Sensory Memory Can Improve Decision Making

This is an image of a school of fish.Conventional wisdom holds that your memory of an experience is strongest right when it’s encoded – after all, if over a century of memory research has taught us anything, it’s that memory traces typically decay over time.

But new research published in the September 2013 issue of Psychological Science suggests that a brief delay between seeing a stimulus and having to make a decision about that stimulus can improve the accuracy of our decision making, even if we don’t receive any new information about what the stimulus looked like in the meantime.

This new research adds an interesting twist to previous findings by revealing that, for a short amount of time afterward, sensory memory can actually enhance recognition of what we’ve just been exposed to.

In their study, psychological scientists Alexandra Vlassova and Joel Pearson of the University of New South Wales had participants watch a random-dot-motion animation, and then indicate which direction most of the dots moved – that is, the direction in which they saw “coherent motion.”

The animations were presented under several conditions, with varying degrees of coherent motion. In some conditions, the participants were instructed to respond right away. In other conditions, the participants were asked to respond after a short delay of half a second, during which a new random-dot diagram was presented or the screen was simply left blank.

When participants experienced the delay with the blank screen, they were almost twice as accurate in detecting the coherent motion as when they had to answer right away or when they were presented with another dot diagram.

These results suggest that people are able to extract information from a sensory memory even after the stimulus is gone.

Importantly, when participants were asked to remember a 10-digit number – a cognitive distraction – this benefit disappeared. Having to remember the number resulted in a cognitive load that seemed to overshadow participants’ ability to extract further information from the sensory memory.

While other studies have shown that our memory lacks detail compared to the actual sensory experience during an event, these results suggest that the unhindered memory just after an experience allows people to accumulate additional evidence and make more accurate decisions.

“Memories typically decay with time, hence immediate inquiry trumps later recall from memory,” note Vlassova and Pearson. “However, the results we report here show the inverse: Inspecting a memory trumps viewing the actual object.”
Vlassova, A. & Pearson, J. (2013). Look before you leap: Sensory memory improves decision making. Psychological Science, 24 (9), 1635-1643. DOI: 10.1177/0956797612474321

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