Enter the Sigma
A new mouse in the office
Women not infrequently ask how they can identify Sigmas in the wild. The answer is relatively simple, but requires understanding that they are not terribly common. If there is a man to whom you react to as if he is an Alpha, but he neither reacts to you nor flirts with you, and if your local Alphas are regarding him a little warily for no reason you can see, there is a chance that he might be.
And if you subsequently try to talk to him and find yourself either a) bewildered by his unexpected failure to warm to your charming attempts to put your best foot forward or b) overwhelmed by his unexpected intensity, then the odds are pretty good.
Enter the “sigmas” in the comments
The comic shows another indicator as well: when a sigma comes around, they tend to be the subject of a disproportionate amount of the group members' side chats and are talked about in a number of different ways. Everyone's heard or seen good things, aggravating things, impressive things, shocking things, etc.
A sigma just showing up tends to stir the seas.