Research to contradict the learning theory was conducted by Schaffer and Emerson, who found that infants tended to form attachments to their mother regardless of whether she was the one who fed them, attachment was due to responding to infants signals and interaction. Furthermore, Field's research into the role of the father, has shown that the best quality attachments are with sensitive and responsive caregivers which go beyond just feeding the infant. Therefore, feeding the infant does not appear to be the most important factor in forming an attachment as the learning theory suggests.