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How knowing helps in searching

Photo: Siddharth Kankaria/ Research Matters

We search for things all the time often with highly variable demands. For instance, at the supermarket snacks aisle you might look for a particular brand of chocolate, any chocolate or a different-looking chocolate. How does knowing what to look for help in finding it? A study by researchers at the Indian Institute of Science (IISc), Bangalore has now revealed a novel insight into how knowing helps you in searching.

To perform this study, Prof. S. P. Arun and his student Sricharan Sunder at the Centre for Neuroscience at IISc devised a task where human volunteers had to find an odd item among a field of identical other distractors. They compared two conditions: trials in which the subjects saw a preview of the odd item before seeing the full field of items, with ones where they saw an unrelated white square. As expected from previous studies, subjects were able to find the odd item faster if they knew what to look for, and they benefited more if this was a hard search to begin with. All this suggested that somehow knowing benefits hard searches more than easy searches, which seemed paradoxical, since this meant the brain needed to know in advance which search was easy or hard.

But on carefully analyzing a variety of searches, Arun & Sricharan discovered something unexpectedly far simpler: if the same data was taken in terms of the reciprocal of the time taken to find the odd item, hard and easy searches were benefited to the same extent. In other words, knowing what to look for makes searching easier, but this benefit accumulates for a longer time in a hard search.

“This brings a new perspective to how people have been thinking about previewing in visual search. We have shown, contrary to earlier research, that the benefit because of preview is a fixed constant irrespective of search difficulty”, adds Sricharan while talking about the research.

“An interesting experiment that we conducted was to look at whether previewing the distractor actually benefited the search and to our surprise it did albeit only weakly! This led to an insight that even knowing what’s irrelevant helps you search” says Sricharan.

“This study demonstrates a simple and elegant insight about how knowing what to look for benefits visual search. It has been gratifying to see such a simple insight hold up to detailed scrutiny”, says Prof Arun who wants to push this finding more to gain better insights into how knowledge influences how we act and perceive.