Sentence:  The mediums with whom the Parapsychology Foundation is working in this experiment <WSD>are</WSD> in a waking or only slightly dissociated state , so that the sitter can make comments , ask and answer questions , instead of talking with a `` control '' who speaks through an entranced sensitive . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)