attention

Meaning: Attention is the limited-capacity process of choosing which information receives conscious processing. Selective attention focuses on one stimulus among many (the cocktail party effect); divided attention splits effort across tasks and usually lowers performance when tasks are demanding. Bottom-up attention is captured by salient stimuli such as a loud noise; top-down attention is steered by goals and expectations. Broadbent's filter model blocks unattended input early; Treisman's attenuation model turns it down, so meaningful items like your own name can still get through; late-selection models analyze meaning before selecting.

On the MCAT: In dichotic listening, different messages go to each ear and the subject shadows one. People report physical features of the unattended message, such as pitch, but little content, which supports early filtering. Noticing one's own name supports attenuation. Inattentional blindness (the invisible gorilla in a ball-passing video) shows that unattended objects can go unnoticed. In visual search, a feature search (a red item among green) is fast regardless of the number of distractors, while a conjunction search (a red circle among red squares and green circles) slows as distractors increase.

Common confusion: Unattended stimuli are still sensed, because receptors keep responding; they are just processed less deeply. Attention is also not the same as arousal or consciousness in general: it is the selection of particular information within awareness.