Male grouping, in the absence of alcohol, sports weaponry, or court order, is a rare event. But the rarest of all male events is men shopping together. The rules here are clear. Men can shop together if they are related by blood or marriage. Beyond that, you will not see men shopping together very often.
Now when I say together, I mean actually being beside each other and commenting on what each other is thinking of buying. You know, sharing. Whatever that is.
There are, however, some exceptions to this rule.
Men can shop together only upon invitation and only when one man is serving as the role of expert guide. For example, if you do not know anything about riding lawnmowers and said lawnmower is a must-have, then you are allowed to ask your friend – the riding lawnmower expert – to accompany you to ponder such a purchase. Now, your friend is not allowed to comment on the wisdom of you purchasing a riding lawnmower to cut your postage stamp of a lawn. That is reserved for your female person-of-interest. Instead, he can only offer general advice regarding the pros and cons of riding lawnmower A as compared to riding lawnmower B.
Men who shop together under the expert-novice rule can evoke this rule for only one item per shopping trip. To push this exception beyond one item creates a level of tension in a male relationship and skirts dangerously close to intimacy. Put another way, you can ask your friend for his expertise on a lawnmower but you cannot then ask for further advice on some other item unless you had carefully and delicately negotiated that at the beginning of the shopping trip.
Now, it is perfectly allowed (and encouraged) for men who shop together to reverse the expert-novice role on the same shopping trip. You help me with riding lawnmowers and I offer my expertise on the cost-utility trade-off between telescoping and non-telescoping toilet snakes. This role reversal maintains harmony within the fragile male relationship universe.
If you are of the female persuasion, you may find all of this vaguely ridiculous and silly. I hear you. You may also be doubtful of the existence of male shopping rules. If so, conduct a field study then next time you are in the mall and count all the men you see shopping together.