I'd be curious to know what behavior you did observe in the infants. I've never seen a circumcision performed live myself, but I've read that some infants exhibit an increased unresponsiveness -- a catatonic torpor induced by shock (as indicated by elevated cortisol levels and decreased body temperature).

I'll refrain from providing references since you said you aren't interested, but they are available. My point is only to question what "not acting traumatized" means.