Does Drug Use Alter Adults’ Liking of Child Faces? Testing the Impact of Heroin and Methamphetamine on the Baby Schema Effect

Human beings possess a deep, automatic instinct to find infants and young children appealing. This reaction is triggered by a specific set of physical features—large eyes, a round face, chubby cheeks, and a small nose—that scientists call the "baby schema." These features act as a biological signal, activating the brain's reward system and encouraging adults to care for and protect the young. This mechanism is considered an evolutionary adaptation designed to ensure the survival of the species, and it typically remains strong until a child reaches about four and a half years old, after which the facial features gradually shift toward those of an adult. While this response is largely innate, it can be influenced by a person's life experiences and their mental state. One area of growing concern is how substance use disorders, which are known to disrupt the brain's reward circuitry, might alter this fundamental drive to care for children.

Researchers in Singapore and China set out to investigate whether the use of specific drugs changes how adults perceive the faces of children. They focused on two of the most widely used illicit substances in China: heroin, an opioid, and methamphetamine, a powerful stimulant. Although both drugs damage the brain's reward system, they do so through different chemical pathways. Heroin works by binding to the body's natural opioid receptors, while methamphetamine directly floods the brain with dopamine, a chemical associated with pleasure and motivation. Because methamphetamine has been linked to specific deficits in social cognition and empathy, the researchers hypothesized that it might blunt the natural attraction to child faces more severely than heroin. They also wanted to see if these effects differed between men and women, and whether having grown up with siblings might offer some protection against these changes.

To test these ideas, the team recruited 108 adults for a study. The group included 39 people with no history of drug use, 28 individuals recovering from heroin use disorder, and 41 individuals recovering from methamphetamine use disorder. All participants were in a state of abstinence for at least three months. The participants viewed a series of neutral photographs on a computer screen. The images featured children ranging from infants to six years old, as well as adults. For each photo, the participants were asked to rate how much they liked the face on a scale from one to seven. The researchers also gathered information about the participants' backgrounds, including whether they had siblings, and screened them for symptoms of depression or difficulty identifying emotions.

The results confirmed that the "baby schema" effect is a robust phenomenon. Across all groups, including those with drug use disorders, participants rated the faces of children as more likable than the faces of adults. This suggests that the basic neural machinery for finding children appealing remains intact even after years of drug use. However, a significant difference emerged when the researchers looked closely at the data by gender and drug type. While men with methamphetamine use disorder showed no difference from the control group, women with methamphetamine use disorder rated the faces of children older than two years as significantly less likable than the women in the control group did. This reduction in liking was not observed in women who used heroin, nor was it found in men who used either drug. The study suggests that methamphetamine use may specifically shorten the window of time during which women find child faces appealing, dampening their response to older children while leaving their reaction to infants largely unchanged.

The researchers also discovered that a person's early social history played a crucial role in this outcome. Among the women with methamphetamine use disorder, those who had grown up with siblings did not show the same reduction in liking for child faces as those who had no siblings. In fact, having siblings appeared to buffer the negative impact of the drug on the brain's response to children. This finding implies that early positive social experiences, such as interacting with brothers or sisters, may help preserve the neural pathways responsible for caregiving, even in the face of significant neurological damage caused by drug use. The study ruled out other factors, such as depression or the age at which the person first started using drugs, as the primary causes for these differences.

Ultimately, the study indicates that while the general ability to find children appealing survives drug use, the specific type of drug and the individual's gender can alter how that feeling is experienced. Methamphetamine use appears to have a unique and gender-specific impact, potentially weakening the emotional connection women feel toward children as they grow older. The presence of siblings seems to act as a protective factor, suggesting that early life experiences can leave a lasting mark on how the brain processes social cues. These findings highlight the complex interplay between biology, environment, and addiction, offering a clearer picture of how drug use disorders might subtly reshape the fundamental human drive to care for the young.