Lorenz and Harlow both conducted animal experiments to ascertain the attachment levels in attachment. Lorenz had two groups of goslings for his study; one group was hatched with him, and the other group of geese were hatched in an incubator with their biological mother. The results of the study showed how the goslings followed who they were hatched with; the group hatched with Lorenz followed him. The results subsequently gave an insight in animal attachment, and how they seemingly attach to the first moving object they see.
Harlow placed monkeys with two mother surrogates, and scared them intentionally. One surrogate dispensed milk, whilst the other was wrapped in cloth, though offered no food. Harlow scared the monkeys using various methods, and the results showed how monkeys often in situations of fear, went to the surrogate with clothing, due to its comforting nature. Such results showed how animals, when in fearful situations, seek for comfort rather than food, therefore casting doubt on previous theories(such as the learning theory, which focused on feeding as a primary attachment method)