Perceiving the centroid of configurations on a rolling wheel

Undergraduates observed configurations of point-lights undergoing wheel-generated motions and judged how wheel-like the movement of each stimulus appeared on a 7-point scale. Viewer judgments were predicted by a metric defining the variable parameters for the motion path of each configuration’s geometric center—the centroid. The effects on judgments of eye movement and the stimulus characteristics of rotation, translation, and configuration were explored in six experiments. First, a strain operation on the dynamic stimuli did not affect the ability of the metric to predict perceptual judgments. Second, the predictive strength of the metric did not interact with the type of eye movements used in viewing the stimuli, though judged wheel-likeness was greater under pursuit vision than under static fixation. Third, variations in the extent of translation yielded little, if any, effect on observers’ judgments, nor did translation in a circular path. Finally, for stimuli having two lights extremely close together in the configuration, the metric’s predictive value was slightly lessened but only at the limits of visual acuity. Thus, within a wide range of presentation conditions, and for a wide variety of configurations, a metric that defined the variable parameters for the motion path of the centroid was an accurate predictor of observers’ judgments of goodness of perceived rotary motion.     

Perceiving parts and shapes from concave surfaces

“A hole is nothing at all, but it can break your neck.” In a similar fashion to the danger illustrated by this folk paradox, concave regions pose difficulties to theories of visual shape perception. We can readily identify their shapes, but according to principles of how observers determine part boundaries, concavities in a planar surface should have very different figural shapes from the ones that we perceive. In three experiments, we tested the hypothesis that observers perceive local image features differently in simulated 3-D concave and convex regions but use them to arrive at similar shape percepts. Stimuli were shape-from-shading images containing regions that appeared either concave or convex in depth, depending on their orientation in the picture plane. The results show that concavities did not benefit from the same global object-based attention or holistic shape encoding as convexities and that the participants relied on separable spatial dimensions to judge figural shape in concavities. Concavities may exploit a secondary process for shape perception that allows regions composed of perceptually independent features to ultimately be perceived as gestalts.     

Perceiving the sweet spot

Many sports involve aligning a hitting implement with a ball trajectory such that contact is made at the implement's center of percussion or 'sweet spot'. This spot is not visibly distinct; its perception must be haptic. Although it is functionally defined with respect to contact--it is the point of impact that produces the least vibration in the hand holding the implement--hitting success requires appreciating the location of the sweet spot prior to contact. Two experiments verified that perceivers (novices as well as expert tennis players) distinguished perception of length from perception of the position of the sweet spot simply on the basis of wielding, both for tennis rackets and for bats contrived from wooden rods with attached masses. Results conformed to previous research on dynamic touch in showing that perceiving the lengths of wielded objects, including selectively perceiving partial lengths, is constrained by inertial properties of the object.     

Perceiving the intensity of light

The relationship between luminance (i.e., the photometric intensity of light) and its perception (i.e., sensations of lightness or brightness) has long been a puzzle. In addition to the mystery of why these perceptual qualities do not scale with luminance in any simple way, "illusions" such as simultaneous brightness contrast, Mach bands, Craik-O'Brien-Cornsweet edge effects, and the Chubb-Sperling-Solomon illusion have all generated much interest but no generally accepted explanation. The authors review evidence that the full range of this perceptual phenomenology can be rationalized in terms of an empirical theory of vision. The implication of these observations is that perceptions of lightness and brightness are generated according to the probability distributions of the possible sources of luminance values in stimuli that are inevitably ambiguous.     

Perceiving the language of films.

Children appear to be familiar with the language of film makers or at least to perceive and remember films less well when the rules of this cinematic language are broken. In this experiment a simple action sequence filmed from a static viewpoint was made up into two films of four shots. One film was edited according to the rules of directional continuity specified by Hollywood cinema, that is the four shots were presented so as to preserve the subject's direction of movement across cuts. The other film was edited disregarding these rules. Apart from this difference both films were identical. Children aged seven, nine, and thirteen years watched either of these films and reconstructed the action using pictures representing the four shots. The children who saw the conventional version were better able to reconstruct what they had seen than those who saw the unconventional version.     

The optimality of the centroid method

The aim of this note is to show that the centroid method has two optimality properties. It yields loadings with the highest sum of absolute values, even in absence of the constraint that the squared component weights be equal. In addition, it yields scores with maximum variance, subject to the constraint that none of the squared component weights be larger than 1.This research is financed by NSERC of Canada. The author is grateful to Michel Tenenhaus for pointing the similarity of the procedures in the centroid method and Q-mode PCA in L₁. The author also thanks the editor and associate editor for providing shorter proofs of the theorems, along with the referees for their helpful comments.     

Perceiving Benefits in the Cancer Experience

The potential for benefits to be construed under stressful circumstances has become a topic of interest for researchers studying psychological reactions to adversity. This paper examines benefit-construal following one such stressful event—cancer. A simple framework is presented to organize qualitative and quantitative data from various literatures, including psychology, nursing, oncology, and social work, into 3 areas in which cancer survivors frequently report deriving benefits: life perspective, interpersonal relationships, and the self. This typology helps to clarify the extent and nature of benefit-finding in cancer survivors and provides directions for future research.     

Perceiving as knowing in the predictive mind

Philosophical Studies - On an ‘internalist’ picture, knowledge isn’t necessary for understanding the nature of perception and perceptual experience. This contrasts with the...     

Perceiving the sequence of speech and non-speech stimuli

The task is to estimate on which syllable of a spoken sentence a click was superimposed. Experiment I confirms Ladefoged and Broadbent's finding of a systematic tendency to prepose the click (negative displacement), but shows also that the tendency is decreased when prior knowledge of the sentence is provided. Experiment II shows that acoustic prior knowledge is not necessary to produce the decrease and that it occurs also with textual prior knowledge. Experiment III shows that the negative displacement is not eliminated by short-term practice on the task, as Fodor and Bever contended. The effect of prior knowledge is inconsistent with the explanation of negative displacement in terms of attention demands suggested by Ladefoged and Broadbent. It is argued that this explanation was unnecessary, and that negative displacement can be expected in a system which analyses speech by discrete units.     

Perceiving communion in the dyadic relationship of others

The present research took an ecological approach to explore a relational issue in social perception ? are the perceived personality characteristics of dyad members and their perceived behavioural exchanges related to perceptions of that dyad’s perceived level of friendship? To this end, observers reported on a dyad they knew well using an indigenous measure of personality perception and the Dyadic Behavioural Exchange Scale, combined with an adapted version of Hays’ Friendship Observation Checklist. Perceived similarity of personality on the dimensions of application, emotional stability (negative) and helpfulness (negative) along with the perceived level of dyadic behaviour exchange were found to be additive predictors of perceived communion or friendship strength. This interplay of personal and interpersonal processes has demonstrated the application of methodological relationalism in the social domain, and broadened the ambit of social cognition to include knowledge of relationship units of which the observer is not a member, but which plays a part in his or her social world.     

Perceiving the present and a systematization of illusions

Over the history of the study of visual perception there has been great success at discovering countless visual illusions. There has been less success in organizing the overwhelming variety of illusions into empirical generalizations (much less explaining them all via a unifying theory). Here, this article shows that it is possible to systematically organize more than 50 kinds of illusion into a 7 × 4 matrix of 28 classes. In particular, this article demonstrates that (1) smaller sizes, (2) slower speeds, (3) greater luminance contrast, (4) farther distance, (5) lower eccentricity, (6) greater proximity to the vanishing point, and (7) greater proximity to the focus of expansion all tend to have similar perceptual effects, namely, to (A) increase perceived size, (B) increase perceived speed, (C) decrease perceived luminance contrast, and (D) decrease perceived distance. The detection of these empirical regularities was motivated by a hypothesis, called "perceiving the present," that the visual system possesses mechanisms for compensating neural delay during forward motion. This article shows how this hypothesis predicts the empirical regularity.     

Perceiving affect from the voice and the face

This experiment examines how emotion is perceived by using facial and vocal cues of a speaker. Three levels of facial affect were presented using a computer-generated face. Three levels of vocal affect were obtained by recording the voice of a male amateur actor who spoke a semantically neutral word in different simulated emotional states. These two independent variables were presented to subjects in all possible permutations—visual cues alone, vocal cues alone, and visual and vocal cues together—which gave a total set of 15 stimuli. The subjects were asked to judge the emotion of the stimuli in a two-alternative forced choice task (either HAPPY or ANGRY). The results indicate that subjects evaluate and integrate information from both modalities to perceive emotion. The influence of one modality was greater to the extent that the other was ambiguous (neutral). The fuzzy logical model of perception (FLMP) fit the judgments significantly better than an additive model, which weakens theories based on an additive combination of modalities, categorical perception, and influence from only a single modality.     

Perceiving numbers affects the subjective temporal midpoint

Temporal experience can be modulated by several environmental factors. There is increasing evidence that numerical quantity may also influence temporal processes. Here, it is shown that merely looking at numbers causes a bias in a time-bisection task that depends on its magnitude. In the first experiment, a group of healthy subjects was submitted to a time-bisection task in which numerical cues were blocked (blocked design). In the second experiment, a new group of participants performed a time-bisection task in which the previous numbers were all randomly arranged in the same block (intermingled design). Results show that temporal performance is biased when numbers of different magnitude are arranged in an intermingled design. These findings argue for a functional interaction between time and numbers, depending on the implicit extrapolation of the size difference between the displayed numbers rather than on the numerical size itself.     

Perceiving the lengths of rods wielded in differentmedia

In two experiments, we investigated the ability of participants to report the lengths of rods wielded in air or water. Homogeneous aluminum rods were employed in Experiment 1. The inertia of the rods was manipulated in Experiment 2 through the use of attached masses. Although the torques required in order to wield rods in water are substantially greater than those required to wield rods in air, the perceived lengths of rods wielded in the two media were very similar. Perceived length was found to be a function primarily of inertia in both media. The experiments also revealed a small influence of resistance due to the denser medium of water. The results demonstrate the ability of perceivers to extract a physical invariant from a complex array of forces. The discussion is focused on the role of invariants in dynamic touch.     

Perceiving the lengths of rods wielded in different media

In two experiments, we investigated the ability of participants to report the lengths of rods wielded in air or water. Homogeneous aluminum rods were employed in Experiment 1. The inertia of the rods was manipulated in Experiment 2 through the use of attached masses. Although the torques required in order to wield rods in water are substantially greater than those required to wield rods in air, the perceived lengths of rods wielded in the two media were very similar. Perceived length was found to be a function primarily of inertia in both media. The experiments also revealed a small influence of resistance due to the denser medium of water. The results demonstrate the ability of perceivers to extract a physical invariant from a complex array of forces. The discussion is focused on the role of invariants in dynamic touch.     

Perceiving the inertial properties of actions in anticipation skill

Inertial properties of throwing or striking actions constrain action outcomes, but their role in anticipation skill has not been investigated yet. Therefore, the aim of this study was to systematically investigate the effect of inertial constraints on anticipation skill. Fifteen semi-professional and fifteen novice soccer players were tasked with determining the kick direction of penalty kicks occluded at 160 ms, 80 ms before ball-foot contact, at ball-foot contact, or 80 ms after ball-foot contact. The inertial constraints were manipulated by loading the kicking leg with a 2.25 kg weight around the shank of the kicking leg and were compared with unloaded kicks. Anticipation accuracy of kick direction, response time, and decision confidence were recorded. It was found that loaded kick directions were anticipated more accurately, faster, and at earlier occlusion periods than unloaded kicks. The higher accuracy for the loaded kicks was found in the earlier occlusion conditions in experts compared to novices, as were the positive relationships between accuracy and confidence. It was concluded that the perception of the inertial constraints of the kicking action allowed for earlier anticipation of kick direction. It is proposed that accurate perception of the biomechanical property radius of gyrations in the body segments linking proximal to distal towards the kicking foot may provide this information.