When you fix your eyes on something, you are in deep thought. The eyes look like wood. That is the body language of the special Chinese character 相（xiang, the fourth tone.)   

The phrase 相面 means the fortune-teller works by having a closed look at your face to tell you what will happen to you in the future.  (面 mian，the fourth tone：face or looking.)

This reminds me another character: 想 （xiang，the third tone) means 'think' or ’thinking'.  The ancient Chinese believed that the function of the heart was to do thinking job. So you can not think without 心（xin, the first,  it means heart.）The main part of 想 is 相 and the latter shows that your eyes might become as inactive as wood when you are in hard thinking.  This is as same as that sculpture named ’thinker'.