Echoic memory is the sensory memory that registers specific to auditory information (sounds). Once an auditory stimulus is heard, it is stored in memory so that it can be processed and understood. Unlike most visual memory, where a person can choose how long to view the stimulus and can reassess it repeatedly, auditory stimuli are usually transient and cannot be reassessed. Since echoic memories are heard once, they are stored for slightly longer periods of time than iconic memories (visual memories). Auditory stimuli are received by the ear one at a time before they can be processed and understood.
It can be said that the echoic memory is conceptually like a "holding tank", where a sound is unprocessed (or held back) until the following sound is heard, and only then can it be made meaningful. This particular sensory store is capable of storing large amounts of auditory information that is only retained for a short period of time (3–4 seconds). This echoic sound resonates in the mind and is replayed for this brief amount of time shortly after being heard. Echoic memory encodes only moderately primitive aspects of the stimuli, for example pitch, which specifies localization to the non-association brain regions.
Overview
Shortly after George Sperling's partial report studies of the visual sensory memory store, researchers began investigating its counterpart in the auditory domain. The term echoic memory was coined in 1967 by Ulric Neisser to describe this brief representation of acoustic information. It was initially studied using similar partial report paradigms to those utilized by Sperling; however, modern neuropsychological techniques have enabled the development of estimations of the capacity, duration, and location of the echoic memory store. Using Sperling's model as an analogue, researchers continue to apply his work to the auditory sensory store using partial and whole report experiments.They found that the echoic memory can store memories for up to 4 seconds. However, different durations have been proposed involving how long the echoic memory stores the information once it is heard. However, different durations have been proposed for the existing echo once the hearing signal has been presented. Guttman and Julesz suggested that it may last approximately one second or less, while Eriksen and Johnson suggested that it can take up to 10 seconds.
Early work
Baddeley's model of working memory consists of the visuospatial sketchpad which is related to iconic memory, and a phonological loop which attends to auditory information processing in two ways. The phonological storage is broken up into two sections. The first is the storage of words that we hear, this tends to have the capacity to retain information for 3–4 seconds before decay, which is a much longer duration than iconic memory (which is less than 1000ms). The second is a sub-vocal rehearsal process to keep refreshing the memory trace by the using one's "inner voice". This consists of the words repeating in a loop in our mind. However, this model fails to provide a detailed description of the relationship between the initial sensory input and ensuing memory processes.
A short-term memory model proposed by Nelson Cowan attempts to address this problem by describing a verbal sensory memory input and storage in more detail. It suggests a pre-attentive sensory storage system that can hold a large amount of accurate information over a short period of time and consists of an initial phase input of 200-400ms and a secondary phase that transfers the information into a more long term memory store to be integrated into working memory that starts to decay after 10-20s.