Pointing Gestures
When someone points at a distant object, an observer understands
that the pointer is looking at something and calling the attention
of other to it. Pointing is often termed an "indicative gesture"
and functions as a way of referring to an object or event (called
"referential pointing"). In this sense, referential pointing
functions similarly to a word. In the wild, chimpanzees have not
been observed using pointing gestures to direct another's attention.
In laboratory conditions featuring extensive contact with
 |
| The chimpanzee is able to choose reliably
when the experimenter's hand is close to the object. |
 |
| The chimpanzee cannot choose reliably when
the experimenter is further away. |
humans, chimps can learn to use pointing to direct a human's attention
to something desired, such as a piece of food or a place to go. Paradoxically,
however, they fail to understand the human's intention when the human
points at something. Thus, in one study the experimenter sat between
two boxes, one of which contained food. The experimenter pointed at
that box. The chimp chose that box reliably only when the experimenter's
outstretched arm and hand almost touched the box. But when the experimenter
moved away from the boxes by 3 meters or so, the chimp no longer reliably
approached the indicated box. The chimp thus failed to understand
referential pointing. We tested the dolphin's understanding of referential
pointing by placing three objects, left, right, and behind the dolphin,
each at approximately 3 meters distance. We could then refer to these
objects by pointing at them or by using the gestural language symbols
familiar to the dolphin. In each case, the dolphin was required to
choose the referenced object and take the action to it indicated by
a gestural symbol (e.g., leaping over it, swimming under it, touching
it with the tail, etc.). For example, we can either sign Hoop Under
using symbolic gestures, or we can point at the hoop and then give
the gestural symbol Under. In either case, the dolphin understood
to swim under the hoop. Surprisingly, the dolphin not only understood
a direct point to an object with arm and finger extended, but also
understood a cross-body point, in which the left arm is extended across
the body to indicate an object to the right, or the right arm is extended
across the body to indicate an object to the left. Moreover, sequences
of points can be used to instruct the dolphin to take the object pointed
to second to the object pointed to first, using the same inverse grammar
as is used in the wholly symbolic language described earlier. The
dolphin was equally adept at carrying out the instruction
whether the two objects were referred to symbolically, or by pointing,
or by some combination. Given the armless anatomy of the dolphin,
it seems surprising that a dolphin would so easily understand the
human pointing gesture, while chimps do not. Possibly, the dolphin
understands because it uses an acoustic analog of pointing, its highly
focused echolocation beam. One dolphin may in fact detect what another
is inspecting through echolocation by listening to the echoes returning
from the emitter's beam.
Herman, L.M., Abinchandani, S.L., Elhajj, A.E.,
Herman, E.Y.K., Sanchez, J.L., & Pack, A.A. (2000). Dolphins
(Tursiops truncatus) comprehend the referential character of the
human pointing journal. Journal of Comparative Psychology, 113(4),
347-364.
Herman,
L. M. & Uyeyama, R. K. (1999). The dolphin's grammatical competency:
Comments on Kako (1998). Animal Learning & Behavior, 27-18-23.
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