Final answer:
Alfred Binet's most significant contribution to psychology was in the area of intelligence testing. He developed the first intelligence test in the early 1900s, which was later modified and standardized into the IQ test.
Step-by-step explanation:
Alfred Binet's most significant contribution to psychology was in the area of intelligence testing. He developed the first intelligence test in the early 1900s at the request of the French government. This test was designed to identify children who might struggle in school. Binet's work was later modified and standardized by Louis Terman, resulting in the normed and standardized IQ test that is still widely used today.