Laughter is not an exclusively human trait. Apes participate in laughter and rats have a sense of humor. The ability to laugh comes from the part of the brain that is involved in communication. Laughter is instinctive, but it takes time for the ability to laugh to develop in human babies. The average time this takes for most human babies is about six months. Just like baby's first steps and first words, baby's first laugh is a delight to parents. Laughter is an expression of happiness necessary for emotional bonding between humans.
Laughter is reciprocal communication. Some disruptive hyperactive children rarely laugh, which causes distinct problems when they are with other children. The study of laughter in early childhood development leads to more understanding of how language and communication skills are formed by children. Laughter is also part of relaxation, so teaching hyperactive children how to laugh helps them achieve a more calm state of mind.
Research into tickling shows that tickling behavior, which induces laughter in others creates a bond of trust between the two people. Using tickling methods on rats produced a high-pitched delighted squeal that is above the range of human hearing but understood by other rats to be a sound of pleasure. This demonstrates the evolution of the brain and how laughter plays a part in the development of language skills.
The study of Attention Deficit Hyperactive Disorder (ADHD) in children shows that having time to play and laugh is essential in reducing disruptive behaviors and increasing the child's ability to interact with others. Children with ADHD learn social bonding while participating in structured play under the supervision of teachers.