Definition
Context dependence is the principle that an act or a stimulus has no fixed meaning — its meaning is set by the circumstances around it. The same hand on the same trigger is a war crime or an act of heroism depending on who, where, when, and why. The same touch is comforting or threatening depending on context.
Behave opens with this idea and never lets go of it. It is the reason the book refuses to ask whether a behavior is good or bad before asking what situation produced it.
Why it matters
How it works
The brain never evaluates a stimulus in isolation. The amygdala's threat appraisal, the frontal cortex's decisions, and even reflexive responses are all conditioned on context — who is present, what category they fall into, what just happened, what the culture expects. A neutral face read as in-group versus out-group activates different circuitry; an identical word lands differently after a priming cue.
This is why Behave keeps widening its causal lens. The hormones of the past hour, the experiences of childhood, the surrounding culture, and the evolutionary past are all forms of context. Each supplies part of the answer to why one situation made a behavior likely. Strip the context away and the behavior becomes inexplicable — or worse, easy to misjudge.