Whereas the previ ous chapter provided a detailed account of beha vi ors that commonly occur in each separ ate episode of the strange situ ation, the present chapter is concerned with the pattern of changes in a given beha vior or class of beha vi ors from one episode to another. The intrinsic design of the strange situ ation was dictated by the hypo thesis that 1year olds who are attached to their mothers will use her as a secure base from which to explore an unfa mil iar envir on ment when she is present. Consequently, it was expec ted that the array of toys would elicit explor at ory beha vior in the presep ar a tion Episode 2, while at the same time the infant would display weak attach ment beha vior, if any. Although it was expec ted that the entrance of the stranger in Episode 3 would attract the baby’s atten tion and there fore lead to a decrease in explor at ory beha vior direc ted toward the toys, no hypo thesis was formu lated in regard to norm at ive trends in attach ment beha vior in Episode 3, because no advance predic tion was made about the extent to which the pres ence of the unfa mil iar person would activ ate fear (or wary) beha vior and/or attach ment beha vior direc ted toward the mother. It was expec ted, however, that attach ment beha vior (crying and search) would be activ ated by the mother’s depar ture and/or absence in the separ a tion epis odes, at the expense of explor at ory beha vior, which would thus decline. It was further expec ted that relev ant forms of prox im ity and contact seeking beha vior would be activ ated in the reunion epis odes (at least initially), also at the expense of explor at ory beha vior.