An Investigation into the Cognition Behind Spontaneous String Pulling in New Caledonian Crows
Figure 2
Standard string-pulling problem and string discrimination tasks.
(A) Standard string-pulling problem. (B) Object discrimination test: circle = meat; rectangle = rock. (C) Overload test: small circle = meat; large circle = 700 g chicken. (D) Slanted-string test. (E) Crossed-string test.