I’m in middle of learning; should I stop to answer Kaddish?
A person who is present in shul while a minyan (halachic prayer quorum) is in session should be careful not to disturb the davening. While the tefillos (prayers) of Kaddish, Barchu, Kedushah, Modim and chazaras hashatz (the repetition of the Amidah prayer) are being recited, they should answer appropriately, even if minyanim follow one another continually.
What about someone who is learning Torah while the minyan davens—of course, while ensuring that he is not disruptive to the minyan and he has his own scheduled time for davening—must he interrupt to answer the tefilos (prayers)? There is no one answer to this question and the particulars engender serious discussion among poskim. Some things to consider are:
Is the minyan one of a stream of minyanim, or is it the regularly scheduled davening?
Is it easily noticeable that the person is learning?
Can an observer discern whether the learner is answering or not? (For example, Kedushah and Modim would require him to stand.)
Is the learner separated from the minyan by a mechitzah (partition)?
Is it a private shiur or talmud Torah d’rabim (communal learning)?
Certainly, if the learner is distracted by the constant interruption to answer the tefillos and it is causing bittul Torah (squandering time dedicated for Torah study), he need not answer. This is especially true if any observer would realize that the learner is endeavoring to avoid bittul Torah. #624