I'm increasingly curious about the hypothesis that motherese
—specifically, a lack of it
—is linked to autism.
I was recently surprised to learn that autism is not purely caused by genetics. A
study at Stanford suggests that environmental factors play a larger role than we had ever thought. They noted that identical twins, where at least one was diagnosed as autistic, did not always share an autism diagnosis
—this hints that nature is not purely to blame. Secondly,
fraternal twins had a curiously high probability of
both developing autism when one was autistic. Remember, these diagnosed pairs did not have the same DNA. This points a finger to something in their shared environment.
The link to maternal depression is also interesting. One
study in California showed that mothers of children with autism were twice as likely to have taken antidepressants before giving birth. The researchers talk about the possible chemical effects of the drug, but I wonder if there's more to it. Maternal bipolar depression has also been
linked to Asperger syndrome. Admitting a lack of proper reference, I can imagine that depressive mothers are unable to express a wide range of emotions when raising their child
—which brings me to motherese.
(from nature.com)
Motherese, also known as baby talk or parentese, is an exaggerated form of speech towards babies, with a highly varying pitch and slower rate. It is very emotionally expressive, happens across cultures, and presents uniquely in front of a baby -- according to Anne Fernald of Stanford University, mothers can't seem to produce it in front of a microphone. The parent places their baby about 30cm* from their face and
coochy-coos, grabbing the baby's attention. Consider this account of a mother in Italy:
Paolo is a six-month-old baby who never looks at his mother, he doesn’t orient
to her voice, sometimes he looks at his father when he uses a vigorous voice [...] she appears very
anxious because Paolo doesn’t pay attention to her call: ‘Paolo, Paolo...look at me...my
baby’. The spectrogram of the mother’s voice is flat without any prosodic pitch or long
pauses.
After some minutes the video shows a totally different scenario where Paolo is
in a rich verbal and visual dialogical interaction with his uncle. The analysis of uncle’s
voice show all the characteristic of the motherese. (--Maestro and Muratori)
Basically, Paulo ignores the flat, yet pleading voice of his mother, but does pay attention to his uncle's melodic voice. Spectrograms can be seen
here**. Paulo will later be diagnosed with autism.
Some child developmental psychologists (
Cohen,
Maestro) have suggested a link between motherese and autism, but statistical evidence is thin. It's difficult to track the amount and quality of interaction a baby gets, barring a
Deb Roy-like Big Brother system in autistic children's homes. Plus, autism is not often noticed until after the first year, when it's perhaps too late.
In my work to make robots emotionally sensitive,
I've suggested that motherese-like interaction could let us learn the link between emotions and parameters like speed, intensity, irregularity, and extent.
"Lim thinks there are certain identifiable qualities to emotional expression, and that when we detect those qualities in the behavior of an animal or the sound of a song, we ascribe the associated emotion to it. “I’m more interested in how we detect emotions in other things, like music or a little puppy jumping around,” she says. Why, for instance, should we ascribe sadness to a particular piece of music? “There’s nothing intrinsically sad about this music, so how do we extract sadness from that?” She uses four parameters: speed, intensity, irregularity, and extent—whether something is small or large, soft or loud. Angry speech might be rapid, loud, rough and broken. So might an angry piece of music. Someone who’s walking at a moderate pace using regular strides and not stomping around might be seen as content, whereas a person slowly shuffling, with small steps and an irregular stride, might be displaying that they’re sad. Lim’s hypothesis, as yet untested, is that mothers convey emotion to their babies through those qualities of speed, intensity, regularity, and extent in their speech and facial expressions—so humans learn to think of them as markers of emotion." —Nautilus
What if autistic babies are not getting this training data? Perhaps they never learn to associate r
apid-loud-rough-broken with anger, or
andante-flowing-large with happy. Perhaps the brain, which is still developing its specific sensory regions during the baby's first year, does not develop these necessary connections.
These parameters also seem to be important for deaf infants, who require "
visual motherese":
"Are you smiling, and letting your signs flow? Are you frowning and signing sharp, emphatic signs as you run to cover the electric outlet? Are you pretending to cry as you see a sad character in a story?" —Boys Town National Research Hospital
We could test whether at-risk babies are learning these basic dynamic traits properly. As early as 7 months old, normally-developing
babies can match happy and angry voices and faces—in other words, the babies look longer when the happy face matches with the happy voice. At that age, they even tell the difference between
happy and angry moving lights. And at 9 months, they can distinguish between
happy and sad music. Have we tried testing babies at-risk for autism with this battery of simple, yet multimodal emotional tests?
Motherese is important for a couple other very important skills associated with autism spectrum disorder (ASD). For instance, motherese, with its accentuated, drawn-out speech is necessary for children to learn language
—TV doesn't cut it. I wonder if a lack of motherese would impair both a child's emotion recognition ability and cause delayed language development. Who knows? Perhaps the rich eye contact between mother and baby also helps develop this other social skill found lacking in those with ASD. As a non-expert in autism but a specialist in artificial emotions, this is speculation, so I welcome critiques and feedback.
So does that mean that we should speak in a sing-song voice to our babies to prevent autism? Well, it could be more specific than that. It's possible that motherese, which also involves a feedback loop of empathy and mirroring, helps a baby
connect what he hears and sees with his own internal emotional state ("My diaper needs changing and I'm sad!", says the mother making a sad face at her daughter). In other words, maybe it's the empathy part of motherese that's important. I don't know.
I don't want to suggest that there is any "fault" to lay to parents of children with ASD. It's clear that all parents love their children and do everything in their power to teach them the skills they need for success. But what if we are simply unaware of the correct way to do it? Where is the guidebook for motherese? What about people who say, "Why are you talking so much to your 3-month-old? She doesn't understand, anyway." How do we teach them about emotions? Should we all take acting classes?
As a lowly roboticist, I can't answer these questions. But I hope these ideas will get to the psychologists and researchers who can. Please repost.
* Newborns focus best on objects around 25cm-30cm from their eyes. Adult-like vision is only developed at around 6 months.
** In French. See under the name of Pedro.
