As each animal grows and develops, three kinds of stimulation have been identified that impact and influence how it will develop and be shaped as an individual. The first stage is called early neurological stimulation and the second stage is called socialization. The first two (early neurological stimulation and socialization) have in common a window of limited time. When Lorenz, (1935) first wrote about the importance of the stimulation process, he wrote about imprinting during early life and its influence on the later development of the individual. He states that it was different from conditioning in that it occurred early in life and took place very rapidly producing results which seemed to be permanent. One of the first and perhaps the most noted research effort involving the larger animals was achieved by Kellogg & Kellogg (1933). As a student of Dr. Kellogg's, I found him and his wife to have an uncanny interest in children and young animals and the changes and the differences that occurred during early development. Their history-making study involved raising their own newborn child with a newborn primate. Both infants were raised together as if they were twins. This study, like others that followed attempted to demonstrate that among the mammals, there are great differences in their speed of physical and mental development. Some are born relatively mature and quickly capable of motion and locomotion, while others are very immature, immobile and slow to develop. For example, the Rhesus monkey shows rapid and precocious development at birth, while the chimpanzee and the other "great apes" take much longer. Last and slowest is the human infant.