As a sometimes engineering manager (I generally prefer to be a staffy, you know, doing analyst functions for the CEO, etc.), this is interesting to me. Can you give me any ideas on what I should be on the look-out for, in terms of behavior, among the team-mates?
I "get" that it's not visible (sort of), but I don't get how to be on guard for it, prevent it or deal with it if we can't see it. How does a manager see the signs of it, somehow, well enough, to deal with it?
Yeah, it's tricky to see for sure. I don't pretend to have all or even some of the answers here, but since you asked, and it's a great question, I'll take a stab at it.
First, I'd just make sure that people are happy. If people are honestly happy and enjoying their job, they probably aren't having a problem. Talk to them and figure it out is the most direct way. Indirect ways I would say include:
Social dynamics: Does a team try to exclude a person from meetings, social discussions at work, social activities, etc? Is one person always alone? This is a bit fuzzier since it's about association, and you can't force people to be friends, but it can show a lot about team cohesion.
Work dynamics: I've worked with people who I was almost sure had it out for me, and they would purposefully drag their feet doing work or responding to issues. While this should reflect poorly on the person sandbagging, it's more common that the recipient is blamed for "not getting enough done." Especially with ramping up or helping out, by excluding certain members of the team, coworkers can basically set that person up to fail, while technically doing nothing wrong.
Reviews: Also look out for when people are punished or otherwise told they aren't doing good enough. The measuring stick for this can change based on the person being measured.
Opportunity. Are minority team members given the same opportunities for leadership and growth? Or does a team always give the best work to one or two people that the boss likes, leaving everyone else to clean up the mess? It's hard to prove that you can do the job if they won't let you. This seems to happen a lot in my experience.
I guess I've been fortunate in that, all of the people being excluded were truly not pulling their own (traditional) weight because they were going through family trauma and on anti-depressants or something. (Divorce, loss of a child, etc.). People were pretty forgiving, but definitely didn't want them in critical path.
The handful (let me say, 5 G, 2L and 2T across 10 small teams over 5 years that I am going to use as a sample, circa 1995~2000) of alphabet people (is that phrase offensive?), were objectively AWESOME in terms of personality and group engagement and work performance. It really was never a problem. Maybe we hired well. Maybe we were lucky. I guess I haven't seen the passive-aggressive exclusionary thing you are talking about, but I will keep an eye out for it in the future.
I "get" that it's not visible (sort of), but I don't get how to be on guard for it, prevent it or deal with it if we can't see it. How does a manager see the signs of it, somehow, well enough, to deal with it?