Where is the Samsung Galaxy setting for answering lock/unlock?

My friend told me that every time someone calls, he must unlock the phone. He wondered if we could change that setting. I looked in my own Samsung Galaxy and I could not find the setting. Do you know what we could do to resolve the issue so that my friend won't have to unlock his phone every time somebody is calling? I think that the problem is vendor- or operator-specific looking at this thread with a similar issue.