GN 233 J79 \* . - ■ \ ■f^-^?>. &H ^.5 3 J 7/f Cornell University Library GN233 .J79 A study of handedness. olin 3 1924 031 144 797 DATE : DUE 1 1 mM^ h-^4##p n jf ^ 15slEa H *"**'WInlv # 1 CAYLORD PRINTED INU.S. A. A Study of Handedness By W. FRANKUN JONES, Ph. D. Head of Depaurtment of Education and DirecStor of Graduate CSurses University of South Dakota I Price 35 cents, prepaid EQUIPMENT FOR DETERMINING HANDEDNESS. In order to meet the demands of school officials, physicians and others interested in the scientific determination of handed- ness, arrangements have been made to supply the brachiometer as described in this bulletin, together with the anthropometric tape and a copy of the "Study of Handedness," by Dr. W. Franklin Jones, at ten dollars for the complete equipment, prepaid to any address. Copies of the "Study of Handedness" will be supplied at 35 cents each, or $3.50 per dozen, prepaid. Capital Supply Company, Pierre, S. Dak. A Study of Handedness By W. FRANKLIN JONES, Ph. D. • Head of Department of Education and Director of Graduate Courses University of South Dakota Price 35 cents, prepaid ^ ■ •^ a H 5 1^ a ^ i ° eg o O c M M Eh A STUDY OF HANDEDNESS. The left handed child has been an educational bone of contention. Tradition has decreed that left handedness is only individual habit, and so its followers have set to work industriously to transform all left handers into right hand- ers. Many cases of left handedness have apparently disap- peared under this treatment, and thus on the surface, at least, tradition has been justified. Only here and there has been found a child so stubbornly left handed that no train- ing, however persistent, has been quite able to transfer him to the right hand and arm ; and it is this little group of sur- vivors that has set many an investigator to work on the problem of handedness. On the other hand, there have been those v/ho, after more or less careful study, have maintained that left handed- ness is a bom trait, and that no parent or teacher should as- sume to interfere with nature's process. They have pointed out that the majority of the human race is undoubtedly right handed born, but that there is a respectable minority that is left handed bom; yet the evidence on which these claims have been based has been without scientific proof, and the proportion of bom right and and born left handed indi- viduals has not been established, indeed can not be estab- lished until some reliable means have been devised for dis- tinguishing bom handedness from acquired handedness. Gould, Cunningham, Jackson and others have made many shrewd observations that give some ground for their claims, and Biervliet and Baldwin are to be given credit for having given us the first scientific data; but we need further evi- dence if the foregoing controversies are to be settled. Finally, we find a third class of students who reason from bilateral symmetry to ambidexterity. "Two equal arms" is their creed, and it has filled England with ambidex- terity societies. These societies seem to feel called upon to rescue the race from "one sided development." That their studies and their teachings have been both industrious and heroic is shown by the fact that their opponents have called them "ambidexterity cranks." They, too, have given us lit- tle evidence. 4 A STUDY OF HANDEDNESS It is cleai' that opinion will never settle these, any more than it has settled other, controversies; and we shall con- tinue variously to treat and perhaps to mistreat the left handed child, both in home and in school, until we know him better. Then, too, if we err because we do not understand left handedness, shall we say we are certain of our dealings with right handedness? If a child is bom with a major and a minor arm, may he not more or less hopelessly injure the major arm and so be forced to adopt the minor arm? May an injury to the major arm early in life shift the child over to the minor arm, unknown to parents, and thus send the child through life mistaken as to his own birthright of hands and arms ? If it is really possible to transfer from one arm to the other by accident, then how is any one to know wheth- er he is actually bom right or left ? If we could but discover some scientific means, some measures or scales, for deter- mining both born handedness and adopted handedness, then we could answer these questions. Other questions arise. If an individual is transferred from the major to the minor arm, either by accident or by purposive interference, what are the consequences? Are the possibilities of the minor arm minor possibilities as com- pared with those of the major arm? Does hand transfer mean ultimate loss of hand skill ? and does this interference, whether accidental or purposive, bring physiological disas- ter? If, again, we had reliable means of determining both born handedness and adopted handedness, we could apply tests of hand skill to right handers, left banders, and trans- fers, and thus discover by experiment the consequence of transfer in terms of hand and arm skill; and this in tum might pave the way to a study of physiological consequences attending hand-transfer. It was in the hope of discovering some means, some measures, or scales, that could make it possible to proceed with a scientific handling of the problems of handedness that this investigation was started and carried on for ten years. Re-stated for the sake of clearness, this investiga- tion deals with the following multiple problem. THE PROBLEM STATED. Part I. (1) HOW CAN WE DETERMINE, de novo, WHETHER A CfflLD IS BORN RIGHT OR LEFT HAND- ED V (2) HOW CAN WE DISTINGUISH BORN HANDED- NESS FROM ACQUIRED HANDEDNESS? Part II. SHOULD THE LEFT HANDED CHILD BE TRANSFERRED TO THE RIGHT HAND? MATERIAL AND HANDLING. The material used in this investigation consists of the following measures taken of each arm of twenty thousand individuals ranging in ages from stillborn to centenarian : 1. Length of the ulna-plus (the ulna plus the hand to the middle knuckle of the little finger) . 2. Circumference of the palm. 3. Circumference of the wrist. 4. Length of the humerus. 5. Circumference of the forearm relaxed. 6. Circumference of the forearm contracted. 7. Circumference of the arm relaxed. 8. Circumference of the arm contracted. Additional material was derived by taking measures of the bones of the arms of a dozen cadavers, and of a dozen unpieced human skeletons. The Brachiometer. To facilitate the work, a simple instrument (called "brachiometer") was devised to give exact and correspond- ing measures of the two arms. It is shown in the cut that follows. It is made of hard wood, with working parts of brass. The base of the instrument is 214 by 6 inches ; and the upright, bearing the measuring scale, the sliding indi- cator, and the metallic arm cuff, is 18 inches in length. The aim cuff is a brass band, in two parts, each part secured to the upright and hinged so as to make it adjustable to arms of varying sizes. The Measuring Details. 1. Ulna-plus. — In taking the ulna-plus the brachiome- ter was usually placed on a low table at which the subject was seated. (The measures may be taken with the subject standing ; but if a table is used it must be low enough to give an acute angle at the elbow.) The bared arm was placed with the point of the elbow pressing firmly downward on the base of the brachiometer and the arm extending along the MEASURING THE ULNA-PLUS 8 A STUDY OF HANDEDNESS upright measuring scale. The forearm, hand, and lower joint of the little finger were carefully held in a straight line, with the little finger bent at right angle at the middle knuckle. (Practice in placing and straightening the arm is required to give reliable measures.) The length of the ulna-plus was then found by sliding the indicator down the scale until it rested on the exposed middle knuckle of the little finger, the reading being taken on the scale just under the indicator. (The length of the ulna-plus is taken, rather than the length of the ulna, for the reason that the former is far more readily derived, as may be seen by trial.) 2. Circumferences of Forearm. — Without removing the arm from the brachiometer, the halves of the metal cuff were pressed against the forearm and a pencil line drawn on each side of the bare forearm along the lower edge (along the upper edge with a long arm) of the metal cuff. The brachiometer was then removed, and with the arm held in the same position as when marked, the circumference of the "forearm relaxed" was found by measuring to the pencil lines with a narrow and flexible tape (anthropometric tape) snugly drawn. (Practice is required to enable the operator to draw the tape at constant tension.) Then, without re- moving the tape, a pencil was slipped into the hand of the arm being measured and the subject was instructed to grip the pencil three times with increasing strength, making the third the maximum grip. During the third grip the meas- ure was taken for the "forearm contracted." (The metal cuff locates approximately the zone of maximum swell of the forearm.) 3. Circumference of Palm. — The palm was fully opened and the fingers held in contact. The tape was snugly drawn around the palm just below (on thumb side) the points where the palm-creases disappear on the edges of the palm. 4. Circumference of Wrist. — The wrist circumference was taken over the extreme bony knobs, with arm muscles relaxed. 5. Length of Humerus. — In taking the length of the humerus the subject was instructed to place his hand on his hip ; then the elbow was forced around to the back as far MEASURING THE MUSCLE SWELL, OF THE ARM FOREARM MEASURING THE CIRCUMFERENCE OF THE WRIST PALM 10 A STUDY OF HANDEDNESS as possible in order to throw the shoulder end of the humer- us out in position to favor the measuring. (The less cloth- ing on the shoulder and arm the better, and no heavy cloth- ing was allowed to cover the shoulder during the measur- ing.) The brachiometer was then placed with its base press- ing firmly against the elbow and the upright scale extending along the outside of the ami to the shoulder. The indicator was pressed snugly against the head of the humerus as shown by its bulge in front of the shoulder during the back- ward movement of the elbow, and the brachiometer reading was taken for the "length of the humerus." 6. Circumference of Arm. — In taking the circumfer- ences of the arm the subject was first instructed to fold the arm upon itself firmly by bending it at the elbow, so as to reveal the zone of maximum swell of the biceps. This zone was pencil marked at its center, and the distance of the mark from the elbow was carefully measured by the brachiometer. Another pencil mark was made on the opposite side of the same arm and at the same distance from the elbow as shown by the brachiometer. Similar points w^ere marked on the other arm, using the same distance from the elbow for the two arms. (The point of maximum swell of the biceps is midway of the humerus ; and since the point of maximum swell is not a mere point but a zone from i^ to % of an inch' in width in different arms, no allowance need ordinaHly bei made for the difference in lengths of the two arms of the- subject.) The brachiometer was then laid aside and the sub-' ject instructed to extend the arm outward in a straight line, j The tape was snugly adjusted about the arm as indicated by; the pencil marks, and the reading was taken for the "arm; relaxed." Without change in the position of the tape, the| subject was instructed to fold the arm firmly upon itself: again and then shake the clenched fist in a brief but violent' quiver. The back and forth range of the quiver was limited to about a fourth of an inch, and a little warming up prac- tice was always given. Three brief efforts of increasing strength were made in each case, and during the third and maximum effort the measure was taken for the "arm con- tracted." MEASURING THE HUMERUS DATA. In the following tabula are given the measures of ap- proximately 300 pairs of arms, selected from the total 20,000 as follows : The first list of 200 serial measures is a random selection, giving a working idea of the general run of arm measures in living beings. The next list is a random selec- tion of 40 serial measures from the group of living left hand- ers, showing the general run of measures of left handed in- dividuals. The third list is a random selection of 60 serial measures from the group of Mving transfers, showing the general run of measures of individuals who have been trans- ferred by one or more of various causes stated or suggested in so far as known. The fourth list gives the arm measures of a half dozen cadavers and of a dozen =^unpieced human skeletons. The cadaver measures show the differences in the bone equipment of the two ai'ms as those differences ap- pear when the bones are freshly removed from the human body. The skeleton measures show the differences as re- vealed by the bones when removed and thoroughly dried. (The skeletons used are a collection of Arikara Indian skele- tons unearthed and prepared by Curator W. H. Over, of the Department of Geology of the University of South Dakota. They are now on exhibition in the University Museum.) The data are tabulated in fifteen columns. In the first column is given the number of the individual as listed; in the second is given the sex, "M" indicating male and "F" female ; and in the third column is given the approximate age. Exact ages are not needed in this study, hence the age is usually specified in years (in months for a few young chil- dren) , referring to the nearest birthday. Age 10 thus means that the individual is over dyi and under lOyi years. In the fourth column is indicated the hand (and arm) whose measures are given, "R" meaning the right hand and "L" the left. In the fifth column is given the length of the ulna- plus ; in the sixth, the circumference of the palm ; in the sev- enth, the circumference of the wrist; in the eighth, the • A skeleton is known as unpieced if all the bones are taken from the same body. Commercial skeletons are often pieced. A STUDY OF HANDEDNESS 13 length of the humerus; in the ninth, the circumference of the forearm relaxed ; and in the tenth, the circumference of the forearm contracted. In the eleventh column is given the percentage of the forearm muscle-swell (computed by dividing the difference of the relaxed and the contracted muscle measures by the relaxed measure). In the twelfth and thirteenth columns are given the circumferences of the arm relaxed and contracted, respectively; and in the four- teenth column is given the percentage of arm muscle-s^v•ell (found by dividing the difference of the relaxed and the contracted muscle measures by the relaxed measure) . In the last column are given explanatory notes. [The measures are recorded in inches, with all fractions of the inch expressed in sixteenths. Since the denominator of every fraction may be understood to be sixteen, no denom- inator is written but it is indicated by the colon. Any fig- ure following the colon indicates so many sixteenths of an inch. Thus 14:8 means 14 8-16 inches, and 6:14 means •6 14-16 inches. This system of recording has been adopted for convenience in tabulating. In reading the records it will be of further material assistance for the reader to remem- ber that the record for the right hand is always given in the first of the two lines of measures across the page, and the record for the left hand is given in the second.] 14 A STUDY OF HANDEDNESS IiaMs JO % po:^OT3j:tuoQ uiav •a c ^ £ ^ 13 O £ be tn f~> rC tij ^ crtfl d :3 -71 tM > 'O d ft w _Q0 eg T-H r-t tH oo-^ Oi era ■*cg oo eg oo rH rH ^CO COCO in Tp t-rH CO OT rlH CO t-r-f COCO <7>O0 eg eg' OiCD coea Oi lO COrH t-iH 1-1 oo CO 00 CO -r-iCO OU3 eg eg TPrH r-liH •(uij'eaao^) IiaMs JO % ■p^:^o'ea:^uo^ 0000 o o ■< iH 00 00 oooo 00 00 oo OS oi 00 oo •pax-BiaH lUJ'Ba.io^ oo b- OCT) iH rH 00 C- OOOO 00 "* 00 00 00 -* 00 00 00 tr- m 1-t 3S CT> O O snaauiriH CD C- !>• 00 -^ 00 00 t- 1>. t- 1- -eg o T-H rH CO CO CD <^ ■ijf e>3 ci CD CD t- l> t- 1- t' t- t- t- 00-^ eg rH t-t- oo t- H 00 CD CO eg ■rji-^ CDCD -^Tt* •^■Tt* 00 CD 00-^ f eq ■* -r-l CD U5 eg o o rH rH rH OO a;j p^^ ^ySi p^j pij p:;j p>j pij p^j i^^j p^j fe ^ g fe 00 rH -M cq A STUDY OF HANDEDNESS IS CD U-3 !>• CD CTj 1— > :a lo -* CO to T-l CO C O D- o-^ ooo CO T-l CO rtt iOO lO CO Ift -W< T— 1 d 00 LO o«J CD "<*' IQ"* c-oo l-CL.-' 00 o cq CO ^ o CO CO 00 T-t OC^ ;il 2 r- CO o t- o o 1-t COCQ rH T-l tHO T-H O Oi Ol OO 00 OO CiOi 0105 T-l O 1-1 w C5 Ci oOO tr- t- OO OOO l>CO eg o 1—1 1-1 lOCSI r-1 C-DO CoOO ^^'E^- oo ooco coco 00 00 L.O t-^ T-l U3 c-co CO t- CM en ■^ o I^- UO CTj T-H ^C oi ^ CO c] in LO t>> CO (M CO cq ■^ CO IC-* CO 0.1 COCM CM CM ■* CO ■^co coc-:i co^ "<*< CO CO CM -^co COCM CO O Ci^ i-ii> ino r-l tH I— 1 T-l t- CO T-\ CO eq OiT-l -* o T— 1 T— 1 CM T-l oo L^ C-J tHOO -HOO 00 CO CO US CO 1-1 iH oo T-l T-l CiCK. 00 00 oooo CI C3 OOOO OOOO o o T-i T-i OO 00 oo c- c- OOOO ooo t-c- CM CM CD m Tt< lOC^ 00 -^ CD"e< OOCM COOO ooco ^CM T-i ^CM CD TJH -s< OO T-i '-' r-i T-l oo t-It-1 CiCi oooo OOOO C-^ c:- OOOO OOOO oo O 00 oocc t- t- OOOO t- t- l> t- ^ 1-i CI T-H Tf CI C-] tH oo o oo T-l o T-l t- Tj- lO o tH CO s^ "* CO T-i 1-t oco rH i-l cg o T^^ TH T-l T-t T— t 1—1 1-* T-H coco tH 1-1 CM CM COCO i-( iH coco CO CO T-l tH -rt*"* coco T-l T-l tH tH tH T-i CM ca T-l T-i eg CM 1-1 T-i oo iH T-i (M O tH tH T— 1 T— ( CO tH tH rH coco CO -^ tH C3 T-i CM O T-t r-t 00 00 C<1 o T-i " CO CI -*CM T-i T-i iHCg tH T-i o T-i t- t- t- CO to lOlO CO to Lo ini CO lO ursco IC lO CO CD coco mlo irsio LOU5 mia inia- •* M CM T-l C- T-l U^ 00"* CO (M CM CM i-H C-l "* el 00 «= -tJiC t- co'=o coco t-t- t-t- CD CO T-l CS CD T-l rH r-l 00^ ^CM CM CV] TfH CM O OOCO ^ CM "* T-i OO ■^00 o T-l CD tH t-I CO CO t-(tH tHiH tH tH COCO iHiH 10-* T— 1 rH iHi-l tH rH s^ CM-^I CM Ol T-i T-i coco tH rH _ "rj< TtH r-i T-i T— 1 T-i p^j cc;j Kj p^j f^ij eiJ p^J pjj p^j piJ p^j frjj p^^j PiJ p^j iH ei fe f^ 16 A STUDY OF HANDEDNESS ■(uijv) ■paxBiSH ■snj3uiT\H •sn[d-'Buiri ■pu-BH ■aSy eta tr- OS IPAVS JO % Osl- U3CC t- Irt m-r-i toirs ooo 00 t- CO rH O 30 rH 00 ooo pst^OBJ^uoo UIJV coo COtH O Oi t- CD CO 00 t- C CO CD t-C- CD CD CDTfH CD CO T~i 00 CD CD OOCO t-c- (M O rH rH C-t- rH CD CD CO (M THrH ■(lua^QJO^) lOCO OOOl CDCO ■^CD CDOl cooq ■-*'CO ■*'cO CO ui 00 CO •pa^o'Ejr^uoo uij-eajo^ ■HiH 00 oo COO rH rH CD CO 00 t- COrH t- to o rHOO COCO iHCO COCO 00 t- OOOO 00 CO CD CD rH rH t- CO Ir- CO t- CO rH •* eo ■^ t- 1- i> t- COCO coco CO "* CO CO CO ■* OJ CI CD ■'*< CO ■* oo rH rH cj rH OOCO ■»*< oJH la LO Tf "-H ^ <>; ^^ c> M t> CO Was oo coco Mas •xic CO eo -^ UD -^ "* cq cq cq cq ^co -* 1-1 CD "* CO i-l ■* CQ iH tH CO 30 -* r-iOO ooco cqoo rH CO CC t- 1- COCO 00 t- OJOi D-t- OiOi 005 t-CO coco t-o t- t- ooco OlOO OO rH rH OiOi 00 CO TjHCO C3 cq tH cq iH cq iHOO CO ■* iH o iH m ■*o rH iH o 00 m cqrH rHO rH rH coco COCO t-c- oooo t-CO crjOO OSCTi co«o COCO coco CO CO c-t- OOOO oo> OOOO ec LO iH •* CiCO CO m cq oo CO CO«> t-00 Tj< ca iHCO t-t- COCO t-C- oooo t- t- Oio:! 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'-Hi-H i-\ ^ coco CO CO lo T-H eg i— i r-i i— i "* t>. 0:1 eo os os t-h eo oa t-h la oi Tf -^ CO ej COCO coco i— f eg coco coco coco eg co -^ tji coco o os coco ei eg coco 1-i -r-l T— It— I r-lT-H tHi— I rHi-H t-HtH t-Ht-H tHiH t— (t— ' t-HtH t-Ht-H t-H 1— 1 t— I tH rH rH rH rH coco CO ^ O CO CO COO OO O n" rH t„ -^ ■«*< rH rH t-\ r-t 00 OS CO l> rH rH CO t- Tf r-l t-I r-l CO rH rH rH rH CD ^ uiia 10 U3 L3 10 U5 U5 in U3 mirs ?d cd cd cd t> t- co lo "^ rt* to cd laia lo us -^ CO rH CO CO CO CO CDLOrH COOlrHCOOJrHrHCO "^ lO r^ CO -^ -rf i-l -rf t£> r-t eg 00 (^ CO CD CDC- c- 1- CD CO COCO COCO t- OO t- 1- OOOO Ir- 1- uro Tt* c- 1- cot- l> t- eg CO rt< CO rH CO eg Oi r^i >— I r-i ■r-{ CO t- i-H 00 CO -^ rH CO rH OO 'J^ OO CO CO rH CO 00 00 eo^ -^ c^ -^ -* -rj* T}H coco coco coco -^ in -^ tj< coco -^j* -^ — i rH -^10 TjH -.34 coco P^J P^J I^J p^hJ pjj P^J P^J P^J P^J piJ P^J P^J fd^ P^J piJ CO iH rHCOCO-^lOCDt-OOOlOrH 38 A STUDY OF HANDEDNESS Hi Xi O O M -d" '6 f^ oc o o OJ d d c — ^ m o ^ H CD 2^ 3 O o ^ 01} ■i-j bjO 2 "5 c CO o y 0) C o t^ ^ d w ^ 1 GO ■(3 •(uijv) C-lO coco '^^CO ffj-^ 'X>T-i en lO -TfH -* n3«s JO % iH CM iH t-H -* c- lOLO t-C^ COC-J rH rH C-D- in-^ OO rH ^ CO ■ra CO rH rH c^ ■ 1 ■^Ci-H Oico rHOO tr- CM rH r-i pa^o-BJjuoo UIJV .H W o o 05 0S CfS OS oc> iO-^ CJOO tH -M iH iH M O CM CO CM ■paxTBiaH UIJV P3 0O i-H rH rr< rHOO rH rH •rfTf OOCD C^l— C5C3 C^ Oi OOOO OOOO ■! iH rH ^ s (uiJTsaaOjj ) en) CO t- OT ^D CO CO IfSOO OT CO CO naAvg JO % "* -:*< COM CO CM ^CO -rji CO CO CM CO CM CO CM a iM O CO "* OO O O S •pajoBa^uoo iH iH T-H iH "-I C^ 00 rHrH 00 tH 00 CO ^ CO lUJB^JO^J OO 00 CO 03 05 tH tH r^ O CM CM CM ■P3X-BI8H ^eo OOiH i-r r-t rHTjH •* ITS IfS t>- "*CO coco g rajijaao^ OO -r-t T-\ OOOO xao OOOO OOOO CD CO OOOO OOOO CDOT tH U3 ■^ CO 00 rH CM U3 rH-rf< OOOO .a •snaeuiriH -^J^-rt* rH t-H Cl CM CO CO COCO ■^.H »q T-H tH T-t T-i rHrH rH rH y-l rH .-1 eg O eg -tji rH •JSiJM tr- I— ( -r-i rH OirH COOO iOZD in LO lO LO C£> to ira in Tj- -rt- inio LOlO -^ O •ri* t- i-H rH rH Tf rH ■^ OO rH C-OO ># •rai-Bd oooo zo tr- to I> c- t- C-b- U3 in coco tr-t> la CO io C) OO ca CO t— CM o CD ^ ■snid--euin 'X'-tO u-oco coco la ui "* r*. r^ T-\ rH rH -r-t rH r-< rH rH rH rH 1-i l-< T-i •puBH ffij a ^ p: J MJ «J MJ tf J CcJJ ■8Sv CO X O ira rH t- CVl -M g CM CM CO J-i rH CO •xag fR 1^ S fa S s ■aaquiriM c^ IT CC ir OC LT o- cc A STUDY OF HANDEDNESS 39 MEASXTBES OF ABM BONES OT CADAVEBS AND OT T7NFIECEB HUMAN SKEI.ETONS. The number to the right of the colon in each case is the numerator of a fraction whose denominator is 16. Circumferences of bones were taken midway of the shaft. Cadavers. c« C8 B '6 3 P. a 5 a o to c o li 3p 5 o q; ■eg fc.s s o 3 E s 3 6 ai S 3 s £ m bj3 '3! CO oi 1 R 16:14 12:5 9:.S 7:12 15:5 L 16:11 12: 9: 7:10 15:1 2 R 14:12 10:5 8:5 7:1 12:15 |L 14:8 10:1 8: 7: 12:10 3R 15:15 11: 9: 7:10 14: L, 8:10 7:8 13:12 4R 16:16 12: 8:8 7:1 15:4 * L 16:12 12:4 8:12 7:4 15:6 5R 15:5 10:12 8:2 7:2 14:4 t |L 15:1 10:9 7:15 -7: 14:5 6R 15:8 10:14 8:12 6:12 13:12 |L 15:4 10:10 8:6 6:11 13:8 Human Skeletons. 1|R| ILL 2|r |L sIr |L 4|r |L sIr |L elR jL 7|R |L I 8|R |L sIr |L I 10|R |L 11|R |L 12R |L |l0:13 10:8 1 1:14 1:11| 2:4 2:2 1 1 12:10 12:5 2:10 2:4 6: 5: 9:14 9:12 1:11 1:10 2:1 2: 10:15 10:12 2: 1:14 2:2 2: 13:2 12:10 3: 2:12 6: 5: 10:1 9:10 1:12 1:11 1:12 1:8 11:5 11:1 2: 1:14 2:4 2: 12:13 12:8 2:12 2:10 5: 4:4 10:6 10:4 1:10 1:9 1:12 1:8 10:10 10:5 2:1 2: 2:2 2: 12:8 12:3 2:12 2:8 4:8 4: 9:12 9:8 1:11 1:10 1:12 1:8 10:6 10:4 1:14 1:13 1:12 1:10 11:12 11:9 2:7 2:5 4: 3:14 9:11 9:9 1:9 1:8 1:8 1:4 10:13 10:9 1:15 1:14 2:2 2: 12:12 12:6 2:9 2:8 4:4 4: 9:12 9:10 1:12 1:11 1:8 1:5 9:9 9:10 1:10 1:12 1:4 1:8 11:8 11:12 2:5 2:6 3:8 4: 8:15 9: 1:7 1:9 1: 1:1 10:14 10:11 1:15 1:14 1:8 1:4 13:1 12:13 3: 2:13 5: 4:4 10:2 10:1 1:13 1:12 1:3 1:1 10:11 10:8 2; 1:13 2:8 1:12 12:10 12:6 2:12 2:11 5:12 5:4 10: 9:12 1:15 1:14 1:12 1:8 10:9 10:4 1:12 1:11 1:8 1:8 12:10 12:6 2:10 2:9 4:4 4: 10: 9:13 1:8 1:7 1:4 1:2 10:12 10:9 1:14 1:12 2: 1:12 12:9 12:2 2:9 2:8 4:8 4:4 10: 9:12 1:10 1:8 1:8 1:4 10:12 10:11 1:13 1:12 1:12 1:8 13: 12:14 2:9 2:8 5: 4:8 9:15 9:13 1:12 1:10 1:8 1:4 • Left handed. t Right humerus had been fractured. 40 A STUDY OF HANDEDNESS TABI^E SHOWING ABM MEASURES PBOM BIRTH TO DECREPIT AGE Bach of the three types of handedness is given for each 20 years. All males. d 0) '6 - d oS Ph ce £1 0} ai K ce £ ■« 0) tH 1-1 a S (U d C 5:1 £ CO s £5 ■^fe s § = 3 to t8 X R ■3 ft 3:10 3:4 3 1) Oo #^ i ° ^5 1 H 4:3 4:2 4:1 * L 5: 3:8 3:3 4:1 4:1 4: 2 n R 4:10 3:6 3:1 3:13 3:14 3:12 t L 4:12 3:8 3:2 3:14 3:15 3:13 3 20 R 14:10 8:8 7: 13:14 10:4 10:12 4.9' 11:1 12:5 11.3 L, 14:8 8:3 6:14 13:10 10: 10:6 3.8 10:13 11:13 9.3 4 20 R 14:6 8:4 7: 14: 10:4 10:10 3.7 11: 12:1 9.7 L 14:9 8:8 7:1 14:2 10:7 10:15 4.8 11:5 12:10 11.6 6 20 R 14:11 8:6 7:2 14:1 10:6 10:14 4.8 10:15 12:3 10.2 L, 14:13 8:10 7:4 14:3 10:5 10:12 4.2 10:13 11:14 9.8 6 40 R 15:5 8:12 7:5 14:4 11:2 11:12 5.6 12: 13: 8.3 L, 15:1 8:5 7:2 14:3 10:14 11:5 4. 11:11 12:9 7.5 7 40 R 15: 8:4 7: 14:1 10:8 11: 4.8 11:4 12:6 10. L 15:3 8:10 7:2 14:3 10:12 11:6 5.8 11:9 12:15 11.9 8 40 R 15:2 8:7 7:1 14:3 11:1 11:8 4. 11:9 12:9 7.9 L, 15:3 8:12 7:3 14:6 11: 11:6 3.4 11:7 12:5 7.7 9 60 R 16: 8:14 7:4 14:14 9:12 10:1 3.2 10:3 10:15 7.5 L 15:13 8:5 7: 14:11 9:8 9:12 2.6 10: 10:10 6.3 10 60 R 15:11 7:12 6:15 14:10 9:7 9:12 3.3 10: 10:15 9.4 L 15:12 8: 7: 14:12 9:11 10:2 4.5 10:3 11:5 11. 11 60 R 15:12 7:13 6:15 14:7 10: 10:5 3.1 10:12 11:13 9.8 L, 15:13 8:4 7:2 14:9 10: 10:4 2.5 10:10 11:9 8.8 12 80 R 13:10 7:12 6:10 12:15 9:1 9:4 2.1 9:1 9:11 6.9 L 13:9 7:8 6:9 12:11 8:14 9: 1.4 8:15 9:7 5.6 13 80 R 14: 7:10 6:8 12:12 9: 9:3 2.1 9:4 9:13 6.1 L 14:2 7:15 6:10 12:13 9:3 9:7 2.7 9:6 10:1 7.3 14 80 R 13:12 7:14 6:11 12:12 8:15 9:2 2.1 9: 9:8 5.6 L 11:10 7:9 6:10 12:11 9:2 9:6 2.7 9:1 9:11 6.9 IB 101 R 13:9 7:11 6:8 12:8 8:2 8:5 2.1 8: 8:8 5.8 L 13:7 7:9 6:7 12:6 8: 8:2 1.6 7:13 8:4 5.6 16 94 R 14:8 7:12 6:13 13:9 8:10 8:13 2.2 9: 9:9 6.3 L 14:9 7:15 6:14 13:10 8:13 9:1 2.8 9:2 9:13 7.5 17 93 R 13: 7:12 6:13 12:3 8:14 9:2 2.8' 9:2 9:11 6.2 L 13:2 8: 6:15 12:6 8:12 8:15 2.1 9:1 9:8 1 4.8 H stillborn. * Ilif^ht hander. t Left hander. t Left to right transfer. § Right to left transfer. A STUDY OF HANDEDNESS 41 'S=' =wo VIO 1 .= 1 CJ3 00 T** 00 Oo ^0 00 e^ 00^0 Oi OJ e^ ^ ^H t- fBJOi -^^0 '^■^o "■go c^ !cj '-'csj o-^ 0-^ i^ rH VI VI Vl ■m.§IH Sutsn t- CO iM 01 Oi 00 oi c^ rH ^ puB 1J3T: uaos iH-^CO a'^ cq +J CD CO *H VI V( S 1 "ijan. suisn iH en -rf Otr- iH CO Oco CO cvi ^ pu^E itjSjH ujog 13 3-" ^-^ C3 p m (H VI Vi •JJ8T suisa .-1 OtJi 00 rH "-^ ^ < puB ijaT UJOH 3 V —1 3 tH s g t|H VI V(^ •juSm Suisn' Oo csi CO ^ S pu'E ^T^Siy; UJOH g» CO o 8 OJ CO 10 rH c ^ S IBitoi. oa T-H 00 -* ft o EO ■3 ■ItlStH "* c— iH tH CD CD A o; 5J8T: ^ •0 i *3 m t. a y p 3 ■MST m ClH 01 iqSiH h o J •papu-BH JJ8T c- CD CO ^ H ujog jsqrariM 'tt* CO Ir- Th 4| M H °fes c^ ujoa aaqwriN CO CO OS ■rtH CO C^l 03 rH CD Ci CO CI k .-^ •sioafqns JO jaqmnN 0" 0' 13 OJ i::! cti HJ CO y ■'^ 0) bjD 0! T!r6 > ■ r-i MOO fa m CN ^ hi <-3ra [11 T-1 3 £1 13 ^ •0 c +-» to CD m »" eii 4J "0 m OJ rt ^ tlD S V 4) c6 > ir3 « ^ s 000 tM Vi W 0) (1) ,£5 ^ £0 V G rt ri rf tfl U P. p CD 5^- ^ c<3 C 0! fl 0=5 s ■-' a as 12 CO £Q* Oj, P. s QJ (1) (1) D w -i5 Jj •H 6-=! £ m^ d rC to "Ci Vl rrt S "^S to t> '^ S 1) P m Bte 0) 3 3 c V( (D VI C ?^ Off? M c6 5;^ ^ dJ TO M w 0) ^ S ^ii .a ^ 0+-' CO CO s ^ 42 A STUDY OF HANDEDNESS Interpretation of Data. An examination of the tabulated data reveals the fact that each of the 300 living subjects has longer bones in one arm than in the other. The cadavers, which readily lend themselves to the most rigid treatment, reveal the same thing. The arm bones of the human skeleton, measured for length, circumference, and weight, show that the bones of one arm are not only longer, but proportionately larger around a^d heavier, the sturdier bones being in the right arms of right handers, and in the left arms of left handers. Finally, the condensed table for ages shows that this differ- ence in bone equipment of the arms is just as evident at birth as in adult life, and just as marked in youth as in decrepit age. We are not only right or left handed, but we are bom right or left handed, and the arms themselves bear the evidence. This, then, is the primal fact revealed by the study; namely, the human being is born with a major and a minor arm; and we have the following MEASURES FOR DETERMINING BORN HANDEDNESS : (The major arm excels the minor arm in these measures.) 1. The length of the ulna-plus. 2. The palm circumference. 3. The wrist circumference. 4. The length of the humerus. A little study of the data will show that these measures, not unlike any measures known to science, must be applied with circumspection. Bone injury and bone diseases are not uncommon, and either injury or disease may enlarge or shorten or stunt the growth of a bone. Any one who at- tempts to diagnose handedness, therefore, must be on the lookout for the signs and the history of arm and shoulder de- formities. Thus ill record 76, on page 19 we find the right humerus shorter than the left, though the measures for the ulna-plus, the palm, and the wrist, all favor the right side. With three witnesses against one it is reasonable to suspect injury. The history of the case showed that the subject had A STUDY OF HANDEDNESS 43 suffered a broken right humerus ten years before, ajid the surgeon who had "set the bone" attributed the shortening of the humerus to an "overriding fracture." Number 12, on page 35 shows the same thing with the left arm. Number 9 on page 34 shows a short right ulna-plus, with the palm measures equal, the wrist measures favoring neither side, and the larger humerus on the right. This case could readily be misinterpreted by a hasty or careless diagnosti- cian. An examination of the arms revealed enlargements of both bones of the right forearm with no evidence of injury to the left arm. This suggested a shortening of the right forearm from bone injury. Further evidence was found in the fact that the right forearm muscle was both small and weak as compared with the left, suggesting disuse of the right forearm. Finally the history of the case revealed a compound fracture of the bones of the right forearm six years before; and so the chain of evidence showing the child a bom right hander was complete. Such cases are often met, as may be seen by the notes accompanying the tabulated measures, and the diagnostician must be ready in their in- terpretation. The first question which this investigation set out to an- swer, namely : "How can we determine, de novo, whether a child is bom right or left handed 1" has found its answer in the bone measures of the arms ; and we may now tum to the second question; namely, "How can we distinguish bom handedness from acquired handedness ?' In record number 64, on page 19, we find that the bone measures favor the left side; that is, the subject is a bom left hander; but we find the muscle swells favoring the right arm. Now muscle grows with use, and the larger percentage of muscle swell reveals the arm that is most in use; that is, the larger percentage of muscle swell reveals the adopted arm. This subject is a bom left hander, but in some way he has acquired a dominant use of his right hand. In the note column we find the history that explains the case ; namely, the parents, following tradition, have suc- ceeded in transferring the child to the right hand. 44 A STUDY OF HANDEDNESS Record number 76, on page 19, reveals a transfer from right to left. The bone measures, excepting the measure of the right humerus as we have already noted for this individ- ual, reveal bom right handedness, while the muscle swells show that she is using the left arm the more freely. The accompanying note in the explanatory note column gives the history that reveals the cause of the transfer. The use of a hand and arm is thus revealed by the mus- cle swells, and the adopted arm sooner or later comes to have the higher percentage of muscle swell. Our answer to the second question; namely, "How can we distinguish bom handedness from acquired handedness?" is therefore at hand. BORN HANDEDNESS IS REVEALED BY THE MEASURES OF THE BONES OF THE ARM, THE MAJOR ARM HAVING THE LARGER BONES; ADOPTED HANDEDNESS IS SHOWN BY THE MUSCLE SWELL, THE ADOPTED, OR PREFERRED, ARM HAVING THE HIGHER PERCENTAGE OF MUSCLE SWELL. A little study of the data again will show that the mus- cle swell, too, must be judged with circumspection if the problem of bom and acquired handedness is to be safely set- tled. Record number 6, on page 34, shows an individual bom left handed, since three witnesses favor the left, though one, the ulna-plus, is- neutral ; but the forearm muscle swell fa- vors the right side, and the arm muscle swell is neutral. An examination of the arms revealed an enlargement of the left ulna just above the wrist, affecting also the wrist measure; and the left hand showed an outward deflection from the line of the arm. We hardly need the history of the case to make it clear that this subject has just passed over the line of transfer, due to a broken left ulna of short time standing, so short time indeed that the forearm muscles of the right arm are but little stronger than those of the left, and the two arm muscles are just on the neutral line. The history given in the explanatory note, however, corroborates the evidence. A STUDY OF HANDEDNESS 45 Record 36, on page 36, shows a right-to-left transfer. The parents were not aware that the child had ever been transferred, and the cause of the transference is not defi- nitely known. The history of the case revealed that the child had fallen down a flight of porch steps at three years of age and injured the right shoulder. The attending physi- cian had the right arm carried in a shng for a few weeks, and soon afterwards the child was "found to be left handed." There is little doubt that the child adopted the left hand while the right arm was in the sling; and then with no at- tention given to the normal handedness when the arm was removed from the sling, the child continued to use the left hand and arm. Turning now to the explanatory note column of the tab- ula, the reader may note that a record is there given of each case of stammering. (The term "stammering" is here used to include both stammering and stuttering, since the two terms are absolutely synonymous in ordinary use. Stammer- ing, technically speaking, is imperfect enunciation due to lack of control over the muscles of articulation, the sounds being properly vocalized; while stuttering is defective vo- calization, or defective voicing of sounds. A stammerer is likely to have trouble in enunciating initial syllables begin- ning with b, p, d, or t, but the stutterer repeats the sylla- bles.) Since the prevalence of stammering is a matter to be determined by mass data, it may best be handled with the table of 'summaries. The table showing the summaries of measures of the 20,000 pairs of arms is given on page 41. In the first column of the table is indicated the number of individuals whose measures are included in the summaries. In the second col- umn in given the number of those (included in the first col- umn) who were found to be bom right handed, and in the third column the number found to be born left handed, ac- cording to the scale of measures already explained. In the fourth and compound column is recorded the number of transfers classified in groups according to the type of hand- 46 A STUDY OF HANDEDNESS edness shown. In the fifth column (also compound) is given the number of stammerers, also classified in groups accord- ing to handedness. At the foot of the table is given the pro- portionate numbers of males and females born right handed and left handed, the total number of stammerers who began to stammer under eight years of age, and the proportion of males and females among the stammerers. The summaries of the first three columns show that out of 20,000 persons whose arms were measured, 19,207 are born right handers, and 793 are born left handers ; that is, 96% OF THE HUMAN RACE ARE RIGHT HANDED BORN, AND •■=4% ARE LEFT HANDED BORN. The summaries further show that out of 19,207 born right handers, 9,502 are males and 9,705 are females, while out of 793 born left handers 498 are males and 295 are fe- males; that is, born left handedness is far more common among males, the ratio being about 5 males to 3 females. [Ballard estimates about 2 to 1 in favor of males, but in his study he made no distinction between born handedness and acquired handedness.] The transfer column shows that out of 20,000 persons, 815 (4%) are transferred. Six hundred one of these (74% of all transfers) are transferred by purposive interference, and 214 (26% of all transfers) are transferred by accident. We find no case of purposive transference from the right to the left hand [Tradition favors the right hand, and left in tradition means unlucky], but out of 793 bom left handers we find that 601 (76% of all born left handers) are trans- ferred to the right hand by purposive interference. We also find that out of 19,207 born right handers, 203 (about 1%) are transferred to the left hand by accident, and out of 793 bom left handers, 11 (about 1%) are transferred to the right by accident. . Restating the facts of transfer. * The literature on handedness is full of estimates of the proportion of right and left handers, running- from 3% to 6%; but since none of the authors distinguish between born handedness and acquired handedness there is little value in making specific comparisons. A STUDY OF HANDEDNESS 47 we have the following *approximate percentages : 4% OF THE RACE ARE TRANSFERRED TO THE MINOR ARM. (1 out of about 25 persons.) 1% OF ALL BORN RIGHT HANDERS ARE TRANS- FERRED TO THE LEFT HAND BY ACCIDENT. 1% OF ALL BORN LEFT HANDERS ARE TRANS- FERRED TO THE RIGHT HAND BY ACCIDENT. 76% OF ALL BORN LEFT HANDERS ARE TRANS- FERRED TO THE RIGHT HAND BY PURPOSIVE INTER- FERENCE. 77% (over three-fourths) OF ALL BORN LEFT HANDERS ARE TRANSFERRED TO THE RIGHT HAND. The stammerer column shows that out of 20,000 per- sons, 390, or nearly 2%, are stammerers or are '''^reported to have been stammerers earlier in life [Ballard estimates not over 2% among normal children, and 17% among left handers who write with the right hand] ; and that 340, or 87%, of these are males, and 51, or 13%, are females. (Medi- cal writers commonly refer to the high percentage of male stammerers ; and the Wisconsin State Department of Educa- tion reports over 85%. — Educational News Bulletin, Wiscon- sin State Department of Education, Madison, February 1, 1917, p. 2.) Out of 19,004 bom right handers who have adopted the right hand, 120 (about ^^ of 1%) are stammerers; while out of 181 bom left handers who have adopted the left hand, 18 (about 1%) are stammerers. Out of 203 right-to-left transfers, 33 (16%) are stammerers, while out of 612 left-to- right transfers, 219 (36%) are stammerers. (Ballard found 17% among his "dextro-sinistrals." — Jour, of Exp. Fed., Vol. 1, No. 4, p. 309.) Finally we note that out of the 390 stam- merers, 203 (52%) are transfers; and that 339 of the 390, or 87% (and 168, or 83%, of the 203 transfers) are reported to have begun to stammer under 8 years of age. [It is safe * The standard deviation of 7.8% makes rough estimates in place here. •* The reports of earlier stammering are believed to be quite reliable, since it is characteristic of the recovered stammerer that he well remem- bers his former condition The readiness to conceal the defect is not hard to offset if the subject is sympathetically approached There were 79 cases of earlier stammering in the total number of 390 cases, and these were carefully questioned for symptoms before accepted as recovered stammerers. 48 A STUDY OF HANDEDNESS to assume that the number of reported cases is somewhat low, since no case was included in the list if the starting time was apparently doubtful. The Wisconsin State Board of Education reports 70% of stammering beginning at 6 years or under. See Educational News Bulletin, Madison, Feb. 1, 1917, p. 2.] A STUDY OF HANDEDNESS 49 One-half of all stammerers are transfers. One-third of all left-to-right transfers are stammerers. 1^^^^^ 1 One-sixth of all right-to-left transfers are stammerers. 1— — 1 Less than 1% per cent of pure handed individuals are stammerers. I RELATION OF HANDEDNESS AND STAMMERING. 50 A STUDY OF HANDEDNESS Restating the *facts of stammering, we have the follow- ing: One-third of left-to-right transfers are stammerers. One-sixth of right-to-left transfers are stammerers. About 1% of pure left handers are stammerers. Less than 1 % of pure right handers are stamm.erers. One-half of all stammerers are transfers, and four-fifths of all stammering begins before the eighth birthday. About seven-eighths of all stammerers are males. Several questions at once arise; namely, (1) How is the high percentage of stammerers among transfers, especially the left-to-right transfers, to be accounted for? (2) Why is the proportion of male stammerers so high, even though we allow for the fact that the ratio of born left handed males to born left handed females is about five to three? and (3) Why does stammering commonly begin during the early years ? Any serious attempt to answer these questions to- day must resort to one or both of two methods; namely, (1) speculation in the field of brain psychology, and (2) experi- mental treatment to derive concrete evidence. We may well combine the two methods. SPECULATIVE TREATMENT of the CAUSAL RELATION BETWEEN HAND TRANSFER- ENCE AND STAMMERING. The fundamental fact of handedness, in so far as we can yet unravel it, is the fact of congenital cerebral asym- metry. The present day knowledge of brain psychology is very incomplete, but a speculative treatment of our problem in terms of the best theory that physiological psychology has to offer will be at least better than no attempt at ex- planation at all. It will at least try the theory ; and theories are established or broken down through use. We may take as our starting point, the prevailing physi- * Since the standard deviation on the average number of stammerers per thousand individuals is 12.7%, the proportions are given as rough fractions rather than as definite percentages. A STUDY OF HANDEDNESS 51 ological theory (1) that there are *four highly speciahzed cortical centers involved in the speech of the normal adult ; namely, two sensory — the auditory and the visual, and two motor— the vocal and the writing (graphic word) centers; (2) that all four of these centers are normally located in one (hence called superior) hemisphere of the brain ; namely, the left hemisphere in the **borii right handed individual, and the right hemisphere in the **born left handed individual; and (3) that though the muscles of the vocal organs are anatomically connect^ with each hemisphere, they are func- tionally connected^^^^^ one ; and in so far as the hand is an organ of speech, at least, it shares the same asymmetry. Since the child hears words freely before he speaks or sees or writes them ; since he speaks them freely before he sees them, and sees them freely before he writes them free- ly, we may reasonably assume that the graphic word, or writing, center is the last to be called into function. We may also assume that the writing center is called into func- tion whenever the child begins to write or scribble, and this is quite certain to be before he is 8 years of age. Suppose a bom left handed child is learning to write. If he is allowed to write with the left hand, then we may assume that the writing center is developed in the right hemisphere — the hemisphere in which the auditory, the vocal, and the visual centers are already located. This unified placem-ont of word centers we may consider normal according to our physiologi- cal theory. But suppose the born left handed child is re- quired to write with his right hand. Then we may assume that the writing center is developed in the left (the inferior) hemisphere. What will happen? We may speculate that any one of three things will occur; namely, (1) the lack of unity resulting from the location of three of the word cen- ters in one hemisphere and one in the other, will bring func- tional disharmony due to the fact that the neural currents * If we take the position with Collier and others (see "Brain," Part CXXIV, Vol. XXXI, 1908. p. 540) that the existence of separate auditory and visual speech centers rests upon the "slenderest facts," it will change our speculation in no significant respect; and few will go so far today as to agree with Marie that there is only one speech center (see Sem. Med., 23 mai, 1906, p. 241.) ** The addition of this word is suggested by this study. 52 A STUDY OF HANDEDNESS are ill-timed or even conflicting, thus giving rise to speech checking, speech hesitation, or stammering; (2) the free use of the right hand in writing may firmly seat the writing cen- ter in the right hemisphere and this may be followed by the transference (the "dragging over" theory) of the three word centers from the left to the right hemisphere, thus giving rise to extreme functional disturbance, for a time at least, that may initiate stammering through lack of co-ordination ; (3) since the child may have attempted some left hand writ- ing before formal wiiting work began, indeed may even con- tinue the same when left free to himself, two writing centers or even two sets of speech centers, one in either hemisphere, may be developed (theory of ambidexterity advocates) which in turn could seriously interfere with neural co-ordina- tions and lead to stammering. In any case we must assume that there is an intimate functional connection among the four word centers, such that whenever the last developed center (the writing center) is functioning, all the word cen- ters are likely to function; and any interference with this functional unity may result in turning the neural currents into wrong or even conflicting channels, thus giving rise to checks, to hesitation, to stammering. The fact that no lesion has so far been discovered, leaves us with only the function to speculate upon; but any one of the above speculations gives us a possible explanation. We may further speculate that one child is more readily set to stammering than another for the reason that the inti- mate functional connection of the four word centers is more readily disturbed in one than in another. The general nerv- ous stability is undoubtedly a detei-mining factor. A child dominantly vocomotor, or linguistic, may be more difficult to unsettle than other types, and we may speculate that it is for this reason that stammering is less common among fe- males. When we come to speculate with the fact that stam- mering commonly begins before the age of 8 years, we may assume that since this is the period when the language cen- ters are being developed, it is also the time when the func- tional unity of these centers is the least stable. The trans- A STUDY OF HANDEDNESS 53 f ers are the likely stammerers, probably for the reason that the unity of language centers is so likely to be disturbed. We may assume (1) that 36% of the left-to-right transfers stammer for the reason that this transference is commonly accomplished under exasperating conditions, such as nag- ging, threatening, hand tying, wearing of mittens, and so on to the limit of tradition and human ingenuity, that in them- selves superinduce morbid sensitivity and nervous instabil- ity; and (2) that 16% of the right-to-left transfers stam- mer because they are transferred by injuries and treatment that are themselves serious attacks on neural stability, though commonly of shorter duration than the nagging era of left-to-right shifting. . We may assume that the per- centage of stammering is higher among pure left banders than among pure right banders for the reason that so few left banders escape traditional interference ; and finally we may believe that there are causes other than hand transfer- ence operating in the direction of stammering. 54 A STUDY OF HANDEDNESS EXPERIMENTAL TREATMENT of the CAUSAL RELATION BETWEEN HAND TRANSFER- ENCE AND STAMMERING. Having concluded the speculative treatment of the causes of stammering, we may now return to experimental means to discover whether or not the main principle assumed in the speculation is sound. We may state our problem as follows : Does writing with the minor hand invite stammer- ing? In the effort to get definite data on this problem, two subjects were chosen who were known to be near the stam- mering line, one just recovering from stammering, the other just beginning to stammer, and subjected to composition writing tests. The recovering stammerer was required to write with the minor arm and the stammering subject with the major arm. The first subject was a 14-year-old boy whose arm measures are recorded under number 5, page 30. This boy was apparently in ordinary health, with a systolic blood pressure (auscultatory method, sitting posture) com- monly ranging from 115 to 120, a pulse pressure of 32, usu- ally quite nervous (esthesiometer reading from 19 to 23 on back of left hand), but with no physical defect revealed by physical examination excepting a * constricted and adherent prepuce. He was a bom left hander and his parents had tried to force the use of the right hand, but gave up when the boy reached his 12th year still dominantly left. He had stammered for several years, but had shown no signs of same for a few months previous to the tests. The second subject was the 8-year-old boy whose record is number 27, on page 36. This child passed a fair physical examination. His hearing range was short, and he had had adenoids re- moved two years before. His nerves were quite unstable (esthesiometer reading 15 to 18) and he carried an unde- scended testicle. He was a left-to-right transfer, due to parental interference, and he was beginning to stammer. The 14-year-old recovering stammerer was set to writ- ing compositions on various subjects of interest to himself, * This defect is significantly common in stammerers. A STUDY OF HANDEDNESS 55 the writing being done with the minor (right) hand. (He had been required to use this hajid in writing during the years he had stammered.) He was required to write for three twenty-minute periods daily, taking up a new subject as soon as he lacked thought on the one in hand, and he was stopped at the end of each twenty-minute period and asked to tell what he had written. If no signs of stammering ap- peared he was excused from speaking and set to writing again. At the end of the eighth twenty-minute period (sec- ond period of the third day) stammering was clearly evi- dent and the subject was excused from further writing. In order to try the counter effect, the boy was set to writing with his left (minor) hand, for one twenty-minute period a day until the results could be determined. The stammer was evident for a period of eleven days, then disappeared with occasional lapses for a period of five weeks. During the last four weeks the formal left hand writing tasks were discontinued but the left hand was used exclusively in what- ever writing was done. At the end of seven weeks from the time of the first experiment, the boy was given another trial at right hand writing, under the same conditions as before, and the stammer returned at the end of the fifth twenty- minute period. Recourse to left ha^d writing was again taken, and the stammer continued for seventeen days with eight weeks of occasional lapses, then the formal writing was ceased but the left hand was used exclusively in wiiting and is in use at the time of the present writing, six months hav- ing elapsed since the stammer disappeared. The eight-year-old, left-to-right transfer, who was just beginning to stammer, was using his right hand in what- ever writing he had to do, including a fifteen-minute daily writing lesson in school. The parents and the teacher con- sented to allow the boy to use his left (major) hand in his writing, in order to see what the result would be in terms of stammering. The boy was then set to writing formal writing lessons for two fifteen-minute periods daily, one in the forenoon and the other in the afternoon. The writing was done with the left (major) hand, and the subject was ready to co-operate by doing all his writing with the same hand. After two weeks, daily compositions on topics of interest to the boy were substituted for the formal writing, 56 A STUDY OF HANDEDNESS in order to involve the speech centers fully. The composi- tions were written in three ten-minute periods, with five- minute intermissions for telling aloud what he had written. The boy was a slow and laborious writer and usually whis- pered the words as he wrote them (*Conradi found that stammerers are as a rule backward in school work, but sug- gests that this is probably due to psychic depression brought about by mockery. We have no evidence so far that shows the stammerer below average mentally, though we do find him below in school work involving speech). His speech during the five-minute "telling intermis- sions" was closely watched. Not until the twenty-second day of composition writing could it be unmistakably seen that the stammer was disappearing. At the end of forty-seven days of composition writing the boy carried on conversation without hesitation, and the composition writing was discon- tinued, though the writing in school and elsewhere was done with the left hand. After a ten-day respite, during which time the boy reported no serious lapse of speech, it was ar- ranged to try writing •with the right (minor) hand. The three ten-minute composition periods, with five-minute "tell- ing intermissions" were used as before, and the school writ- ing was discontinued by two weeks of vacation. On the third day of the composition writing with the right (minor) hand, evidence of stammering reappeared; and on the fifth day the child was unable to handle words beginning with the letter "h." The writing was then resumed with the left (major) hand and carried on as before for twenty-seven days before the stammer was lost. These two bits of experimental evidence, insufficient in themselves to settle questions that arise, but rather point- ing the way for further study, are unmistakable evidence that there is an intimate relation between minor hand writ- ing and stammering. They seem to give depth of meaning to the experimental evidence already produced, and they strengthen faith in the fundamental theories of brain psy- chology. We are driven to the conclusion at least that the tradition that would force all left handed children to write with the right hand is a tradition as dangerous as it is ig- norant of possible consequences. • Journal of Kducational Psy., Vol. Ill, No. 1, pp. 35-38. PART II. SHOULD THE LEFT HANDED CHILD BE TRAINED TO ADOPT THE RIGHT HAND? PROBLEM— SHOULD THE LEFT HANDED CHILD BE TRAINED TO ADOPT THE RIGHT HAND? Material and Handling. The material for this part of the study consists of the measures of hand and arm skill of 1125 individuals of whom one-third, or 375, were pure right handers (born right and adopted right), one-third, or 375, pure left handers (born left and adopted left) and one-third, or 375, transfers (part right-to-left, and part left-to-right). Subjects were chosen to reveal the hand skill of young children, of youth, and of adults of both sexes. The individuals represent purely chance selection within the age limits specified. Three tests of hand and arm skill were used ; namely, 1. The shot tube test. 2. The peg board test. 3. The tapping rate test. The shot tube test was chosen for a test chiefly of hand skill ; the tapping rate test, a test chiefly of arm ability, and the peg board test, a test of combined hand and arm skill in about equal proportion. All three of the tests give scores large enough to show comparative skill. DESCRIPTION OF SKILL TESTS. 1. Shot Tube Test. The shot tube test is a test to determine the number of seconds required for the subj ect to pick up with the fingers 25 quarter-inch steel balls, one at a time, and drop them into a vertical tube 6>4 inches high and with a mouth three- eights of an inch in diameter. Thirty-five of the steel balls, called "shot" for convenience, were placed in a wooden dish made with a hopper bottom so that the shot could always be readily located. The dish containing the shot was placed just to the right of the loading tube when the loading was to be done with the right hand, and similarly to the left of the tube for the left hand. Each subject was allowed three THE SHOT TUBE TEST 60 A STUDY OF HANDEDNESS trials with each hand before the test began, and he was en- couraged to load as fast as possible. When ready for the test, the subject was instructed to hold the tube firmly with one hand, and to place the other hand (hand to be tested) with the fingers at the mouth of the tube as if preparing to drop a shot. A stop watch was held at his ear with instruc- tions to begin picking and loading the instant the stop watch was clicked to start, and to continue until the tube was filled with shot irrespective of the number dropped. The operator stopped the watch the instant the 25th ball clicked in its place in the tube. Two series of record trials, four trials in each series, were made in the following order: First series — first trial with the major hand, second and third trials with the minor hand, fourth trial with the major hand. After a pause of two minutes, the second series was given — first trial with the minor hand, second and third trials with the major hand, and the fourth with the minor hand. The average of the four records made with each hand was tabulated for the final record. 2. The Peg Board Test. The peg board test is a test to determine the number of pegs the individual can place, or load, in an ordinary kin- dergarten peg board (Mrs. Putnam's Peg Board) in 30 sec- onds. The subject was seated at a table with a 100-hole peg board in front of him. The 100 pegs were contained in the pasteboard box placed just to the right of the peg board when the loading was to be done with the right hand, and in a similar position on the left when the loading was to be done with the left hand. Each subject was allowed three trials with each hand before the test began. He was in- structed to load as fast as possible and to place the pegs in order in the 25 holes, beginning at the hole farthest from the peg box. When ready for the test the subject was directed to place the index finger of the loading hand over the first hole to be loaded, and to steady the peg board with the other hand. A stop watch was held at his ear with the under- A STUDY OF HANDEDNESS 61 standing that the loading was to begin when the watch was dicked to start and that the loading was to continue until the watch was clicked to stop. Two series of record trials, four trials in each series, were made and recorded as already described in the shot tube test. 3. The Tapping Rate Test. The tapping rate test used was the familiar test to de- termine the number of taps with a pencil that the arm is able to make in a given time. The subject was seated at a table across which was drawn a long strip of adding machine pa- per. She was handed a hard lead pencil about four inches long and instructed that the object was to make as many taps (dots) on the paper as possible in 30 seconds, holding the hand in one position while the operator moved the pa- per slowly along. (No machinery for moving or recording was used.) The operator sat to the left of the subject and moved the paper slowly from right to left when the tapping was done with the right hand, and to the right of the sub- ject with the movement of the paper reversed when the tap- ping was done with the left hand. When ready for the test the operator took the stop watch in one hand and seized the end of the paper strip with the other hand. The subject was instructed to begin tapping the instant the stop watch was clicked at his ear and to continue until the paper was jerked from under his pencil at the end of the 30 seconds. One practice trial with each hand was allowed before the record trials began. Two record trials with each hand were made, the first with the major hand, the second and third with the minor hand, and the last with the major hand. The taps were counted by marking them off in fives, and the average of the two trials with each hand was tabulated for the final record. 62 A STUDY OF HANDEDNESS DATA. In the first of the following tabula (page 63) are given the measures of the hand and arm skill of seventy-five boys from 14 to 16 years of age, as shown by the shot tube test. Twenty-five of these boys were shown by brachiometer measures to be pure right handers, that, is bom right hand- ed and using right; twenty-five were pure left handers (bom left and using left), and twenty-five were transfers. The tabulated record for each individual shows five facts; namely, (1) the number of the individual in the list; (2) the age — given to the nearest birthday for adults, but expressed in years and months for individuals under 25 years of age. [Age 16:2 means 16 years and 2 months] ; (3) the record made by the right hand in the given test: (4) the record made by the left hand, and (5) the range of skill, or the dif- ference between the skill records of right and left hands. • [Since part of the transfers are right-to-left, and part left- to-right, their records are given in the same columns under the headings "Major" and "Minor" instead of "R" (right) and "L" (left) hands.] In the second tabulum (page 64) are recorded the meas- ures of hand and arm skill of seventy-five women (twenty- five of each handedness group) from 21 to 24 years of age, as shown by the peg board test. The five columns of data are given under headings the same as for the shot tube test just explained. In the third tabulum (page 65) the measures of hand and arm skill of seventy-five girls (twenty-five of each handedness group) from 7 to 9 years of age, as shown by the tapping rate test. The five columns of data are given under headings the same as for the shot tube and peg board tests. The column average is given at the foot of each column to show the central tendency, and the average deviation (A. D.) from the average is given to show the deviation from the central tendency. A STUDY OF HANDEDNESS 63 SHOT TUBE TEST. (Records indicate number of seconds and lOths of seconds required to load 25 shot.) 14 to 15 Year Old Boys. (Over 13V4 and Under l^Vi Years.) Pure Right Handers. | Pure I^eft Handers. | Transfers. C o s 3 < ,■3 -^ S D CO ft; < 43 TO 6.2 6 < 16?5 it 41.2 II 42.6 6 to c 1 .. 16:2 39.4 44.2 4.8 16:2 35.2 30. '1.4 2 .. 16:5 30.6 39. 8.4 15:11 41.2 38.4 2.8 14:5 47. 49.2 2.2 3 . . 15:4 35.6 42.6 7. 15:7 42.6 39. 3.6 13:10 49.4 50.4 1. 4 . . 16:4 35.4 41.2 5.8 15:5 45.4 40.2 5.2 16: 36.2 38. 2 2. 5 .. 15:4 34.8 40. 5.2 14:3 44.8 42. 2.8 13:9 48.6 51.2 2.6 6 .. 15:1 38.4 44.2 5.8 15:9 40.8 35.2 5.6 16:1 36.2 38.4 2.2 7 . . 15:8 33.8 40. 6.2 14:3 45.6 40.4 5.2 |15:3 43.6 41.6 1. 8 .. 14:8 44.2 50.2 6. 15:4 51.2 45.2 6. 15:11 38.4 39.4 1. 9 ... 14: 44.4 51.6 7.2 14:3 43.2 40.4 2.8 15:11 39.2 41.6 2.4 10 . . 14:9 33.4 40.2 6.8 15: 42.2 39. 3.2 16:4 33. 34.2 1.2 11 . . 14:2 39.4 44.4 5. 16:4 36. 32.8 3.2 13:8 42.6 44.2 1.6 12 .. 15:2 37.2 45.6 8.4 16:3 40.2 36.2 4. 16:2 33. 36.6 3.6 13 .. 13:6 47.4 52.2 4.8 13:6 52.2 46.4 5.8 13:9 44.2 45.8 1.6 14 .. 15:7 40.6 44.8 4.2 13:9 50.6 45.8 4.8 13:10 48.8 50.4 1.6 15 .. 15:9 39.6 46. 6.4 13:7 52. 47.2 4.8 14:4 43. 45.4 2.4 16 .. 14:3 46.2 50.8 4.6 14:5 46. 42.6 3.4 15:9 43.2 44. .8 17 .. 14:10 45.2 49.2 4. 16:2 41.8 35.8 6. 14:5 47.2 49.4 2.2 18 .. 15:1 38.2 43.4 5.2 14:10 47.6 40.2 7.4 15:7 39.2 39. 4 .2 19 .. 13:9 43. 48.8 5.8 15:8 45. 38.8 6.2 13:7 45.6 46.4 .8 20 .. 13:11 46.8 52.8 6. 15:3 44.2 40.2 4. 15:1 40.2 44.8 4.6 21 .. 14:3 37.4 43. 5.6 14:7 45.6 41. 4.6 15:2 45.2 45.6 .4 22 .. 13:8 39.6 44.2 4.6 13:10 51.4 44.2 7.2 14:11 44.8 45.6 .8 23 16:1 32.2 38.4 6.2 15:9 42.2 37.8 4.4 15:4 40.8 43.8 3. 24 . . 15:4 38.2 44.8 6.6 14:1 48.2 42.6 5.6 15:4 40.4 41. .6 25 .. 14: 40. 45.2 5.2 14:7 53.2 44.8 8.4 15:10 38.6 40. 1.4 373:1 981.0 11126.8 145.8 |374:6 1128.4 1006.2 122.211376 :8|1049.6|1092.2|42. 6 Av. *A. D. 14:11 39.24 3.65 45.072 3.33 5.832 |15: .88 1 45.136 3.79 40.248 3.19 4.888||15:1 1 1.2111 41.984143. 68811.70 3.791 3.641 .81 * Average Deviation from the average which is shown just above in each case. 64 A STUDY OF HANDEDNESS FEG' BOARS. (Records indicate number of pegs placed in 30 seconds.) 21 to 24 Year Oia Women. (Over 20^ and Under 24^ Years.) Pure Right Handers. Pure Left Handers. Transfers. 6 6 ^■2 fan ^ .•a 6 fan ^ 03 bo S 6 fan K .1^ 6 to s 3 to .™c« ^ d oj till .™o! {D cd tS to .™0J

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