I like to relate grown-ups and duration by suggesting you look at it this way. You and I are having a great conversation, you have my attention and I have yours. We are responding to each other’s emotional bids. Now along comes a friend of mine. I now ignore you and talk to my other friend. How would you feel? Left out, upset, wondering why you aren’t being included in this conversation? Part of how you feel will depend on your understanding of what is going on. If you are young and still learning the rules of social interactions I should not expect you to wait long before expecting my attention or at least acknowledgement.
A two-year-old human toddler will need to be reinforced more frequently for his quiet waiting than say your husband who has figured out how this works. So, while I can expect my clicker super stars who have had a long reinforcement history of grown-ups to have good duration, I cannot nor should not expect little Eggo to stand very long at all without reinforcement. His rate of reinforcement will be high, possibly as fast as I can click and treat.
I tend to feel like I am being rude to my horse if I suddenly exclude them from the conversation. I know how I feel when someone interrupts a great session and suspect they feel likewise. How you view interruptions is, of course, a very individual reaction, but try and put yourself in your horse’s shoes. I will often acknowledge the person and ask them to give me a moment to finish up. I can then prepare my horse by asking for grown-ups and work on that behaviour while I am visiting or finish and put him away. I don’t feel right just abandon him to play with someone else. I expect his attention to be on me and not something he finds more interesting so I need to pay him the same courtesy.