Page 378 - Sensing, Intelligence, Motion : How Robots and Humans Move in an Unstructured World

RESULTS—EXPERIMENT ONE 353

• The primary focus in the study is on tests with the arm manipulator (see
Figure 7.5). The labyrinth test is used only as a benchmark, for introducing
the subjects to the tests and the study’s underlying ideas.
• The bulk of the subject pool for this study was paid undergraduate stu-
dents and also some graduate students. (There was no statistical difference
in performance between the two groups.)
• In the first session, about one hour long, a subject would be taught how to
carry out a test and would be given a pilot test to ascertain that he/she can
be submitted to the test; the latter would be different from the pilot test.
• The maximum time a subject was given to finish the test with the arm
manipulator was 15 minutes. Much less was allowed for the labyrinth test:
As a rule, 1–2 minutes were enough. These limits were chosen as a rough
estimate of the time the subjects would need to complete a test without
feeling time pressure. Most subjects finished their tasks well within the
time allocation; those few who didn’t were not likely to finish even with
significantly more time.
• Measures were taken to eliminate the effect of a subject’s memory recall, or
information passing, from one task to another. In the invisible version of the
arm test, rotating the whole scene on the computer screen for a consequent
session would practically eliminate the effect of memorization from prior
sessions. This also helps from the test protocol standpoint: Using the same
scene in subsequent tests allows for an “apples-with-apples” assessment of
subjects’ performance.

7.4 RESULTS—EXPERIMENT ONE

The basic (descriptive) statistics for motion planning tests carried out in Experi-
ment One are given in Table 7.1. Statistics are given separately for each depen-
dent variable, the length of path (Path) and the time to completion in seconds
(Time), and within each dependent variable for each of the eight tasks listed
in Section 7.3.1. Each line in Table 7.1 refers to a given task and includes the
number of tested subjects (“Valid N” statistics) as well as the mean, minimum,
maximum, and standard deviation of the correspondent variable.
A quick glance at the table provides a few observations that we will address
in more detail later. One surprise is that the subjects’ performance with the right-
to-left direction of motion was significantly worse than their performance with
the left-to-right direction of motion: Depending on the task, the mean length of
path for the right-to-left direction is about two to five times longer than that for
the left-to-right direction. 10

10 This alone would make a smart robot conclude that we humans are terribly inconsistent: What
prevents one, the robot would think, from going from point B to point A along the same path one
takes when going from A to B!