Kelly S. Mix is an American developmental psychologist known for her research on the development of numerical concepts and their origins in infancy and toddlerhood.
Mix is known for her cognitive developmental research on number concepts, mathematical reasoning, and symbol grounding.
In her book with Huttenlocher and Levine, which focused on quantitative development in infancy through the preschool years, Mix put forth the view that infants begin life without an understanding of discrete numbers, yet are capable of distinguishing and representing quantitative amounts.
[2][5] In her research on the emergence of number concepts prior to formal schooling, Mix emphasizes how preschool children exhibit verbal skills, such as counting, and basic mathematical concepts of equivalence, ordinality, quantitative transformation, and place value prior to instruction.
In Number Versus Contour Length in Infants' Discrimination of Small Visual Sets, Clearfield and Mix used a visual habituation paradigm to examine infants' use of length as a cue to quantity in a number discrimination task.