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Imagine walking down a busy street. You see cars zooming by, hear people chatting, smell food from nearby restaurants and feel the breeze on your skin. How does your brain handle all this information at once? The answer lies in your sensory memory store - the first stage in your memory system!
Key Definitions:
Sensory memory acts like a buffer, briefly holding onto all the sensory information bombarding us every second. It gives our brain a chance to decide what's important enough to pay attention to and process further. Without sensory memory, we'd be overwhelmed by the constant stream of sensory input!
In Atkinson and Shiffrin's Multi-Store Model (1968), sensory memory is the first stage of memory processing. Information flows from sensory memory to short-term memory, but only if we pay attention to it. Otherwise, the information quickly fades away through a process called decay.
One of the most striking features of sensory memory is how briefly it holds information:
This ultra-short duration explains why you can sometimes "see" an image briefly after closing your eyes, or why you can remember what someone just said even if you weren't actively listening when they spoke.
Unlike short-term memory which can only hold about 7±2 items, sensory memory has a much larger capacity. It can briefly hold almost everything your senses detect, but most of this information is lost within fractions of a second unless attention is directed to it.
In 1960, George Sperling conducted groundbreaking experiments that revealed the nature of iconic memory. He showed participants a grid of 12 letters for just 50 milliseconds (too fast to consciously read them all). When asked to recall all letters, participants could only remember about 4-5 letters (full report). However, when Sperling used a tone after the display disappeared to indicate which row to report, participants could recall most letters from that row. This proved that all 12 letters were briefly available in iconic memory, but faded before they could all be reported.
Holds visual information for about half a second. It's why you can see "trails" when someone waves a sparkler in the dark, or why movies (which are actually a series of still images) appear to show continuous movement.
Stores sounds for 2-4 seconds. It's why you can remember the last few words someone said even if you weren't actively listening. It's also crucial for understanding speech, as it lets us hold onto the beginning of a sentence until we hear the end.
Retains touch sensations briefly. It helps us recognize objects by touch and maintain awareness of our body position. It's how you can still "feel" your phone in your pocket for a moment after you've removed it.
Not all information in sensory memory makes it to the next stage. The process works like this:
Only information we pay attention to moves from sensory memory to short-term memory. This selective attention is crucial - it prevents our memory system from being overwhelmed. Think of it like a bouncer at a club, only letting in the VIPs (Very Important Perceptions)!
Information in sensory memory that doesn't receive attention quickly fades away through a process called decay. This happens automatically and very rapidly. It's why you don't remember every detail of scenes you walk past or every sound in the background.
As mentioned in our case study, George Sperling's iconic memory experiments provided crucial evidence for sensory memory. His clever "partial report technique" showed that people briefly store more visual information than they can report, supporting the existence of a large-capacity, rapidly-decaying visual sensory store.
These researchers investigated echoic memory by playing participants three sets of three letters (one set to each ear and one set with both ears). When cued which set to recall, participants could do so accurately, showing that all nine letters were briefly held in echoic memory.
Understanding sensory memory has practical applications in many areas:
Sensory memory might be brief, but it's absolutely crucial for how we experience and interact with the world. It gives us a momentary buffer of sensory information, allowing our attention system to select what's important before the information fades away. Without sensory memory, we'd be unable to process the continuous stream of information from our environment in a meaningful way.
Remember that sensory memory is just the first stage in our memory system. Information that receives attention moves to short-term memory and with rehearsal and processing, potentially to long-term memory. Each stage plays a vital role in how we remember our experiences and learn about the world.
In exams, be prepared to: