal component and use it to match stimuli that only apparently move in the same direction. (shrink)

A new motion illusion is discussed in relation to the idea of vision as a Grand Illusion. An experiment shows that this 'Tinkerbell effect' is a good example of a visual illusion supported by low-level stimulus information, but resulting from integration principles probably necessary for normal perception.

This article, which seeks to connect philosophy, polite culture, and the Enlightenment, shows how Malebranche’s Cartesian science presented a full-frontal attack on the worldly notion of a good taste aligned with reason. It did this by arguing that the aesthetic tastes that people experience were the result of mechanically-transmitted sensations that, like all physical sensations, were inaccurate, erroneous and relativistic. The mechanics of this process is explored in detail to show how Malebranche was challenging honnête thinking. The article suggests that (...) Malebranche’s demystifying approach was at once a hallmark of the Enlightenment, and that his views would ironically come to inform much Enlightenment thought about taste in ways he would have despised. (shrink)

A mime presented on videotape Adler’s six great ideas of truth, goodness, beauty, liberty, equality, and justice; their opposites; and the transitions from the positive or “good” concepts to their opposites. Using Johansson’s (1973) technique, the performer’s 12 joints were marked with points of light. Overall, the viewers had marginal success in identifying the concepts, but females were much more successful than males in identifying the “bad” ones of evil, slavery, falsehood, and ugliness, averaging 62% correct to the males’ 23%. (...) The results agree with Hall’s (1984) discussion of sex differences in the interpretation of nonverbal behavior. (shrink)