Affordance Competition
The brain doesn't decide what to do and then do it. It prepares several possible actions simultaneously, and they compete for selection---biased by context, goals, urgency, and reward. The action you perform is the one that won.
Walk into your kitchen in the morning and notice what happens. Before you've consciously decided anything, your brain has already started preparing several actions: open the fridge, fill the kettle, check your phone on the counter. These aren't idle thoughts. They're action plans---partially specified motor programmes running in premotor and parietal cortex, each one primed by something in the environment. The mug by the sink primes reaching. The kettle primes filling. The phone primes checking. Your brain hasn't decided what you're doing yet. It's running a competition.
This is the affordance competition hypothesis, and it overturns a comfortable assumption about how action works. The traditional picture is sequential: you perceive the environment, you deliberate, you decide, you act. Neat and tidy. But the neural evidence tells a different story. Action specification begins almost immediately after perception, well before anything resembling a decision. Multiple actions are prepared in parallel, each one an affordance---an action possibility that the environment offers and the body can execute. These affordances compete for selection, and the competition is biased by everything the brain knows: what your current goal is, what context you're in, how urgent the situation feels, and how rewarding each option has been in the past.
The competition plays out across a network of areas. Posterior parietal cortex represents the available actions in terms of the body's current state and the objects in reach. Premotor cortex specifies the motor details. Prefrontal cortex biases the competition towards actions that serve the current goal. Basal ganglia gate the result---they inhibit all the competing plans and selectively release the winner. This is why action can feel both automatic and chosen: the competition runs without your conscious involvement, but the biases that shape it reflect your goals, your history, and your context.
The practical implication is this: the environment doesn't just contain objects. It contains action invitations, each one activating motor preparation before you've decided whether to accept. A door handle invites pulling. A chair invites sitting. A colleague's open posture invites speaking. Your behaviour in any given moment is less about what you've decided and more about which affordance won the competition---and the competition is rigged by everything around you. This is why situations shape behaviour so powerfully: the situation determines which actions enter the race, and the environment loads the dice.
There's a temporal dimension too. The competition isn't a single snapshot. As you move through the environment and as context shifts, the field of competing affordances changes continuously. Actions that were available a moment ago drop out; new ones appear. The system is constantly re-evaluating, which is why smooth behaviour in complex environments---cooking dinner while watching a child, for instance---looks so effortless despite being computationally extraordinary. The brain is running a rolling competition, updating the candidates and their biases in real time, and the winning action at each moment is the one that best fits the converging constraints.
How can you think with this?
01.
The environment loads the competition
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The input-output machine maps inputs to outputs, and affordance competition tells us how. The inputs aren't just triggers that fire a single response. They're invitations that activate multiple potential responses simultaneously. The mug, the kettle, and the phone each load a different action plan, and the output is whichever plan wins the competition. Change the inputs---move the phone to another room---and you change which actions compete. You haven't changed your character or your intentions; you've changed the field of candidates.
Key takeaway: to change what someone does, change what actions the environment invites. The competition will take care of the rest.
02.
The cheapest action wins by default
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In affordance competition, the action that requires the least additional biasing tends to win. Well-practised actions in familiar contexts are already heavily primed---they've won this competition many times before, and the pathways are strong. Deliberate control has to actively boost a less-primed alternative to overcome that advantage, which costs metabolic resources the system would rather not spend. So the habitual action wins unless something---a conflict signal, a strong goal, an interruption---forces the controller to intervene.
Key takeaway: the competition defaults to the most practised option; changing the outcome means either practising the alternative until it's competitive, or restructuring the environment so the old option doesn't enter the race.
03.
Predictions bias which actions compete
The brain predicts what should happen next---in the world and in the body. When predictions fail, you feel something, attention pivots, and behaviour updates.
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The prediction engine shapes the competition before it begins. As you approach the kitchen, your brain is already generating predictions about what you'll do---based on time of day, bodily state, and thousands of previous mornings. Those predictions pre-activate certain affordances and suppress others. The kettle is a stronger competitor in the morning because the system predicts tea. After dinner, the same object barely registers. The affordances are objectively the same; the predictions change which ones matter.
Key takeaway: the prediction determines the starting position. To change which action wins, change what the system expects---through practice, through cue design, or through disrupting the context that loads the old prediction.
04.
Goals constrain the race from above
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Affordance competition is where top-down and bottom-up converge. Bottom-up signals from the environment specify which actions are physically available. Top-down signals from prefrontal cortex bias the competition towards actions that serve the current goal. When both align---you want tea and the kettle is right there---action is fast and fluent. When they conflict---you want to work but the phone is right there---you get the characteristic feeling of being pulled in two directions, because competing action plans are genuinely active simultaneously.
Key takeaway: if top-down goals aren't strong enough, bottom-up affordances win by default. Load the goal before you encounter the environment, or the environment will choose for you.