Children with autism may not find human speech pleasurable because of weaker connections between voice recognition and reward centers in their brains.

From ordering coffee to conveying your ideas in a meeting at work to engaging with friends and family afterward, language and speech are a key part of everyday life. We use language so frequently that it’s easy to take language skills for granted.

But for those living with autism, developing language skills and understanding emotions and intent in human speech can be extremely difficult. Researchers at Stanford University have found that in autistic children, the pathways in the brain that connect speech recognition to the brain’s reward centers are wired differently than in typically developing brains.

“Unlike typically developing children, children with autism are often insensitive to speech,” said study author Daniel Abrams, Ph.D., a postdoctoral scholar in psychiatry and behavioral sciences at Stanford.

On average, developing babies are extremely attracted and attentive to the sounds of speech, even though they have no idea what is being said. In contrast, children with autism often do not respond to speech. “This indifference to speech is thought to precipitate speech and communication deficits in these individuals,” Abrams said.

Why autistic children are insensitive to speech has remained a mystery until recently, when researchers compared the brains of children with autism spectrum disorders (ASD) to those of typically developing (TD) children.

“Specifically, we wanted to know if there are differences between these groups in the way that voice-selective brain regions connect to the rest of their brain,” Abrams said. And once they knew where to look, the picture became all the more clear.

In ASD children, the reward pathway in the brain is not as well connected as it is in TD children. “Children with autism showed weak brain connectivity between voice-selective parts of their brain and the reward pathway, a series of brain structures that are critical for anticipating and experiencing reward,” Abrams said.

While “reward pathway” sounds like an abstract and slightly simplified version of what goes on in your brain (and it certainly is), it’s not something to be underestimated. Think about the reaction you have to listening to music or eating chocolate. When you engage in those sorts of pleasurable activities, the reward pathways in your brain become active. In ASD children, a similar reaction should take place when they hear speech, but it simply doesn’t.

“This result is exciting because it strongly suggests that impaired reward circuitry in the brain could be a key component to speech insensitivity in children with autism,” Abrams said.

In addition, there is weak connectivity between the voice-selective cortex and the amygdala, which processes emotions, in the brains of ASD children. “This…is important because it may help explain why children with autism often have difficulty interpreting emotional content that is conveyed in speech,” Abrams said.

While these findings are only preliminary, they point to a potentially more connected and communicative future for autistic children.

Consider the pathways between the voice-selective cortex, the reward centers of the brain, and the amygdala as a bridge. In ASD children, that bridge is weak. To strengthen the bridge connections, these findings suggest that more exaggerated and emphatic communication could help.

“[It] would seem that attempting to make speech communication as exciting, engaging, and rewarding as possible would be a logical recommendation,” Abrams said. “It is conceivable that speech-like games or play that can engage a child with autism may help orient these individuals to these sounds.”

In the study, researchers compared magnetic resonance imaging (MRI) scans from 20 children with ASD and 19 TD children who had been age- and intelligence-matched. From the MRIs, the researchers were able to make out a pattern of underconnectivity in the voice-selective bilateral posterior superior temporal sulcus (pSTS) in the brains of children with ASD. Children with ASD also showed underconnectivity between the right hemisphere pSTS and the amygdala.

“Aberrant brain connectivity has been shown in many studies of autism, and is thought to be an important brain signature of this disorder,” Abrams said.

While these findings have uncovered a promising clue to the difference between children with ASD and their peers, unfortunately, the “why” behind this difference is still unknown. “This is an important question and an area for future research,” Abrams said.