sensory register

Meaning: The sensory register, also called sensory memory, is the first stage of the Atkinson–Shiffrin information-processing model. It holds a large amount of raw, unanalyzed sensory input for a very short time. Iconic memory is the visual form and lasts a fraction of a second. Echoic memory is the auditory form and lasts a few seconds. Information that receives attention moves into short-term (working) memory, while unattended input fades.

On the MCAT: Passages often describe Sperling's partial-report experiment. Subjects shown a grid of letters for a fraction of a second recall only a few letters when asked for the whole grid. They recall most of a row when a tone cues which row to report. This shows the register briefly holds more than can be reported before it decays. Questions also ask where processing fails when a person does not attend, and the order of stages: sensory register, short-term memory, long-term memory.

Common confusion: Students mix the register up with short-term memory or with sensation itself. Short-term memory has a limited capacity, often given as about seven items (Miller's 7 ± 2), and lasts roughly 20 to 30 seconds without rehearsal. The register has a much larger capacity but a far shorter duration, and it holds only a fleeting copy of the stimulus, not its meaning.