Swiss psychologist Jean Piaget's theories on the cognitive development of children shaped the American education system, particularly in the 1970s and beyond. Piaget posited that a child learns by constantly adapting to his environment, assimilating information and accommodating it. Piaget also theorized that a child's cognitive development occurs in stages: the sensorimotor stage, the preoperational stage, the concrete operational stage and the formal operational stage. Piaget's theories were widely adapted for education in Europe and North America, although many modern researchers believe a child's cognitive development happens at an earlier age than Piaget outlined.
The results of a 1975 study that compared children's cognitive skills to their reading ability indicated a clear correlation existed. The paper, titled "The Correlation between Children's Reading Ability and Their Cognitive Development, as Measured by Their Performance on a Piagetian-Based Test," studied a random sample of 138 sixth- and seventh-grade students on a test based on Piaget's principles and the reading and language portions of the standardized Comprehensive Tests of Basic Skills. The results of this sample indicated that "reading ability is a positive correlate of cognitive development as defined by Piaget."
A 1989 academic paper titled "Foreign Language in the Elementary School (FLES) Improves Cognitive Skills" studied whether studying a foreign language could improve a student's cognitive skills. The study divided 67 students into four different groups receiving varying degrees of instruction in French. The results of the study indicated that students who received foreign language instruction scored higher on tasks involving evaluation and students who studied French the longest performed the best.
According to the American Council on the Teaching of Foreign Languages (ACTFL), children who can speak more than one language demonstrate a higher level of achievement on standardized tests, which remain the most accurate measures of cognitive development. The ACTFL references numerous studies that conclude introducing a child to a second language has a measurable effect on cognitive development.