"Global" here would mean "overall."
The point here is that someone who comes across as unfriendly is going to get lower ratings on his individual attributes than someone who is warm and friendly.
Seems like a dumb study. If someone is annoying in general, people would tend to rate their mannerisms and accent as annoying.
How, exactly, did this same person act "cold" while maintaining the same mannerisms?
Student or Learner