Evaluation points into animal studies of attachment in terms of internal validity and generalisability.

. - Harlow: The cloth mother had a more attractive/monkey-like face = confounding variable = low internal validity . - Harlow: Human behaviours (towards caregivers) may be more under our conscious control compared to monkeys​ so lacks generalisability thus lacks validity . + Harlow: Support by Schaffer and Emerson who say that a primary attachment figure is more likely to be the caregiver who showed sensitive responsiveness = conformt may be more important than feeding . +/- Lorenz: Support by Guitton (1966) that found that leghorn chicks imprinted to yellow rubber gloves and tried to mate with them, HOWEVER after spending time with their own species the effects of imprinting reversed