The field of social neuroscience has long been interested in how the brain supports our ability to cooperate. Most of what we know to date, however, is based on studies that measured brain activity in single individuals, typically playing computer games designed to simulate social interaction in isolation. Recent advances in neuroimaging methods now allow for the simultaneous measurement of brain activity across multiple individuals. As a result, there is growing interest in capturing how brain activity could become coordinated or synchronized between people working together toward a common goal.
Such inter-brain synchrony may be particularly relevant during cooperation in close relationships, like those between parents and their children. We, therefore, assessed whether we could see inter-brain synchrony between mothers and children during cooperation, and whether this synchrony might be associated with mother-child relationship quality.
Our study used dual functional near-infrared spectroscopy (fNIRS) to measure brain activity in 28 mothers and their children (15 girls; 8 to 12 years of age) at the same time. Although fNIRS can only detect a change in activity at the surface of the brain, it is much less susceptible to data artifacts related to head motion compared to other neuroimaging techniques. This makes fNIRS a particularly useful tool for studying children and parent-child pairs.
In our study, mother-child pairs played a cooperative computer game. They both sat in front of separate screens that presented cues to press a button. The goal of the game was for mothers and their children to align their button presses to be as close as possible in time in order to earn points. After each button press, both players were given feedback about whether they were slower or faster than the other player. In a separate control condition, mothers and children played the same game but without cooperation. Instead, they were instructed to press the button as fast as possible when presented with the cue and told that their performance was independent of each other.
We found that mothers and children showed stronger synchrony in the right prefrontal and temporoparietal areas of the brain, particularly in the dorsolateral and frontopolar prefrontal cortex, when they played the cooperation game (compared to when they played the independent game). Interestingly, the above brain regions have repeatedly been found to be important for executive functions involved in planning and goal-directed behaviors, as well as social cognitive processes such as thinking about the thoughts and goals of others. One interpretation of our findings, therefore, is that increased inter-brain synchrony elicited by cooperation may reflect that mothers and their children are using similar psychological processes at the same time; in other words, inter-brain synchrony may reflect their effort to get on the same psychological wavelength.
Besides looking at overall inter-brain synchrony across all mother-child pairs, we were also interested in seeing whether there were any sex-differences, i.e. whether mother-daughter pairs differed from mother-son pairs in their inter-brain synchrony patterns. And indeed, we observed a stronger difference in inter-brain synchrony during the cooperation versus the independent game in mother-son as compared to mother-daughter pairs. Because these neural sex-differences did not merely reflect differences in behavior (i.e. reaction times), they may be more indicative of a change in approach to the game – for example, boys have previously been shown to be more prone to engaging in competition than girls. More data is needed, however, to better understand the nature of sex-differences in inter-brain synchrony in parent-child pairs, including differences in mothers versus fathers.
Our study was also the first to test whether inter-brain synchrony during cooperation in mother-child pairs was associated with differences in relationship quality. To that end, we used an age-appropriate attachment questionnaire to ask children about how close they felt to their mother.
Subsequent analyses revealed preliminary evidence that inter-brain synchrony in the right frontopolar prefrontal cortex during the cooperation game (as compared to the independent game) was weaker for those children who reported a more avoidant attachment toward their mother (i.e., are more emotionally distant). However, it should be noted that this association between inter-brain synchrony and child attachment toward the mother did not survive more conservative statistical procedures, and that future work is necessary to replicate and build on this initial observation. In addition, we did not find that inter-brain synchrony was related to how well mother-child pairs cooperated on a behavioral level. Much more research is needed to determine whether mother-child inter-brain synchrony is meaningful in terms of the relationship and performance in cooperative contexts.
This was the first study in a program of research aimed at understanding inter-brain synchrony in mothers and children using dual fNIRS. Currently, we are running studies in mother-child and father-child pairs (with children aged 5 years) using cooperation games that more closely resemble everyday experiences faced by parents and children. We are also obtaining a more extensive assessment of relationship quality in the context of attachment theory.
We hope that the results of these studies will reveal a clearer picture of the role that inter-brain synchrony might play in parent-child cooperation, how it differs as a function of both parent and child sex, and whether it may serve as an additional measure of relationship quality. Ultimately, we want to know whether parent-child inter-brain synchrony could be used as a tool in the design of new prevention and intervention strategies for families at-risk for attachment-related problems. We believe our study represents a first step toward that goal.
These findings are described in the article entitled Inter-brain synchrony in mother-child dyads during cooperation: An fNIRS hyperscanning study, recently published in the journal Neuropsychologia.