Key Takeaways
1. The Mind Extends Beyond Skin and Skull
Where does the mind stop and the rest of the world begin?
Challenging boundaries. The Extended Mind (EM) hypothesis fundamentally questions the traditional assumption that the mind is confined solely within the brain or body. It proposes that our cognitive processes and even mental states can be distributed across biological and nonbiological realms, forming hybrid systems. This perspective suggests that the boundary of the intelligent system is far more fluid and plastic than commonly supposed.
Cognitive systems as hybrids. EM posits that when humans are appropriately linked with external entities, the entire arrangement constitutes a cognitive system in its own right. This means that elements beyond the skin and skull—such as tools, technologies, or even other people—can play a constitutive role in our thinking. The implication is that the "object" can become part of the "subject," giving things a cognitive life.
Beyond the brain. This view is not merely about the brain using external tools; it's about the external elements becoming part of the cognitive process itself. This radical re-evaluation of mental boundaries opens up new avenues for understanding human intelligence, suggesting that our minds are inherently "leaky" and constantly incorporating external resources.
2. Active Externalism Focuses on Dynamic Interaction
We advocate a very different sort of externalism: an active externalism, based on the active role of the environment in driving cognitive processes.
Dynamic engagement. Active externalism distinguishes itself from traditional externalism (like Putnam's or Burge's) by focusing on the active and here-and-now role of the environment in cognitive processes. Unlike passive externalism, where external features are distal and historical, active externalism emphasizes that relevant external features are "in the loop," directly impacting the organism and its behavior.
Causal relevance. In these coupled systems, external features are just as causally relevant as internal brain features. If these external components are removed, the system's behavioral competence drops, similar to removing a part of the brain. This direct, two-way interaction creates a unified cognitive system where external elements play an ineliminable role in driving cognition.
Explaining action. This perspective offers a more natural and less complex explanation for many actions. For instance, choosing words in Scrabble can be seen as an extended cognitive process involving the physical rearrangement of tiles, rather than solely internal processes with a long series of inputs and actions. The environment is not just a backdrop but an active participant in thought.
3. The Parity Principle Challenges Bio-Chauvinism
If, as we confront some task, a part of the world functions as a process which were it done in the head, we would have no hesitation in recognizing as part of the cognitive process, then that part of the world is (so we claim) part of the cognitive process.
Intuition pump. The Parity Principle serves as a heuristic to overcome "bio-chauvinistic prejudices" that restrict cognition to biological processes. It asks us to consider if an external process, if performed internally, would be readily accepted as cognitive. If so, its external location should not disqualify it.
Functionalist credentials. This principle introduces the functionalist aspect of EM: if a process performs a cognitive function and is causally integrated with other cognitive processes, its location is irrelevant. It's not about physical similarity between internal and external processes, but about their functional role in completing a cognitive task.
Addressing misinterpretations. Critics often misinterpret parity as demanding exact mechanistic or physical similarity between internal and external processes. However, EM theorists clarify that the principle focuses on functional equivalence at a higher level of abstraction, aiming to free us from arbitrary skin-and-skull boundaries in defining cognitive systems.
4. Reliable Coupling Integrates External Resources
If the resources of my calculator or my Filofax are always there when I need them, then they are coupled with me as reliably as we need.
Defining coupling. A coupled system involves a human organism linked with an external entity in a two-way interaction, where all components play an active causal role and jointly govern behavior. The removal of the external component would diminish the system's behavioral competence, akin to removing part of the brain.
Portability and reliability. Critics argue that external couplings are too contingent and easily decoupled to be considered part of a stable cognitive core. However, EM proponents counter that reliable coupling is key. If external resources are consistently available and integrated into daily routines, they become part of the "basic package of cognitive resources," much like internal biological systems.
Evolutionary and developmental factors. The biological brain itself has evolved and matured by factoring in the reliable presence of a manipulable external environment. Language, for instance, is a central example of such reliable coupling, where the brain develops to complement external linguistic structures, forming a unified, densely coupled system.
5. Dispositional Beliefs Can Be Externally Stored
The moral is that when it comes to belief, there is nothing sacred about skull and skin.
Otto and Inga. The classic example of Otto, an Alzheimer's patient relying on a notebook for memory, and Inga, who uses biological memory, illustrates how dispositional beliefs can be externally constituted. For Otto, the notebook functions like biological memory, providing reliably available information that guides his actions.
Functional equivalence. Clark and Chalmers argue that the information in Otto's notebook has the same "functional poise" as Inga's biological memory for controlling behavior. To deny Otto's belief until he consults his notebook would be "pointlessly complex," ignoring the notebook's constant and transparent role in his life.
Addressing objections. Critics raise concerns like the "Otto two-step" (Otto believes the address is in the notebook, then looks it up) or issues of first-person authority. However, proponents argue that for Otto, the notebook is transparent equipment, and the functional role of belief in guiding action is met, regardless of the information's location.
6. The Coupling-Constitution Fallacy is Disputed
The fact that object or process X is coupled to object or process Y does not entail that X is part of Y.
Causal vs. constitutive. Fred Adams and Ken Aizawa's primary criticism of EM is the "coupling-constitution fallacy." They argue that simply because an object or process (X) is causally coupled to a cognitive agent (Y), it doesn't mean X constitutes part of Y's cognitive apparatus. They emphasize the distinction between causal relations and constitutive relations.
Clark's rebuttal. Andy Clark responds by clarifying that the aim is not to make the external object itself "cognitive," but to integrate it as a proper part of a larger cognitive system. The question is "when is some physical object or process part of a larger system?" not "when is some candidate part itself cognitive?" This shifts the focus from the part's intrinsic nature to its role within the whole.
Critique of the distinction. Don Ross and James Ladyman further challenge the very causal-constitutive distinction, arguing it's often deployed by philosophers without clear motivation and is not consistently used in mature sciences like physics or economics. They suggest it's rooted in a "containment metaphor" that doesn't align with modern scientific understanding of composition as dynamic and emergent.
7. "Mark of the Cognitive" and Scientific Kinds are Contentious
A first essential condition on the cognitive is that cognitive states must involve intrinsic, non-derived content.
Adams & Aizawa's criterion. Critics like Adams and Aizawa propose that a "mark of the cognitive" is the involvement of "intrinsic, non-derived content" and specific causal processes. They argue that external artifacts, like notebooks, only possess derived content and do not exhibit the law-like regularities (e.g., primacy, recency effects in memory) found in intracranial cognition.
Clark's counter-arguments. Clark challenges this by questioning if every part of a cognitive process must involve non-derived content, pointing out that even internal mental images can have conventionally determined meanings. He also argues against judging the potential for "interesting scientific regularities" from an armchair, suggesting that cognition should be individuated by its characteristic effects rather than its causes.
The "motley crew" debate. Critics contend that extended systems would form an "unscientific motley" of disparate causal processes, precluding a unified cognitive science. Proponents, however, suggest that internal cognitive processes themselves might be a "motley crew" at a mechanistic level, and that a higher-level, systems-based approach can find unifying principles despite underlying physical diversity.
8. Complementarity, Not Just Parity, Drives Extension
The argument for the extended mind thus turns primarily on the way disparate inner and outer components may co-operate so as to yield integrated larger systems capable of supporting various (often quite advanced) forms of adaptive success.
Beyond functional mimicry. The "second wave" of EM thinking, championed by John Sutton and Richard Menary, moves beyond the strict functional isomorphism implied by the Parity Principle. It emphasizes a "complementarity principle," where external states and processes need not mimic internal ones but can play different but complementary roles within an integrated cognitive system.
Leveraging differences. This approach recognizes that the distinct properties of "exograms" (external memories) compared to "engrams" (biological memories)—such as stability, capacity, and manipulability—are precisely what make them valuable for extending cognition. The brain learns to "interface with the external media in ways that maximally exploit their particular virtues."
Interdisciplinary implications. Complementarity fosters a richer, more interdisciplinary cognitive science, encouraging detailed study of the unique features of various cognitive artifacts and their interactions with the brain and body. This allows for investigations into individual differences in reliance on external resources and the specific ways different media transform cognitive tasks.
9. Cognitive Integration Emphasizes Embodied Manipulation
Cognitive processes are not located exclusively in the skin of cognising organisms because such processes are, in part, made up of physical or bodily manipulation of structures in the environments of such organisms.
Hybrid cognition. Cognitive integration, a core aspect of second-wave EM, views cognition as a hybrid process comprising both neural processes and bodily manipulations of environmental vehicles. It starts from the "brute fact of our embodiment" and how our initial cognitive engagements with the world are sensorimotor.
The manipulation thesis. This thesis states that cognitive processes are partly constituted by the physical or bodily manipulation of environmental structures. These manipulations are not mere inputs but integral to the cognitive task. Examples include:
- Biological coupling (e.g., animate vision)
- Epistemic actions (e.g., Tetris players rotating shapes on screen)
- Self-correcting actions (e.g., using spoken language to guide tasks)
- Cognitive practices (e.g., using pen and paper for math)
Normativity of practice. Crucially, these manipulations are governed by "cognitive norms" acquired through learning and training. These norms dictate how external representations are manipulated to achieve cognitive goals, such as solving problems or making inferences. This normative dimension is essential for understanding the integrated nature of hybrid cognitive processes.
10. Consciousness Can Be Broadly Construed as Disclosing Activity
What it is like to have an experience does not supervene on what is going on inside the head of a conscious subject.
Intentional core of experience. Mark Rowlands argues that conscious experiences, particularly intentional ones, contain a non-eliminable "intentional core" that consists in a form of "revealing or disclosing activity." This activity is what allows objects in the world to be presented to us as having certain aspects.
Beyond internal apprehension. Drawing an analogy with Frege's concept of "sense," Rowlands distinguishes between consciousness as an object of apprehension (what we are aware of) and consciousness as a determinant of reference (that in virtue of which we are aware). He argues that the latter, transcendental mode of presentation, is the non-eliminable core of intentional experience.
Extended disclosure. This "disclosing activity" is not confined to neural processes but typically "straddles neural processes, bodily processes, and things we do in and to the world." Examples include:
- Saccadic eye movements (part of visual disclosure)
- Probing and exploratory sensorimotor activity (e.g., in enactive perception)
- Manipulation of the optic array (e.g., by moving to gain information)
These activities are vehicles of disclosure, through which consciousness "lives through" to the world, implying that conscious experience itself can extend.
11. Extended Functionalism Provides a Theoretical Framework
What makes something a mental state of a particular type does not depend on its internal constitution, but rather on the way it functions, or the role it plays, in the system of which it is a part.
Functionalism and multiple realizability. Michael Wheeler argues that the Extended Cognition Hypothesis (ExC) is best understood as "extended functionalism." Functionalism posits that mental states are defined by their causal-functional roles, not their physical constitution, thus allowing for "multiple realizability" across different physical substrates.
Extending the functionalist scope. By generalizing functionalism to allow cognitive system boundaries to fall outside the organic body, extended functionalism provides a principled basis for ExC. The Parity Principle, in this context, suggests that if an external element performs a cognitive function equivalent to an internal one, it should be granted cognitive status, regardless of its location.
Defending against critiques. Wheeler defends extended functionalism against criticisms like Adams and Aizawa's "distinctiveness principle" (expecting distinctive higher-level processes to be realized by distinctive lower-level ones) by citing biological examples of "functional convergence" (e.g., alcohol dehydrogenases in different species). He also addresses the "Rowlands deadlock" by arguing for a higher-level, liberal grain of functional analysis that accommodates cognitive diversity without sacrificing explanatory power.
12. Language Scaffolds, But Doesn't Necessarily Extend, the Mind
Language profoundly influences our thoughts and greatly affects the development of the human cognitive system. Nevertheless, if we understand 'cognitive system' in such a way that the location of a cognitive system bears on the mind’s location, external bits of language do not become part of that system.
Critique of language-based inference. Robert Rupert challenges the idea that language, despite its immense importance, literally extends the mind. He argues that while language profoundly influences human cognition and development, external linguistic resources do not become part of the cognitive system in a way that justifies inferring an extended mind.
Persisting systems vs. fleeting couplings. Rupert emphasizes that cognitive science primarily investigates the persisting capacities of persisting systems (human organisms). He argues that the often fleeting nature of coupled systems (organism + external language) cannot support the systematic, long-term capacities of interest to cognitive science, such as consistent language use across contexts.
Dependence-reasoning fallacy. Rupert criticizes "dependence-reasoning"—the inference that if cognition depends strongly on factor X, then X is part of the cognitive system. He argues this is unreliable, as many external factors (like the sun for vision) are trivially dependent but not constitutive of the mind. He concludes that language acts as a scaffold or tool for internal cognition, rather than becoming a literal part of the mind itself.
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