left-handedness

taken from The backward child [9] by Cyril Burt

a briefing document

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summary by abelard
chapter X: left-handedness by Cyril Burt
end notes

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summary by abelard

The excerpt below on left-handedness starts with a lot of stuff on defining and counting left-handedness/right-handedness.

Burt notes more left-handedness among mentally backward and more among boys (5.8%) than girls (3.7%).

Burt speculates that the increase among backward may be weakness of both arms, rather than preference.

Further figures:

So the percentage of lefthanders is rising. This abstraction is from the 1951 printing. The first edition was in 1937, the second in 1946, and the third in 1950.
Thus it is very likely that most of this dates from 1937.

When I’ve done checks, left-handedness is nearer to 10%, and I did not notice a sex difference, but I was not very interested! I expect that, like most statistics, the values vary in different populations.

Burt comes to the belief that people are not really dvided by left- and right-handedness, but the left and right hand work together as a team, with the traditionally nominated, dominate hand being assigned to tasks requiring precision, and the other, more specialised, being used for strength or steadying purposes. One hand writes while the other steadies the paper, one hand guides the broom, while the other anchors it.

Burt notes that more tics, nervousness and other problems in left-handers. On page 290, he refers to, “[...] the older practice which maintained that any child holding a pen in his left hand should have his knuckles rapped [...] ”, but does not make the rather obvious connection between this sort of action and other emotional difficulties.

CHAPTER X
LEFT -HANDEDNESS

I. Methods, (definitions. The whole section on left-handedness comprises 90 pages: pp. 270 - 359.)

Complexity of the Problem.—Of all the special motor disabilities found among school children, that which interferes most widely with the ordinary tasks of the classroom is left-handedness; and no question is put by the teacher to the school psychologist more frequently than this: ‘How should I deal with a left-handed pupil?’ A condition so common and so perplexing will require examination at some length.

One fact must be emphasized at the outset. Left-handedness is by no means so definite a characteristic as is popularly supposed. Right-handedness and left-handedness are relative terms - indeed, somewhat ambiguous terms, not sharply defined alternatives, mutually exclusive and absolutely opposed. To describe a child as left-handed without further explanatory details conveys very little information about his manual habits generally and still less about his neuro-muscular co-ordination as a whole. Usually it simply means that the teacher has observed the child regularly writing with his left hand, and is tempted to infer some inherent and abnormal asymmetry in his nervous organization or brain.

Closer inquiry soon reveals that left-handedness can manifest itself in very different forms and with very different degrees of strength. Moreover, the mixed forms and the milder degrees prove quite as common as the thoroughgoing or extreme. How many persons are consistently left-handed—or, for that matter, consistently right-handed—for every transaction in which hands are required? We shall find ample evidence to show that, quite apart from any general inclination such as might be ascribed to an innate or hereditary tendency, individual preferences in this movement or in that are dictated now by habit, now by special circumstance, and now by the intrinsic delicacy of the muscular co-ordinations involved. Accordingly, mere casual observation of some particular stereotyped action, like writing or drawing, will be of little value by itself: such observations need to be supplemented by an inquiry into the conditions under which the action has been learnt, and by specially devised tests which will estimate the strength of any original or ineradicable bias.

Definition and Tests.—Before we can devise a proper test, we must clarify our conception of what left-handedness denotes. An exact definition is essential. By left-handedness [1] I understand a consistent tendency (whether congenital, or induced post-natally by accident or by some other change in the hand or its neuro-muscular apparatus) to undertake new dexterities with the left hand rather than with the right. It must be judged, therefore, not so much by long-standing habits as by an unfamiliar task, and not by a single action, but by several. The points to observe are not merely the child's customary mode of using the pencil or pen, but his power to throw a ball or pick up a weight, to hammer or bore, to sort marbles, deal cards, cut with a knife or scissors, stir with a teaspoon in a cup, turn a handle or wind cotton round a reel, more easily with the one hand than with the other. Probably the best single test for rapid use is to ask the child to cut paper with loose-riveted scissors. [2] Incidentally it is at times instructive to make a note of any half-unconscious manual habits that are not influenced by social pressure. For example, in clasping the hands, which thumb is placed on top? And perhaps a little more significant-in folding the arms, which hand is placed on top of the opposite arm?

If quantitative measurements are required, any of the tests of manual dexterity described above may be employed. The child carries out the test first with the hand that he usually writes with, and then with the other. The index of left-handedness most commonly adopted (generally, but inaccurately, termed ‘index of right-handedness’ or ‘dextrality’) is given by the simple formula L/R x 100, where R and L denote the number of marks scored with the right hand and with the left respectively; a somewhat better measure of right-handedness is given by the formula R-L/R+L.

So important is it to detect tendencies towards left-handedness at the earliest possible moment that a word or two may be added on the testing of young infants. The critical period lies between six and fifteen months. At this tender age a rough ‘reacting test’ is the easiest to apply. Provisionally, in default of first-hand studies in this country, I suggest that the experimenter should adopt the procedure and the norms worked out by Gesell in America. ‘A red rod’ (e.g. a red pencil) ‘is held in the median plane, and the child is encouraged to make repeated efforts to grasp it’. With the shy, the dull, and the mentally deficient, a sweet wrapped in coloured paper is sometimes more effective. The examiner is also instructed to note ‘whether the child uses one hand independently in his own spontaneous manipulations’—e.g. in picking things up or flinging them down.[3]

Right- and Left-handedness in Two-handed Operations.—With older children more recent investigators have urged that tests such as I have mentioned, which they regard as tests of uni-manual activities only, should be accompanied by tests and inquiries upon bi-manual activities. These they divide into two sub-groups on a basis which at first sight seems purely empirical. The typical activities chosen are (i) throwing a ball (for the uni-manual test), and (for the bi-manual tests) (ii) using a cricket bat, a golf club, or an axe, and (iii) using a pitchfork, a shovel, or a broom—the use of the bat and the broom being generally taken as the most representative. A ‘handedness formula’ is then proposed which will indicate, by three letters, each individual’s habits in each of the three directions. Thus if he (i) throws with his right hand, (ii) bats with his left, and (iii) sweeps and digs with his right, he is classed as R L R. But what are we to regard as ‘right-handed’ batting or sweeping, when by hypothesis both hands are used? The criterion proposed is the hand which is held ‘nearer the business end of the instrument’—that is, the lower end, the end farthest from the shoulders.

To me this latter principle appears quite mistaken. The real question is-which of the two hands executes the greatest movement and consequently undertakes the more delicate and more active task of guiding or directing the instrument? In batting, as in wielding a hockey stick or golf club, the fulcrum is near the body, and the ‘business end’ executes the wider movement. The right-handed bats man, therefore, almost always places his right hand below the left. But in sweeping or digging it is usually the nearer end of the broom or spade that is chiefly moved. With the broom, it is true, various methods may be adopted. But in digging the movements are fairly uniform: the left hand generally holds the middle of the spade and supplies a fulcrum; the right hand moves the handle to balance the heavy earth at the other end. Should we call the ordinary method of using a billiard cue ‘left-handed’ because the left hand is ‘nearer the business end’? With each of these instruments, apart from special conditions (e.g. sweeping in awkward corners), the dominating tendency is for the operator to work always on the same side of the body. Thus a right-handed person keeps the handle of the bat, broom, or spade mainly on his right. It follows that the relative positions of the two hands on the handle will naturally be inverted for swinging and for thrusting movements respectively—for swinging as in using a cricket bat, and for thrusting as in sweeping, digging, or striking with a spear or pushing with a cue.

If these observations are correct, the third letter in the usual ‘handedness formula’ should evidently be reversed: R R L should be called R R R, and so throughout the series. And, in point of fact, the figures given by all investigators show that, in using the spade or broom, the vast majority of persons, who are otherwise right-handed, place the left hand down—i.e. ‘nearer the business end’. It seems wholly illogical to designate this a left-handed procedure.

Manual Types.—Those who lay stress on the difference between bi-manual and uni-manual operations believe that we must recognize a number of clear-cut types. Instead of splitting the whole population into two simple categories, the right-handed and the left-handed respectively, there are, they assert, at least half a dozen subdivisions. Each type is different in nature, and calls for a different treatment in the classroom. Hence they argue that all the earlier work on left-handedness as it affects the child at school is invalidated from the outset. It over-simplifies the problem.

Their detailed classification follows from the formula given above. A twofold division, as we have seen, is applied and re-applied on three successive principles. In theory this should furnish 2³ = 8 possible types. But in practice, it is said, ‘there is no such combination as R L R and L R L .... When a man is seen throwing with the right hand and batting with the left hand, then it is certain that he will sweep and pitch hay with the left hand.’ Hence we are left with only six.[5]

The suggestion emanates from America, where most of the more recent inquiries have been carried out. To check their deductions, and to verify my own hypotheses, I have collected the following data from English adults. The right-handed persons were mainly post-graduate students at a training college; and to obtain a larger number of left-handed types I have extended my investigations to all the alleged cases of left-handedness I have encountered at public lectures or in private life. The following table summarizes the chief results (Table XVIII)

At first sight the variety of combinations appears somewhat bewildering. They are largely accounted for when we look more closely into the nature of those two-handed activities that are taken as the basis of the sub-classification. As we have already seen, the movements in the first set (using a bat or a golf club) involve a swinging stroke, carefully aimed and skilfully applied: they are, in fact, difficult and dexterous operations; moreover, they are learnt and practised in teams or social groups; hence nonconforming methods are apt to be quizzed and criticized until they are brought into line. The activities in the second set (sweeping and digging) are by comparison coarse and unskilled processes: as usually carried out, they involve a push or thrust, and demand strength rather than precision. They are generally undertaken alone; hence individual oddities may pass uncorrected.[6]

The following conclusions, suggested by the figures in the table, will now become intelligible.

1. The commonest type of all is the type that is consistent throughout.[7] The right-handed tend to be right-handed for all the operations tested; the left-handed (except for male cricketers) tend to be left-handed. But the tendency is far from universal: taken together, the exceptions are more numerous than the rule.
2. In the main, it is the degree of skill required, much more than the number of hands involved, that determines how the hands shall be used. Thus hand-preference is much more likely to vary in the different two-handed operations, which may be either skilled or unskilled, than in different skilled operations, which may be either one-handed or two-handed. It follows that, among right-handed and left-handed alike, the preference in skilled two-handed activities, such as batting, nearly always follows the preference in one-handed activities, such as throwing. The only noteworthy instance to the contrary is that of right-handed batting among left-handed men, which is explicable by social pressure.
3. Among the many who consequently employ the same hand for aIl difficult or delicate movements, whether the total operation is of the one-handed type or of the skilled two-handed type, the procedure adopted for operations of the unskilled twohanded type is fairly well divided. Sorne keep the skilled hand near the business end, so preserving the same position for all two-handed operations, skilled or unskilled, and holding brooms as though they were bats. Others, more appropriately, keep the skilled hand near the guiding end—that is, near the free end of the handle, and so follow out their one-handed tendency; this practice is commoner among the women-no doubt because for them sweeping is a relatively skilled operation.
4. Among the right-handed, those who throw with one hand and bat with the opposite are distinctly scarce, especially when the batsman is a male. Among the left-handed they are more abundant, and, indeed, with the males provide the commonest type. These latter are mainly men in whom a left-handed tendency is present to a mild degree: for batting they have learnt the orthodox right-handed fashion, but have kept or cultivated a left-handed method for bowling, throwing, and tossmg.[8]
5. Finally, when a person uses opposite hands for onehanded and for skilled two-handed operations respectively, the procedure which is most consistent with both of these practices is almost invariably adopted for unskilled two-handed operations: e.g. the man who throws with the left hand and bats with the right, will use his left hand to guide a broom in sweeping and keep his right hand down on the handle-thus holding the broom much as he holds a bat.
   
   I conclude that we cannot regard these differences as signalizing fundamentally distinct or basic types. The right- or left-handed aptitude, whichever it may be, tends to dominate throughout, though in differing degrees with different persons. When comparatively weak, it may be easily overcome by circumstance or tradition, and may never. come definitely into play in activities that require little skill and can be performed in various ways according to the conditions of the moment (as, for example, wielding an axe or a broom). When strong, it may influence every action.
   How far do these considerations affect inquiries on children of school age? Plainly, among boys and girls of the class we are studying, it would be all. but useless to· attempt such classifications. Among the elementary school population in London few of the girls play cricket or hockey; and not many of the boys use a shovel or a broom. So far as my observations go, the younger boys at cricket and the younger girls in sweeping seem to follow almost without exception their one-handed preferences. The older left-handed boys who play under the supervision of a master are usually taught to comply with the traditional practice; and the older girls who attend housewifery classes accept the methods of mopping and sweeping in which they are instructed. Though the degree of skill achieved by a left-handed child with a right-handed method is admittedly a little poorer, in neither case does there seem to be any irksome struggle in ma king the adaptations required. Doubtless because no fine accuracy is imperatively demanded, there is nothing like the conflicts that are observable in learning to use the pen. Accordingly, if my view is right, these further subdivisions have no wide bearing on the problem of the teacher, and, so far as children are concerned, are of interest only here and there in analysing the general tendencies of certain individuals. In every case what we really need are tests of ease of learning, not of habits already learnt. I have, therefore, not considered it necessary to supplement what some would regard as uni-manual tests with extensive testing for bi-manual activities.[4] In the main I have contented myself with the methods and observations described above.

Questionnaires and Group-tests.—For group inquiries a questionnaire on the following lines will pick out about 90 per cent. of those with left-handed tendencies.
‘Which hand would you use

1. to write,
2. to draw or paint,
3. to throw a ball,
4. to strike with a racket, stick, or bat,
5. to hold a penknife,
6. to cut with a pair of scissors,
7. to carry a cup of water or lift a glass in drinking,
8. to clean your teeth,
9. to wind a clock or watch or musical-box,
10. to reach a book or plate on a high shelf almost out of your reach?

Imagine yourself doing these things before you answer; and underline the true reply’. The words ‘left’, ‘right’, ‘either hand’, are printed as alternative answers against each question.

For group-tests in class the simpler of the tests of manual speed and dexterity can be readily applied. In my own investigations the ‘tapping’, ‘aiming’, and ‘tracing’ tests were chiefly employed.[8]

end note

1. The etymology of the word is suggestive. In the present sense the word, ‘left’ is not connected, as is so often supposed (e.g. by Webster’s Dictionary, s.v.), with the verb ‘to leave’. It is derived from the Anglo-Saxon ‘lyft’ = weak, broken (akin to ‘lopt’ or ‘lopped’ and possibly to the German ‘lieht’ and ‘leieht’, and to ‘light’ in the sense of fragile). Thus to the Saxon the left arm meant the weak arm: to the Latin and the Greek (if we may trust the usual derivation) the left hand meant the shield hand (laeva, laia—archaic and poetic words), or, later on, the pocket hand (sinister, a less poetic word, from the ‘sinus’ of the toga). These designations, as we shall see in a moment, might almost be taken as emblematic of the two contrasting theories of the function of the left hand in man.
   
   
2. In their earlier experiments investigators relied solely or mainly upon the dynamometer. The data collected by the Galton laboratory and analysed by Pearson and Woo were based on strength of grip; and similarly with much of the evidence in regard to primitive races. But the dynamometer is primarily a test of strength; whereas right- or left-handedness as I have defined it turns primarily on capacity for skill. I find that as many as 41 per cent. of those who habitually use the left hand for skilled actions nevertheless have a stronger grip with the right (see also Whipple, loc. cit.).
   
   
3. Mental Growth of the Pre-School Child, p. 80. Something a little more precise and detailed, however, is urgently needed in regard to both methods and results. Miss Woolley’s method (loc. cit. inf.)—placing two coloured discs side by side in front of the child—though adopted by many early investigators, seems still less satisfactory. It yields one fact of theoretical interest: with this procedure one can often observe a definite tendency to look towards the disc on the right quite apart from any movement of the right hand.
   
   
4. The suggestion seems first to have been put forward by J. Merle Rife (‘Types of Dextrality,’ Psycho. Rev., XXIX, 1922, pp. 474-81). An extended investigation along these lines, made with the aid of a grant from the American National Research Council, is described by June E. Downey, ‘Types of Dextrality and their Implications,’ Am. Journ. Psych., XXXVIII, 1927 (pp. 317 et seq.).
   
   
5. Rife, loc. cit., p. 4-77. No figures, however, are given in support of this assertion. According to my own results (cf, Table XVIII, last line), the rejected combinations, though rare, are by no means non-existent.
   
   
6. Generally speaking, with the unsophisticated sweeper the natural movement in pushing a broom is rather like the movement in pushing a billiard cue, a bayonet, or a spear. The butt end tends to swing back past the body; the active hand is therefore nearer the butt. That this is the main factor in determining the relative position of the hands in sweeping may be seen on contrasting it with the opposite motion of paddling. In paddling a canoe it is the blade and not the handle that comes back past the body; consequently, the active hand must now be nearer the blade, while the other hand rests on the butt end. This resembles the position in batting, except that, since the strong stroke is now a backward pull instead of a forward drive, the palm curves round the front of the handle instead of round the back. For efficient sweeping indoors, however, some skill is required; and the movements, and consequently the hand positions, may often be altered according to the part of the room to be swept. Indeed, many women consider themselves ambidextrous for sweeping. Further, at housewifery classes, sweeping is generally performed under criticism and instruction. Hence girls tend to adopt a more conventional and therefore a more nearly unanimous position. In sweeping indoors the girl is usually instructed to pull or draw rather than to thrust or push, and to press and keep the bristles down rather than to fling them (and the dust) up and away. The position of the hands relative to each other will usually remain the same; but (and this is a point that is missed by psychological writers) the same position of each hand relative to the handle is now reversed: the left palm is now nearly always placed over the handle, and the right usually under it, because the ‘business end’ has to be pressed down—a motion which is given best by the left hand with right-handed persons. In lifting the ‘business end’ of such an instrument up (as in using a pitchfork) the left palm will be under the handle and the right usually above it. In thrusting (e.g. in striking with a spear) the palms are usually at the side. Observe that, when a right-handed man thrusts, the positions of his hands, both as regards each other and as regards the surface of the handle, are very similar to those adopted when a left-handed man bats. Hence the man’s method of holding the more familiar bat often influences him when he comes to handle the less familiar broom, for the male method of sweeping is generally to thrust or shove: and thus he is sometimes tempted to sweep left-handed. Similarly, the woman’s method of holding the broom often influences her when she comes to pick up a bat. These somewhat thoughtless and awkward positions, assumed with unfamiliar instruments, are especially noticeable among those who are less efficient in novel activities of every kind, i.e. among the less intelligent.
   
   
7. This may seem at first sight to contradict Rife’s statement that ‘the type which throws, bats, and uses the spade right-handed ... seems to be the least common’ (pp. 474-5); but it must be remembered that what Rife terms a right-handed use of the spade is here regarded as left-handed.
   
   
8. In golf, it may be noted, and in mowing, the right-handed form of the club and scythe often compels the learner to follow the traditional method. It is true that golf clubs and cricket bats exist for the left-handed; but I have never heard of a left-handed scythe.
   
   
   
9. A questionnaire and a series of such tests, specially devised for discovering left-handedness, together with the results obtained by their use, have recently been described by Durost, loc.cit.sup.
   
   
10. The backward child by Cyril Burt,
    University of London Press Ltd, 1951
    [first published 1937]
    quote taken from pp270 - 280 of 3rd edition. reprint.

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