Finding Out the Close-Mouthed
One quality entering into the ability to keep a secret is the degree of suggestibility of the individual. That person who most quickly and automatically obeys and responds to suggested commands possesses the least degree of conscious self-control. The quality referred to is illustrated by the child's game of "thumbs up, thumbs
down," and "Simon says thumbs up" and "Simon says thumbs down." Those persons who are unable to wait for the "Simon says," but mechanically obey the command "thumbs up" or "thumbs down" would be those least able to resist a trap artfully laid to compel them to disclose what they wished to conceal. Like efficiency in observation, attention and memory, however, suggestibility is specific, not general, in character—that is to say, persons may be easily influenced by certain kinds of suggestion while possessing a strong degree of resistance to other kinds. Consequently actual tests of this quality cannot be limited to one method.
DETERMINING SUGGESTIBILITY BY PROGRESSIVE LINE TEST PRIVATE LABORATORY, SOCIETY OF APPLIED PSYCHOLOGY
For purposes of illustration, here is a simple form of what is known as the
"line" test for suggestibility. The subject is seated about two feet away from and in front of a revolving drum on which is a strip of white paper. On this strip of white paper are drawn twenty parallel straight lines. These lines begin at varying distances from the left-hand margin. Each of the first four lines is fifty per cent longer than the one before it, but the remaining sixteen lines are all of the same length.
A Test for Suggestibility
The examiner says to the subject, "I want to see how good your 'eye' is. I'll show you a line, say an inch or two long, and I want you to reproduce it right afterwards from memory. Some persons make bad mistakes; they may make a line two inches long when I show them one three inches long;
others make one four or five inches long. Let's see how well you can do. I shall show you the line through this slit. Take just one look at it, then make a mark on this paper [cross-section paper] just the distance from this left-hand margin that the line is long. Do that with each line as it appears."