From birth to 3 months babies will react to bright, primary colors, in high contrasting, yet simple designs. Infants at this age are just discovering how to use their arms, legs, eyes and other senses, which is why you'll find that most baby toys are colorful, textured, or make noise. Toys at this stage should be soft and easily handled.

Between 4 and 6 months babies will refine the concept of cause and effect. They wave a rattle, it makes noise, so they do it again and again. Once they realize they can cause a reaction, they'll begin to explore other ways to make things happen. So at this stage, toys that respond to baby's actions are most popular.