Although babies may not be able to tell you, they remember the good times, according to a new study.

Meaning that times associated with positive emotion, such as when parents are playing, talking to and laughing with their 5-month-old, stood out in babies' minds.

"People study memory in infants, they study discrimination in emotional affect, but we are the first ones to study how these emotions influence memory," psychology professor Ross Flom of Brigham Young University, lead author of the study, said in a statement.

Since babies can't tell you how they feel, researchers monitored the infants' eye movements and how long they look at a test image to gauge their emotions. The young participants were placed in front of monitor where a person on screen would speak to them with either a happy, neutral or angry voice. Then, the researchers would show them a geometric shape.

Follow-up tests were also conducted, during which the babies were shown two side-by-side geometric shapes, only this time a brand new one accompanied the original one from the study.

Based on observations of how long and how often the babies looked at an image, it turns out babies' memories didn't improve if the shape had been paired with a negative voice.

However, their memories significantly improved when the image was associated with a positive voice.

"We think what happens is that the positive affect heightens the babies' attentional system and arousal," Flom explained. "By heightening those systems, we heighten their ability to process and perhaps remember this geometric pattern."

The study results are described in the journal Infant Behavior and Development.

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