Lurz & Krachun 2011, figure 1
There’s a competitor, two graps and some size-distorting glass ... can
Subject predict that Competitor will choose not the largest grape but
the one which appears largest?
‘The objective here is to test whether chimpanzees are capable of anticipating (as evidenced by their
looking behavior) the actions of a human competitor by understanding how an illusory stimulus (grape)
looks to the human.’ \citep{lurz:2011_how}
‘the competitor is absent when the grapes are placed inside the containers (as in the pretest stage),
he does not observe the change in apparent size of the grapes as they are placed inside the
containers, as the chimpanzee does. After the grapes are placed, the competitor enters the room, sits
at the table, looks at each grape through the sides of the containers’
\citep[p.~476]{lurz:2011_how}
‘dependent measure is anticipatory looking’.
In this case, the subjects (chimps) know which grape is which and how they appear.
Also a Krachun-like competitive version (in this case, the chimps have to
infer which is larger from the failed reach of the human competitor)...
Also a Krachun-like reaching measure:
‘After the competitor has acted in one of these two ways toward the container with the large grape,
the experimenter places opaque coverings completely over each container and moves the platform toward
the chimpanzee. Once the platform is in place before the chimpanzee, the chimpanzee is allowed to
choose one of the two containers (by pointing to it through a finger hole). Since the containers are
covered, the chimpanzee cannot make its choice by seeing the grape or grapes inside the containers.
Rather, to make its preferred choice (which we assume will be the remaining small grape in
competitor-first success trials and the large grape in competitor-first failure trials) the chimpanzee
must attend to the selection process of the competitor.’
\citep[p.~475]{lurz:2011_how}
Karg et al, 2015 figure 4 (Experiment 2)
Experiment 2: chimp attempts to steal from human,
who will remove food if she sees the chimp approach.
One cover is transparent, the other opaque. But actually when they are down,
both look opaque from the chimp’s point of view.
Karg et al, 2015 figure 5 (Experiment 2)
(This is just a photo of the apparatus, with covers up (top) and down (bottom).)
Karg et al, 2015 figure 5 (Experiment 2)
‘Mean percentage of trials with the choice of the opaque box across the three conditions. In the
transparent condition, one lid was opaque, the other transparent. In the screen condition, one lid
was a screen, the other opaque. The control was like the transparent condition, but without the
experimenter's presence at the time of choice. Error bars indicate 95% CI. The horizontal line
indicates chance level (50%). *P < 0.05; **P < 0.01’
\citep{karg:2015_goggles}.