Nested prospectivity in perception: perceived maximum reaching height reflects anticipated changes in reaching ability

Perception of possibilities for behavior is a necessarily prospective (i.e., forward-looking) act. Such prospectivity is highlighted by the fact that, in general, behaviors are nested within behaviors over a number of spatial and temporal scales. Participants reported their maximum vertical reaching height when they expected to walk across the room and (1) reach for an object while standing on the floor, (2) step up on a step stool and then reach for the object, and (3) pick up a plastic rod and use it to reach for the object. The results show that perception of maximum reaching height was action scaled both when participants expected to perform a nested behavior that would change their action capabilities and when they expected to perform a nested behavior that would not do so. Moreover, the results suggest that nested behaviors that change reaching ability in functionally equivalent ways may bring about functionally equivalent changes in perception of maximum reaching height.     

An information-based approach to action understanding

It has been proposed that the ability to make sense of other agents' behavior relies on the activation of internal mechanisms that map action perception onto action execution. In this study we explored the constraints on this ability introduced by eyeheight-scaled information in the optic array. Short and tall participants provided maximum overhead reaching judgments for themselves and another participant. Perceptual information was manipulated by changing the participants' optically specified eyeheight. Observers were modestly accurate in perceiving maximum overhead reach for themselves and for another actor whose action capabilities differed. Perceived maximum overhead reach increased for both self- and other-judgments when the perceiver's eyeheight was increased. The results suggest an important role of perceptual information that has gone unrecognized in existing accounts of action understanding and prediction.     

Visual Information and Object Size in the Control of Reaching

The role of vision in the control of reaching and grasping was investigated by varying the available visual information. Adults (N = 7) reached in conditions that had full visual information, visual information about the target object but not the hand or surrounding environment, and no visual information. Four different object diameters were used. The results indicated that as visual information and object size decreased, subjects used longer movement times, had slower speeds, and more asymmetrical hand-speed profiles. Subjects matched grasp aperture to object diameter, but overcompensated with larger grasp apertures when visual information was reduced. Subjects also qualitatively differed in reach kinematics when challenged with reduced visual information or smaller object size. These results emphasize the importance of vision of the target in reaching and show that subjects do not simply scale a command template with task difficulty.     

Roles of Visual Information for Control of Reaching Movements in Children

What visual information do children normally require for the control of reaching movements? How is performance affected when children do not have access to the preferred mode of perceptual information? These questions were studied in 28 children who were tested on 3 occasions: at 6, 7, and 8 years of age. The task was to pick beads, 1 at a time, from 1 cup and carry them to another cup. With the aid of a mirror arrangement and a curtain, the amount of visual information was manipulated with regard to both the target and the performing hand. The movements were monitored with an optoelectronic device (SELSPOT II) and analyzed in terms of transport and object-handling phases. Results showed that object handling required visual information on both hand and target. For the transport phase of the movement, visual information on the spatial location of the target was sufficient, and sight of the hand did not improve performance. In contrast to adult subjects, when children did not have access to the required visual information, their performances deteriorated markedly. These results indicate that from the age of 6, children use visual information for control of arm movements in a manner like that of adults, although with less accuracy and speed. However, even 8-year-old children are limited in their ability to use alternative perceptual strategies for movement control, and they therefore become less flexible and more dependent on visual information.     

Within reach but not so reachable: Obstacles matter in visual perception of distances

A large number of studies have shown that effort influences the visual perception of reaching distance. These studies have mainly focused on the effects of reach-relevant properties of the body and of the objects that people intend to reach. However, any influence of the reach-relevant properties of the surrounding environment remains still speculative. We investigated this topic in terms of the role of obstacle width in perceiving distances. Participants had to estimate the straight-line distance to a cylinder located just behind a transparent barrier of varying width. The results showed that participants perceived the straight-line distance to the cylinder as being longer when they intended to grasp the cylinder by reaching around a wide transparent barrier rather than by reaching around narrower ones. Interestingly, this effect might be due to the anticipated effort involved in reaching. Together, our results show that reach-relevant properties of the surrounding environment influence perceived distances, thereby supporting an embodied view of the visual perception of space.     

The Effect of Posture on Early Reaching Movements

Infants of about 5 months of age who have just mastered the ability to reach succeed more frequently in contacting an object when they are seated upright than when they are supine or reclined. That effect of posture disappears in the subsequent months. Whether that effect can be attributed either to insufficient muscular strength or to insufficient control over the mechanically unstable arm was the subject of the present investigation. Kinematics and electromyography (EMG) of reaching movements of 8 sitting and supine infants at 12, 16, and 20 weeks of age were recorded. Maximum levels of shoulder torque as well as kinematic stability measures were similar in both postures. Coactivation levels and the frequency of on-off switching of muscles turned out to be higher in the sitting than in the supine posture. The authors suggest that the difference in reaching behavior resulted from the degree of error in the feedforward control signal that was allowed by the different postures rather than either insufficient muscular strength or insufficient control over the mechanically unstable arm.     

Doggone affordances: Canine perception of affordances for reaching

Performing any behavior requires perceiving affordances—whether and how that behavior can be performed. Perception of affordances exhibits action scaling—choices about when to transition between two different modes of behavior reflect the fit between action capabilities and environmental properties. The boundary between distances that are perceived to be reachable with an arm-only reach and those that are perceived to be reachable with an arm-plus-torso reach occurs at farther distances for long-armed than for short-armed people, but at the same ratio of object-distance-to-arm length for both groups. To the extent that perception of affordances is supported by detection of invariant stimulation patterns, perception of a given affordance ought to exhibit action scaling regardless of species. We investigated the heights at which dogs chose to transition from reaching with the head only to rearing (i.e., reaching with the head plus torso). This transition occurred at a taller height for tall than for short dogs, but at the same ratio of shoulder-height-to-treat-height for both groups. The results demonstrate a similarity in perception of affordances across species and suggest that perception of affordances is supported by detection of lawfully structured stimulation patterns that may be invariant across species.     

Out of Sight Is Not Out of Mind: Developmental Changes in Infants' Understanding of Visual Perception During the Second Year

Three experiments investigated 14-, 18-, and 24- month-old infants' understanding of visual perception. Infants viewed films in which a protagonist was either able to view the location of a hidden object (Visual Access condition) or was blindfolded when the object location was revealed (No Visual Access condition). When requested to find the object, the protagonist pointed either at the correct location or at the incorrect location. Across experiments, 18-month-olds looked longer at the unexpected action (e.g., person pointing at the incorrect location in the Visual Access condition). By 24 month of age, infants could infer the correct search behavior from gaze alone. These findings suggest that by the middle of the second year of life, infants understand the psychological relation between an observer and an object, even if the object is no longer visible.     

The way the ball bounces: visual and auditory perception of elasticity and control of the bounce pass

Human observers may perceive not only spatial and temporal dimensions of the environment, but also dynamic physical properties that are useful for the control of behavior. A study is presented in which visual and auditory perception of elasticity in bouncing objects, which was specified by kinematic (spatiotemporal) patterns of object motion, were examined. In experiment 1, observers could perceive the elasticity of a bouncing ball and were able to regulate the impulse applied to the ball in a bounce pass. In experiments 2 and 3, it was demonstrated that visual perception of elasticity was based on relative height information, when it was available, and on the duration of a single period under other conditions. Observers did not make effective use of velocity information. In experiment 4, visual and auditory period information were compared and equivalent performance in both modalities was found. The results are interpreted as support for the view that dynamic properties of environmental events are perceived by means of kinematic information.     

Impact of Tourette’s Disorder on Parent Reported Stress

We examined the relationship between Tourette’s Disorder (TD) and parent reported stress. About 84 parents of children with TD participated by completing questionnaires assessing parental stress, TD symptom severity, co-morbid disorders, services received by the child, and parents’ perception of their child’s academic ability. The results indicate that parent reported stress reached clinically significant levels when a co-morbid disorder was present, but not with a diagnosis of TD alone. Similarly, parents report higher levels of stress when they view their child as performing below other students academically. Finally, the types of services that the child receives were found to have little or no relationship to parent reported stress. Limitations of this study, directions for future research, and implications for intervention are discussed.     

Perceiving children's behavior and reaching limits in a risk environment

The purpose of this study was to investigate the accuracy of parents' perception of children's reaching limits in a risk scenario. A sample of 68 parents of 1- to 4-year-olds were asked to make a prior estimate of their children's behavior and action limits in a task that involved retrieving a toy out of the water. The action modes used for reaching, accuracy of estimates, and error tendency were investigated. Several morphological variables, walking experience, and swimming program experience were analyzed as predictors of maximum and estimated maximum reachability. Most children sat to retrieve the toy out of the water and fell in while attempting to grasp beyond their reaching limit. Nearly 80% of the parents correctly predicted their children's behavior when the toy was unreachable. Parents were cautious in predicting their children's maximum reachability (>50% underestimates). Mothers were more accurate than fathers in estimating their children's reaching limit. The prediction of children's capabilities was based partially on body dimensions and proportions.     

Scared stiff: The influence of anxiety on the perception of action capabilities

Influences on the perception of affordances (i.e., opportunities for actions) have been primarily studied by manipulating the functional morphology of the body. However, affordances are not just determined by the functional morphology of the perceiver, but also by the physiological state of the perceiver. States of anxiety have been shown to lead to marked changes in individuals' physiological state and their behaviour. To assess the influence of emotional state on affordance perception, the perception of action capabilities in near space was examined after participants completed an anxiety-provoking task. Anxiety was induced immediately prior to tasks that assessed participants' perceived reaching ability in Experiment 1, grasping ability in Experiment 2, and the ability to pass their hands through apertures in Experiment 3. Results indicated that those participants who experienced changes in anxiety underestimated their reaching, grasping, and passing ability compared to non-anxious participants. In other words, anxious participants were more conservative in their estimations of their action capabilities. These results suggest that anxiety influences the perception for affordances in near space and are consistent with the notion that anxiety induces withdrawal behaviours.     

Scared stiff: The influence of anxiety on the perception of action capabilities

Influences on the perception of affordances (i.e., opportunities for actions) have been primarily studied by manipulating the functional morphology of the body. However, affordances are not just determined by the functional morphology of the perceiver, but also by the physiological state of the perceiver. States of anxiety have been shown to lead to marked changes in individuals’ physiological state and their behaviour. To assess the influence of emotional state on affordance perception, the perception of action capabilities in near space was examined after participants completed an anxiety-provoking task. Anxiety was induced immediately prior to tasks that assessed participants' perceived reaching ability in Experiment 1, grasping ability in Experiment 2, and the ability to pass their hands through apertures in Experiment 3. Results indicated that those participants who experienced changes in anxiety underestimated their reaching, grasping, and passing ability compared to non-anxious participants. In other words, anxious participants were more conservative in their estimations of their action capabilities. These results suggest that anxiety influences the perception for affordances in near space and are consistent with the notion that anxiety induces withdrawal behaviours.     

Occlusion Is Hard: Comparing Predictive Reaching for Visible and Hidden Objects in Infants and Adults

Infants can anticipate the future location of a moving object and execute a predictive reach to intercept the object. When a moving object is temporarily hidden by darkness or occlusion, 6‐month‐old infants’ reaching is perturbed, but performance on darkness trials is significantly better than occlusion trials. How does this reaching behavior change over development? Experiment 1 tested predictive reaching of 6‐ and 9‐month‐old infants. While there was an increase in the overall number of reaches with increasing age, there were significantly fewer predictive reaches during the occlusion compared to visible trials and no age‐related changes in this pattern. The decrease in performance found in Experiment 1 is likely to apply not only to the object representations formed by infants but also those formed by adults. In Experiment 2 we tested adults with a similar reaching task. Like infants, the adults were most accurate when the target was continuously visible and performance in darkness trials was significantly better than occlusion trials, providing evidence that there is something specific about occlusion that makes it more difficult than merely lack of visibility. Together, these findings suggest that infants’ and adults’ capacities to represent objects have similar signatures throughout development.     

On the automatic evaluation of social exemplars

The present article focuses on the automatic evaluation of exemplars whose category membership has been learned in the past. Studies 1 and 2 confirmed the hypothesis that once an exemplar has been encoded as a member of a given group, at a later encounter the evaluation associated with the group will be unintentionally retrieved from memory, even when no perceptual cue indicates the exemplar's category membership. Study 3 extended the results to the domain of in-group/out-group differentiation. In addition. Studies 4 and 5 confirmed the hypothesis that stored evaluations can be retrieved and affect responses even when the semantic information on which the evaluations were originally based is no longer available for retrieval. Finally, Study 6 investigated spontaneous approach-avoidance behavior tendencies. Overall, results demonstrate the pervasive effects of person-based representations, and they are discussed in terms of recent models of person perception and out-group discrimination.     

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.     

Alternative solutions to kinetic stimulus transformations

It has been assumed that certain stimulus transformations lead directly to depth effects, that is, that such transformations are the necessary and sufficient conditions for kinetically generated depth perception. An alternative is to view such perception as the preferred solution to the problem posed by the transforming stimulus as to what even in the world is producing that transformation. In several experiments it is shown that when other solutions are supportable by the stimulus, those same transformations will no longer lead to depth perception. These other solutions become preferred on the basis of rejection of certain coincidental features of the stimulus that otherwise would have to be accepted were the kinetic depth solution to be maintained. The findings are interpreted as challenging any theory that perception is simply the direct result of stimulation or of extraction of stimulus information and as supporting the Helmkoltzian rule of perception as a construction of the most reasonable representation.     

Predictive Reaching for Occluded Objects by 6-Month-Old Infants

Infants were presented with an object that moved into reaching space on a path that was either continuously visible or interrupted by an occluder. Infants' reaching was reduced sharply when an occluder was present, even though the occluder itself was out of reach and did not serve as a barrier to direct reaching for the object. We account for these findings and for the apparently contrasting findings of experiments using preferential looking methods to assess infants' object representations, by proposing that (a) object representations increase in precision over the infancy period, and (b) the precision of object representations varies in common ways at all ages as a function of object visibility and task demands.     

Influence of Different Sitting Positions on Healthy Infants' Reaching Movements

The authors analyze the influence of different sitting positions (ring and flexion) on the reaching performance (spatiotemporal variables) of full-term infants 6 and 7 months old. In addition, they correlated level of trunk control, measured by the Segmental Assessment of Trunk Control, with performance during reaching. The different sitting positions only influenced the reaching movements of 6-month-old infants, who showed the best performance in the ring position. However, this influence was observed only for the trunk displacement, deceleration time, movement units, straightness index and mean velocity. In contrast, there was no influence of positions on 7-month-old infants’ reaching performance. Regarding the correlations, it was observed that infants with more level of trunk control showed a better performance when reaching, regardless of position and the age assessed.     

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.