Introduction

The concept of affordances was originally found in the work of ecological psychologist James Gibson (1966), where he proposed that perceptions should be understood in a comprehensive perceptual system instead of channels of sensation. The theory of affordance was therefore first developed in Gibson (1977), and expanded in his later work (2014;1986). The theory of affordances refers to the action possibilities that objects and environments offer to an organism (1977;2014;1986). From the handle on a door to the button on a smartphone, affordances exist everywhere, and they guide how we interact with the world, often without us consciously realising it.

Gibson developed his view of affordances more comprehensively in his book "The Theory of Affordances" (1977), where he described affordances as the relationship between an agent and their environment. Gibson believed that studying an animal's perception in isolation from its environment would result in a false understanding. Thus, "… the affordances of the environment are what it offers the animal, what it provides or furnishes, either for good or ill" (Gieseking et al., 2014:p127). He claimed that we perceive things based on the combination of mediums, surfaces, and substances offered to us, rather than at the level of particles and atoms.

Gibson's concept of affordances is broader than the organism-and-object relationship suggested by earlier theorists. Before Gibson's definition, the idea of affordances had arisen in different ways and forms. The Gestalt school first published a concept similar to affordance. Jakob von Uexküll used the term "functional colouring" to describe how organisms might perceive the world in terms of its action possibilities (0598767185). Later work by (1935) also described perceived affordances in a similar fashion. Although Jakob and Koffka did not use the term of affordances, they argued that an object is not defined solely by its abstract properties, rather, it also carries functional meanings or action possibilities for the organism. For example, an apple is not just a round, red object, it is something edible. However, these initial ideas were limited because they tended to describe affordances as based on perception alone and were confined to dyadic relationships between an agent (or organism) and an object.

In contrast to the previous conceptualisations, Gibson believed that multiple parts of the environment might be important in enabling a possible action. From this perspective, affordances can be understood as action possibilities that exist in the environment that related to an actor's capabilities and goals and can be perceived directly. The theory provides a basis for examining ecological perception, which explains perception in an evolutionary and agent-based context. In this view, perception functions primarily to enable adaptive action, helping actors such as humans and animals perceive their environment in order to act effectively within it.

Affordance theory is not an abstract theory. It has practical implications and functional value. Perception is not merely for its own sake. It is for enabling beneficial actions, such as avoiding danger or finding necessities for life. Affordances are therefore useful and important, as they provide competitive advantages to those who have the ability to detect and act upon them. In other words, those who perceive affordances effectively and well are more likely to survive and thrive well.

Theory

An affordance refers to what is offered, provided, or furnished to someone or something by an object from an ecological psychologist's perspective (Bransford & Shaw, 1977;Gieseking et al., 2014;Gibson, 1986). According to Gibson (1986), rather than humans and animals directly receiving information associated with their needs from objects in their environment, they perceive what the objects could offer, rather than the properties of the objects. This is what is called "affordances." Affordances, hence, are defined as "the acts or behaviours that are afforded or permitted by an object, place, or event" (Michaels, 1981:p17). As an example, humans do not perceive chairs and pencils in terms of their material properties. Instead, they perceive them as opportunities to sit and write.

There are three foundations of an affordance: first, an affordance exists relative to a particular actor's action capabilities; second, an affordance exists independently of the actor's ability to perceive it; third, an affordance does not change despite changes in the actor's needs and goals (10.20380/GI2000.24;Gieseking et al., 2014;Gibson, 1986). Elaborating on the first foundation, an affordance that exists for one actor does not necessarily exist for other actors, even if the same object is given. It is worth noting that an affordance is not a property of the experience of an actor, but rather the action capabilities of the actor. For example, a chair affords support to one actor, but it may not afford support to others, which may be due to differences in weight or size. Further, the fact that the chair affords support exists independently, even if the actor does not need the support. This highlights the second and third foundations of affordance: that affordances exist independently and do not change despite changes in the actor's goals and needs.

Described in this way, affordances blur the line between being subjective and objective. An affordance is objective, meaning that its existence does not depend on value, meaning, or interpretation. Yet, it is subjective because it requires an actor's frame of (10.20380/GI2000.24). By blurring the line between the objective and subjective, Gibson proposed the idea that an affordance is an actor-environment mutuality, where the actor and the environment form the fundamental and inseparable pair that generates an affordance (Kaptelinin & Nardi, 2012). This concept also evolved in Gibson's own thinking as he developed the theory of affordances (Wells, 2002). In his initial work, Gibson framed affordances largely within the theory of "information pickup" (Wells, 2002:p144), describing them as part of the information available in the environment, "what things furnish, for good or ill" (Gibson, 1966:p285). In his 1977 work (Bransford & Shaw, 1977), Gibson began to address the role of the animal in the theory of affordances, although he did not yet discuss animal properties in detail. In his later work (2014;1986), he strengthened the idea of mutuality between environment and animal and introduced the term complementarity to describe their relationship. Gibson also explicitly rejected dualism, arguing that the relation between the environment and the observer (i.e., the animal or actor) "is wholly inconsistent with dualism in any form, either mind–matter dualism or mind–body dualism. The awareness of the world and of one's complementary relations to the world are not separable" (Gieseking et al., 2014;Gibson, 1986:p 141).

Gibson further noted that an affordance can be directly perceived and does not require mediation or internal processing by an actor (Gieseking et al., 2014; 10.20380/GI2000.24). Direct perception occurs when an affordance exists independently, and there is information embedded in the environment that uniquely specifies that affordance. For instance, one can perceive another person walking forward when one sees a solid surface underneath their feet. The affordance in this instance is walkability, which is perceived through information from the environment that specifies a solid surface of a certain size (10.20380/GI2000.24). Direct perception relies on the actor's ability to collect information in a particular environment that specifies the affordance, which may be relevant to the actor's experiences and culture (10.20380/GI2000.24). However, while the affordance exists independently of someone's experience and culture, their ability to perceive the affordance may depend on these factors, such as their experiences and cultural background. Therefore, one needs to learn to separate the information in order to perceive directly. Learning in this way can be viewed as a process of recognising patterns in the world, rather than supplementing sensory information with past experiences (10.20380/GI2000.24).

However, there are cases that indicate that affordances exist independently even when there is no information to specify them, further demonstrating that affordances exist independently of one's direct and visual perception (10.20380/GI2000.24). For instance, a hidden door in a room with panelled walls still offers the affordance of passage. The door can be opened and walked through by everyone, but only if someone knows where the door is. There is no clear information indicating the presence of the door, such as a door handle or gap. Therefore, while the affordance exists, namely the door offers the possibility to pass through it, there is no immediate and clear information indicating its existence to help individuals recognise it. In such a case, direct visual perception is impossible because there are no visual cues to help recognise the hidden door. Yet, the door still exists and offers the action possibility of passing through it (10.20380/GI2000.24).

Scholars (10.20380/GI2000.24*). argue that there are two properties of affordances that Gibson implied, but never clearly stated. The first is that an affordance either offers the possibility for an action or it does not. For example, a staircase is either climbable by an actor or not. Gibson defines this as binary with no middle ground. However, he does not specifically address actions that are technically possible but difficult to achieve. For instance, a staircase that is climbable only with great effort due to it being achievable only with great difficulty, such as being steep, slippery, or blocked. Such ‘in-between' cases highlight a grey area that remained unexplored by Gibson.

The second property is that Gibson implies affordances can be nested (10.20380/GI2000.24). This means that one action possibility can be made up of multiple smaller action possibilities. For instance, an apple provides the affordance of eating. Eating the apple itself involves multiple smaller actions: one needs to bite, chew, and swallow. These individual actions, such as biting, chewing, and swallowing, are smaller affordances offered by the apple. In other words, the apple affords eating, but eating itself is composed of several smaller actions, all of which are also affordances provided by the apple. This concept of nesting means that affordances can be part of a larger set of affordances. Affordances, therefore, are not always simple, single, or isolated. They can be part of a hierarchy, where one action is made up of several smaller actions, and each of those smaller actions also provides its own affordances.

Theory Extensions

Norman's affordances

Norman's (1989) concept of affordances was first introduced in his book The Psychology of Everyday Things. He refers to affordances as "…the perceived and actual properties of the thing, primarily those fundamental properties that determine just how the thing could possibly be used. A chair affords (‘is for') support and, therefore, affords sitting. A chair can also be carried" (Norman, 1989:p 9). In Norman's view, there is a difference between actual properties and perceived properties. He argues that perceived properties may not align with actual properties, but they are still considered affordances. This contradicts Gibson's view of affordances as direct and objective, as Gibson believed that an object inherently suggests certain actions to any actor, and affordances exist independently of how they are perceived by actors. However, Norman believed that there is a distinction between perceived and actual properties. Specifically, perceived properties refer to how an actor interprets or perceives an object. For example, a button may appear pressable to an actor because of its shape and size, even if the button itself cannot be functionally pressed. Actual properties, on the other hand, refer to the real, inherent qualities of an object. For instance, the button is functional when pressed. Norman believed that an affordance exists regardless of whether the perceived property matches the actual property. So, if an actor perceives an object as having an affordance, even if it is not actually functional in reality, like a button appearing pressable, it is still considered an affordance. Norman emphasised the point that affordances are tied to an object's fundamental properties, such as its shape, size, texture, and function, which suggest possible actions. In addition, in Norman's view, understanding an affordance does not necessarily involve an actor. In his framework, affordances are primarily defined by the object itself and its properties, and the focus is on how actors perceive those properties. Gibson, on the other hand, places the actor at the centre of understanding affordances. In Gibson's view, affordances are action possibilities that are directly perceived by an actor within the context of their environment, and he emphasises that the relationship between the actor and the object is key to understanding what affordances exist.

Gaver's affordance

Gaver's (1991) theory of affordances builds on Gibson's ecological view but adapts and extends it for the context of human computer interaction. Like Gibson, Gaver emphasises the point that affordances are action possibilities enabled by the environment, and that these affordances exist independently of whether an actor notices them. For instance, a scroll bar can be dragged even if a novice user does not realise it can move. However, Gaver advances Gibson's concept by showing that affordances can take a variety of forms, such as perceptible, hidden, and false. Gaver strengthens Gibson's relational view while providing a more systematic and design-relevant account than Norman's perception-centred interpretation. Because Gaver's contributions are grounded in technological contexts, he argues that effective interfaces should support learning through exploration, not through instructions or metaphors. His work demonstrates how usability issues arise when perception does not match actual action possibilities. For example, a trash-bin icon that clearly resembles a physical bin invites users to drag files into it to delete them (a perceptible affordance). A photo that can be zoomed by pinching on a trackpad provides a hidden affordance when there is no visual cue to signal that zooming is possible. A word or image underlined in blue that looks like a hyperlink but does nothing when clicked illustrates a false affordance. This view also differs from Norman's notion of perceived affordances, in which affordances are defined by the user's interpretation. Unlike Norman's emphasis on mental models shaped by background, experience, and culture, Gaver highlights the direct link between perception and action, arguing that interfaces should reveal their affordances through visual, tactile, or auditory information. For instance, a camera app that briefly flashes on the screen and plays a shutter sound signals that a photo has been taken, even if the user does not immediately see the image.

Gaver (1991) also introduces concepts such as sequential affordances, in which one action reveals another over time. For example, a user may first perceive that a handle affords grasping; once grasped, tactile feedback reveals that it affords turning, and once turned, it affords pulling. This sequence shows how one action can provide new information that reveals additional affordances. He also introduces nested affordances, which are smaller affordances that combine to support a larger action. A handle may afford pulling and a door may afford manipulation, but only together do they afford opening the door.

Needs-affordances-features

Combing the concepts of affordances, technology and psychology, (Karahanna et al., 2018) proposed a framework of needs-affordances-features (NAF) to understand how different digital features, rather than technology as a whole, generate salient affordances that meet the various psychological needs of users. Karahanna et al. (2018) believed that individuals use specific features primarily to fulfil situational motivations, such as accomplishing a task or performing well at work, and there are underlying needs driving the use of these specific features. Therefore, a needs-based affordance theory provides a powerful lens to explain why individuals use a particular digital feature, especially in contexts where people use it personally and voluntarily, without mandates or work-related goals. Therefore, they define needs-affordances-features (NAF) in the following terms: "…individuals' psychological needs motivate their use of social media applications to the extent to which these applications provide affordances that satisfy these needs" (10.25300/MISQ/2018/1149: p738).

To apply NAF in the social media context, for example, using digital features such as adding, deleting, and editing content on Wikipedia generates the affordance of collaboration. This allows users to collaborate with each other to create content in a social media setting, satisfying needs such as competence and self-discovery. Competence is an individual psychological need to be effective in dealing with the environment, where the person feels they can have an impact on themselves, others, and the environment, as well as achieve valuable outcomes. Another example is using digital features like creating avatars in Second Life, which generates the affordance of self-presentation. This refers to users revealing and sharing information about themselves online to portray who they are, what they like, and the experiences, values, and beliefs they hold. These affordances further satisfy users' needs for autonomy (i.e., the need to be the causal agent of one's own life and act in harmony with one's integrated self), having a place (i.e., the need to possess a certain territory or space to have a home where they dwell), maintaining continuity of self-identity (i.e., the need to maintain an emotional connection between their current self-identity and their past), expressing self-identity, and relatedness (i.e., the need to communicate or express themselves to others).

NAF is useful and has various implications. For instance, using NAF can help identify the different psychological needs motivating the use of specific social media applications, such as Facebook and Wikipedia. By doing so, NAF allows for the model testing of user behaviours in specific technological applications within the social media context. Further, NAF can inspire the design science of social media. Through NAF, systems can be designed with specific social media features that meet users' needs and foster greater engagement in social media settings.

NAF can also be applied beyond technology. The current formulation of NAF (Karahanna et al., 2018) is built on universal psychological needs, such as autonomy, competence, relatedness, self-identity, and having a place derived from well-established theories (e.g., psychological ownership). These needs exist across many human activities, not just digital contexts. Similarly, the role of affordances is generalisable beyond technology and can be applied to any environment. For instance, NAF can be used in urban design by examining which psychological needs a public space should satisfy (e.g., the need for relatedness to connect with others), identifying the affordances the space should provide (e.g., affording social interaction), and then specifying the features that instantiate those affordances (e.g., open seating areas, playgrounds, and walking paths). This demonstrates that NAF can be meaningfully applied across diverse non-technological contexts. Table 1 summarises different views of affordances.