Parents who adjust their speaking voices while communicating with babies may see their efforts pay off. A new study published in the journal Infant Behavior and Development suggests that infants are better able to recall positive memories compared to those that are negative.

“[When] people study memory in infants, they study discrimination in emotional affect. But we are the first ones to study how these emotions influence memory,” lead author Ross Flom, a psychology professor at Brigham Young University, said in a news release.

In their research, study authors showed 5-month-old babies a geometric shape immediately after exposing them to either a happy, neutral or angry voice. The voice was projected from a person who appeared on a screen, which the babies listened to and watched.

In two separate trials— five minutes later and one day later— the researchers tested the babies’ memories by showing them two geometric shapes side by side: a new one, and the original one from the study.

Because 5-month-olds can’t talk, study authors monitored their eye movements and how long they looked at the test images to analyze their responses, according to the news release.

After monitoring the infants’ responses to the new and previously seen images, researchers observed that their memories didn’t improve if the shape had been paired with a negative voice. However, the babies were significantly better at recalling the shapes associated with positive voices.

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