Attention capture is what signal becomes when its purpose shifts from informing a participant to occupying and steering them. It is the manipulative pole of a spectrum whose healthy pole is discovery — telling someone that something useful they did not know about exists. A useful message says here is something relevant you may want to know; a capturing one says I will keep entering your perceptual field until your preferences bend. The clean line between them:
Good marketing expands informed choice. Bad marketing captures attention in order to manufacture behavior.
Why the model treats it as depletion
Capture is not measured by whether it works (whether someone bought) but by what it costs — the attention, interruption, repetition, and cognitive load consumed, weighed against the genuine awareness produced. Because attention is a renewable but vulnerable resource, signal that captures rather than informs is a form of ecological depletion: it consumes attention and erodes reflective choice while dressed as service. Its most dangerous form, where a system exploits modeled psychological vulnerabilities, is ecological predation. See The Marketing Test.