Some conversation partners ratchet up the intellectual level of a conversation, inspiring deeper insights in their conversation partner.

Some conversation partners bring the conversation to a more bland, dull place.

Does a given conversation partner tend to make conversations they're added to more or less interesting?

More interesting means more distinctive, more engaging, further from the bland, average, centroid conversation about something like the weather.

If the stakes are high (you have something to prove) a conversation partner that makes a conversation more interesting can be stressful.

If the stakes aren't high it can be euphoric.

If you have nothing to prove in a conversation, having an interesting conversation partner can feel like laughing, floating, flying.