Home cage fear test #2. Frightened by the mechanical toy, the infant Rhesus monkey (Macaca mulatta) flees to its cloth mother. Again, regardless of which surrogate supplies its feeding, the infants always ignored the wire mother when frightened. Maternal deprivation experiments performed by Harry Harlow of the University of Wisconsin in the 1950's involved separating infant monkeys from their mothers and rearing them with surrogate mothers made of wire or cloth. The monkeys were kept in partial or total isolation, in wire cages or in "pits" or "wells of despair." These experiments found that comfort, security and affection are necessary for a monkey's healthy psychosocial development. As in the open field test, once the terrified infant monkey reached the security of the surrogate cloth mother, its fears abated and it turned to inspect the previously frightening teddy bear.