I'm looking for an adequate expression or a word in the context:

The effect of reciprocity has the same value in the positive direction, in a sense of feeli.ng moral obligation and the need to respond to the good in the same way/manner.

Thank you
If you don't want to use the word 'reciprocate', which is probably the best single word, (however, it's the same as the phrase you are defining--'effect of reciprocity'), you might consider this instead: ...and the need to respond in like manner.

(Your sentence, as written, is a little hard to understand.)
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Thank you for your suggestions

Is it good to say: respond to the good?
How about goodness rather than the good?
I guess it is Ok. Thank you
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"respond in kind" is the phrase I would have used.