Apprehending a series of numerals and subsequently repeating them in their correct sequence must either involve the ordered storage of the individual items or the storage of information relating to that order. Both information identifying an item and information defining its place in the sequence must be available for the S for successful performance of the task.
The potential separability of the two kinds of information involved is not easy to demonstrate. If a subject makes a single error of identity, reporting either an incorrect number or a blank, it may indicate that he has lost only identity information. This argument, however, is inconclusive, because if the subject had acquired no information at all regarding the offending item, but complete information regarding other items, the outcome would be the same. The inversion of two digits or the permutation of three or more digits, on the other hand, furnishes a compelling argument because it is prima facie evidence that the identity information is accurate while the positional information is incomplete or distorted.
The purposes of the present study were to demonstrate that the phenomenon of transposition could be observed under laboratory conditions and to describe the locus of its probable occurrences in a given sequence.
METHOD
The stimulus materials were 80 4x6 notecards upon which digit sequences were typed in elite type. The 80 sequences were divided into four sets of 20 cards each. The first set showed sequences 5 digits in length; the second and third sets showed 6-digit sequences; the fourth set showed 7-digit sequences. The sequences contained the digits 1-9 with never more than a single digit repeated on a given card. The repeated digit, if any, never occurred without at least one intervening digit. The sets were presented in the order given above. A random arrangement was made of each set. This arrangement was used in the forward order for half the Ss and in reverse order for the remainder. The materials were presented in a mirror-type tachistoscope.
The Ss were 14 undergraduates in introductory psychology courses. The S held a plunger switch which activated the tachistoscope. The E gave a ready signal when the stimulus card was in place. The S activated the tachistoscope when he was ready. He was instructed to say the digit sequence aloud immediately after its appearance, and was encouraged to guess if he was not sure of one or several items. The S always knew how many digits were shown. Responses were recorded on a tape recorder. Only one exposure per sequence was given and the S was not given any information about the correctness of his response.
Two practice sequences with ascending limits were given to accustom the S to the apparatus and to provide the E with some information on threshold. The test sets were then presented. One-minute rest periods were given after each set.
Exposure duration was individually adjusted for each S. Pilot work suggested that transpositions occurred most readily at the point where the S was beginning to miss single digits in the sequence. Therefore, the E attempted to have the exposure interval long enough that the proper number of digits would be reported but short enough that they were not always reported with complete accuracy. After every five cards the E decided whether to keep the exposure the same or to change it. Since there were practice effects in the task and since the task became appreciably more difficult, E continued to modify the presentation time during the course of the experiment. Generally 10-msec steps were employed in such changes but with an occasional S whose performance was markedly inferior the step span was increased.
RESULTS AND DISCUSSION
Responses were transcribed from the tape and scored. The following categories were employed:
C -- correct E -- gross error I -- one digit incorrect, or 'blank' reported for a single missing digit T -- transposition of adjacent pairs of digits with rest of sequence correct T1 -- transposition of three or more digits with remainder correct IT -- transposition of two or more digits and one digit incorrect O -- other errors, usually experimental or equipment errors
Results are given in terms of these scoring categories in Table I. Examination of the table shows that transposition provides an important source of errors. It is, however, difficult to find a statistical model which would provide a precise evaluation of the statistical significance of such errors. As Woodworth and Schlosberg [4] point out in their discussion of scoring memory span, any scoring system which attempts to provide separate credit for accuracy and order is arbitrary. Thus, any statistical model must make assumptions about the S's strategies on the one hand (e.g., Did the S note that digits can repeat within a sequence and, if so, did this alter his guessing behaviour in the appropriate manner?) and the interrelationships of error types (which we do not yet know) on the other. Fortunately, the question is not crucial for present purposes. The only question that need be asked here is whether there is more transposition than would be expected by chance (however chance is to be defined).
Table I. Distribution of Responses by Categories for Each Stimulus Set (280 items) --------------------------------------------------------------- Scoring code 5 digits 6 digits 6 digits 7 digits --------------------------------------------------------------- C 130 60 65 12 E 21 67 47 122 I 50 43 50 21 T 23 23 32 12 T1 2 14 5 9 IT 44 64 73 96 O 10 9 8 8 ---------------------------------------------------------------
We think the answer to that is clear. Of the 140 errors on the 5-digit sequences, 69 involve transpositions; of the 211 and 207 errors on the 6-digit sequences, 101 and 110 respectively contain transpositions; of the 260 errors on the 7-digit set, 117 contain a transposition. It is evident that until the task becomes exceedingly difficult (and the response unscorable), approximately half the errors involve transpositions. No reasonable 'guessing' or chance model we have contrived can account for this finding. It seems simplest to conclude that in a large portion of the errors the S has the correct information as to the identity of some of the digits but has lost the information as to their precise location.
As a first step in describing the phenomenon, the distribution of errors over positions was obtained for the simplest errors of both types. Table II shows the location of the error for each instance when one digit was incorrect (I error). Table III gives the location of the pair of items transposed when only single transposition was observed (T error). It can be seen that both sets of distributions for all sequence lengths show the same serial position effect, suggesting that both kinds of error are susceptible to the same form of interference. If one has all the individual items, he is least likely to have precise position information in the latter half of the sequence. Conversely, if one lacks the identity of an item, it is most likely to be one from a position in the latter half of the list. The most probable transposition for any particular length of sequence appears to involve the inversion in order of the item in the most difficult position in the sequence and the item immediately preceding it.
The psychological nature of each kind of error is not at all clear but it seems likely that future work will help narrow the alternatives. It would be particularly interesting to know, for example, whether transposition is equally common when the experiment is conducted with Sperling's procedure or with a rapid sequential procedure such as that used in short-term memory research.
While we cannot at present make any decision as to the underlying nature of the transposition phenomenon, we feel that this experiment concurs with common experience in pointing to a pervasive distortion in the visual perception and reporting system which theories of information processing must take into account.
Table II. Position of Errors in Cases of a Single Incorrect Digit Position ------------------------------------- Sequence 1 2 3 4 5 6 7 -------------------------------------------------- 5-digit 1 1 4 34 10 - - 6-digit 0 2 1 4 31 6 - 6-digit 0 1 3 11 25 10 - 7-digit 0 0 2 0 7 8 4 -------------------------------------------------- Table III. Position of Transposed Digits in Errors Involving a Single Transposition Positions transposed Sequence 1-2 2-3 3-4 4-5 5-6 6-7 5-digit 0 2 18 3 --- --- 6-digit 0 2 1 17 3 --- 6-digit 0 5 1 21 5 --- 7-digit 0 0 0 3 7 2
APPEN
DIX III
NOTES ON THE AUTONOMIC NERVOUS SYSTEM* * See p. 140.
In general (but there are, as we have seen, important exceptions) the action of the two divisions is mutually antagonistic: they equilibrate each other. The sympathetic division prepares the animal for emergency reactions under the stress of hunger, pain, rage and fear. It accelerates the pulse, increases blood pressure, provides added blood-sugar as a source of energy. The parasympathetic division does in almost every respect the opposite: it lowers blood pressure, slows the heart, neutralizes excesses of blood-sugar, facilitates digestion and the disposal of body wastes, activates the tear glands -- it is generally calming and carthartic.
Both divisions of the autonomic nervous system are controlled by the limbic brain (the hypothalamus and adjacent structures). Different authors have described their functions in different terms. Allport [1] related the pleasurable emotions to the parasympathetic, the unpleasant ones to the sympathetic. Olds [2] distinguishes between 'positive' and 'negative' emotive systems, activated respectively by the parasympathetic and sympathetic centres in the hypothalamus. From a quite different theoretical approach, Hebb also arrived at the conclusion that a distinction should be made between two categories of emotion, 'those in which the tendency is to maintain or increase the original stimulating conditions (pleasurable or integrative emotions)' and 'those in which the tendency is to abolish or decrease the stimulus (rage, fear, disgust)'. [3] Pribram has made a similar distinction between 'preparatory' (warding-off) and 'participatory' emotions. [4] Hebb and Gellhorn distinguish between an ergotropic (energy-consuming) system operating through the sympathetic division to ward off threatening stimuli, and a trophotropic (energy-conserving) system which operates through the parasympathetic in response to peaceful or attractive stimuli. [5] Gellhorn has summarized the emotional effects of two different types of drugs: on the one hand the 'pep pills', such as benzedrine, and on the other the tranquilizers, such as chlorpromazine. The former activates the sympathetic, the latter the parasympathetic, division. When administrated in small doses, the tranquillizers cause 'slight shifts in the hypothalamic balance to the parasympathetic side, resulting in calm and contentment, apparently similar to the state before falling asleep, whereas more marked alterations lead to a depressive mood'. [6] The benzedrine-type drugs, on the other hand, activate the sympathetic division, cause increased aggressiveness in animals, and in man in small doses alertness and euphoria, in larger doses over-excitation and manic behaviour. Lastly, Cobb has summed up the implicit contrast in a pointed form: 'Rage is called the most adrenergic, and love the most cholinergic characteristically parasympathetic reaction'. [7]
What this short survey indicates is, in the first place, a general trend among authorities in this field to distinguish between two basic categories of emotion -- though the definitions of the categories differ. In the second place, there is a general feeling that the two categories are correlated to the two divisions of the autonomic nervous system.
APPENDIX IV
UFOs: A FESTIVAL OF ABSURDITY*
* See above, Chapter XIV.
There is an understandable, but questionable connection in the public's mind between CETI (communication with extraterrestrial intelligence) and UFOs (unidentified flying objects, vulgarly called flying saucers). At the CETI conference in 1971*, UFOs were only mentioned in passing, and none of the participants suggested that they were of extra-terrestrial origin. The main reasons for this scepticism were summed up by the astrophysicist Carl Sagan:
Such [advanced extraterrestrial] civilisations will be inconceivably in advance of our own. We have only to consider the changes in mankind in the last 104 years and the potential difficulties which our Pleistocene ancestors would have in accommodating to our present society to realize what an unfathomable gap 108 to 1010 years represents, even with a tiny rate of intellectual advance. Such societies will have discovered laws of nature and invented technologies whose applications will appear to us indistinguishable from magic. There is a serious question about whether such societies are concerned with communicating with us, any more than we are concerned with communicating with our Protozoan or bacterial forebears. We may study microorganisms, but we do not usually communicate with them. I therefore raise the possibility that a horizon in communications interest exists in the evolution of technological societies, and that a civilization very much more advanced than we will be engaged in a busy communications traffic with its peers; but not with us, and not via technologies accessible to us. We may be like the inhabitants of the valleys of New Guinea who may communicate by runner or drum, but who are ignorant of the vast international radio and cable traffic passing over, around and through them [my italics].' * See above, p. 282a.
The words that I italicized refer -- as the context indicates -- to the hypothesis that UFOs may be space-vehicles, or automated probes released from larger mother-ships (like the landers released from the Viking orbiters). In spite of the aerial acrobatics which they are reported to perform, the appearance and behaviour of UFOs is too close to 'technologies accessible to us' to qualify as fit for magicians. As to the argument that we are too primitive to be worthy of study, one could of course object that our ethologists and anthropologists do not share this arrogant attitude towards lowlier forms of life and culture. But there is again a counter-argument: if our galaxy is as brimful with life as the astrophysicists tell us, then there must be some system of priorities for the magicians' exploratory survey-programmes, and even among lowly civilizations we may not be of special interest. If, on the other hand, we are as interesting as our terran chauvinism whispers into our ears, then why do UFOs so studiously avoid contact with us, by radio, or lasers or holographs -- not to mention some advanced techniques of ESP? Evasion of contact is indeed the chief characteristic and common element in the antics of flying saucers. And as for the few cases in which contact with 'humanoid' UFO passengers is alleged, they represent, as one eminent ufologist wrote, 'a veritable festival of absurdity'. [2]
Why, then, bring up this disreputable subject at all? Firstly, because it seems to me that it would be cowardly, after discussing extraterrestrial civilizations, to pass over UFOs in silence -- although, as I said, the two subjects may be unconnected. In the second place, UFOs -- unidentified (or unexplained) flying objects as distinct from IFOs (identified flying objects) do seem to exist, whatever their origin. This belief is apparently shared by nearly a half of American astronomers. The following extract is from an article in the New Scientist:
Unidentified flying objects (UFOs) 'certainly', 'probably' or at least 'possibly' deserve scientific study, say 80 per cent of respondents to a questionnaire sent to members of the prestigious American Astronomical Society (AAS). Of the 2,611 members, 1,356 replied and of these only 20 per cent thought the study unnecessary. This means that some 40 per cent of the AAS members would support a UFO investigation. Sixty-two respondents to the questionnaire even claimed to have seen a UFO, says a report from Stanford University, California, where the survey was conducted . . . In five of the reported sightings the objects were seen through telescopes and in three cases though binoculars. In seven cases there were photographs; the organizer of the survey, Professor Peter Sturrock. a Stanford astrophysicist, believes he can find non-UFO explanations for two of them. Sturrock is a strong supporter of a renewed investigation of UFOs. He criticizes the Condon Report of 1969, which dismissed the UFO phenomenon and closed 'Project Blue Book', the US Air Force's listing of UFO sightings by its personnel. 'It is essential that scientists begin an exchange of relevant information,' says Sturrock, 'if they are to contribute to the resolution of the UFO problem.' [3]
What is particularly impressive are those sixty-two astronomers -- that is, five per cent of the respondents -- who claimed to have actually seen a UFO. This is much more remarkable than the last Gallup poll on the subject, in 1973, which indicated that 15 million Americans had claimed to have seen UFOs, and that 51 per cent of the population believed
that the UFO phenomenon exists.' Where the general population is concerned, such figures can always be explained, or explained away, as the result of mass-hysteria and optical illusions. But professional astronomers one assumes to be immune to such errors.
The term 'ufology' was coined by Air-Marshal Sir Victor Goddard in 1946, when he represented the Royal Air Force on the combined Chiefs of Staff advisory committee in Washington. He then thought UFOs were a hoax, and was instrumental in persuading President Truman to call off the search for UFOs by the US Air Force, which Truman had inaugurated earlier to probe the rumours of intruders in the American air space. But later on Goddard changed his mind. In his book, Flight Towards Reality, he writes:
In nearly thirty years there must have been two hundred thousand claims of UFO sightings recorded in one hundred countries at the least. That is the kind of basis of UFO statistics now available in North and South America. Reports upon ten thousand thorough-going checks have furnished evidence which leads to two conclusions: The first is that only six per cent of so-called UFO sightings remain unsolved and unexplained; the second is that, of the unsolved residue -- twelve thousand unidentified by now -- some surely were quite rightly held to be what they were claimed to be -- objects of reality but unknown in origin and technicality . . . So, they were UFO -- nothing else -- and that is not to be denied even by sceptics of the deepest dye. [5]