Sensory memory and short-term memory: memory requires information that is gathered by the senses to be perceived and encoded. iconic memories sensory memories that are visually-based. echoic memories sensory memories that are sound-based. Iconic memory studies are based on use of tachistoscope which permits stimuli to be presented for extremely short periods of time. delays between viewing letter array and reporting letters: delays of approx. 500ms resulted in the largest decrease in iconic memory. letters are transferred to a more durable format in order for them to be able to be recalled a short time later. Ionic memory: color, motion, shape: two sides of the brain function equally well in iconic memory. Echoic memory: very fragile and temporary memory store, echoic memory studies participants are typically presented with a series of brief tones and asked to indicate when they hear a second tone.