These gestures change or negate the message conveyed by other gestures.
Testing (chi-square) showed that a significantly larger number of
strings containing “negative” gestures resulted in “no contact (within 5
seconds)" between gorillas; whereas, non-negative gestures resulted in contact within 5 seconds.
Examples: hide playface, wrist glance
hide playfaces can you find in the video clip?
For more information:
Tanner, Joanne E. &
Byrne, Richard W. (1993). Concealing facial evidence of mood: perspective-taking
in a captive gorilla? Primates, 34(4), 451-457.