Bilinguals perform better in the false belief task

Anything you do for an extended period of time has neurological and cognitive effects. Speaking another language is one thing that seems to have a wide range of effects, one of which being performance in tasks involving reasoning about other people’s beliefs, such as the false belief task.

The False Belief Task

The false belief task had usually been applied to samples of children (and you’ll soon understand why), but Rubio-Fernández and Glucksberg (2011) of UCL and Princeton applied it to a sample of adults — after a few modifications

The task involves a puppet show (told you), where two puppets, Sally and Anne are playing with a toy. Then then put the toy in a box, and Anne leaves the scene. While Anne is away, Sally puts the toy in a different box before she returns. When Anne does get back, the participants are asked where she will look for the toy.

Monolingual children start getting this right at about age four on average. It’s part of the idea of a “Theory of Mind,” where you adopt the belief that other people have a mind just like yours, but separate, and with different knowledge to  you have they will take different actions.

However, bilingual children are better at this task, correctly guessing that Anne will look in the box where she saw it last, as opposed to where they saw Sally place it, from around age three.

The idea is that because bilingual kids have experience talking to people in one language and receiving blank stares, they learn earlier that other people have a separate mind to their own. Which is also in line with the idea that the theory of mind is just a social construct, something that people “figure out” as opposed to a module that develops.

The adult version (not what you’re thinking…)

The False Belief task. Ecological validity?

Although everybody loves a good puppet show, you might see a difficulty in applying this same task to adult bilinguals – adults are all going to answer the task correctly, regardless of their lingual status. So the researchers added an eye tracking element to the test.

Rather than using the participant’s guess as to the location of the toy as the dependent variable, they used eye movements – did the participants first look at the box where the toy actually was (using their own knowledge) before looking at the original box (reasoning about other people’s beliefs)?

Oh, and the puppet show was replaced with a cartoon on a computer (I know, I was disappointed too).

How did the adults do?

As with the children, the adult bilinguals out-performed their monolingual peers. Comparisons of gaze directions between the two groups just sneaked under the holy .05 significance level: X2(1, N = 45) = 3.94, p < .048. So did the fixation latency – the time take to focus the gaze on the correct box – at t(44) = 2.07, p < .045, as you might expect given that more monolinguals looked in the wrong place first.

The Simon Task

The researchers also used another test – the Simon Task. In this, a key is assigned for “LEFT” and another for “RIGHT.” the words LEFT and RIGHT flash up on the screen, and you have to press the right key. Only, sometimes, “RIGHT” appears on the left of the screen, and vice-versa. If you want to give it a go, you can play a Java version here.

Success in this game relies on overriding your natural instinct to press the button on the right, even when the game tries to trick you into doing so. This is called “Executive Control” in cognitive psychology, after the catch-all term “Central Executive” which is used to describe pretty much anything we don’t understand yet. 🙂 See this article on working memory for more information.

As with the False Belief test, the bilinguals did better here too. Why would this be? It’s thought to be because this sort of executive control is old hat to bilinguals. They have to suppress the other language while speaking and thinking, and this transfers to other tasks involving executive control.

Combining the Two

The paper also reports a correlation between performance on the Simon task and performance on the False Belief task – so presumably, the same cognitive ability is involved in both tasks, and bilingualism is the cause of this improved ability – or something that goes hand-in-hand with bilingualism, at the least.

What’s a bilingual?

Bilinguals performed better, but at what point in second language acquisition does this effect occur? The authors note that “all participants were to some extent familiar with a second language.” So that includes people designated as monolingual. The actual criteria they used was:

  1. Learned the language before age 9
  2. Used it regularly for over 10 years

However, the bulk of the group achieved bilingual status much sooner, with a self-reported mean acquisition age of 3. The extent of foreign language familiarity of the monolinguals was not reported. It could be a few years at school, it could be they bought a Spanish CD and listened to it twice.

Presumably, this effect would occur no matter when in life the second language was acquired. This fits with the executive control explanation. I’m not sure how to explain these results without it, but if they did the same test on people who acquired language two after, say, age 30, and didn’t get the same results, it might be interesting to try to reconcile the two.


This is one of many studies demonstrating cognitive differences between bilinguals and monolinguals. Low ecological validity, and only marginally significant results (probably due to the fairly low sample size), also necessarily a quasi-experiment (non-random group assignment by default). However, the results are in line with a lot of other evidence – although bilinguals perform worse on some tasks, on this one they seem to do better.


Rubio-Fernández P, & Glucksberg S (2011). Reasoning about other people’s beliefs: Bilinguals have an advantage. Journal of experimental psychology. Learning, memory, and cognition PMID: 21875251


  • Diana Lopez says:

    Very interesting research. It opens the door for future studies that may seek to look further into the differences of social intelligence and socio-cognitive abilities among bilinguals.
    It also contributes to the ongoing debate of TOM as a learned strucure vs. module. The studies on autistic children show vast of evidence of TOM as a domain of social cognition..but researches like this one give us a ot to think about.

    I am trying to create a blogroll for the new blog I just created. Its a bilingual blog of psychology.
    I would love to add your blog to my list with your permission.

    • Warren Davies says:


      Qué tal? Gracias por tu mensaje. Si claro, puedes añadir el blog!

      Yeah I’ve been meaning to post more about bilingualism, but haven’t really gotten round to it. I’m sure I will eventually…

  • Sydney says:

    My 2 y.o. daughter spkaes 3 languages fluently and never had a delay. A lot of people around me constantly try to discourage me with their lack of confidence in their ability to believe in their child. The possibllities are endless. The sky is the limit. As long as learning is fun, kids will learn anything. i think if you are enthusiastic about something, your kids will be the same. Don`t lose the opportunity to teach your kids a new language! Little Pim is great!

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