Defiant Human: "You can't make me talk! You know damn well how tough we are, so do your damndest I won't break!"
Interrogator: "Are you sure about that?"
Defiant Human: "Try me."
Interrogator: "You asked for it." Calls to their associates who brings out a box of the cutest, most adorable, little fuzzballs on the planet. Several young kids giggle and begin to play with, and cuddle the fuzzballs that coo and burble sweetly.
Human: "What's that supposed to do??"
Human - a few hours later: "Ok, ok enough, I'll talk! I'll talk.. please! Please... just let me pet the furballs already!" -- Fighting Fit
Violence does not work as a means to extract information. Even if the interrogator does know what levels of violence are appropriate for the subject, the odds are that the subject will say anything at all to make the torment stop. This includes what the subject thinks the interrogator wants to hear.
There are less destructive ways to gain information out of an uncooperative subject. Ones that don't leave trauma in their wake. Ones that are effective even against the toughest of the tough. It did require very specific knowledge of what the species in question found tempting.
Humans... are relatively easy. They will pet anything, but they are particularly vulnerable to soft, fluffy, baby animals. Humans have a knack for being able to identify the young of any species and it is astonishing the range of creatures that they find adorable. To that end, Interrogator Zeph employed three larvae from the corporate daycare, and an entire nest of Floffles.