A paper on the logic of infants in Science

March 20, 2018

The principles of our reasoning abilities motivated psychological investigations since psychology became an academic discipline. But the origin of these abilities in early infancy was never really in the focus of systematic experimentation.

A new contribution regarding infant’s logical inferences was recently published in Science. The paper is the most recent outcome of a long and fruitful collaboration between several members of our lab (Nicoló Cesana-Arlotti, Liza Vorobyova, and Ernő Téglás) with the infant research group at Pompeo Fabra University (Barcelona, Spain) led by Luca Bonatti. The study explored whether preverbal infants are capable of an essential form of logical inference: the process of elimination. In the process of elimination a conclusion is drawn after considering alternative possibilities and by the elimination of those that turn to be false. This reasoning strategy is captured by the logical rule disjunctive syllogism (A or B, not A, therefore B). 

In these experiments 12- and 19-month-old infants were presented with computer controlled video-animations depicting a series of events that unfolded in accordance with the steps of such an inference. It is often the case for infants that certain objects that they play with share certain visual properties. If the objects are in occlusion, but only their shared fragment is visible, their unambiguous re-identification will be prevented. The experiments explored similar situations. In the clips infants see two objects (e.g., a toy dinosaur and a toy flower) being hidden behind a wall, they also see that a cup scooped one of them relocating it to a separate part of the stage. Importantly, these objects have an identically looking upper part, so that when the lower half of those objects is covered, they look identical and there is no way to tell which of the two objects is inside the cup. Infants, however, may consider the two possibilities for the identity of the object inside the cup: either it is the dinosaur or it is the flower but not both. At the end of the scenes the wall is removed revealing which object has been left outside the cup (e.g., the flower). This piece of information can be used to infer by the process of elimination which object must be inside the cup: the dinosaur, in our example. Can infants, that have not yet mastered the logical vocabulary, reach such logical conclusion?

A set of converging measures, like the patterns of eye-movements, pupil dilation and sustained attention to surprising events demonstrate the presence of this of this basic form of logical reasoning already 12 months of age. Thus, certain elementary logical structures that may serve as precursors of adults’ more sophisticated thinking and reasoning abilities may be available to infants before many language abilities have been mastered and the elementary logical vocabulary is acquired.

Nicoló Cesana-Arlotti, Ana Martín, Ernő Téglás, Liza Vorobyova, Ryszard Cetnarski, Luca L. Bonatti. s. Science, 2018; 359 (6381): 1263 DOI: 10.1126/science.aao3539