skinner,_a_case_history___

skinner,_a_case_history___ - A CASE HISTORY IN SCIENTIFIC...

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Unformatted text preview: A CASE HISTORY IN SCIENTIFIC METHOD1 B. F. SKINNER Harvard University profession for which there is no professional training, and it is commonly argued that this is because our graduate schools train scholars and scientists rather than teachers. We are more con- cerned with the discovery of knowledge than with its dissemination. But can we justify ourselves quite so easily? It is a bold thing to say that we know how to train a man to be a scientist. Scien- tific thinking is the most complex and probably the most subtle of all human activities. Do we actually know how to shape up such behavior, or do we simply mean that some of the people who attend our graduate schools eventually become scientists? Except for a laboratory course which acquaints the student with standard apparatus and stand- ard procedures, the only explicit training in scien- tific method generally received by a young psy- chologist is a course in statistics——not the intro- ductory course, which is often required of so many kinds of students that it is scarcely scientific at all, but an advanced course which includes “model building,” “theory construction,” and “experimen- tal design.” But it is a mistake to identify scientific practice with the formalized construc- tions of statistics and scientific method. These disciplines have their place, but it does not coin- cide with the place of scientific research. They offer a method of science but not, as is so often implied, the method. As formal disciplines they arose very late in the history of science, and most of the facts of science have been discovered without their aid. It takes a great deal of skill to fit Fara- day with his wires and magnets into the picture which statistics gives us of scientific thinking. And most current scientific practice would be equally refractory, especially in the important initial stages. It is no wonder that the laboratory scientist is puzzled and often dismayed when he discovers how his behavior has been reconstructed in the formal analyses of scientific method. He is likely to pro- IT has been said that college teaching is the only , 1Address of the President at the Eastern Psychological Association meetings in Philadelphia, April 1955. test that this is not at all a fair representation of what he does. But his protest is not likely to be heard. For the prestige of statistics and scientific methodology is enormous. Much of it is borrowed from the high repute of mathematics and logic, but much of it derives from the flourishing state of the art itself. Some statisticians are professional people employed by scientific and commercial enterprises. Some are teachers and pure researchers who give their col- leagues the same kind of service for nothing—or at most a note of acknowledgement. Many are zealous people who, with the best of intentions, are anxious to show the nonstatistical scientist how he can do his job more efficiently and assess his results more accurately. There are strong professional societies devoted to the advancement of statistics, and hundreds of technical books and journals are published annually. Against this, the practicing scientist has very little to offer. He cannot refer the young psycholo- gist to a book which will tell him how to find out all there is to know about a subject matter, how to have the good hunch which will lead him to devise a suitable piece of apparatus, how to develop an efficient experimental routine, how to abandon an unprofitable line of attack, how to move on most rapidly to later stages of his research. The work habits which have become second nature to him have not been formalized by anyone, and he may feel that they possibly never will be. As Richter (5) has pointed out, “Some of the most important discoveries have been made without any plan of research,” and “there are researchers who do not work on a verbal plane, who cannot put into words what they are doing.” If we are interested in perpetuating the practices responsible for the present corpus of scientific knowledge, we must keep in mind that some very important parts of the scientific process do not now lend themselves to mathematical, logical, or any other formal treatment. We do not know enough about human behavior to know how the scientist does what he does. Although statisticians and 221 222 methodologists may seem to tell us, or at least imply, how the mind works—how problems arise, how hypotheses are formed, deductions made, and crucial experiments designed—we as psychologists are in a position to remind them that they do not have methods appropriate to the empirical observa- tion or the functional analysis of such data. These are aspects of human behavior, and no one knows better than we how little can at the moment be said about them. Some day we shall be better able to express the distinction between empirical analysis and formal reconstruction, for we shall have an alternative ac- count of the behavior of Man Thinking. Such an account will not only plausibly reconstruct what a particular scientist did in any given case, it will permit us to evaluate practices and, I believe, to teach scientific thinking. But that day is some little distance in the future. Meanwhile we can only fall back on examples. Some time ago the director of Project A of the American Psychological Association asked me to describe my activities as a research psychologist. I went through a trunkful of old notes and records and, for my pains, reread some of my earlier publi- cations. This has made me all the more aware of the contrast between the reconstructions of for- malized scientific method and at least one case of actual practice. Instead of amplifying the points I have just made by resorting to a generalized ac- count which is not available, I should like to discuss Lg» FIG. 1. THE AMERICAN PSYCHOLOGIST a case history. It is not one of the case histories we should most like to have, but what it lacks in importance is perhaps somewhat offset by accessi- bility. I therefore ask you to imagine that you are all clinical psychologists—a task which becomes easier and easier as the years go by—while I sit across the desk from you or stretch out upon this comfortable leather couch. The first thing I can remember happened when i I was only twenty-two years old. Shortly after I had graduated from college Bertrand Russell pub- lished a series of articles in the old Dial magazine on the epistemology of John B. Watson’s Be- haviorism. I had had no psychology as an under- graduate but I had had a lot of biology, and two of the books which 'my biology professor had put into . my hands were Loeb’s Physiology of the Brain and the newly published Oxford edition of Pavlov’s Conditioned Reflexes. And now here was Russell extrapolating the principles of an objective formula- tion of behavior to the problem of knowledge! Many years later when I told Lord Russell that his articles were responsible for my interest in behavior, he could only exclaim, “Good Heavens! I had always supposed that those articles had demolished Behaviorism! ” But at any rate he had taken Wat- son seriously, and so did I. _ When I arrived at Harvard for graduate study, the air was not exactly full of behavior, but Walter Hunter was coming in once a week from Clark Uni- versity to give a seminar, and Fred Keller, also a graduate student, was an expert in both the tech- nical details and the sophistry of Behaviorism. A CASE HISTORY IN SCIENTIFIC METHOD Many a time he saved me as I sank into the quick- sands of an amateurish discussion of “What is an image?” or “Where is red?” I soon came into con- tact with W. J. Crozier, who had studied under Loeb. It had been said of Loeb, and might have been said of Crozier, that he “resented the nervous system.” Whether this was true or not, the fact was that both these men talked about animal be- havior Without mentioning the nervous system and with surprising success. So far as I was concerned, they cancelled out the physiological theorizing of Pavlov and Sherrington and thus clarified what re- mained of the work of these men as the beginnings of an independent science of behavior. My doctoral thesis was in part an operational analysis of Sher- rington’s synapse, in which behavioral laws were substituted for supposed states of the central nerv- ous system. But the part of my thesis at issue here was ex- perimental. So far as I can see, I began simply by looking for lawful processes in the behavior of the intact organism. Pavlov had shown the way; but I could not then, as I cannot now, move without a jolt from salivary reflexes to the important business of the organism in everyday life. Sherrington and Magnus had found order in surgical segments of the organism. Could not something of the same sort be found, to use Loeb’s phrase, in “the organism as a whole”? I had the clue from Pavlov: control your conditions and you will see order. It is not surprising that my first gadget was a silent release box, operated by compressed air and designed to eliminate disturbances when introducing a rat into an apparatus. I used this first in study- ing the way a rat adapted to anovel stimulus. I built a soundproofed box containing a specially 223 FIG. 4. structured space. Arat was released, pneumatically, at the far end of a darkened tunnel from which it emerged in exploratory fashion into a well-lighted area. To accentuate its progress and to facilitate recording, the tunnel was placed at the top of a flight of steps, something like a functional Parthe- non (Figure 1). The rat would peek out from the tunnel, perhaps glancing suspiciously at the one- way window through which I was watching it, then stretch itself cautiously down the steps. A soft . click (carefully calibrated, of course) would cause it to pull back into the tunnel and remain there for some time. But repeated clicks had less and less of an effect. I recorded the rat’s advances and retreats by moving a pen back and forth across a moving paper tape. The major result of this experiment was that some of my rats had babies. I began to watch young rats. I saw them right themselves and crawl about very much like the decerebrate or thalamic cats and rabbits of Magnus. So I set about study- ing the postural reflexes of young rats. Here was a first principle not formally recognized by scientific methodologists: When you run onto something in- teresting, drop everything else and study it. I tore up the Parthenon and started over. If you hold a young rat on one hand and pull it gently by the tail, it will resist you by pulling for- ward and then, with a sudden sharp spring which usually disengages its tail, it will leap out into space. 22‘4 ' FIG. 5. I decided to study this behavior quantitatively. I built a light platform covered with cloth and mounted it on tightly stretched piano wires (Figure 2). Here was a version of Sherringon’s torsion-wire myograph, originally designed to record the isometric contrac- tion of the tibialis anticus of a cat, but here adapted to the response of a whole organism. When the tail of the young rat was gently pulled, the rat clung to the cloth floor and tugged forward. By amplifying the fine movements of the platform, it was possible to get a good kymograph record of the tremor in this motion and then, as the pull against the tail was increased, of the desperate spring into the air (Figure 3). ' Now, baby rats have very little future, except as adult rats. Their behavior is literally infantile and cannot be usefully extrapolated to everyday life. But if this technique would work with a baby, why not try it on a mature rat? To avoid attaching anything to the rat, it should be possible to record, not a pull against the substrate, but the ballistic thrust exerted as the rat runs forward or suddenly stops in response to my calibrated click. So, in- voking the first principle of scientific practice again, I threw away the piano-wire platform, and built a runway, eight feet long. This was constructed of light wood, in the form of a U girder, mounted rigidly on vertical glass plates, the elasticity of which permitted a very slight longitudinal move- ment (Figure 4). The runway became the floor of a long tunnel, not shown, at one end of which I placed my soundless release box and at the other THE AMERICAN PSYCHOLOGIs-r end myself, prepared to reinforce the rat for com- ing down the runway by giving it a bit of wet mash, to sound a click from time to time when it had reached the middle of the runway, and to harvest kymograph records of the vibrations of the sub- strate. Now for a second unformalized principle of scientific practice: Some ways of doing research are easier than others. I got tired of carrying the rat back to the other end of the runway. A back alley was therefore added (Figure 5). Now the rat could eat a bit of mash at point C, go down the back alley A, around the end as shown, and back home by runway B. The experimenter at E could collect records from the kymograph at D in com— fort. In this way a great many records were made of the forces exerted against the substratum as rats ran down the alley and occasionally stopped dead in their tracks as a click sounded (Figure 6). There was one annoying detail, however. The rat would often wait an inordinately long time at C before starting down the back alley on the next run. There seemed to be no explanation for this. When I timed these delays with a stop watch, how- ever, and plotted them, they seemed to show orderly changes (Figure 7). This was, of course, the kind of thing I was looking for. I forgot all about the movements of the substratum and began to run rats for the sake of the delay measurements alone. But there was now no reason why the runway had to be eight feet long and, as the second principle came into play again, I saw no reason why the rat could not deliver its own reinforcement. A new apparatus was built. In Figure 8 we see the rat eating a piece of food just after completing a run. It produced the food Iby its own action. As it ran down the back alley A to the far end of the rectangular,runway, its weight caused the whole runway to tilt slightly on the axis C and this move- ment turned the wooden disc D, permitting a piece of food in one of the holes around its perimeter to drop through a funnel into a food dish. The food was pearl barley, the only kind I could find in the grocery stores in reasonably uniform pieces. The rat had only to complete its journey by coming TIMI -' CLICK Q fl .__. _ M— Fro. 6. A CASE HISTORY IN SCIENTIFIC METHOD 225 3ELAY Run 5 FIG. 7. down the home stretch B to enjoy its reward. The experimenter was able to enjoy his reward at the same time, for he had only to load the magazine, put in a rat, and relax. Each tilt was recorded on a slowly moving kymograph. A third unformalized principle of scientific prac- tice: Some people are lucky. The disc of wood from which I had fashioned the food magazine was taken from a store room of discarded apparatus. It happened to have a central spindle, which for- tunately I had not bothered to cut off. One day it occurred to me that if I wound a string around the spindle and allowed it to unwind as the magazine was emptied (Figure 9), I would get a different kind of record. Instead of a mere report of the of the up-and-down movement of the runway, as a series of pips as in a polygraph, I would get a curve. And I knew that science made great use of curves, although, so far as I could discover, very little of pips on a polygram. The difference between the old type of record at A (Figure 10) and the new at B may not seem great, but as it turned out the curve revealed things in the rate of responding, and in changes in that rate, which would certainly other- wise have been missed. By allowing the string to unwind rather than to wind, I had got my curve in an awkward Cartesian quadrant, but that was easily remedied. Psychologists have adopted cumu- lative curves only very slowly, but I think it is fair to say that they have become an indispensable tool for certain purposes of analysis. Eventually, of course, the runway was seen to FIG. 8. be unnecessary. The rat could simply reach into a covered tray for pieces of food, and each move- ment of the cover could operate a solenoid to move a pen one step in a cumulative curve. The first major change in rate observed in this way was due to ingestion. Curves showing how the rate of eat- ing declined with the time of eating comprised the other part of my thesis. But a refinement was needed. The behavior of the rat in pushing open the door was not a normal part of the ingestive be- havior of Rattus rattus. The act was obviously learned but its status as part of the final performance was not clear. It seemed wise to add an initial conditioned response connected with ingestion in a quite arbitrary way. I chose the first device which came to hand—a horizontal bar or lever placed where it could be conveniently depressed by the rat to close a switch which operated a magnetic maga- zine. Ingestion curves obtained with this initial response in the chain were found to have the same properties as those without it. Now, as soon as you begin to complicate an ap- paratus, you necessarily invoke a fourth principle of scientific practice: Apparatuses sometimes break down. I had only to wait for the food magazine to jam to get an extinction curve. At first I treated this as a defect and hastened to remedy the dif- FIG. 10. 3. , if. a‘.‘ a. 226 ' ‘ESMISSS TIME FIG. 11. ficulty. But eventually, of course, I deliberately V disconnected the magazine. I can easily recall the excitement of that first complete extinction curve (Figure 11). I had made contact with Pavlov at last! Here was a curve uncorrupted by the physio- logical process of ingestion. It was an orderly change due to nothing more than a special con- tingency of reinforcement. It was pure behavior! I am not saying that I would not have got around to extinction curves without a breakdown in the apparatus; Pavlov had given too strong a lead in that direction. But it is still no exaggeration to say that some of the most interesting and surprising results have turned up first because of similar ac- cidents. Foolproof apparatus is no doubt highly desirable, but Charles Ferster and I in recently re- viewing the data from a five-year program of re- search found many occasions to congratulate our~ selves on the fallibility of relays and vacuum tubes. I then built four soundproofed ventilated boxes, each containing a lever and a food magazine and supplied with a cumulative recorder, and was on my way to an intensive study of conditioned reflexes in skeletal behavior. I would reinforce every response for several days and then extinguish for a day or two, varying the number of reinforcements, the amount of previous magazine training, and so on. At this point I made my first use of the deductive method. I had long since given up pearl barley as too unbalanced a diet for steady use. A neighbor- hood druggist had shown me his pill machine, and I had had one made along the same lines (Figure 12). It consisted of a fluted brass bed across which one laid a long cylinder of stiff paste (in my case a MacCollum formula for an adequate rat diet). A similarly fluted cutter was then lowered onto the cylinder and rolled slowly back and forth, convert- ing the paste into about a dozen spherical pellets. These were dried for a day or so before use. The procedure was painstaking and laborious. Eight rats eating a hundred pellets each per day could easily keep up with production. One pleasant Saturday afternoon I surveyed my supply of dry pellets, and, appealing to certain elemental theorems THE AMERICAN PSYCHOLOGIST in arithmetic, deduced that unless I spent the rest of that afternoon and evening at the pill machine, the supply would be exhausted by ten-thirty Monday morning. Since I do not wish to deprecate the hypothetica- deductive method, I am glad to testify here to its > usefulnes...
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