S- Based on 2-way interactions, parents rewarding the babies showing them loving behaviours - reciprocity.
W- Lack of support from animal studies (Harlow and Lorenz showing that there are other factors (not food) that are used in attachment).
W- Lack of support from human studies (Schaffer and Emerson show that the mother was the PCG regardless of she fed them) making food not the main factor in forming relationships.
W- Ethical issues due to testing on babies.