Certain conversations Kate has will contain decisions, rather than just topics of conversation. These can be identified by an animated ... in between the conversation choices.
At this point, hold
and the lightbulb icons near the conversation options should light up. With
still held, when you press the button for the decision, you'll hear Kate's thoughts on it, rather than making that decision.
I got this shortly after the first conversation with Olga, having heard Kate's thoughts on both options for the one choice you have to make in it. The earliest you can do this is when you sit down in the doctor's office for his test, when choosing whether to lie or not.
There is a very brief tutorial on this mechanic during the sit-down with the doctor.