Harry Harlow conducted a controversial study involving rhesus monkeys and observed that monkeys reared with a " terry cloth mother, " a wire feeding apparatus wrapped in soft terry cloth that provided a level of tactile stimulation and comfort, the monkey who had the real parent were considerably more emotionally stable as adults than those with a mere wire mother ( Harlow, 1958 ).
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By 1987 G . S . Losey wrote less optimistically " Cleaners are nothing but very clever behavioral parasites . . . that have taken advantage of the rewarding aspects of tactile stimulation, found in nearly all vertebrates . " Poulin and Grutter remark that " Over the last few decades, . . . the opinion of scientists regarding cleaning symbioses has changed, from selfless cooperation, to a mutually beneficial interaction, and finally to a one-sided exploitation ."
