Sentence:  It <WSD>is</WSD> our hypothesis that Kohnstamm-positive subjects are less hesitant about relinquishing control than are Kohnstamm-negative subjects ; that they can give up their control and allow themselves to be reactors rather than actors . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)