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.     

Visual and haptic perception of postural affordances in children and adults

The present study compared how children and adults perceived affordances for upright stance when information was available either visually or haptically. 12 adults (mean age=26.5 years) and 13 children (mean age=4.5 years) examined an adjustable wooden platform that was randomly set at five different degrees of inclination (17, 22, 27, 33, 39). In the haptic condition, a masking curtain excluded vision of the platform and the surface was explored with a hand-held, wooden dowel. Results showed that for both children and adults there was closer agreement between perceptual judgments and action capabilities in the visual condition. Children overestimated their ability to stand on the steeper slopes, took equal amounts of time to make their judgments across all slopes, and were equally confident in their judgments across all slopes. In contrast, adults were more accurate than children at judging the affordances for upright stance, took longer to respond close to the actual action boundary, and were less confident close to the action boundary. Furthermore, adults took longer to respond and were less confident in the haptic condition whereas children had similar response times and were equally confident in both conditions. These important differences between adults and children in the perception of a basic affordance are discussed with reference to the coupling between perception and action at different phases of the lifespan and to the factors that might influence the organization of this coupling. Finally, implications are drawn for the prevention of accidents and the promotion of basic motor competence in children.     

Adaptive perception of changes in affordances for walking on a ship at sea

Ocean waves cause oscillatory motion of ships. Oscillatory ship motion typically is greater in roll (i.e., the ship rolling from side to side) than in pitch (i.e., tipping from front to back). Affordances for walking on a ship at sea should be differentially influenced by ship motion in roll and pitch. When roll exceeds pitch, the maximum walkable distance within a defined path should be greater when walking along the ship’s short, or athwart axis than when walking along its long, or fore-aft axis. When pitch exceeds roll, this relation should be reversed. We asked whether such changes in ship motion would be reflected in judgments of direction-specific affordances for walking. Participants (experienced maritime crewmembers) judged how far they could walk along a narrow path on the ship deck. On different days, sailing conditions were such that the relative magnitude of pitch and roll was reversed. Judgments of direction-specific affordances for walking mirrored these changes in ship motion. The accuracy of judgments was consistent across directions, and across changes in ship motion. We conclude that experienced maritime crewmembers were sensitive to dynamic variations in affordances for walking that were, themselves, a function of dynamic properties of the animal-environment system.     

Direct perception of action-scaled affordances: the shrinking gap problem

The aim of this study was to investigate the perception of possibilities for action (i.e., affordances) that depend on one's movement capabilities, and more specifically, the passability of a shrinking gap between converging obstacles. We introduce a new optical invariant that specifies in intrinsic units the minimum locomotor speed needed to safely pass through a shrinking gap. Detecting this information during self-motion requires recovering the component of the obstacles' local optical expansion attributable to obstacle motion, independent of self-motion. In principle, recovering the obstacle motion component could involve either visual or non-visual self-motion information. We investigated the visual and non-visual contributions in two experiments in which subjects walked through a virtual environment and made judgments about whether it was possible to pass through a shrinking gap. On a small percentage of trials, visual and non-visual self-motion information were independently manipulated by varying the speed with which subjects moved through the virtual environment. Comparisons of judgments on such catch trials with judgments on normal trials revealed both visual and non-visual contributions to the detection of information about minimum walking speed.     

The perception of nested affordances: An examination of expert climbers

Nested affordances in climbing comprise of multiple sequential actions, encompassing more than isolated reaching and grasping. This study examined the extent to which the perception of (multiple) nested affordances in climbing can be understood relative to body-scaled anthropometrics (arm span) and action-scaled (maximal action capabilities) measures, in relation to sequential task-goals of varying complexity. The utilisation of functionally equivalent actions during the actualisation of nested affordances was also investigated. Participants were required to estimate the maximal distance a handhold could be reached in four conditions of varying complexity: nested affordances (reach to Touch; reach to Grasp) vs. multiple nested affordances (reach to grasp with one hand followed by Removing the other hand from the starting handhold; reach to grasp with one hand followed by Moving up to another handhold). Ten expert climbers first had to estimate their maximal reaching distance in these different conditions (Touch, Grasp, Remove, Move Up) before performing the climbing movement. This sequence of estimation-action was repeated four times in each condition. Results revealed that action-scaling measures better captured nested affordances when multiple sequential behaviours are nested than body-scaled measures. Our findings also suggest that expert climbers utilise functionally equivalent movements during the realisation of multiple nested affordances (Remove and Move Up conditions).     

Kinetic potential influences visual and remote haptic perception of affordances for standing on an inclined surface

The ability of a perceiver–actor to perform a particular behaviour depends on their ability to generate and control the muscular forces required to perform that behaviour. If an intended behaviour is to be successful, perception must be relative to this ability. We investigated whether perceiver–actors were sensitive to how changes in their mass distribution influenced their ability to stand on an inclined surface. Participants reported whether they would be able to stand on an inclined surface while wearing a weighted backpack on their back, while wearing a weighted backpack on their front, and while not wearing a weighted backpack. In addition, participants performed this task by either viewing the surface or exploring it with a hand-held rod (while blindfolded). The results showed that perception of affordances for standing on the inclined surface depended on how the backpack influenced the ability of the participant to stand on the surface. Specifically, perceptual boundaries occurred at steeper inclinations when participants wore the backpack on their front than when they wore it on their back. Moreover, this pattern occurred regardless of the perceptual modality by which the participants explored the inclined surface.     

Changing affordances in stair climbing: the perception of maximum climbability in young and older adults.

This experiment extended Warren's leg-length model by investigating the relevance of leg strength and joint flexibility on perceptual judgments of climbability. From a set of 8 stairs (riser heights: 38-91 cm), 24 older and 24 young adults were asked to identify the highest stair they could climb without using their hands or knees. Ss then attempted to climb the selected stair. Tall and short young observers perceived similar action boundaries despite leg-length differences. Tall and short older adults had divergent action boundaries when a single-scale leg-length model was applied. A regression model that used flexibility and leg-strength measurements provided a better fit of the older adult data, indicating that models applying functional (kinematic and kinetic) criteria might be useful in describing lawful relationships between organisms and the environment.     

Artifacts and affordances

What are the affordances of artifacts? One view is that the affordances of artifacts, just as the affordances of natural objects, pertain to possible ways in which they can be manipulated (e.g., a computer keyboard affords grasping). Another view maintains that, given that artifacts are sociocultural objects, their affordances pertain primarily to their culturally-derived function (e.g., a computer keyboard affords typing). Whereas some have tried to provide a unifying notion of affordance to capture both aspects, here I argue that they should be kept separate. In this paper, I introduce a distinction between standard affordances, which concern the function of artifacts, and ad-hoc affordances, which refer to how artifacts are manipulated. I then argue for the neuropsychological plausibility of such a distinction, linking it to the dissociation between function knowledge and manipulation knowledge. Finally, I defend the equal status of these forms of knowledge and, hence, of standard and ad-hoc affordances, and I show that this has some implications for the debate on the role of motor processes in the conceptual knowledge of artifacts.

     

Perceiving affordances for joint actions

Two individuals acting together to achieve a shared goal often have an emergent set of afforded behavioral possibilities that may not easily reduce to either acting alone. In a series of experiments we examined the critical boundaries for transitions in behavior for individuals walking through an aperture alone or alongside another actor as a dyad. Results from experiment 1 indicated that an intrinsically scaled critical boundary for behavioral transitions was different in individuals than in dyads performing a similar task. Experiment 2 demonstrated that observers are perceptually sensitive to the difference in action parameters for the dyad, while still maintaining perceptual sensitivity about the boundaries of action relative to individuals. In experiment 3, we determined that observers' perception of critical action boundaries for individuals and dyads has a similar informational basis (eye-height scaling). In experiment 4, we demonstrated that observers were able to perceive critical action boundaries for other dyads independently of membership. Together, these results suggest that individuals are sensitive to the affordances related to a joint action, and that this process may not entirely reduce to the perception of the affordances for each individual.     

Inviting affordances and agency

Recently several authors have suggested that affordances are not mere possibilities for action but can also invite behavior. This reconceptualization of affordances asks for a reconsideration of the ecological approach to agency. After a portrayal of the role of agency in ecological psychology, we draw upon phenomenology to reveal what it means for an agent to be invited by affordances. We sketch a dynamical model of the animal-environment relationship that aims to do justice to this analysis. In the model, agency is conceptualized as the capacity to modulate the coupling strength with the environment—the agent can influence to what extent he or she is influenced by the different invitations. This account of agency keeps us far from the Cartesian idea that the agent imposes behavior. Indeed, by modulating the coupling strength, the agent simply alters the dynamics of the animal-environment interactions and thus the behavior that emerges.     

Scaling affordances for human reach actions

A methodology developed by Cesari and Newell [Cesari, P., & Newell, K. M. (1999). The scaling of human grip configuration. Journal of Experimental Psychology: Human Perception and Performance 25, 927-935; Cesari, P., & Newell, K. M. (2000). The body-scaling of grip configurations in children aged 6-12 years. Developmental Psychobiology 36, 301-310] was used to delineate the roles of an object's weight (W) and distance (D) as well as the actor's strength (S) in determining the macroscopic action used to reach for the object. Participants reached for objects of five different weights placed at 10 distances. The findings of a single discriminant analysis revealed that when object weight is scaled in terms of each individual's strength and reach distance is scaled in terms of each individual's maximum-seated reach distance, a single discriminant analysis was able to predict 90% of the reach modes used by both men and women. The result of the discriminant analysis was used to construct a body-scaled equation, K=lnD+ln(W/S)/36, similar in form to the one derived by Cesari and Newell, accurately predicted the reach action used. Our findings indicate that Cesari and Newell's method can identify a complex relationship between geometric and dynamic constraints that determine the affordances for different reach actions.     

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.     

Dissociating object-based and space-based affordances

In what we term the orientation effect, faster spatial responses are made to the corresponding task irrelevant orientation of an object. We ask how this effect relates to object affordances, how attention may be involved, and how the effect relates to the better understood Simon effect. Two separate stimulus-response compatibility effects (an orientation effect and a Simon effect) were observed when spatial responses were made to photographs of objects whose orientation and location had been simultaneously manipulated. When attentional demands were high these separate effects were found using hand responses and foot responses, suggesting an abstract rather than specific coding of object affordances. However, when attentional demands were low only the Simon effect was observed, suggesting that, in order to obtain the orientation effect, objects must be represented at the level of an object.     

Body-scaled affordances in sensory substitution

The research field on sensory substitution devices has strong implications for theoretical work on perceptual consciousness. One of these implications concerns the extent to which the devices allow distal attribution. The present study applies a classic empirical approach on the perception of affordances to the field of sensory substitution. The reported experiment considers the perception of the stair-climbing affordance. Participants judged the climbability of steps apprehended through a vibrotactile sensory substitution device. If measured with standard metric units, climbability judgments of tall and short participants differed, but if measured in units of leg length, judgments did not differ. These results are similar to paradigmatic results in regular visual perception. We conclude that our sensory substitution device allows the perception of affordances. More generally, we argue that the theory of affordances may enrich theoretical debates concerning sensory substitution to a larger extent than has hitherto been the case.     

Actions and affordances in syntactic ambiguity resolution

In 2 experiments, eye movements were monitored as participants followed instructions containing temporary syntactic ambiguities (e.g., "Pour the egg in the bowl over the flour"). The authors varied the affordances of task-relevant objects with respect to the action required by the instruction (e.g., whether 1 or both eggs in the visual workspace were in liquid form, allowing them to be poured). The number of candidate objects that could afford the action was found to determine whether listeners initially misinterpreted the ambiguous phrase ("in the bowl") as specifying a location. The findings indicate that syntactic decisions are guided by the listener's situation-specific evaluation of how to achieve the behavioral goal of an utterance.     

Posture-related affordances guide attacks in basketball

Objectives

The purpose of this study was to investigate the decision made by the attacker to drive to the left or right of the defender.

Method

Participants were 32 novice and intermediate basketball players who were assigned the role of attacker or defender in a one-on-one subphase. We manipulated the defender’s posture and measured both the postures of defenders and attackers and the ensuing decision on drive direction.

Results

As hypothesized, the posture of defenders guided the decision behavior of the attacker. Both novice and intermediate attackers made the same affordance-based decision by driving to the side of the defender’s most advanced foot, but only when the distance between attacker and defender was small. Moreover, novice attackers conveyed postural information regarding their upcoming drive direction while intermediate attackers were better able to conceal this information.

Conclusions

These results lend further support to the notion of information-based control of interpersonal actions in sport contexts.     

Trusted strangers: social affordances for social cohesion

Phenomenology and the Cognitive Sciences - How could the paradigm shift towards enactive embodied cognitive science have implications for society and politics? Translating insights form enactive...     

Husserlian horizons,cognitive affordances and motivating reasons for action

Phenomenology and the Cognitive Sciences - According to Husserl’s phenomenology, the intentional horizon is a general structure of experience. However, its characterisation beyond perceptual...     

Judging and actualizing intrapersonal and interpersonal affordances

The current study investigated the perception of intrapersonal, interpersonal, and tool-based grasping possibilities. In Experiment 1, participants judged whether they would grasp planks of wood-presented in ascending, descending, and random orders of length-using one hand (1H), two hands (2H), or with a tool that extended their reach (TH). In Experiment 2, participants physically grasped the planks using 1H, 2H, or TH. In Experiments 3 and 4, the choice of TH was replaced with a choice of grasping the planks with another person (2P). The results showed that presentation order influenced the participants' behavior differently in the judgment and action experiments. The same behavioral patterns, however, were observed when participants switched between 1H and 2H, 2H and TH, and 2H and 2P grasping. The point at which participants judged they would switch between the different modes of grasping, as well as the point at which participants physically switched between the grasping modes, occurred at similar action-scaled ratios. The equivalence of perceiving intrapersonal and interpersonal affordances is discussed.     

The role of affordances in inhibition of return

Inhibition of return (IOR) is a response delay that occurs when the target is preceded by an irrelevant stimulus (cue) at the same location. IOR can be object based, as well as location based. The aim of the present study was to investigate the role of the pragmatic features of a visually presented object in causing IOR. Two experiments were carried out using different objects as stimuli, for which the graspable part (affordance) was clearly defined. The presentation of a whole object, with the part commonly used to grasp it located below, served as a cue. The presentation of either the graspable or the ungraspable part of the cued or uncued object served as the target Results showed that responses were slower when the graspable part was shown in the cued location than when the ungraspable part was shown in the same location. The effect was apparently linked to the kind of action necessary to grasp an object.