The psychophysics of bouncing: Perceptual constraints, physical constraints, animacy, and phenomenal causality

Visually-Perceived Momentum in Biological Motion: The Influence of Changes in Running Velocity

The objective of this study was to elucidate the characteristics of visually perceived momentum of others' motions. Twenty participants watched and compared two consecutive point-light running motions: one at a fixed velocity of 8.0 km/h and the other at one of seven velocities (5.6, 6.4, 7.2, 8.0, 8.8, 9.6, and 10.4 km/h). They then evaluated which had greater momentum, or if they were the same. The results indicated that as the velocity deviated from the standard velocity of 8.0 km/h, the correct rates increased; in particular, the correct rate at 5.6 km/h, which differed the most from the standard velocity, was the greatest (p < .001). Additionally, the mean response times at 5.6 and 6.4 km/h, which were relatively smaller than the standard velocity, were significantly lower (both p < .05). This study indicates that humans can accurately perceive the momentum of others' motions, consistent with previous studies demonstrating an accurate perception of the physical and mechanical properties of human-like motion.

The Blindfold Test: Helping to decide whether an effect reflects visual processing or higher-level judgment

Experimenters often ask subjects to rate displays in terms of high-level visual properties, such as animacy. When do such studies measure subjects' visual impressions, and when do they merely reflect their judgments that certain features should indicate animacy? Here we introduce the 'Blindfold Test' for helping to evaluate the evidence for whether an effect reflects perception or judgment. If the same effect can be obtained not only with visual displays but also by simply describing those displays, then subjects' responses may reflect higher-level reasoning rather than visual processing-and so other evidence is needed in order to support a 'perceptual' interpretation. We applied the Blindfold Test to three past studies in which observers made subjective reports about what they were seeing. In the first two examples, subjects rated stimuli in terms of high-level properties: animacy and physical forces. In both cases, the key findings replicated even when the visual stimuli were replaced with (mere) descriptions, and we conclude that these studies cannot by themselves license conclusions about perception. In contrast, a third example (involving motion-induced blindness) passed the test: subjects produced very different responses when given descriptions of the displays, compared to the visual stimuli themselves-providing compelling evidence that the original responses did not merely reflect such higher-level reasoning. The Blindfold Test may thus help to constrain interpretations of the mental processes underlying certain experimental results-especially for studies of properties that can be apprehended by both seeing and thinking.

Computational account for the naturalness perception of others' jumping motion based on a vertical projectile motion model

The visual naturalness of a rendered character's motion is an important factor in computer graphics work, and the rendering of jumping motions is no exception to this. However, the computational mechanism that underlies the observer's judgement of the naturalness of a jumping motion has not yet been fully elucidated. We hypothesized that observers would perceive a jumping motion as more natural when the jump trajectory was consistent with the trajectory of a vertical projectile motion based on Earth's gravity. We asked human participants to evaluate the naturalness of point-light jumping motions whose height and duration were modulated. The results showed that the observers' naturalness rating varied with the modulation ratios of the jump height and duration. Interestingly, the ratings were high even when the height and duration differed from the actual jump. To explain this tendency, we constructed computational models that predicted the theoretical trajectory of a jump based on the projectile motion formula and calculated the errors between the theoretical and observed trajectories. The pattern of the errors correlated closely with the participants' ratings. Our results suggest that observers judge the naturalness of observed jumping motion based on the error between observed and predicted jump trajectories.

Exploring the influence of self-identification on perceptual judgments of physical and social causality

People tend to overestimate the causal contribution of the self to the observed outcome in various situations, a cognitive bias known as the 'illusion of control.' This study delves into whether this cognitive bias impacts causality judgments in animations depicting physical and social causal interactions. In two experiments, participants were instructed to associate themselves and a hypothetical stranger identity with two geometrical shapes (a circle and a square). Subsequently, they viewed animations portraying these shapes assuming the roles of agent and patient in causal interactions. Within one block, the shape related to the self served as the agent, while the shape associated with the stranger played the role of the patient. Conversely, in the other block, the identity-role association was reversed. We posited that the perception of the self as a causal agent might influence explicit judgments of physical and social causality. Experiment 1 demonstrated that physical causality ratings were solely shaped by kinematic cues. In Experiment 2, emphasising social causality, the dominance of kinematic parameters was confirmed. Therefore, contrary to the hypothesis anticipating diminished causality ratings with specific identity-role associations, results indicated negligible impact of our manipulation. The study contributes to understanding the interplay between kinematic and non-kinematic cues in human causal reasoning. It suggests that explicit judgments of causality in simple animations primarily rely on low-level kinematic cues, with the cognitive bias of overestimating the self's contribution playing a negligible role.

Grounding Intuitive Physics in Perceptual Experience

This review article explores the foundation of laypeople's understanding of the physical world rooted in perceptual experience. Beginning with a concise historical overview of the study of intuitive physics, the article presents the hypothesis that laypeople possess accurate internalized representations of physical laws. A key aspect of this hypothesis is the contention that correct representations of physical laws emerge in ecological experimental conditions, where the scenario being examined resembles everyday life experiences. The article critically examines empirical evidence both supporting and challenging this claim, revealing that despite everyday-life-like conditions, fundamental misconceptions often persist. Many of these misconceptions can be attributed to a domain-general heuristic that arises from the overgeneralization of perceptual-motor experiences with physical objects. To conclude, the article delves into ongoing controversies and highlights promising future avenues in the field of intuitive physics, including action-judgment dissociations, insights from developmental psychology, and computational models integrating artificial intelligence.

Perceiving animacy from kinematics: visual specification of life-likeness in simple geometric patterns

Since the seminal work of Heider and Simmel, and Michotte's research, many studies have shown that, under appropriate conditions, displays of simple geometric shapes elicit rich and vivid impressions of animacy and intentionality. The main purpose of this review is to emphasize the close relationship between kinematics and perceived animacy by showing which specific motion cues and spatiotemporal patterns automatically trigger visual perceptions of animacy and intentionality. The animacy phenomenon has been demonstrated to be rather fast, automatic, irresistible, and highly stimulus-driven. Moreover, there is growing evidence that animacy attributions, although usually associated with higher-level cognition and long-term memory, may reflect highly specialized visual processes that have evolved to support adaptive behaviors critical for survival. The hypothesis of a life-detector hardwired in the perceptual system is also supported by recent studies in early development and animal cognition, as well as by the issue of the "irresistibility" criterion, i.e., the persistence of animacy perception in adulthood even in the face of conflicting background knowledge. Finally, further support for the hypothesis that animacy is processed in the earliest stages of vision comes from recent experimental evidence on the interaction of animacy with other visual processes, such as visuomotor performance, visual memory, and speed estimation. Summarizing, the ability to detect animacy in all its nuances may be related to the visual system's sensitivity to those changes in kinematics - considered as a multifactorial relational system - that are associated with the presence of living beings, as opposed to the natural, inert behavior of physically constrained, form-invariant objects, or even mutually independent moving agents. This broad predisposition would allow the observer not only to identify the presence of animates and to distinguish them from inanimate, but also to quickly grasp their psychological, emotional, and social characteristics.