As to what is meant by the input “being in a certain state”— it is
The state that would be shown on a snapshot of the controls. Also
Let us assume that the output consists of a set of dials, attached to
The Box and affected by the mechanism inside, so that the pointers
On the dials show, by their positions at any particular moment, the
State of the output.
We now see the experimenter much like the engineer in a ship,
Who sits before a set of levers and telegraphs by which he may act
On the engines, and who can observe the results on a row of dials.
The representation, though it may seem unnatural, is in fact, of
Course, capable of representing the great majority of natural sys-
Tems, even if biological or economic.
The Investigation. A man cannot step twice into the same
Water; neither can he twice conduct the same experiment. What he
Can do is to perform another experiment which differs from the
First only in some way that is agreed to be negligible.
The same fact applies to an examination of the Black Box. The
Sic data will always be of the form:
Time
States of input and
Output
sible input states α and β, and possible output states f, g, h and j,
a typical protocol might read (and be yet another transformation!):
Time: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
State: α g α j α f α f α f β f β h β h α h α j β f α h β j β f α h β j α f
(Parentheses have been omitted for brevity.)
This form, though it may seem artificial and unnatural, is in fact
Typical and general. It will represent anything from the investiga-
Tion of an electrical network by putting in a sinusoidal voltage and
Observing the output, to a psychiatric interview at which questions
α, β were put and answers g, f, h, j elicited.
Thus, the primary data of any investigation of a Black Box con-
Sists of a sequence of values of the vector with two components:
Input state, output state).
The possibility is not excluded that each component may itself
Be a vector (S.3/5).)
From this there follows the fundamental deduction that all
Knowledge obtainable from a Black Box (of given input and out-
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Put) is such as can be obtained by re-coding the protocol; all that,
And nothing more.
Ex.: Tabulate the transitions observed in the system that started at αγ. Find some
Regularities in them.
………
………
In which, at each of a sequence of times, the states of the Box’s
Various parts, input and output, are recorded. Thus, the Box that
Fell from the Flying Saucer might lead to the protocol:
↓
Time
A.m.
11.19
11.20
…
State
I did nothing— the Box emitted a steady hum at 240 c/s.
I pushed over the switch marked K: the note rose to 480 c/s and
Remained steady.
Accidentally I pushed the button marked “!”— the Box increased
in temperature by 20 °C.
Etc.
(The word protocol will be reserved for such a form and
Sequence.)
Thus every system, fundamentally, is investigated by the col-
Lection of a long protocol, drawn out in time, showing the
Sequence of input and output states. Thus if one system had pos-
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It will be noticed that nothing has been said about the skill of
The experimenter in manipulating the input. The omission was
deliberate, for no skill is called for! We are assuming, remember,
That nothing is known about the Box, and when this is so the
Method of making merely random variations (e.g. guided by
Throws of a die) on the input-switches is as defensible as any other
Method, for no facts yet exist that could be appealed to as justifi-
Cation for preferring any particular method. With terrestrial
Machinery— industrial, biological, neuronic— the experimenter
Has often had previous experiences with Boxes of the same class.
When this is so he may be able to use a method that explores what
He does not know about the present Box more efficiently than
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Some other method. (These matters, of exploring a partly known
System, lead into questions of altogether more advanced type, and
Their consideration must be postponed; a little is said on the sub-
Ject in S.13/5 and onwards.)
Absoluteness. When a generous length of record has been
Obtained, the experimenter will look for regularities, for repeti-
Tiveness in the behaviour (S.7/19). He may notice, for instance, in
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A N I N T R O D UC T I O N T O C Y B E R NE T I C S
TH E BL AC K B O X
Ex. 6/3/1, that α j is always followed by either αf or βf —that
although the α’s transition is not single-valued, that of the j is.
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