Continuous versus discrete quantity in infant multiple object tracking

Many studies have found that infants in the first year of life use only continuous quantities to represent small sets of objects. In two studies using a paradigm that forces infants to track the changing locations of objects and sets of objects on a trial by trial basis, we obtain evidence that 12-month-old use discrete quantity representations when continuous quantity differences are insufficiently large to detect. In the first study, infants were surprised to see both one and three objects when two objects were expected, despite the total surface area of the sets remaining constant. A second study demonstrates that infants tracked the locations of a singleton and a pair and were surprised when the sets unexpectedly swapped positions. Infants may flexibly tailor their use of discrete and continuous quantity information according to the nature of the task.