According to researchers from the Utah-based Brigham Young University, babies are more likely to remember an incident if there is a positive emotion or affect that accompanies it.
"People study memory in infants, they study discrimination in emotional affect, but we are the first ones to study how these emotions influence memory," said lead author and psychology professor Ross Flom.
The researchers monitored the infants' eye movements and how long they look at a test image.
The babies were set in front of flat-panelled monitors and then exposed to a person on screen speaking to them with either a happy, neutral or angry voice. Immediately following the emotional exposure, they were shown a geometric shape.
To test their memory, the team did follow-up tests five minutes later and again one day later. In the follow-up test, babies were shown two side-by-side geometric shapes: a brand new one, and the original one from the study.
The researchers then were able to record how many times the baby looked from one image to the next and how long they spent looking at each image. The babiesÂ’ memories did not improve if the shape had been paired with a negative voice, but they performed significantly better at remembering shapes attached to positive voices.
"We think what happens is that the positive affect heightens the babies' attentional system and arousal," the authors added.
The study was published in the journal Infant Behavior and Development.