Turkish people use unique body language as follows.

Most of the Turks indicate 'YES'(evet) by nodding the head up and down. To say NO(Hayir in Turkish) they nod their head up and back, while lifting their eyebrows at the same time. Or they just raise their eyebrows, means NO.

For example, when a Turk got an offer for something to eat, first being in polite, he or she will say you Thank you (TESEKKUR EDERIM, in Turkish). While he or she mostly nods head. without giving you in correct way a complete answer by saying 'yes' or 'no'. So, the meaning of the conversation can be understood by his or her head's movement and a warm smile.

Again, if head get nods up and down, this means usually 'yes', but if head get nods up and back, that means 'No'.

头往后仰，跟点头的方向相反。