Time and again, we’ve heard the assertion that we’re attracted to partners who look like our parents. The, rather uncomfortable, theory was originally put forth more than a century ago by Austrian neurologist Sigmund Freud who dubbed it the Oedipus complex in males. An analogous theory proposed by Carl Jung is known as the Electra complex in females. The theories suggest that all boys between the ages of three and five sexually desire their mothers and that little girls covet their fathers. 

Today, Freud's Oedipus complex and Jung’s Electra complex serve as textbook examples of poorly devised notions according to scientific criteria, ones that often draw scorn during psychology lectures. It is, therefore, important to be skeptical of any research that claims these ideas to be fact.

An example is a study in which Scottish researcher David Perrett of the University of St. Andrews found that men often favor women who resemble their mother when choosing mates. Similarly, the study showed that women prefer male faces that resemble their fathers. These findings were later reported in a 2002 New Scientist magazine article titled “Like Father Like Husband."

Upon closer examination of the study, the interpretation that was offered by scientists and in the piece in New Scientist seems questionable. During the study, researchers presented subjects with photos of strange men and women for a fraction of a second. What the participants didn't know was that among the photos they were shown was a photo of themselves altered to look like that of the opposite sex—feminized or masculinized versions of themselves. Participants found these altered photos particularly attractive and researchers believed this was because the pictures reminded test subjects of their mothers or fathers. 

The explanation of the researchers, however, wasn’t necessarily in line with Freud's idea. In these faces, subjects recognized the physical and behavioral appearance of their own opposite-sex parent as it was when the participants were still babies. While such findings can be taken as an indication of possible sexual imprinting, where a young person develops preferences for a mate by using a parent model, this interpretation has a catch: a partner who looks like our parents, looks similar to ourselves. After all, on average, we share 50 percent of our genetic material with our mothers and 50 percent of our genetic material with our fathers. That means we can inherit a variety of traits, like hair and eye color, from our parents.

So, what was it that people liked about the manipulated faces: a resemblance to their own mother or father or perhaps similarities to themselves? Or was it just that the photos were somehow recognizable? It has long been known that we have a general preference for things we are familiar with. Researchers refer to this as the mere-exposure effect, a phenomenon where people develop a liking to things just because they are familiar with them. Accordingly, faces that are similar to our own generally appear more likable, or sympathetic, to us. This does not necessarily have anything to do with likeness to a parent. In one study of 130 students in a college class, four women posed as students and each attended zero, five, 10 or 15 classes. None of them interacted with the students. Afterwards, students in the class who were shown slides and asked to rate the women on looks found the women who attended a greater number of classes more attractive.

Research has also shown numerous external characteristics are demonstrably more important for emotional evaluation and partner choice. These include youthfulness and health, especially the appearance of skin; gender-typical characteristics such as an angular chin or large eyes; and the absence of negatively perceived characteristics such as strong asymmetry or obesity. When, in a 2015 PLOS ONE study, researchers asked a group of 44 heterosexual males to rate the attractiveness of 266 female Spanish students based on their photos, they found that facial symmetry was deemed attractive. This metric has been found to be perceived as a measure of youthfulness and health, a potential signifier of fertility.

Beyond physical characteristics, similarities like comparable education level, social environment, worldview, value systems and lifestyles tend to promote mutual attraction. Or, as the saying goes, “Birds of a feather flock together.” It should be noted though that a partner who resembles us in these characteristics also tends to resemble our parents, precisely because we ourselves have a lot in common with our mothers and fathers. However, this connection may simply be too trivial to draw meaningful conclusions and produce headlines.