Babies can use logic to figure out others’ preferences in the absence of observable evidence

Since Piaget there is a long-lasting disagreement among psychologists about the availability of logical concepts at different stages of development. When do children arrive to make logical inferences? Is there logic before language? While developmental findings from the last 30 years have changed our view of the young infant highlighting many amazing capacities (e.g. efficient learning from statistical evidence, tracking numerical information, etc.), it is still a question whether pre-verbal infants are equipped with a logical apparatus that would help them go beyond the available perceptual evidence in the process of learning.

In contrast to the predominant view, suggesting that infants and young children cannot reason logically, a new study ( published in Nature Communications on November 26 show that infants already at 14 months rely on an essential form of logical inference, and more surprisingly, they can even integrate logical conclusions into new inferences that they make about the social world.

Infants, like adults, do not always have access to all necessary information at a specific time. Their visual access may be blocked, some objects may be occluded by others, or they may just not pay enough attention to all details. Young infants can learn very well from observation. But can they also learn from the unobservable? Can young infants, just as adults, use logical inferences to learn not only about the psychical but also about the social world, and in particular about the internal states of other people? For instance, could an infant, in the absence of direct evidence use logic to infer the particular preference that may guide someone’s actions?

Nicolo Cesana-Arlotti (Johns Hopkins University), Agnes Melinda Kovacs (CEU) and Erno Teglas (CEU) provide the first evidence that infants are not helpless in situations where directly observable information is scarce, and can flexibly use logical inferences (e.g. disjunction, A or B, not A, therefore B) to aid knowledge acquisition in the social domain. They consider the relevant possibilities, eliminate those against which they collected negative evidence, and use the product of this reasoning for learning about the motivations underlying other people’s actions. Logic seems to provide a special toolbox that can enrich learning at the age where such support is much needed: in infancy.

Scientific key points:
A new study published in Nature Communications on November 26, 2020, finds that babies as young at 14 months old can reason logically to learn about the social world even if perceptually available data are scant. Specifically, they are able to infer via elimination of alternatives what other people may prefer. This reveals an essential logical route to knowledge acquisition that is available to infants very early on, before they can speak (“Infants recruit logic to learn about the social world”).

The experiment:
In a series of studies performed at the Babylab of Central European University (CEU), Nicolo Cesana-Arlotti (Johns Hopkins University) together with Agnes Melinda Kovacs (CEU) and Erno Teglas (CEU) asked whether 14-month-old infants can use a preverbal form of logical reasoning (i.e., the process of elimination) to correctly infer the motivations driving other people’s actions. It is often the case that we witness situations in which the preference of a protagonist is unclear, as critical perceptual evidence is missing, but we can figure it out by thinking logically (e.g. tea or coffee, not tea, therefore she must prefer coffee). Something that is easy for an adult, may be challenging for an infant. Not only does one have to represent the two mutually exclusive possibilities and negate one of them, but the outcome of the deductive operation has to be employed as an input for preference attribution. Importantly, however, such inferences may help infants to gain crucial knowledge about the social world by applying logical operations. We asked whether the ability to integrate logical conclusions with other cognitive processes is present early in development in absence of language.

During the study infants were shown movies where an agent demonstrated a preference choosing not between tea or coffee, but between objects that babies care for more: a toy car and a ball. However, at the moment of the demonstration, the objects were hidden and the infants had to infer the actual choice of the agent with a logical inference by elimination.

After such preference demonstrations, in consequent scenes the agent’s choices were either consistent with her preference (e.g., the agent choose the toy car) or inconsistent (e.g., the ball was chosen instead of the toy car). The authors measured how long infants attended to consistent and inconsistent choices. Babies’ longer looks triggered by the inconsistent choices revealed that they inferred logically the correct preference of the agent.

Why this matters:
When observable data is scant, human adults use logical deduction for successful learning to disclose evidence otherwise not available. However, it was unclear whether this use of logical reasoning is available early in life, when learning is much needed. Here, the authors show that this logical route to knowledge acquisition is available to pre-verbal infants and can help them learn about the social world.