Animal studies like Harlows monkey study contradict the learning theory of attachment.
Evolutionary studies, which suggest attachment is innate, contradict the learning theory.
The learning theory may be less valid as there are other explanations that tell us why they form and not just how . For example Bowlby's Monotropic theory.
Schaffer and emerson's study contradicts learning theory as they found that 39% of the samples main attachment figures was someone other than the person who fed them.
Schaffer and emerson's (1964) shows that not all infants strive to form attachments based on food like learning theory suggests.
Harlow found that the monkeys preferred comfort more than food - spending up to 15 hours a day with the comfort mother and just 1 hour with the wire mother.