A biodynamic basis for perceived categories of action: a study of sitting and stair climbing

Actors must determine whether the properties of the surface layout are sufficient to meet their specific requirements for performing an action. Warren's (1984) study of bipedal stair climbing has demonstrated the significance of intrinsic, body-scaled measures of environmental properties for defining perceptual categories relevant to action. Whereas the absolute measure of the perceptual boundary between "climbable" and "not climbable" varied according to the actor's size and mass, the perceived boundary was a constant proportion of each actor's leg length. Our current study examined the perceived maximum seat height (SHmax) for the act of sitting. Experiment 1 delineated the range of surface heights that were perceived to afford sitting on. When expressed as a function of each person's leg length (L), SHmax was remarkably stable across individuals. Unexpectedly, it was quite close to the maximum riser height determined by Warren. Experiment 2 examined whether this similarity reflected a common biodynamic requirement, since climbing and sitting require actors to lift their center of gravity above the surface of support. Perceived critical heights were obtained for both acts using the same methods and apparatus. The perceived maximum heights for each act were virtually identical. These findings are consistent with the possibility that the information used in determining critical action boundaries is already scaled with reference to some physical dimension of the actor.     

Eyeheight-scaled information about affordances: a study of sitting and stair climbing

Previous work has shown that both the perceived and actual critical (maximum) heights of surfaces that afford "sitting on " and "climbing on" can be expressed as constant proportions of each actor's leg length. The current study provides evidence that these judgments of critical action boundaries are based on an existing source of size and distance information that is already scaled with reference to the actor's eyeheight. In Experiment 1 changes in judgments of "perceived eyeheight" (an index of the intrinsic scalar) as a function of viewing distance were shown to be highly correlated with changes in the maximum height that was perceived to afford sitting on or climbing on. In Experiments 2 and 3 observers wore 10-cm blocks and made judgments about whether the heights of various surfaces afforded sitting or climbing. The use of eyeheight-scaled information as the basis for their estimates predicted the obtained pattern of errors in these judgments. With a modicum of experience wearing the blocks, however, observers were able to retune accurately their critical action boundary to a degree that would not have been predicted from their consistent overestimation of the height of the block on which they were standing. These results have implications for understanding how observers obtain information about their specific action boundary.     

A Rich Landscape of Affordances

Mark (1987) reported that observers, whose sitting capabilities had been altered by having them wear 10-cm blocks, were able to discover their own maximum height of a surface that afforded sitting on (SHmax), in the absence of an opportunity to practice sitting while wearing blocks. The current investigation attempted to identify conditions under which returning of an observer's SHmax, occurred. Returning of SH@, judgments readily occurred when observers were able to locomote between trials (Experiment 1), and rotate their heads, lean forward and to the side while making their judgments (Experiments I-2). However, they were unable to retune their SHmax, when the viewing conditions restricted all but the most basic actions (Experiments 3-5). Observers' actions during and between trials also were critical to the accuracy of their judgments when they did not wear the blocks. Overall, these findings strongly implicate observers' own activities as crucial for revealing information about their own S@ under both conditions when they are and are not familiar with their own sitting capabilities. Experiment 6 bolstered this conclusion by showing that prior practice with the act of sitting was not sufficient to enable observers to retune their own SHmax, (block condition) or to perceive their own SHmax under familiar circumstances (no block).     

Standing distance in climbability of stairs.

The purpose of this experiment was to make a preliminary examination of the distance one needs to stand from a stair to successfully climb up without using arms for support. Using an adjustable stair structure to create different heights of risers, a group of 10 tall and of 10 short participants made perceptual judgments and physical attempts at heights that represented 83% and 93% of each group's mean leg length. Choice of maximum and minimum distance from the stair was measured for each participant. Analysis showed that perceptual judgments and physical capabilities were highly correlated (tall: Pearson r = .92); short: Pearson r = .93). Moreover, the ability to climb the two heights depended on the standing distance from the stair. The findings suggest that standing distance may be a consideration in stair climbing and that stair height alone may not be sufficient to specify climbability.     

The influence of athletic experience and kinematic information on skill-relevant affordance perception

Humans can perceive affordances both for themselves and for others, and affordance perception is a function of perceptual–motor experience involved in playing a sport. Two experiments investigated the enhanced affordance perception of athletes. In Experiment 1, basketball players and nonbasketball players provided perceptual reports for sports-relevant (maximum standing-reach and reach-with-jump heights) and non-sports-relevant (maximum sitting height) affordances for self and other. Basketball players were more accurate at perceiving maximum reach-with-jump for another person than were nonbasketball players, but were no better at perceiving maximum reach or sitting heights. Experiment 2 investigated the informational basis for this enhanced perceptual ability of basketball players by evaluating whether kinematics inform perceivers about action-scaled (e.g., force-production dependent), but not body-scaled (i.e., geometrically determined), affordances for others, and whether basketball experience enhances sensitivity to kinematic information. Only basketball players improved at perceiving an action-scaled affordance (maximum reach-with-jump), but not body-scaled affordances (maximum standing-reach and sit) with exposure to kinematic information, suggesting that action-scaled affordances may be specified by kinematic information to which athletes are already attuned by virtue of their sport experience.     

Perceiving affordances for another person's actions

The perception of affordances for the actions of other people (actors) was examined. Observers judged the maximum and preferred sitting heights of tall and short actors. Judgments were scaled in centimeters, as a proportion of the observer's leg length, and as a proportion of each actor's leg length. In Experiment 1 observers viewed live actors standing next to a chair. When judgments were scaled by actor leg length, they reflected the actual ordinal relation between the capabilities of the actors. The perception of affordances from kinematic displays was then evaluated. Observers differentiated tall and short actors, but only when the displays contained direct information about relations between the actors and the chair. It is concluded that observers can perceive affordances for the actions of actors and that kinematic displays can be enough to support such percepts if they preserve actor-environment relations that define affordances.     

The influence of athletic experience and kinematic information on skill-relevant affordance perception

Humans can perceive affordances both for themselves and for others, and affordance perception is a function of perceptual-motor experience involved in playing a sport. Two experiments investigated the enhanced affordance perception of athletes. In Experiment 1, basketball players and nonbasketball players provided perceptual reports for sports-relevant (maximum standing-reach and reach-with-jump heights) and non-sports-relevant (maximum sitting height) affordances for self and other. Basketball players were more accurate at perceiving maximum reach-with-jump for another person than were nonbasketball players, but were no better at perceiving maximum reach or sitting heights. Experiment 2 investigated the informational basis for this enhanced perceptual ability of basketball players by evaluating whether kinematics inform perceivers about action-scaled (e.g., force-production dependent), but not body-scaled (i.e., geometrically determined), affordances for others, and whether basketball experience enhances sensitivity to kinematic information. Only basketball players improved at perceiving an action-scaled affordance (maximum reach-with-jump), but not body-scaled affordances (maximum standing-reach and sit) with exposure to kinematic information, suggesting that action-scaled affordances may be specified by kinematic information to which athletes are already attuned by virtue of their sport experience.     

The Role of Anxiety in Perceiving and Realizing Affordances

Three experiments were conducted to examine the role of anxiety in perceiving and realizing affordances in wall climbing. Identical traverses were situated high and low on a climbing wall to manipulate anxiety. In Experiment 1, participants judged their maximal overhead reachability and performed maximal reaches on the climbing wall. Anxiety was found to reduce both perceived and actual maximal reaching height. In Experiment 2, participants climbed from right to left and back again on the high and low traverses, which now entailed an abundance of holds. Consistent with the reduction of perceived and actual maximal reaching height found in Experiment 1, anxiety led to the use of more holds. Finally, in Experiment 3, points of light were sequentially projected around the participants while they were climbing to measure attention. As participants detected fewer lights in the high-anxiety condition, it was concluded that anxiety narrowed attention. In general, the results underscored that the actor's emotional state plays an important role in perceiving and realizing affordances and that the perception of affordances changes as the accompanying action capabilities change.     

Watch this! Observed tool use affects perceived distance

Recent research has shown that being able to interact with an object causes it to be perceived as being closer than objects that cannot be interacted with. In the present study, we examined whether that compression of perceived space would be experienced by people who simply observed such interactions by others with no intention of performing the action themselves. Participants judged the distance to targets after observing an actor reach to an otherwise unreachable target with a tool (Experiment 1) or illuminate a distant target with a laser pointer (Experiment 2). Observing either type of interaction caused a compression of perceived space, revealing that a person’s perception of space can be altered through mere observation. These results indicate that shared representations between an actor and observer are engaged at the perceptual level easily and perhaps automatically, even in the absence of cooperation or an observer’s own intention to interact.     

Perceptual equivalence of acoustic cues in speech and nonspeech perception

Trading relations show that diverse acoustic consequences of minimal contrasts in speech are equivalent in perception of phonetic categories. This perceptual equivalence received stronger support from a recent finding that discrimination was differentially affected by the phonetic cooperation or conflict between two cues for the /slIt/-/splIt/contrast. Experiment 1 extended the trading relations and perceptual equivalence findings to the /sei/-/stei/contrast. With a more sensitive discrimination test, Experiment 2 found that cue equivalence is a characteristic of perceptual sensitivity to phonetic information. Using “sine-wave analogues” of the /sei/-/stei/stimuli, Experiment 3 showed that perceptual integration of the cues was phonetic, not psychoacoustic, in origin. Only subjects who perceived the sine-wave stimuli as “say” and “stay” showed a trading relation and perceptual equivalence; subjects who perceived them as nonspeech failed to integrate the two dimensions perceptually. Moreover, the pattern of differences between obtained and predicted discrimination was quite similar across the first two experiments and the “say”-“stay” group of Experiment 3, and suggested that phonetic perception was responsible even for better-than-predicted performance by these groups. Trading relations between speech cues, and the perceptual equivalence that underlies them, thus appear to derive specifically from perception of phonetic information.     

Tuning in to another person's action capabilities: perceiving maximal jumping-reach height from walking kinematics

Three experiments investigated the ability to perceive the maximum height to which another actor could jump to reach an object. Experiment 1 determined the accuracy of estimates for another actor's maximal reach-with-jump height and compared these estimates to estimates of the actor's standing maximal reaching height and to estimates of the perceiver's own maximal reaching and reach-with-jump height. Perception of another actor's maximum reach-with-jump height was less accurate than the other estimates, but still accurate to within 8% error. The actor's reach-with-jump height was modified in Experiment 2 by attaching weights around the actor's ankles. Perceivers, who were explicitly aware of the manipulation, adjusted their maximum reach-with-jump estimates for the actor accordingly. In Experiment 3, perceivers were not explicitly aware of the weight manipulation, but provided significantly lower maximum reach-with-jump estimates after watching the actor walk while wearing the weights compared to estimates obtained after watching the actor walk while not wearing the weights. The results suggest that the actor's walking pattern was informative about the actor's capacity to produce a different action, jumping to reach an object.     

Nonvisual judgment of the crossability of path gaps.

The ability of persons to locomote without vision with the aid of a hand-held probe was investigated in 4 experiments focusing on the negotiation of gaps in a pathway. In Experiment 1, Ss of extreme heights judged under sighted and blindfolded conditions whether gaps of different sizes could be crossed by walking. Crossability boundaries were lower for shorter Ss, but the height effect disappeared under normalization by leg length. Experiments 2-4 altered mechanical aspects of the probe (length and mass distribution) in the nonvisual case. Ss' performance was still reliable in each experiment, and their performances were constrained by parameters of the gap and of their action systems. Probe variables, however, had surprisingly little influence on the judgments of crossability. Results were discussed in terms of potential roles for information in different perceptual modalities.     

Perception of Sex From Complex Body Movement in Young Children

This article reports on a study of the perception of sex from complex body movement. Studies by Cutting and his associates (Barclay, Cutting, & Kozlowski, 1978; Kozlowski & Cutting, 1977) and by Runeson and Frykholm (1983) have shown that adult observers of both adult and child actors (11-12 years old) can reliably recognize the sex of the actor. In this study, prepubescent actors (4-5 years old) were employed, and the role of familiarity of observers with children of this age was also examined. Ten children (4-5 years old), 5 boys and 5 girls, performed 7 actions similar to those employed in Runeson and Frykholm's study: walking in a circle, running in a circle, throwing a ball, lifting a box, sitting on the floor, sitting on a chair, and climbing onto a chair and jumping down. Point-light displays were made of each child performing each action. Each actor was recorded performing each action once. An experimental tape was prepared in which all 70 acts from the source tape appeared in a counterbalanced order such that each child appeared once in each block of 10 trials and each action appeared once in each block of 7 trials. The effect of familiarity was explored by employing 3 different groups of observers: the parents of the child actors, a group of adults familiar with children of this age, and a student group of young adults not familiar with children of this age. The overall detection rate was only just above chance and none of the observer groups performed better than chance. Sex was reliably perceived, however, for particular actors and for particular actions. The implications of these findings for Runeson and Frykholm's kinematics specifies dynamics principle are noted.     

Does own experience affect perception of others’ actions in capuchin monkeys (Cebus apella)?

Anticipating another’s actions is an important ability in social animals. Recent research suggests that in human adults and infants one’s own action experience facilitates understanding and anticipation of others’ actions. We investigated the link between first-person experience and perception of another’s action in adult tufted capuchin monkeys (Sapajus apella spp., formerly Cebus apella spp.). In Experiment 1, the monkeys observed a familiar human (actor) trying to open a container using either a familiar or an unfamiliar action. They looked for longer when the actor tried to open the container using a familiar action. In Experiment 2, the actor performed two novel actions on a new container. The monkeys looked equally at the two actions. In Experiment 3, the monkeys were trained to open the container using one of the novel actions in Experiment 2. After training, we repeated the same procedure as in Experiment 2. The monkeys looked for longer when the actor manipulated the container using the action they had practiced than when she used the unfamiliar action. These results show that knowledge derived from one’s own experience impacts perception of another’s action in these New World monkeys.     

Representational momentum in dynamic facial expressions is modulated by the level of expressed pain: Amplitude and direction effects

Humans have developed a specific capacity to rapidly perceive and anticipate other people’s facial expressions so as to get an immediate impression of their emotional state of mind. We carried out two experiments to examine the perceptual and memory dynamics of facial expressions of pain. In the first experiment, we investigated how people estimate other people’s levels of pain based on the perception of various dynamic facial expressions; these differ both in terms of the amount and intensity of activated action units. A second experiment used a representational momentum (RM) paradigm to study the emotional anticipation (memory bias) elicited by the same facial expressions of pain studied in Experiment 1. Our results highlighted the relationship between the level of perceived pain (in Experiment 1) and the direction and magnitude of memory bias (in Experiment 2): When perceived pain increases, the memory bias tends to be reduced (if positive) and ultimately becomes negative. Dynamic facial expressions of pain may reenact an “immediate perceptual history” in the perceiver before leading to an emotional anticipation of the agent’s upcoming state. Thus, a subtle facial expression of pain (i.e., a low contraction around the eyes) that leads to a significant positive anticipation can be considered an adaptive process—one through which we can swiftly and involuntarily detect other people’s pain.     

充分条件句语义关系知觉对条件推理的影响

作者通过实验考察了大学生被试对五种充分条件句语义关系知觉对其条件推理的影响。两个实验的结果表明,被试对条件句中前后件之间语义关系的知觉理解影响和调节其相应的条件推理的成绩。实验1新发现,被试对充分条件句后件对前件必要性的知觉理解存在难易差异,对许可句和定义句的后件必要性容易知觉,对偶然句、义务句和因果句的后件必要性难以知觉。实验2新发现,被试对充分条件句后件对前件必要性的知觉理解的难易差异导致被试在否定后件式推理成绩上的差异,对许可句和定义句的否定后件式推理成绩显著高于对偶然句、义务句和因果句的否定后件式推理成绩,对充分条件句否定后件式推理成绩随对后件必要性知觉增加而增加。     

Carrying the height of the world on your ankles: Encumbering observers reduces estimates of how high an actor can jump

The authors investigated how changes in action capabilities affect estimation of affordances for another actor. Observers estimated maximum jumping-reach height for themselves and another actor. Half of the observers wore ankle weights that reduced their jumping ability. The ankle weights reduced estimates of maximum jumping-reach height that observers made for themselves and for the other actor, but only after observers had the opportunity to walk while wearing the weights. Changes in estimates closely matched changes in actual jumping-reach ability. Results confirm and extend recent investigations that indicate that perception of the spatial layout of surfaces in the environment is scaled to an observer's capacity to act, and they link that approach to another embodied cognition perspective that posits a link between one's own action capabilities and perception of the actions of other agents.     

The influence of motor expertise and motor experience on action and actor recognition

Two experiments examined whether different levels of motor and visual experience influence action perception and whether this effect depends on the type of perceptual task. Within an action recognition task (Experiment 1), professional basketball players and novice college students were asked to identify basketball dribbles from point-light displays. Results showed faster reaction times and greater accuracy in experts, but no advantage when observing either own or teammates’ actions compared with unknown expert players. Within an actor recognition task (Experiment 2), the same expert players were asked to identify the model actors. Results showed poor discrimination between teammates and players from another team, but a more accurate assignment of own actions to the own team. When asked to name the actor, experts recognised themselves slightly better than teammates. Results support the hypothesis that motor experience influences action recognition. They also show that the influence of motor experience on the perception of own actions depends on the type of perceptual task.     

A common perceptual parameter for stair climbing for children,young and old adults

In this paper we examine whether a common perceptual parameter is available for guiding old adults, young adults and children in climbing the highest stair mountable in a bipedal fashion. Previous works have shown that the ratio between the height of the stair and the hip height was the body-scaled invariance adopted as information for selecting the highest stair by young adults [Journal of Experimental Psychology: Human Perception and Performance 10 (1984) 683-703] but not by older adults [Journal of Experimental Psychology: Human Perception and Performance 3 (1992) 691-697]. Indeed, for older adults additional bio-mechanical parameters needed to be added to the model due to their decrease in leg strength and flexibility.Up to now, no perceptual invariant has been identified yet for determining the relevant information used for guiding the stair climbing action for normal healthy people. We propose a new parameter as the angle defined by the ratio between the height of the stair and the distance taken from the feet to the top edge of the stair before the initiation of the movement. We show that this angle is the same for children, young adults and older adults despite the different kinematics of the motion, the anthropometrics and the skill ability exhibit by the participants. In summary we show that even when the climbability judgments, based on the simple ratio leg length-stair height, are influenced by differences in age, participants use a common perceptual variable when they are coordinating their stair climbing action.     

Measuring perceived ceiling height in a visual comparison task

When judging interior space, a dark ceiling is judged to be lower than a light ceiling. The method of metric judgments (e.g., on a centimetre scale) that has typically been used in such tasks may reflect a genuine perceptual effect or it may reflect a cognitively mediated impression. We employed a height-matching method in which perceived ceiling height had to be matched with an adjustable pillar, thus obtaining psychometric functions that allowed for an estimation of the point of subjective equality (PSE) and the difference limen (DL). The height-matching method developed in this paper allows for a direct visual match and does not require metric judgment. It has the added advantage of providing superior precision. Experiment 1 used ceiling heights between 2.90?m and 3.00?m. The PSE proved sensitive to slight changes in perceived ceiling height. The DL was about 3% of the physical ceiling height. Experiment 2 found similar results for lower (2.30?m to 2.50?m) and higher (3.30?m to 3.50?m) ceilings. In Experiment 3, we additionally varied ceiling lightness (light grey vs. dark grey). The height matches showed that the light ceiling appeared significantly higher than the darker ceiling. We therefore attribute the influence of ceiling lightness on perceived ceiling height to a direct perceptual rather than a cognitive effect.