Sensory Memory
Sensory memory refers to very short-term memories about perceptions of the world through the five senses of sight, hearing, smell, touch, and taste. A fraction of the information captured in sensory memory immediately after perception is thought to be transferred to short-term memory, some of which ultimately persists in some form in long-term memory.
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Sensory memory holds on to perceptual information for a very brief moment—details of what people see, hear, and otherwise sense that they may either pay attention to (and remember for longer), or ignore and lose almost immediately. Visual memory in this short-term cache is called iconic memory and is thought to hold information for less than a second. Sensory memory of something one has heard, or echoic memory, may persist for up to several seconds.
Sensory memories include rapidly vanishing snapshots of things just perceived, from a set of numbers on a screen to the sound of a word that was just spoken to, perhaps, the sensation of a fleeting scent in the air or the feel of an object just touched.
Sensory memory is thought to provide the initial storage for information about what a person has just perceived, from which one can draw a select amount into longer-term forms of memory for use and preservation. Sensory memory may also enhance perception by, for example, smoothing the transition between visual images (by briefly retaining details of a preceding image).
The brevity of sensory memories is one distinguishing characteristic. Sensory memories have also been theorized to differ from other kinds of memory in that they capture relatively raw perceptual information that may be free of abstract meaning. That information may be especially detailed, allowing one to compare different images or sounds that rapidly follow each other.
While sensory memory usually refers to memory that immediately and briefly follows perception, sensory impressions can leave traces in memory that last for years. The forms of memory related to these senses are typically described in terms of which sense they reflect.
Visual-spatial memory captures details about where visible things are located relative to each other. Auditory memory, olfactory memory, and haptic memory are terms for stored sensory impressions of sounds, smells, and skin sensations, respectively. We can, of course, remember and recognize tastes as well.
The impressions of sensory experiences that survive in long-term memory enable people to accomplish the critical task of identification—of people (by their faces or the sounds of their voices), objects, symbols, and anything we can distinguish using the senses. Spatial memory, which includes memory for the appearance of places and for routes between different places (among other kinds of information), provides a foundation for navigating through the environment.
Memories of scenes, faces, sounds, smells, physical feelings, and other phenomena are a key part of episodic memory, the mental record of personal experiences. Memory related to sensory experience can be a meaningful part of autobiographical (self-focused) memory, as when a familiar scent suddenly recalls a related childhood experience. And sense-based information, including images that represent abstract concepts (like “cat” or “dog”) are connected to semantic memory, or one’s knowledge about the world.