Here is a self-administered test to answer this question. You must imagine the following scenario: you have gone to a party, where you unexpectedly bump into your ex. You get on reasonably well, but don't get much of a chance to talk. At the end of the night you find that the buses home are not running, so the owner of the house offers to let you sleep in the spare room. As the party is winding down, you notice that your ex is getting a bit up-close with one of the other residents of the house. You shrug it off for the moment. But as you are settling down in the spare room, you hear giggling from the next room. It is your ex and the other resident. Over the next hour you are subjected to the sound of your ex having excellent, slightly drunken, rollercoaster-ride animalistic sex in the next room, including headboard banging and loud ululations. There will be a point where you think it has finished then it will start again.
Note at this point it is normal to register some annoyance at this; nobody likes to be kept awake by the sound of heavy fucking.
Now use your human mind to predict your response to this scenario.
Predicted outcome A: you are crying, fingers in ears, huddled under the sheets. Interpretation: you should not be friends with you ex.
Predicted outcome B: "good for them." Interpretation: congratulations! You have a green light for being friends with your ex.
Predicted outcome C: wanking. Interpretation: I dunno, I'm not comfortable talking about this one