Behaviorism, as it will be understood here, is the view that terms used to describe mental phenomena can be replaced, without loss of meaning, with terms which make reference only to dispositions to exhibit overt behavior in response to environmental stimuli.  Behaviorism holds that in the absence of such dispositions, there is no proper application of mental terms to a subject.

If Harry is hungry, then he is disposed to exhibit hunger behavior. He might utter "I am hungry" or make for the kitchen, hold his stomach, or check his watch to see whether it's lunchtime.  He may do none of these things, but still be likely to do so.  If Harry is hungry then he's likely to assent to the question: "Are you hungry?"  If Harry is not disposed to issue any of the behaviors associated with hunger, then he's not hungry.

What about thinking to oneself in the quiet of the study or in the solitude of an empty beach or mountain vista?  What behavioral dispositions correspond to thinking to oneself?  Watson held that thought involved behavioral dispositions to produce utterances.  Thinking to oneself, then, is just a matter of speaking softly, very softly.  A person thinking to themselves is producing sub-vocal speech.  All the behavioral dispositions are in place except the actual production of sound.  The muscles of the throat and mouth are moving; just not enough to produce sound.

It is this claim, that thinking to oneself occurs only when there is overt muscle movement, which was empirically refuted in 1947.  The purpose of the experiment was not to challenge behaviorism. Rather, the experiment was carried out by a team of anesthesiologists who were interested in whether d-Tubocurarine, a commercially available preparation of curare, was an anesthetic, or merely a paralytic.

Animal studies of the effects of curare were inconclusive.  Some human patients who had been administered curare for surgery reported later that they experienced pain during surgery.  Such reports had been discounted as unreliable, due to the effects of other drugs, stress, and the traumatic nature of surgical procedures.

The Experiment

An anesthesiologist agreed to be subject to complete paralysis. While completely paralyzed, the subject's vital signs were monitored throughout.  As long as the patient was able to move muscles voluntarily, he answered questions asked by the experimenters. Once fully paralyzed, the subject was asked to  keep mental notes of his experiences, to be transcribed immediately after recovery of voluntary muscles.  In addition, an electro-encephalogram  recorded brain activity throughout. The subject was a healthy male, aged 34, weighing 80 Kg.
 

The subject was administered d-tubocurarine and through intravenous infusion.  Oxygen was administered as needed via a rebreathing bag and face mask.  The subject was intubated for six minutes during complete paralysis, and was suctioned as needed.

Results

A log of changes in the status of the patient was kept, beginning at 2 p.m. on January 10, 1946, ten minutes prior to the administration of d-tubocurarine, through 6 p.m. when patient recovered use of skeletal muscles.  The following is are selections from the log:
 

2:11 D-Tubocurarine chloride injected intravenously at a slow constant rate so that 200 units were administered over a fifteen-minute period.  Feels " a little bit dizzy and quite a 'golow.'"  "A little hard to focus on anything."  Weakness in jaw muscles noted.  "Hard to talk."  Difficulty in swallowing and keeping eyes open.  "No unpleasant sensations, legs feel weak."

2:18 Upon subject's request, oxygen administration with face mask started.  "Can hardly bring teeth together."  Complains of residual odor from rebreathing bag.  Alpha rhythm in electro-encephalogram prominent and inhibited by pattern vision.  Total of 100 units of d-tubocurarine chloride given.  B.P., 130/70;  pulse rate, 112; respiratory rate, 16.

2:20 Speech no longer possible.  Can hear distinctly.  Still able to nod head and ot move hands slightly,  but can scarcely move fingers.

2:24 Head movement impossible.  Unable to open eyes.  Can wrinkle forehead slightly and indicates in this manner, in response to inquiry,  that he can see clearly when his eyelids are manually elevated.

2:26  Ability to comprehend and answer questions accurately is indicated by correctness of replies when the inquiries are restated in the negative or double negative.  Indicates he desires the experiment to continue.  Upon request, moves feet and hands slightly.  Total of 200 units given.  Some spasmodic diaphragmatic movements out of rhythm and artificial respirations.  Slight snoring sound on exhalation.

2:37  Subject signals in answer to inquiries that sensorium is normal,  airway is not troublesome,  and painful stimuli are felt.  Additional 100 units d-tubocurarine chloride given rapidly.

2:45 Subject now unable to signal response to inquiries,  due to complete skeletal paralysis.  Endotracheal catheter inserted with ease due to very relaxed pharynx and vocal cords.  and artificial respiration continued through it.

2:48 Eyelids manually opened.  Alpha rhythm of electro-encephalogram inhibited by pattern vision (object head in line of gaze).  Subject stated upon recovery that he was "clear as a bell" all this period.

Beginning at 2:51 Neostigmine methylsulfate, 0.5 mg. was administered intravenously to hasten the recovery from paralysis.   Patient could open eyes at 3:06 with difficulty, more easily at 3:35.  Patient still drowsy and experiences nausea at 5:25. Muscle weakness persisted through the evening.
 

Conclusion

The subject maintained consciousness, including full awareness of the sensorium and full comprehension of verbal stimuli. D-tubocurarine does not suppress the central nervous system, and is thus not a general anesthetic.  The subject clearly thought to himself during the period when he was completely paralyzed. Therefore overt muscle movement is not required for thinking.

Comment

This experiment is extraordinary event in the history of science. First, it investigated questions of both of great medical and philosophical importance. Curare had been administered as an anesthetic. But, as the experiment demonstrated, curare has no effect on the experience of pain or any other sensory stimulation.  Behaviorists held that thought implicated muscles in the vicinity of the larynx. The experiment demonstrates that this is not the case.  But the most extraordinary aspect of the experiment can only be appreciated from a careful reading of the log.  Undergoing complete paralysis is a potentially dangerous procedure, one not lightly undertaken by an otherwise healthy individual. It is not without significant risk, and certainly not without discomfort.
 
 
 

1. Smith, Scott M., Brown, Hugh O., Toman, james E.P., and Goodman, Louis S., "The Lack of Cerebral Effects of d-Tubocurarine", Anesthesiology Vol. 8, No. 1, (January, 1947) pp. 1-14.

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Copyright 1997, Saul Traiger