New York, March 29 (IANS) Ever wondered why we remember certain scenes from films or books without much effort while forgetting others despite paying attention? New research suggests that people tend to remember only those things better that they expect to have future relevance.

Much of what a person can remember is based on their expectation of the information they will need to recall, the study said.

"What we're showing is that attention is not enough to ensure accurate memory," said one of the researchers Brad Wyble, assistant professor of psychology at Pennsylvania State University in the US. 

"You need some kind of expectation that attributing certain features to the object is important," Wyble noted.

The findings were published in the journal Cognition.

The researchers tested 60 participants and asked them to watch videos in which two balls were thrown between multiple people. 

The first ball thrown was the target ball. Participants counted the number of times the ball was passed. The second ball was the distractor ball. Each participant watched 36 trials, recording their counts of the target ball after each. The balls in each video were red, green, blue or purple. 

For the first 31 trials, participants chose only the number of passes made with the target ball.

After the thirty-second trial, a message popped up on the participant's screen that read, "This is a surprise memory test! Here we test the “colour” of the target ball. Press a corresponding number to indicate the 'colour' of the target ball."

To this question, 37 percent of participants -- 22 of 60 -- responded with the incorrect colour of the ball, and 16 of these 22 incorrect responses selected the colour of the distractor ball.

In further experiments, the researchers found that once participants realised they would need to report the colour of the ball, they were able to do so with high accuracy.

This indicates that much of what a person can remember is based on their expectation of the information they will need to recall.

"The key discovery was that attending an object for an extended period of time does not ensure that all of the features of that object will be correctly associated with it in memory," Wyble noted.​