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Perceiving Affordances: Visual Guidance of Stair Climbing

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How do animals visually guide their activities in a cluttered environment? Gibson (1979) proposed that they perceive what environmental objects offer or afford for action. An analysis of affordances in terms of the dynamics of an animal-environment system is presented. Critical points, corresponding to phase transitions in behavior, and optimal points, corresponding to stable, preferred regions of minimum energy expenditure, emerge from variation in the animal-environment fit. It is hypothesized that these points are constants across physically similar systems and that they provide a natural basis for perceptual categories and preferences. In three experiments these hypotheses are examined for the activity of human stair climbing, by varying riser height with respect to leg length. The perceptual category boundary between "climbable" and "unclimbable" stairs is predicted by a biomechanical model, and visually preferred riser height is predicted from measurements of minimum energy expenditure during climbing. It is concluded that perception for the control of action reflects the underlying dynamics of the animal-environment system.
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... Consistent with this principle, in a landmark study Warren quantified affordance in an intrinsic manner to support the relational understanding of affordances. Warren (1984) found that the boundary between climbable and unclimbable stairways corresponds to a fixed ratio between riser height and leg length. That is, instead of the stairway having the affordance of "climbability" on its own, the affordance is rather a relational property-one to which participants in Warren's study were found to be perceptually sensitive. ...
... This research introduced a methodology called intrinsic measurement to quantify affordances, as the unit of climbability is not an extrinsic measure, such as centimeters, but rather an intrinsic one tied to the body-environment relation, dependent on leg lengths. (Warren, 1984). ...
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According to the view of ecological psychology, affordances are perceived directly through the interaction between the observer and the environment, and thus body scaled. Considering the actions from different object agent distances, Tosoni and colleagues have provided a conceptual distinction concerning two types of affordances: macro affordances (also called environmental affordance) and micro affordances. Both of these two types of affordances have been investigated in psychological research since the beginning of this century. However, most of the environmental affordances have not yet been manipulated with a body-scaled setting in the prior research protocol. Inspired by the intrinsic measurement introduced by ecological psychologist Warren (1984) and focusing on environmental affordances, the present study adapted the task of Djebbara et al. (2019) by defining transitional affordance as the body-door height ratios. The current results from subjective data, EEG data and behavioral data showed that affordance can be manipulated intrinsically and covaried with agents' experience, perception and motor interaction. The perception of environmental affordances was based on intrinsic optical information for the relationship between environmental properties and capacities of the observer's own action system. It thus provides empirical support for the need to link ecological psychology and neuro-architecture in experimental protocols.
... When the controller disengages, the CoP undergoes a spiraling 145 expansion, moving outward in a circular pattern from its central point. We can identify 146 this saddle-type control in fractal temporal correlations along traditional AP and ML 147 axes. CoP tends to exhibit increased fractal scaling along the AP axis and diminished 148 scaling along the ML axis, indicating more proactive and passive control along these 149 axes, respectively [36,42,78] (Fig. 1a). ...
... The topology is no more reducible as a causal result of 774 perturbation than the more classic affordances (e.g., "step-on-ability," "pass-ability," and 775 "sit-on-ability") have been. Like the classic affordances, these postural topologies reflect 776 a scaling relationship emerging from task constraints without asymmetries of bodily 777 structure [104,[146][147][148]. Whereas step-on-ability of pass-ability depends on the vertical 778 arrangement of limbs pointed forward in sitting or standing, the affordances of the 779 postural system depend on mechanics of anatomical linkages at hip, knee, and ankle 780 that can poise postural control around two sometimes orthogonal axes [149][150][151][152][153][154][155][156]. ...
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Contemporary dynamical models of human postural control propose an intermittent controller regulating the postural centre of pressure (CoP) about a stable saddle-shaped manifold along anatomical anteroposterior (AP) and mediolateral (ML) axes, releasing CoP in an outwards spiral when inactive. Experimental manipulations can evoke this saddle-type topology in fractal temporal correlations along the AP axis and reducing correlations along the ML axis. However, true effects of task demands may often manifest within angular space between anatomical AP and ML axes—a space not typically modelled explicitly. We tested how instability and attentional load influence postural control across the full angular range of fractal variability along the two-dimensional (2D) support surface. Forty-eight healthy young adults performed a suprapostural Trail Making Test (TMT) while standing on a wobble board, inducing continuous perturbations along the ML axis. Stable, quiet standing exhibited classic saddle-like topology, with stronger fractal temporal correlations in CoP displacements along AP axes. The attentional demand of the TMT did not affect angular variation or strength of fractal temporal correlations across the 2Dsupport surface. However, maintaining upright balance on the wobble board reshaped and reoriented the angular distribution of fractal temporal correlations, accentuating saddle-like angular variation and rotating the strongest fractal temporal correlations predominantly along the ML axis. Stabilizing posture in the face of wobble board instability prompted the saddle-type angular distribution of fractal temporal correlations. These findings challenge the traditional dependence of postural control theories exclusively on external force-plate axes and underscore the significance of multifractality in defining control parameters that govern postural stability across the full angular range of the 2D support surface.
... Data was processed and variables extracted with well-established methods used in previous research (e.g., Harris & Wilmut, 2020;Warren, 1984;Wilmut et al., 2015). Any gaps in the 3-D movement data were filled and then filtered using an optimised low pass Woltring filter with a 12 Hz cut off point to screen any noise and smooth the data. ...
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Background: Anxiety and movement consistency both influence movement in individuals with Developmental Coordination Disorder (DCD). Aims: This study investigated the influence of anxiety, self-efficacy, resilience and movement variability on perceptions and actions of adults with and without DCD. Methods: 17 adults with DCD and 17 adults with typical motor skills (TMS) (age and sex-matched) completed a questionnaire and three experimental tasks: two perceptual judgement tasks (static and dynamic conditions), and an executed action task involving judging and walking through different-sized gaps between doors. Results: No significant relationships were detected between general or movement-specific anxiety, self-efficacy or resilience and perceptual judgement or movement behaviour; however, movement consistency did significantly relate to movement execution in both groups. Correlations showed adults with DCD with lower movement-specific self-efficacy left bigger safety margins, and indicated stronger links between perception and action in TMS adults. In the adults with DCD there was no significant correlation between the point of behaviour change (critical ratio) in the perceptual judgement and executed action tasks, suggesting a less smoothly linked perception-action cycle than in the TMS adults. Conclusions and implications: Results highlight the importance of movement variability and motor control in the movement behaviour of adults with DCD, while illustrating the importance of studying perception and action together, especially when comparing populations, to elucidate how these may be constrained differently by individual-, task-and environmental-based constraints. What this paper adds: Our relationship with movement is vital in our ability to survive, adapt, and thrive. Understanding the factors which may influence or change how we move is therefore important, and especially so for individuals with DCD. This paper offers further insight into how adults with movement difficulties use awareness of their own movement abilities as a fundamental adaptive strategy to avoid harm during movement. Its findings also add to initial insights into the role that inherent task-based risk may have in the relationship between how we feel and how we move, and how this may be constrained differently in adults with DCD compared to adults with typical motor skills. This paper moreover calls attention to the pivotal role choices of measurement tools may have in detecting possibly highly nuanced relationships between the factors under study and movement behaviour in people with and without DCD. This could be fertile ground for future research given the relative sparseness of evidence to date. The findings furthermore add to a growing evidence base suggesting that adults with DCD could benefit from strategies for managing their movement difficulties based around their awareness of their own movement abilities. This could facilitate the safe and effective completion of movements in a way that suits them, rather than trying to move like those with typical motor skills. The implications of this may relate not only to more safe and effective movement, but to individuals with DCD feeling better about themselves and their abilities to navigate the world around them.
... At its core, affordance refers to the clues or suggestions that the environment offers to an observer about how it can be used [17]. In the field of psychology, can still be described as "a resource or support that the environment offers" [51] and "factors of perception and action that make interfaces easy to learn and use" [16]. ...
... Subsequent scholars like Heft [43] and Turvey and Shaw [44] expanded on Gibson's ideas, emphasizing affordances' dynamic, relational, and subjective nature, and their constancy across contexts. Research by Warren [45] and others further developed the theory, applying it to areas like locomotion, educational psychology, and ecological psychology, stressing that affordances are shaped by both physical and social systems and are crucial for learning and development. Chemero [46] and Ingold [47] introduced complex systems and anthropological perspectives, respectively, arguing that affordances are relational and culturally embedded. ...
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This paper investigates the connection between affordance theory and pattern language in the design of hybrid creative spaces. It introduces the concept of "creative affordance" as a key mechanism that mediates the indirect relationship between design patterns and the creativity these spaces cultivate. Through a narrative review of literature from environmental psychology, human-computer interaction , architecture, and extended realities, this paper underscores the importance of affordance theory in understanding the dynamic interactions between humans and their physical and non-physical environments. The analysis reveals how integrating affordance theory with pattern language can result in more engaging, intuitive, and effective design solutions. Building on this notion, this paper proposes a framework for hybrid creative spaces that explains the relationship between hybrid environments, creative affordances, and creativity. Alexander's pattern language is shown to be both theoretically and practically relevant for design researchers and practitioners, particularly in addressing complex interdisciplinary challenges beyond physical space. While pattern language emphasizes the structural properties of design, affordance theory focuses on its usability and interaction potential. The findings contribute to existing knowledge on design creativity through the combined lens of affordance theory and pattern language.
... Take, for example, stairs as a technology (Davis & Chouinard, 2017;McGenere & Ho, 2000). Stairs afford climbing, but it is the architectural design of stairs that influences their perceived and actual "climbability" (Warren, 1984). An affordance approach might consider the extent to which stairs enable climbing, whereas an architectural approach would examine how climbability is directly influenced by specific properties of the technology: the distance between steps, the angle of the rise, and other aspects relating to the structure's form. ...
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The present study argues that political communication on social media is mediated by a platform's digital architecture, defined as the technical protocols that enable, constrain, and shape user behavior in a virtual space. A framework for understanding digital architectures is introduced, and four platforms (Facebook, Twitter, Instagram, and Snapchat) are compared along the typology. Using the 2016 US election as a case, interviews with three Republican digital strategists are combined with social media data to qualify the studyies theoretical claim that a platform's network structure, functionality, algorithmic filtering, and datafication model affect political campaign strategy on social media.
... That work has shown that humans converge toward energetic optima. For example, walkers adopt a preferred gait that constitutes an energetic minimum given their own biomechanics (Warren, 1984;Warren et al., 1986;Kuo et al., 2005;Selinger et al., 2015;Finley et al., 2013;Lee and Harris, 2018;Rock et al., 2018;Yokoyama et al., 2018;O'Connor et al., 2012). ...
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Relatively little is known about the way vision is used to guide locomotion in the natural world. What visual features are used to choose paths in natural complex terrain? To answer this question, we measured eye and body movements while participants walked in natural outdoor environments. We incorporated measurements of the three-dimensional (3D) terrain structure into our analyses and reconstructed the terrain along the walker’s path, applying photogrammetry techniques to the eye tracker’s scene camera videos. Combining these reconstructions with the walker’s body movements, we demonstrate that walkers take terrain structure into account when selecting paths through an environment. We find that they change direction to avoid taking steeper steps that involve large height changes, instead of choosing more circuitous, relatively flat paths. Our data suggest walkers plan the location of individual footholds and plan ahead to select flatter paths. These results provide evidence that locomotor behavior in natural environments is controlled by decision mechanisms that account for multiple factors, including sensory and motor information, costs, and path planning.
... In other words, affordances are ecological properties of animal-environment relationships (Chemero, 2003(Chemero, , 2009Stoffregen, 2003). 10 For instance, whether a surface is step-on-able depends on the relationship between the properties of the surface and one's leg length (Mark, 1987;Mark & Vogele, 1987;Warren, 1984), leg extensor strength and hip flexibility (Konczak et al., 1992), and current distance from the surface (Cesari et al., 2003). 11 Animals each have multiple such relationships with their environments; these relationships comprise their way of life, or ecological niche. ...
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Quality physical education (PE) promotes physical activity and, consequently, children’s health and wellbeing. The provision of quality PE depends largely on the interactions between PE teachers and students. PE teachers use observation to guide these interactions and, therefore, require perceptual skill. Perceptual skill in PE teachers is traditionally viewed as the accurate perception of students’ movement errors—deviations from a normative movement pattern. However, this view has three major limitations: motor learning is more about movement function than form, PE is about more than motor learning, and perception is more about the environment’s functions—its possibilities for action, or affordances—than its forms. We present a novel, ecological approach in which perceptual skill in PE teachers is instead considered in terms of the field of teaching affordances—the dynamic set of possibilities for teaching students within a situation. Perceptual skill, we argue, is a PE teacher’s tendency to perceive a more differentiated field of affordances: a broader range of affordances, extending further into the future, with greater variation in their relevance. Compared with accurate perception of movement errors, this tendency better aids a PE teacher in interacting with students, navigating towards their educational goals, and, ultimately, providing quality PE.
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This thesis investigates visually guided actions of urban traffic users, specifically drivers and cyclists, through different theoretical frameworks. It is divided into two parts, each employing distinct guides to discovery. Part 1: The focus is on drivers' gaze behaviour during virtual navigation grounded in cognitivist approaches. Three experiments investigate the relationship between visual attention and driving performance among vulnerable driver groups. Study 1 explores the impact of anxiety on attention and performance in driving, revealing that while anxiety impairs processing efficiency and performance effectiveness for both inexperienced and experienced drivers, it shows that attentional shifts differ based on experience level. Study 2 investigates how race gaming experience influences gaze behaviour and driving performance, showing that drivers with gaming experience allocate more attention to task-relevant source of information, highlighting how virtual experience can be used as good training for enhancing gaze behaviour and driving performance. Study 3 examines gaze behaviour and driving performance among drivers with Parkinson's disease (PD) and healthy older and younger adults, finding that PD affects performance and gaze behaviour negatively. PD drivers had more collisions and spent less time within the speed zone. Their gaze behaviour was more random, with increased fixations on irrelevant areas and higher visual entropy. Older drivers concentrated their visual search on the lane to detect threats. Part 2: I shift my guide to discovery to the ecological concept of affordances, investigating the role of perceiving affordances in movement control. Study 4 investigates whether the visual control of braking in cycling is affordance-based. Maximum achievable deceleration was manipulated by adding weights to the bike, and two approach distances are used to vary speed. Participants increased brake adjustments as they approached the action boundary, indicating an affordance-based control strategy. Active cyclists predominantly used the aggressive style, suggesting experience influences braking strategies. Finally, Study 5 explores action scaling in braking relative to preferred and maximum deceleration in cycling on different terrain slopes. Participants began braking earlier with lower deceleration on the downhill slope. Aggressive braking style was more prevalent during the uphill than the downhill slope. Both styles adjust braking magnitude as deceleration increases, supporting the affordance-based approach. In summary, this thesis advances our understanding of visually guided actions in urban traffic through the study of different theoretical frameworks. Due to its greater ecological representativity and more parsimonious explanation, the affordance-based control approach emerges as the most appropriate perspective for investigating visual perception-action coupling in traffic navigation.
Chapter
This chapter explores the intersection of postcognitivism and sensory substitution, introducing the concept of affordance within ecological psychology. It posits that the risks associated with expanding the concept of affordance outweigh those of maintaining specificity, which fosters the perception of a direct process. The chapter showcases five devices explicitly embracing a post-cognitivist approach to sensory substitution (enactive or ecological devices). The discussion encompasses three key features for an affordance-based approach to sensory substitution: tactile stimulation contingent on distance to surfaces, the acknowledgment of perception as an active process, and the recognition of perceptual training as a valuable tool for enhancing perceptual learning. The chapter culminates in a proposal outlining how affordances substantiate a sensory substitution approach that surpasses mere functional replacement of sensory modalities. This proposal is also intricately linked to observed behavior concerning distal attribution. By exploring these facets, the chapter contributes to a deeper understanding of the intersection between postcognitivism, affordances, and sensory substitution, emphasizing the nuanced dynamics and potential advancements in this interdisciplinary realm.
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In this paper we pursue the argument that where a group of muscles functions as a single unit the resulting coordinative structure, to a first approximation, exhibits behavior qualitatively like that of a force-driven mass-spring system. Data are presented illustrating the generative and context-independent characteristics of this system in tasks that require animals and humans to produce accurate limb movements in spite of unpredictable changes in initial conditions, perturbations during the movement and functional deafferentation. Analogous findings come from studies of articulatory compensation in speech production. Finally we provide evidence suggesting that one classically-defined source of information for movement, namely proprioception, may not be dimension-specific in its contribution to coordination and control.
Chapter
Many problems in fluid mechanics cannot be solved by direct analysis as in the preceding chapters.
Chapter
Several acceptations of ‘measure’ are distinguished from one another and from ‘measurement’, which denotes an empirical operation. The concept of quantitative measure, or quantity, or magnitude, is elucidated in mathematical terms. It is argued that a scale is involved in every quantity or magnitude. Also, a unit is involved in the very construction of any magnitude endowed with a dimension. The extensive-intensive distinction, misunderstood in much of the literature, is clarified. It is shown that intensive magnitudes are often theoretically more basic than the corresponding extensive quantities. Finally the notions of index or objectifier, and standard (or materialization of a unit) are analyzed. The departures from the standard theory of “measurement” (introduction and clarification of scientific concepts) are pointed out. It is shown that no a priori theory of quantities, independent of natural or social laws, can be adequate, as we should have learned from the non-additivity of mass and entropy for interacting systems.
Chapter
Equations predicting the energy expenditure during human walking are discussed. It is shown that a hyperbolic equation adequately predicts energy expenditure over the entire range of normal walking speeds, while an equation of quadratic form is adequate for speeds up to about 100 m/min, and also predicts energy expenditure at competition speeds.
Chapter
Activity takes place in a space-time world. It therefore requires spatio-temporal information for its guidance. Where does this information come from? Since activity involves movement relative to the environment it generates a constantly changing optic array at the eye-a spatio-temporal optic flow field. This paper sets out to examine the cooperative relationship between vision and action-how the optic flow field yields spatio-temporal information for guiding activity and how activity makes that information available. The central thesis is that the visual system and the motor system are functionally inseparable: they are components of a unified perceptuo-motor system, which is itself a component of the organism-environment system.