金纳是一位久负盛名的心理学家，堪称行为主义之父，他是著名的“斯金纳箱”的发明者，此外他还出版了 10 多本著作，发表了 70多篇科学论文。斯金纳的理论用一句简单的话来概括就是：在任一特定的情况下，你的行为都很可能伴随着某种结果，比如得到赞扬、报酬或解决问题后的满足感，那么随后在类似的情况下，你很可能重复这一行为；这些结果被称为强化。如果你的行为伴随着另一种结果，比如疼痛或尴尬，那么你在以后的相似情况下就很少会重复这种行为；这些结果被称为“惩罚”。
斯金纳在此项研究中使用了“斯金纳箱”，但做了重要的变化：即为了研究迷信行为，食物分发器被设定为每隔 15秒落下食丸，不管动物当时在做什么。可以看到这便产生了非关联性强化。换句话说，不管动物做了什么，每隔 15 秒它将得到一份奖励。
研究中的被试是 8只鸽子。连续几天对这些鸽子喂少于他们正常进食量的食物，以便在测试时，它们处于饥饿状态。由此增强寻找食物的动机（这增加了强化的效果）。让每只鸽子每天在实验箱里待几分钟，对其行为不作任何限制。在这期间，每个15 秒强化自动出现。几天后，两个独立的观测者记录了鸽子在箱中的行为。
斯金纳在报告中写道：“ 8 只鸽子中的 6 只产生了非常明显的反应，两名观察者得到了完全一致的记录。一只鸽子形成了在箱子中逆时针转圈的条件反射，在两次强化之间转2 － 3圈；另一只反复将头撞向箱子上方的一个角落；第三只只显现出一种上举反应，似乎把头放在一根看不见的杆下面并反复抬起它。还有两只鸽子的头和身体呈现出一种摇摆似的动作，它们头部前伸，并且从右向左大幅度摇摆，接着再慢慢的转过来，它们的身子也顺势移动，动作幅度过大时还会向前走几步。还有一只鸽子形成了不完整的啄击或轻触的条件反应，动作直冲地面但并不接触。”
接下来，斯金纳想知道如果两次强化之间的间隔被拉长了，又会发生什么。他用了一只摇头的鸽子，然后把两次投放食丸的时间间隔慢慢增加到 1分钟。这时，鸽子表现的更加精力充沛，直到最后在两次强化间的 1 分钟内，这只鸽子像在表演一种舞蹈（好像一种“鸽子食物舞”）。
'SUPERSTITION' IN THE PIGEON
B. F. Skinner
First published in Journal of Experimental Psychology, 38, 168-172.
To say that a reinforcement is contingent upon a response may mean nothing morethan that it follows the response. It may follow because of some mechanicalconnection or because of the mediation of another organism; but conditioningtakes place presumably because of the temporal relation only, expressed in termsof the order and proximity of response and reinforcement. Whenever we present astate of affairs which is known to be reinforcing at a given drive, we mustsuppose that conditioning takes place, even though we have paid no attention tothe behavior of the organism in making the presentation. A simple experimentdemonstrates this to be the case.
A pigeon is brought to a stable state of hunger by reducing it to 75 percent ofits weight when well fed. It is put into an experimental cage for a few minuteseach day. A food hopper attached to the cage may be swung into place so that thepigeon can eat from it. A solenoid and a timing relay hold the hopper in placefor five sec. at each reinforcement.
If a clock is now arranged to present the food hopper at regular intervals withno reference whatsoever to the bird's behavior, operant conditioning usuallytakes place. In six out of eight cases the resulting responses were so clearlydefined that two observers could agree perfectly in counting instances. One birdwas conditioned to turn counter-clockwise about the cage, making two or threeturns between reinforcements. Another repeatedly thrust its head into one of theupper corners of the cage. A third developed a 'tossing' response, as if placingits head beneath an invisible bar and lifting it repeatedly. Two birds developeda pendulum motion of the head and body, in which the head was extended forwardand swung from right to left with a sharp movement followed by a somewhat slowerreturn. The body generally followed the movement and a few steps might be takenwhen it was extensive. Another bird was conditioned to make incomplete peckingor brushing movements directed toward but not touching the floor. None of theseresponses appeared in any noticeable strength during adaptation to the cage oruntil the food hopper was periodically presented. In the remaining two cases,conditioned responses were not clearly marked.
The conditioning process is usually obvious. The bird happens to be executingsome response as the hopper appears; as a result it tends to repeat thisresponse. If the interval before the next presentation is not so great thatextinction takes place, a second 'contingency' is probable. This strengthens theresponse still further and subsequent reinforcement becomes more probable. It istrue that some responses go unreinforced and [p. 169] some reinforcements appearwhen the response has not just been made, but the net result is the developmentof a considerable state of strength.
With the exception of the counter-clockwise turn, each response was almostalways repeated in the same part of the cage, and it generally involved anorientation toward some feature of the cage. The effect of the reinforcement wasto condition the bird to respond to some aspect of the environment rather thanmerely to execute a series of movements. All responses came to be repeatedrapidly between reinforcements -- typically five or six times in 15 sec.
The effect appears to depend upon the rate of reinforcement. In general, weshould expect that the shorter the intervening interval, the speedier and moremarked the conditioning. One reason is that the pigeon's behavior becomes morediverse as time passes after reinforcement. A hundred photographs, each takentwo sec. after withdrawal of the hopper, would show fairly uniform behavior. Thebird would be in the same part of the cage, near the hopper, and probablyoriented toward the wall where the hopper has disappeared or turning to one sideor the other. A hundred photographs taken after 10 sec., on the other hand,would find the bird in various parts of the cage responding to many differentaspects of the environment. The sooner a second reinforcement appears,therefore, the more likely it is that the second reinforced response will besimilar to the first, and also that they will both have one of a few standardforms. In the limiting case of a very brief interval the behavior to be expectedwould be holding the head toward the opening through which the magazine hasdisappeared.
Another reason for the greater effectiveness of short intervals is that thelonger the interval, the greater the number of intervening responses emittedwithout reinforcement. The resulting extinction cancels the effect of anoccasional reinforcement.
According to this interpretation the effective interval will depend upon therate of conditioning and the rate of extinction, and will therefore vary withthe drive and also presumably between species. Fifteen sec. is a very effectiveinterval at the drive level indicated above. One min. is much less so. When aresponse has once been set up, however, the interval can be lengthened. In onecase it was extended to two min., and a high rate of responding was maintainedwith no sign of weakening. In another case, many hours of responding wereobserved with an interval of one min. between reinforcements.
In the latter case, the response showed a noticeable drift in topography. Itbegan as a sharp movement of the head from the middle position to the left. Thismovement became more energetic, and eventually the whole body of the bird turnedin the same direction, and a step or two would be taken. After many hours, thestepping response became the predominant feature. The bird made a well definedhopping step from the right to the left foot, meanwhile turning its head andbody to the left as before.
When the stepping response became strong, it was possible to obtain a mechanicalrecord by putting the bird on a large tambour directly connected with a smalltambour which made a delicate electric contact each time [p. 170] stepping tookplace. By watching the bird and listening to the sound of the recorder it waspossible to confirm the fact that a fairly authentic record was being made. Itwas possible for the bird to hear the recorder at each step, but this was, ofcourse, in no way correlated with feeding. The record obtained when the magazinewas presented once every min. resembles in every respect the characteristiccurve for the pigeon under periodic reinforcement of a standard selectedresponse. A well marked temporal discrimination develops. The bird does notrespond immediately after eating, but when 10 or 15 or even 20 sec. have elapsedit begins to respond rapidly and continues until the reinforcement is received.
Fig. 1. 'Reconditioning' of a superstitious response after extinction. Theresponse of hopping from right to left had been thoroughly extinguished justbefore the record was taken. The arrows indicate the automatic presentation offood at one-min. intervals without reference to the pigeon's behavior.
In this case it was possible to record the 'extinction' of the response when theclock was turned off and the magazine was no longer presented at any time. Thebird continued to respond with its characteristic side to side hop. More thanl0,000 responses were recorded before 'extinction' had reached the point atwhich few if any responses were made during a 10 or 15 min interval. When theclock was again started, the periodic presentation of the magazine (stillwithout any connection whatsoever with the bird's behavior) brought out atypical curve for reconditioning after periodic reinforcement, shown in Fig. 1.The record had been essentially horizontal for 20 min. prior to the beginning ofthis curve. The first reinforcement had some slight effect and the second agreater effect. There is a smooth positive acceleration in rate as the birdreturns to the rate of responding which prevailed when it was reinforced everymin.
When the response was again extinguished and the periodic presentation of foodthen resumed, a different response was picked up. This consisted of aprogressive walking response in which the bird moved about the cage. [p. 171]The response of hopping from side to side never reappeared and could not, ofcourse, be obtained deliberately without making the reinforcement contingentupon the behavior.
The experiment might be said to demonstrate a sort of superstition. The birdbehaves as if there were a causal relation between its behavior and thepresentation of food, although such a relation is lacking. There are manyanalogies in human behavior. Rituals for changing one's luck at cards are goodexamples. A few accidental connections between a ritual and favorableconsequences suffice to set up and maintain the behavior in spite of manyunreinforced instances. The bowler who has released a ball down the alley butcontinues to behave as if he were controlling it by twisting and turning his armand shoulder is another case in point. These behaviors have, of course, no realeffect upon one's luck or upon a ball half way down an alley, just as in thepresent case the food would appear as often if the pigeon did nothing -- or,more strictly speaking, did something else.
It is perhaps not quite correct to say that conditioned behavior has been set upwithout any previously determined contingency whatsoever. We have appealed to auniform sequence of responses in the behavior of the pigeon to obtain anover-all net contingency. When we arrange a clock to present food every 15 sec.,we are in effect basing our reinforcement upon a limited set of responses whichfrequently occur 15 sec. after reinforcement. When a response has beenstrengthened (and this may result from one reinforcement), the setting of theclock implies an even more restricted contingency. Something of the same sort istrue of the bowler. It is not quite correct to say that there is no connectionbetween his twisting and turning and the course taken by the ball at the far endof the alley. The connection was established before the ball left the bowler'shand, but since both the path of the ball and the behavior of the bowler aredetermined, some relation survives. The subsequent behavior of the bowler mayhave no effect upon the ball, but the behavior of the ball has an effect uponthe bowler. The contingency, though not perfect, is enough to maintain thebehavior in strength. The particular form of the behavior adopted by the bowleris due to induction from responses in which there is actual contact with theball. It is clearly a movement appropriate to changing the ball's direction. Butthis does not invalidate the comparison, since we are not concerned with whatresponse is selected but with why it persists in strength. In rituals forchanging luck the inductive strengthening of a particular form of behavior isgenerally absent. The behavior of the pigeon in this experiment is of the lattersort, as the variety of responses obtained from different pigeons indicates.Whether there is any unconditioned [p. 172] behavior in the pigeon appropriateto a given effect upon the environment is under investigation.
The results throws some light on incidental behavior observed in experiments inwhich a discriminative stimulus is frequently presented. Such a stimulus hasreinforcing value and can set up superstitious behavior. A pigeon will oftendevelop some response such as turning, twisting, pecking near the locus of thediscriminative stimulus, flapping its wings, etc. In much of the work to date inthis field the interval between presentations of the discriminative stimulus hasbeen one min. and many of these superstitious responses are short-lived. Theirappearance as the result of accidental correlations with the presentation of thestimulus is unmistakable.
(Manuscript received June 5, 1947)