Babies as young as three weeks will be shown videos by psychology researchers trying to find out how they understand other people.
Not rude, but research: babies will be tested for their reaction
The Cardiff University team are looking for up to 80 infants for the private screenings to discover how early in life children learn to imitate adults.
The babies' response will be filmed to a clip of an adult pulling faces.
Dr Mary Fagan at the School of Psychology said: "We still have a lot to learn about this younger age."
The researchers are looking for infants aged no more than five weeks old.
She said: "We are very interested in how imitation begins and develops. It has already been documented that babies begin to imitate within a few hours of birth.
"Imitation is firmly established in older children.
"What we're interested in is whether or not they are imitating the faces that the adults are making and also under what conditions they imitate."
She said previous similar studies had used a live face, with someone poking their head through a hole cut out of a curtain.
Each film has an audience of two - a mother and her child
The video screening ensures every child is exposed to the same stimuli of images and sounds.
"We want to see if the children will continue to imitate... this two-dimensional role, and (the video) is a way for us to ensure they see exactly the same face in exactly the same way."
Every baby receives a T-shirt for lending their time.
Cardiff mother Klara Wagg took her four-month-old daughter Daisy to the study in its pilot stage. Daisy sat on her lap while the video was screened in a darkened corner of a room.
"The researcher was sticking her tongue out. She did sort of smile and opened her mouth. She was very interested in the screen and the lady.
"I was able to see what observations that they had seen, so it was quite nice to see what the reactions were."
The study is part of the psychology school's project involving children from birth to 24 months to discover how babies come to understand the minds of other people.
Toddlers aged 14-18 months are studied for use of toys and their ability to say which toy they want, while 18-36-month-olds are studied for emotional contact with an adult during a reading session.