Whether it’s seeing Jesus in burnt toast, a goofy grin in the grooves of a cheese grater, or simply the man in the moon, humans have long perceived faces in unlikely places.
Now researchers say the tendency may not be fixed in adults, suggesting it appears to be enhanced in women who have just given birth.
The scientists suggest the finding could be down to postpartum women having higher levels of oxytocin, colloquially referred to as the “love” or “trust” hormone because of its role in social bonding.
“These data, collected online, suggest that our sensitivity to face-like patterns is not fixed and may change throughout adulthood,” the team write.
Writing in the journal Biology Letters, researchers from Australia’s University of Queensland and the University of the Sunshine Coast describe how they set out to investigate whether the propensity to see faces in inanimate objects – a phenomenon known as face pareidolia – changes during life.
Previous research has suggested that when humans are given oxytocin, their ability to recognise certain emotions in faces increases. As a result, the team wanted to explore if the hormone could play a role in how sensitive individuals are towards seeing faces in inanimate objects.
The researchers used an online platform to recruit women, with participants asked if they were pregnant or had just given birth – the latter being a period when oxytocin levels are generally increased.
The women were each shown 320 images in a random order online and asked to rate on an 11-point scale how easily they could see a face. While 32 of the images were of human faces, 256 were of inanimate objects with patterns that could be said to resemble a face, and 32 depicted inanimate objects with no such facial patterns.
The team gathered data from 84 pregnant women, 79 women who had given birth in the past year, and 216 women who did not report being pregnant or having recently had a baby.
The results reveal that all participants easily recognised the images of human faces, and found it difficult to see faces in the 32 images of inanimate objects lacking facial patterns.
However, women who had recently had a baby reported being able to see the 256 illusionary faces more easily than the pregnant women.
The team say the results suggest sensitivity to perceiving faces is not stable throughout adulthood and changes during early parenthood, possibly to increase social bonding, adding this may be driven by higher levels of oxytocin.
But, they note, since oxytocin levels were not measured in participants it is possible the results could be explained by other differences, such as levels of anxiety or stress.
Joydeep Bhattacharya, a professor of psychology at Goldsmiths University of London who was not involved in the work, said it made sense to expect an increase in face processing in new mothers to help them read an infant’s facial expressions.
But, he said, the study did not delve into whether the ease of detecting faces in objects by postpartum women was linked to how baby-like the faces were or the expressions they were deemed to have, while levels of oxytocin were not measured, making it unclear whether the hormone was indeed involved.
He added that the study was only conducted at one point in time and did not track how an individual’s propensity to see faces in objects changed before and after having a baby, despite Bhattacharya noting previous studies showing huge variations in face pareidolia across individuals.
“The findings elicit curiosity,” he said. “But we need more robust replications and proper measurements to make any reliable conclusion.”