7.4 : Sensory Memory

Sensory memory captures information from the environment in its original form for a very brief duration, just long enough to be exposed to visual, auditory, and other senses. This type of memory is detailed and rich but quickly lost unless certain strategies are employed to transfer it into short-term or long-term memory. Sensory information is continuously bombarding the human brain, yet only a small fraction is absorbed, as most of it does not significantly impact daily life. For instance, recalling what a professor wore in the last class is usually irrelevant as long as the attire is appropriate. Similarly, sounds such as the hum of a refrigerator or the distant noise of traffic are typically forgotten unless they hold particular importance.

Sensory information about sights, sounds, smells, and textures that are not deemed valuable are discarded. For example, the feel of a chair or background noise in a coffee shop usually does not persist in memory unless there is a conscious effort to focus on it. If certain information is considered valuable, it moves into the short-term memory system.

There are two types of sensory memory: echoic and iconic. Echoic memory, derived from the word "echo," refers to auditory sensory memory, which is retained for up to several seconds. An example of echoic memory is the ability to momentarily recall the last few words of a conversation even when not actively listening. Iconic memory, from the word "icon," meaning image, pertains to visual sensory memory, which lasts for approximately one-quarter of a second. An example of iconic memory is the ability to briefly visualize a scene after a quick glance before the image fades.