The presence of an unfamiliar person significantly slows down the time children take to complete tests. That is the conclusion of a recent study carried out on 123 children and it is no small discovery. Rather, it stresses the importance of taking a child’s physical and social environment into account because it affects a brain function called cognitive control performance.

Psychologists are very interested in the development of cognitive control in children. It is well known that the development of cognitive control partly determines success in school, health, and surprisingly future incomes. In the classroom, pupils make daily use of it, for example when they have to resist to talk when they’d like to and wait until their turn to speak.

Given the importance of cognitive control, researchers have long wanted to develop a way to improve it, especially among children who lack such control. Until now results have been mixed. “This is why we decided to look at the role the social and cultural environment plays in cognitive control” explained Professor Valérie Camos of the University of Fribourg’s Department of Psychology.

The role of context
First, research in this area is nothing new! As early as 1904 the psychologist F.H. Allport was able to show that students between the ages of 8 and 14 performed better in reading and arithmetic when they worked in groups rather than alone, a phenomenon he called “social facilitation.”

In adults, psychologists have observed that the presence of one or more persons has a positive effect when carrying a simple task, but it negatively impacts performance in a complex task that demands greater concentration and deeper thinking.

But what about preschool and school-age children? Is it possible to improve their performance, or hinder it, by bringing in an unknown person, as might be the case during an exam? The study, published on 18 February 2025 in the journal Scientific Reports, is one of the first to address the question.

Experiment carried out in China
The experiment took place in Beijing, where the first author the study Aurélien Frick was supposed to do postdoctoral research but could not because of the COVID-19 pandemic. It was Chinese students instead who ran the testing of children. They gave 123 children of two age groups (4 to 5 and 8 to 9 years old) a series of cognitive tests. In one condition, each child was left alone in a room; in the second, the child was in the room with an adult, who looked at them 60% of the (the standard procedure in social presence studies).

“We observed that the mere presence of an experimenter increased reaction times, especially in the younger children” Professor Camos pointed out. This presence, however, does not seem to affect the quality of the answers, in both age groups.

The research team thinks that the unknown observer, simply by being present in the room, diverts some of the available cognitive resources , especially those needed in anticipating events and reflection. “This presence disrupts what is called proactive control, the control that enables a child to think about the best response to give,” Professor Camos said. “It probably monopolizes part of the child’s attention, particularly among the 4-to-5-year-old age group, reducing then their ability to actively keep in mind the information needed for the task.”

Applications for learning and teaching
These results have important implications for education and learning. It is possible, for example, that a child who has difficulties reading or doing math, tasks that demand strong cognitive control, is more affected by the presence of an unknown adult. “With this study, we showed the importance of the environment, be it physical or social. This parameter must be taken into account, especially by school psychologists who assess children they do not know. For the children, they are strangers and now we know the impact that has on cognitive control,” Professor Camos concluded.

Source:
Frick, A., Belletier, C., Tan, W., Ning Meng, Qiang Zhou, Stella Christie & Valérie Camos. The effects of an unfamiliar experimenter on proactive and reactive control in children. Sci Rep 15, 5860 (2025). https://doi.org/10.1038/s41598-025-89193-9