( ( That is ) ( , ( ( ( the feedback ) ( ( is then ) ( positive ( rather ( than negative ) ) ) ) ) . ) ) )
(ROOT (S (INTJ (DT That) (VBZ is)) (, ,) (S (NP (DT the) (NN feedback)) (VP (VBZ is) (ADVP (RB then)) (ADJP (JJ positive) (PP (RB rather) (IN than) (ADJP (JJ negative)))))) (. .)))
That is, the feedback is then positive rather than negative.
(ROOT (S (NP (JJ Positive) (NN feedback)) (VP (VP (VBZ intensifies) (NP (NP (DT a) (NN change)) (PP (IN in) (NP (NP (DT the) (NN body) (POS 's)) (JJ physiological) (NN condition))))) (CONJP (RB rather) (IN than)) (VP (VBG reversing) (NP (PRP it)))) (. .)))