Page 371 - Sensing, Intelligence, Motion : How Robots and Humans Move in an Unstructured World

346 HUMAN PERFORMANCE IN MOTION PLANNING

arcs in the path; see Figure 7.6. Because neither technique seems inher-
ently better or easier than the other, for subjects’ convenience both types
of control should be available to them during the test.
3. Since working with a bird’s-eye view (complete information) as opposed to
“in the dark” (incomplete information) makes a difference—clearly so in
the labyrinth test and seemingly less so in the arm manipulator test—this
dichotomy should be consistently checked out in the comprehensive study.
4. In the arm manipulator test it has been observed that the direction of arm
motion may have a consistent effect on the subjects’ performance. Obvi-
ously, in the labyrinth test this effect appears only when operating with
incomplete information (“moving in the dark”). This effect is, however,
quite pronounced in either test with the arm manipulator, with complete
or with incomplete information. Namely, in the setting of Figure 7.5, the
generated path and the time to finish were noted to be consistently longer
when moving from position T to S than when moving from S to T .This
suggests that it is worthwhile to include the direction of motion as a fac-
tor in the overall test battery. (And, the test protocol should be set up so
that the order of subtests has no effect on the test results.) One possi-
ble reason for this peculiar phenomenon is a psychological effect of one’s
paying more attention to route alternatives that are closer to the direction
of the intended route than to those in other directions. Consider the sim-
ple “labyrinth” shown in Figure 7.9: The task is to reach one point (S or
T ) from the other while moving “in the dark.” When walking from S to
T , most subjects will be less inclined to explore the dead-end corridor A
because it leads in a direction almost opposite to the direction toward T ,
and they will on average produce shorter paths. On the other hand, when
walking from T to S, more subjects will perceive corridor A as a promising
direction and will, on average, produce longer paths. Such considerations
are harder to pinpoint for the arm test, but they do seem to play a role. 5
5. The less-than-ideal performance of the subjects in the arm manipulator tests
makes one wonder if something else is at work here. Can it be that the
human–computer interface offered to the subjects is somewhat “unnatural”
for them—and this fact, rather than their cognitive abilities, is to blame
for their poor performance? Some subjects did indeed blame the computer
6
interface for their poor performance. Some subjects believed that their
performance would improve dramatically if they had a chance to operate a
physical arm rather than a virtual arm on the computer screen (“if I had a
real thing to grab and move in physical space, I would do much better.. .”).
This is a serious argument; it suggests that adding a physical test to the
overall test battery might provide interesting results.

5 Of course, no such effect can be expected for the computer algorithm.
6 An “unscientific” observation made here was that older subjects, such as visiting professors who
graciously agreed to participate in the experiment, were more critical of the human–computer inter-
face than younger subjects. The latter were more willing than the former to accept the test results
as measuring their real spatial reasoning abilities.