[Illustration: _Recording equipment used in the experiment._]
delay = (θ)/(360) ρ, where ρ is the period of rotation in seconds
“Can people converse over an echo-free, four-wire circuit that has delay
like that of a synchronous satellite?”—that is one way of putting the
question we isolated to study. The next problem was to find a way of
setting up this question in the form of an experiment whose results
might be interpreted as a meaningful answer. The problem of apparatus,
fortunately, was fairly simple. Two telephone sets in separate rooms
were connected by four wires, with one pair going directly from each
transmitter to the other receiver, so that no echo would go back the way
it came. This gave us the “echo-free, four-wire circuit” we wanted. To
simulate the satellite, I inserted a magnetic delay device (_see
sketch_) between one of the transmitters and the other receiver. This
had a revolving drum on which speech could be recorded and then played
back a short interval later. By moving the playback head, I could
produce any amount of delay up to two satellite bounces’ worth. At this
point, the equipment was ready, but there were still two major problems:
(1) how to get people to converse over the circuit in a natural way, and
(2) what to observe and measure that would give us an answer to our
question.
When you think about the first problem, you soon realize that it is hard
to say exactly what a “natural” conversation is. But even if we can’t
describe it, we can try to find examples of it. I experimented with
several ways of making people talk that could be recognized as
_un_natural: word games, list-checking, shape description and
recognition, and a system of rewards for spurts of talk. None of these
schemes seemed to generate the real conversational interplay we wanted.
Finally, I noticed that my coworkers often got involved in vigorous
conversations on political and social issues at the lunch table. So I
circulated a questionnaire to help me pick pairs of people who might
enter into lively discussions on one or more topics. I arranged seven
conversations of this sort, and they became the basic material of my
study. Only one of these lacked sufficient spirit to yield good data,
and six out of seven is a pretty good percentage when you try to study
human behavior in such a free situation. Note that the conversers
expressed ideas that came from _within_ them at the time—not from any
external materials—and that they usually felt rather strongly about what
they were saying to the other fellow, who disagreed and therefore needed
some convincing. Of course, these conversations do not represent the
whole range of possible conversations; they are only a small sample of
one type. This doesn’t limit the truth of the particular result we got,
but it does limit how far we may generalize from these results.
What Should We Observe?
You might think we could solve this problem simply by asking the
conversers their opinions. We found out long ago, however, that the
opinions you get are affected by a lot of things: how you ask the
question, the attitude of the respondent, and his unrelated experiences
outside the experiment. So we usually try a more subtle approach. In
this case, my basic observation was of what psychologists call _escape
behavior_. The conversers were told that they would start talking over a
normal circuit, and that delay would be introduced at some point. (The
delay was inserted in such a way that an abrupt change could not be
noticed.) All the conversers had pushbuttons for signaling the
experimenter. If they thought they noticed a delay, they were told that
it would be removed if they pushed the button. Thus they could always
escape from this possibly unpleasant condition.
My reasoning was this: If the conversers found it very difficult to talk
with delay in the circuit, they would surely push the button soon after
the delay was introduced. On the other hand, any time when they
continued to converse without pushing the button—while delay was in the
circuit—was obviously also a time when the delay did _not_ make
conversation impossible. So we had at least one measurable quantity—the
time taken to detect delay—which we could interpret as an answer to our
question. Note that we could tell if people pushed the button “just to
be on the safe side” by seeing how often they did this when there
actually was no delay in the circuit.
There are just a few more necessary details before we discuss the
results:
—I recorded the conversations for later analysis, but the conversers
knew that the recordings would be held in confidence.
—The amount of delay used was 1.2 seconds, which represents the total
round-trip delay for a circuit using two satellites, including the
delay in typical end connections on the ground. We used this much
delay because our preliminary tests indicated that it would be more
likely to produce an effect than would the 0.6 second delay in a
one-satellite link.
—The entire 1.2 seconds of delay was put into one of the lines, since we
had discovered that, where there is no echo, conversers cannot tell
the difference between a delay of 2_t_ seconds in one line and a delay
of _t_ seconds in each of two lines. I did this for the sake of
convenience, so that I could introduce delay in the quiet line while
the other one was active.
—After someone detected delay, I removed it immediately and then waited
at least a minute before putting it back in.
—Altogether, I collected about two hours of conversation and introduced
delay 22 times.