Preferences, beliefs, goals… do babies understand our mental states?

When we interact with others, it is essential to know how to read their minds. I am not talking about supernatural skills like telepathy or those that are acquired with a few sleight of hand and hard training like mentalism, but of skills shared by the vast majority of human beings that we bring together under the term of theory of mind. Their goals? Explain and anticipate the behavior of our fellow human beings. For example, if you see a friend searching for the latest cookiecookie in the cookie jar when you have just eaten it, you immediately understand that your friend has the following false belief: there is one cookie left in the cookie jar. Without this ability, you will find him extremely strange. Do you think babies have these kinds of skills? The answer is yes and probably much sooner than you think.

A historic controversy

Research in developmental psychology has long tended to consider infants as dumber than they are. Indeed, for many years, we thought that the development of a representative theory of mind (TER) – where we understand that others have mental representations which are not necessarily a reflection of reality – was emerging. around the age of four. Methodology gold standard of the time to assess the presence or absence of TER was a task (elicited-prediction tasks, in English in literature) in which a story was told to children. In it, a first character hid a marble in a shoe, then a second character in a box without the first knowing.

The children then had to answer the following question: where will the first character go to get the marble? The majority of 4-year-old children successfully complete this task by providing appropriate justifications. On the other hand, most 3-year-olds fail. But that’s not the end of the story. Several researchers believed that TER was present much earlier in children and were not convinced by its robustness. They give credence to an auxiliary hypothesis to explain the observed results: the task involves linguistic and computational difficulties that prevent younger children from succeeding in it.

A perceptive intelligence

Since then, when we study the cognitive development of infants or young children, we avoid developing tasks where motor or language skills could explain babies’ failure. Today, we consider that baby’s intelligence is above all perceptual. From there, several methodologies developed such as visual preference (1), reaction to novelty (2) and impossible event/expectation violation (3). The principle is extremely simple: if the baby doordoor his gaze more often and for longer on something means that he prefers it (1), that he manages to discriminate (2) or that he does not expect that (3). From these methodological principles arise numerous hypotheses which do not always achieve consensus. To investigate the question of the absence or presence of TER, several experiments have emerged and one of them has been a landmark in the field.

But where is the watermelon hidden?

In this study published in 2005 in the journal Science15-month-old children watch an actor hide a toy (a piece of watermelonwatermelon in plasticplastic) in a green box or a yellow box. Then the toy changes boxes with the knowledge, or without the knowledge, of the actor who then becomes the bearer of a true or false belief about the location of the toy. The question is: if the actor does not act in accordance with the belief he carries when he goes to get the toy, will this violate the children’s expectations? This study answers in the affirmative. On average, children stare significantly longer at scenes where the actor acts in opposition to the belief he is supposed to have.

Does this mean that the 15 month old child has a TER? In reality, this is not the only possible interpretation. It may be that through repeated observations of scenes, children simply expect the actor to look for the object in the place where he or she last saw it. This interpretation suggests that children at this age distinguish their perceptions from those of others, can track what the actor sees and does not see, and understand that the actor’s perceptions can be used to predict his or her behavior.

Researchers support the TER interpretation for two reasons. The first is theoretical. Indeed, these two researchers belong to the nativist movement which considers that the newborn comes into the world with a computational system which guides its interpretations concerning the behavior of others. The second is empirical and is based on other results which suggest that the child can predict the actor’s behavior without necessarily following his gaze, but simply using environmental signs.

A prolific field of research…

Obviously, the research didn’t stop there. Hundreds of other experiments have taken place since then, mixing different tasks, scenarios and methodologies. Specialist researchers in the field discuss in detail the development of this field of research in two recent articles, one dating from 2010 and the other from 2017, both published in the journal Trends in Cognitive Sciences.

The different tasks

In the literature, there are spontaneous tasks (Spontaneous-Response Tasks, in English) which do not require any motor action on the part of the baby. From now on, there are also intervention tasks (Elicited-Intervention Tasks, in English) where the young child is invited to help an actor in difficulty. The helping action requires that the child take into account the actor’s false beliefs. Recently, we have also found so-called low cognitive demand tasks (low-inhibition task, in English).

The different scenarios

There are a multitude of scenarios and objects used (the ethics committees ensure that no toy was mistreated during the experiments) and making an exhaustive list would be difficult. Let us simply mention the fact that induced false beliefs can concern the presence, location, identity, properties of objects and even the valencevalence morals of other people.

The different indices and methodologies

Within these tasks, we can use different methodologies (violation of expectations, anticipatory gaze, anticipatory pointing, visual preference, affective response) and measure different parameters (neural correlates, fixation time, facial expressions, etc.)

What the research suggests

Using these different tasks, scenarios and methods, modern research suggests this about young children: TER also applies to non-human agents, they understand that communication can have an impact on individuals’ beliefs, they anticipate where an actor goes to look for an object in relation to the belief he holds, they understand that a false perception can hinder the pursuit of an actor’s goal (typically, retrieving his favorite toy), etc. The young child can therefore attribute a set of very complex mental states to others: his preferences, his goals, his beliefs, his perceptions and make the link between these elements to infer how others will behave.

…which is still steeped in controversy

Despite everything, this field of research is still young and includes many debates within it. The question that divides researchers is how it is possible to reconcile the results of traditional verbal tasks and those of spontaneous tasks. Two major visions oppose each other.

Some think that spontaneous tasks suggest the presence of lower-level mechanisms, but do not imply understanding of mental states like false beliefs (or minimal understanding). For them, the development of the TER is therefore discontinuous and there is a fundamental change (this position is found under the name of fundamental-change view in English literature) which occurs around the age of 4, when traditional verbal tasks are successful.

Others argue for understanding mental states like false beliefs and suggest that verbal tasks are too difficult in terms of mattermatter processing and transcribing information: interpreting the question, keeping it in mind, generating an answer and inhibiting other possible answers that come to him at the same time. For them, the development of the TER is therefore continuous (this position is found under the name of substantial-continuity view in the English-speaking literature) and there is no fundamental change in the understanding of mental states, it simply becoming more effective and more nuanced with time and experience.

Finally, within these currents themselves, researchers do not all agree on the theoretical systems to be used to explain their positions. Only one thing is certain: the psychology of cognitive development still has many things to help us discover.

Warning: this article was written using sources from authors affiliated with the nativist movement. Even if the article aims to be neutral with regard to the different theoretical positions, it is possible that this influenced its remarks. Currently, there is no strong consensus on this subject among researchers in developmental psychology.