One of the first things every new parent learns is that babies love faces. Infants study them endlessly and prefer them over almost anything else they might see. Now, we have the first evidence that this preference for faces may, in fact, develop in the womb.

Researchers reported today in Current Biology that developing fetuses at 34 weeks consistently turned toward face-like images projected on the inside of the womb over other objects. The study is the first to show that it may, in fact, be possible to examine visual cognition of babies before they are born.

How they did it: The researchers projected light through the uterine walls of 39 mothers and displayed images of faces both upright and upside down. They then observed the fetuses' reactions using 4D ultrasound as the images moved across their field of vision. Developing babies turned their heads more often to look at the images of faces that were upright than those that were shown to them upside down. Advancements in ultrasound technology and the realization that light could project through uterine walls made the work possible.

Expert's voice: "There was the possibility that the fetus would find any shape interesting due to the novelty of the stimulus. If this was the case, we would have seen no difference in how they responded to the upright and upside-down versions of the stimuli. But it turned out that they responded in a way that was very similar to infants," said Vincent Reid from Lancaster University who was a co-author of the study.