The name is absent

The Brain and Behavior        63

justment and intellectual performance after the operation
were such that, in spite of careful medical and psychiatric
screening, the patient was accepted by the army and spent
ten months overseas before an epileptic attack, apparently
brought on by hard labor, resulted in his discharge. Hebb
was disturbed by the absence of gross defect in this patient
in contrast to the reports from other cases which involved
similar operations, so he made a careful analysis of such
studies.

Pared to its essentials, Hebb’s critique may be stated
simply. Previous studies reporting extreme behavioral deficit
had drawn their conclusions on the basis of a common logical
paradigm. They had removed tissue from the frontal lobes
and changes in behavior had been observed; therefore, they
argued that the tissue removal had caused the changes in be-
havior. This logical device of post hoc ergo propter hoc is
fallacious, and Hebb hastened to point it out. Simple succes-
sion in time is not sufficient to establish causal relations. A
more detailed description of the operation and the context in
which it was performed will clarify tire problems Hebb
found in interpreting previous results : (a) Prior to the opera-
tion the patient was hospitalized for some neurological dis-
order which may have had a history of many years duration,
(b) Immediately before the operation the patient’s behavior
was observed and studies were made of his performance on
certain tests, (c) During the operation, incisions were made
in the brain, and certain amounts of tissue were removed,
(d) After the operation, the patient’s behavior was observed,
and studies were made of his performance on certain tests. It
seemed to Hebb that for each of these four conditions influ-
ences were present which made it impossible to attribute
changes in behavior solely to tissue removal.

(a) The previous history of the patient must be considered.

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