Data Store Insert Problems - Two Where Parameters Acting as OR Rather Than AND

I have a data store responses into which I am inserting a value like this:

responses.update({question: id, attendee_number: this_attendee_number.value},{response: i_question_type_s.value})

My expectation is that this will insert into the data store where question=id AND attendee_number=this_attendee_number.value

However it is inserting into the datastore where question=id OR attendee_number=this_attendee_number.value

Do I understand this incorrectly?

If so, how can the insert find the record using the AND rather than OR of the two where parameters?