Selective: processing restricted to a subset of possible stimuli. Internal: attending to one line of thought over another or selecting one response over another. Overt: directing a sense organ toward a stimulus, like pointing your eyes or turning your head (also called exogenous) Covert: attending without giving an outward sign you are doing so (also called endogenous) It is impossible to process everything at once. People react faster to the target when there is a valid cue compared to an invalid cue. It takes time for the cue to be processed and for attention to be deployed. The reaction time depends on the stimulus onset asynchrony (soa) between cue and stimulus. Spotlight model: attention moves from one point to the next. Zoom lens model: attention expands from fixation grows to fill whole region shrinks to include just cued location. The efficiency of visual search is the average increase in rt for each item added to the display.