A constraint-based approach to ecological affordances

Ko and Neuberg define ecological affordances as the opportunities and threats an environment poses for one’s goal achievement. We suggest an avenue of thought that might enrich or nuance this account by understanding environment, opportunities, threats, and goals through the language of constraints. More precisely, we argue that ecological affordances can be understood as arising due to constraints on strategies for goal achievement. With this framing, it is possible to render a more precise account of how exactly ecological affordances capture the normative dimension implied by the terms opportunity and threat. While it would be too ambitious to provide a fully fleshed account within this commentary, we aim to provide a general and streamlined overview of the idea, omitting several interesting aspects. With that in mind, let’s turn to constraints.

Constraints are limitations on degrees of freedom (Deacon, Reference Deacon2012; Hooker, Reference Hooker2013; Juarrero, Reference Juarrero2023). The laws of physics limit what can and cannot happen, the banks of a river limit the flow of water and legal systems limit the behaviour of citizens. This directly implies the notion of constraints being disabling. Events that could have otherwise happened were disabled by the constraint. However, constraints can also be enabling (Pattee, Reference Pattee, Pattee and Rączaszek-Leonardi2012). The possibility of playing chess is a product of a set of constraints that we call rules. If players were allowed to move any piece anywhere at any time, there would be no game. The game is enabled by how the rules limit the degrees of freedom of each move. Similarly, the possibility of walking is enabled by the limitations that the kneecaps impose on the joints. More generally, constraints at one level can give rise to new possibilities at another, because they stabilise patterns or sequences that would otherwise only happen by accident.

The set of possible behaviours of an individual will always be a product of a myriad of constraints at different levels, such as laws of physics, legal systems, and kneecaps. Even the possibility of the individual itself, with all its cognitive and behavioural capacities, can be seen as enabled by the constraints of its biological makeup. However, we can theoretically (and for the simplicity of this commentary) set aside most of these constraints and construe an action space of an individual which contains all the actions that an individual can do (walk, eat, sleep, jump, smile, etc.). The execution of a plan would then be a trajectory or path in this space (e.g., walk to the tree, then jump and grab an apple, then eat the apple). Since this is inevitably executed within an environment, the environment naturally poses as a constraint on the possible paths in this space. Here, environmental features can disable paths by limiting the possibility of actions along the path, while in turn enabling reliable execution of other paths. For instance, traffic lights disable certain action paths to enable a coordinated flow consisting of otherwise unreliable and inefficient paths in the action space of pedestrians.

Introducing goals adds another layer of constraint to the action space. Once an individual sets a goal, actions come to be perceived as either desirable or undesirable for goal achievement. The undesirable actions, due to goals, are constrained away. For example, when the goal is to secure a mate, many otherwise possible trajectories, such as ignoring or avoiding potential partners, become undesirable, while making desirable those that lead to mating. Likewise, for the goal of protecting kin, trajectories that risk their safety are ruled out by the individual, whereas those that support and defend them are favoured. This effectively acts as a value-based self-imposed constraint on the action space, further limiting the set of paths an individual will execute. Similar to environmental constraints that shape the action space by determining what paths are possible to realise, goals shape this space by ruling out paths which do not contribute to goal achievement as well as selecting for, among this constrained set of paths, those that are perceived as more likely to realise one’s goal. However, the shape of the space is never fixed. Changes in environmental constraints, the individual’s capacities, or their goals (e.g., through development) alter the available and desirable paths by shifting the constraints on the action space.

Once a goal is introduced, the trajectories that are perceived to realise the goal take on the role of strategies. Attracting attention, deterring rivals, or investing in the families of a potential mate all represent distinct strategies, each comprising a set of similar action paths perceived as leading to realising the goal of mating. Environmental features, however, can both enable and disable such strategies. We suggest that opportunities are the way environmental constraints enable some strategies, and threats are the way they either disable them or make them less likely to succeed. Importantly, as such, threats and opportunities are always relative to particular strategies, which themselves are relative to goals, making threats and opportunities only indirectly related to goals. Thus, the same environmental feature may function as a threat in relation to one strategy while simultaneously serving as an opportunity for another, thus being both opportunity and threat with respect to the goal.

With these elements in place, we have a constraint-based account of ecological affordances which specifies the normative character of ecological affordances as emerging from how well strategies in the action space lead to goal realisation. Moreover, as individuals develop new capacities, as environments shift through ecological or social change, and as goals evolve across life stages, the action space and the strategies within it are continuously reshaped. Thus, an environmental feature that once disabled a strategy may later enable it, and what counted as a threat at one stage of life may count as an opportunity at another. This aligns particularly well with Ko and Neuberg’s account but provides a more precise notion of the relation between opportunities, threats, goals, and strategies, capturing each through a language of constraints.