The relative sensitivity of men and women at the nape of the neck  

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The relative sensitivity of men and women at the nape of the neck (1894) is a study by Francis Galton on skin sensitivity in women and men.

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'T'HE difference in the sensitivity of the two sexes has been discussed often and from various points of view, but still, as it would seem, upon insufficient data. More observations being wanted, I submit the following, partly for such value as they have in themselves, parily to show an easy method of observation which others may pursue with advan- tage, and partly as a good illustration of the method of per- centiles, or centiles.

The test employed is one of a familiar kind, made with the pnints of a pair of compasses, and usually associated with the name of Weber. If one person becomes just conscious of the doubleness of the pricks when the distance between the points is a, and another person does so when the interval is i>, then the ratio of a to i> may fairly be taken to express the relative obtuseness of the two persons, so far as concerns the form of sensitivity tested, and the inverse ratio of /' to a to represent its relative delicacy. The particular test used was one that has three especial merits : it requires no minuteness of measurement, no uncovering, and the person tested is unable to see the operation. It consists in pressing the points of the compasses against the nape of the neck .ind across the line of the spine, while the experimenlee sits with his or her head bowed forward. The just-perceptible interval at the nape of the neck averages as much as half an inch or thereabouts, while its variation in different persons is large. Consequently there is no need for extreme delicacy of measurement, neither does the varying thickness of cuticle caused by various degrees of usage, interfere materially with the results, as it does when like experiments are made, as is usual, on the finger-tips. The varying delicacy of perception due to difl'ering amounts of practice is here entirely eliminated, because all persons are equally unpractised, no one occupying himself or herself in attempts to discriminate between two simultaneous pressures on the nape of his or her neck, while everybody has life-long practice in discriminating roughnesses, thi ugh in various and unascertainable degrees, with his or her fingertips. There are parts of the body, such as the back, which are still less dis- criminative than the nape of the neck, but there is no other equally suitable part that is so get-at-able, in respect to the the ordinary dress of man or woman Lastly, the attitude of the person who is being tested, entirely precludes him from watching the operator, and guessing Irom the hands or move- ments ofthe latter, whether he is applying two points, or only one, at the moment when he asks what is (elt. The observations were all made by .Sergeant Randall, who superintends my laboratory ; he employed the two points of a Flower's ciani- ometcr, which was handy for use, as it was wanted to make other measurements of the same persons. The observations were carried on for some months, until a suflicient number had accumulated lo justify discussion. Stature was included among them, but, failing on examination to trace any notable relation between stature and the just-perceptible interval on the nape of the neck, I have disregarded stature altogether in the following summary, and age too, so far that the person tested was often not fully grown.

The observations made on males and females, reipectively, arc summarised in the first and third lines of Table I. Their sums, reckoned in each case from the beginning of the series, are entered in lines 2 and 4, while the percentages of those sums are given in lines 3 and 6, but .solely for the purpose of graphic projection in the form of dots, in Fig. I. Those dots are joined by straight lines, forming traces for the males and females respectively. The lengths ofthe ordinates to the traces, which are drawn at the lOlh, 20ih, &c. divisions of the b.ise, are the loth, 20lh, &:c. percentiles, or centiles; or, in still briefer language, the Isl, 2nd, &c. "deciles." Their values, obtained by simple interpolation from the entries in lines>

May io, 1894]



land 2 of Table I., are entered in Fig. I. Thus 13S milli- metres is the just-perceptible interval of the median man, and 1 1 8 that of the median female. In one sense, but only in an imperfect one, the relative sensitivity of the two sexes is given by these figures as being about 7 to 6. Much more has, how-

observed values could be obtained by closer attention to the second decimals, but such minuteness is uncalled for in a case like this. It will be seen from columns B, C, and b, c, in Table II., that the sums of the ol)served and calculated deciles closely accord, and that the differences between the several

Table I.

Summary of Observations ^932 .Vales and 377 Females, showing the number in whom a just-perceptible feeling of doubleness was given by the pressure of two points across the nape of the neck, and separated by the various intervals, as below.

Length of the just-perceptible interval in millimetres

  • These figures are protracted in both cases as go '5, inasmuch as the accordance of the two preceding and of the four subsequent entries make the

correction reasonable as well as convenient.

ever, to be specified before the relation can be adequately ex- pressed, because it is obvious from the diagram, that what is true 'for persons having medium sensitivity, is not true for those having ihigh, and still less for those having low, sensitivity. We are, how-

pairs of them, headed B — C and /' — c, are as nearly alike as we have a right to expeC. The calculated deciles, and the curves drawn through them, in Fig. 2, may therefore be accepted as a just rendering of what is more roughly indicated by the obser- vations in Table I. and Fig. I. In the following remarks reference will be made almost exclusively to the calculated values, but the results can and will usually be checked by reference to the observed ones, with which they tally sufficiently well.

Table II.



jFlG. I. — Traces and deciles from observations. The dots refer to the ob- served values as given in the 3rd and 6th lines of the table. They are connected by straight lines. The figures are the values of the corre- sponding deciles — that is, of the ordinates to the traces erected at each successive tenth part of the base.

iver, able to specify what is wanted very compendiously, because 30th of the traces conform fairly well to the law of frequency of

rror, at least between the limits of the ist and the gth decile. In

he case of nial -s, the median is taken at y^o millimetres, and

Fig. 2. — Deciles and curves by calculation. Data for males : median = i3'5o, // = 3"25 mm. Dat.i for females : median = i2'oo, ^ ^ 3'7o mm.

he (/ (= half the difference between the two quartiles, a v.ilue vhich is identical with that of the ± probable error of a single bservation) at 3'25 ; in females, the corresponding values are 2"00 and 370. A somewhat nearer approximation to the

NO. 1280, VOL. 50]

The average ratio between the sensitivities of the females and males is the same as that between the sums (or means) of columns C and c in Table II., namely as 125'5 Io loSi ; or to speak more modestly, as no trust can be reposed on the minute pre-



[May lo, 1.894

cision of such values as these, the average delicacy of female discrimioation li«tween the two points is to that of the male, in a ratio that lies somewhere between 7 to 6 and S to 7, or thereabouts. It will be recollected that the former ratio was that between the median female and the median male.

The variahilily of the discriminative power appears from the ' observations to he distinctly higher amon^j females than among males. Measuring it in the usual way, by the half difference between the two quarliles, which is the same thing as the prohal'U error o{ a single observation, or else by any multiple of this, as by the mean error, we find that the variability among females is to that among males as 370 to 325, say as 8 to 7. It is in consequence of this that so large a difference is shown between the relative sensitivity of the two sexes, at the right and left extremes of their respective curves in Fig. 2. We find from Table II. that the value of C— ^at the 1st decile is 23 milli- metres, and at the 9th decile it is only 07, the differences between ihe intermediate pairs decreasing regularly. The regularity of the decrease is not apparent in the actual obser- %'ations,as shown in Fig. I, nor in Table I., still there is nothing in what we see there that is incompatible with Fig. 2, while Ihe fact of the difference between the right ends of the traces being much less than that between the left, is conspicuous.

Is it. however, a physiological fact that women are more variable than males in respect to discriminative touch, or are the observations affected by any extraneous cause of variability ? I think that the recorded variability may in a very small part lie accounted for by the fact that women vary much more than men in the exercise of sustained attention. Carelessness would affect the results in the same direction as diminished sensitivity. Thus suppose one part of a large number of persons who were all really alike in sensitivity, to be very careless, and the re- mainder to be scrupulously careful : the mind^ of the careless would be apt to wander ; they would then fail lo notice the first just-perceptible sense of doubleness, and would appear, in consequence, to be more obtuse than the careful ones. Though the range of variability was in reality ;/;'/, the existence of care- lessness would introduce variability into the records. Some women are religiously painstaking, as much so as any men ; but the frivolity of numerous girls, and their incapacity of, or un- willingness to give, serious attention, is certainly more marked than among men of similar ages. Women may, however, be really more variable than men in respect to sensiiivity, because they seeui more vaiiable in a few other respects, such as in stature and obe-ity. Many more very tall girls aie to be seen now a- days among the upper classes than foimerly, but the run of the statures among men has not altered <|uite so much. The multitude of extraordinarily obese women who used to frequent Vichy for the cure of fatness, were wonderful to behold ; but they are no longer to be seen in their former abundance, as the fashion of treatment has changed wiihin recent years. Again, it appears that women vary much more widely than men in respect of their morality ; to which assertion I would quote Tcnny-nn as a corroborative witness, who writes as follows, in Merlin's soliloquy on the character of \ivien : —

" Formeo at most dilTer as heaven and cinh, Itul women l>ett and wor»t as heaven and hell."

Since Fig 2 is true lo scale, it is easy to utilise it for ascertaining Ihe class-place of any man or woman in respect to the form of sensitivity now in question. The whole process would be as follows : — Take a pair of compasses, and find with them by experiment the just-perceptible interval across on the nape of the neck of the person tested ; then apply the compavses, to Fig. 2, keeping one (the lower) of its points always on the base line of the Fig., and holding the compasses so that the line joining its points shall be perpendi- cular to that base line. .Slide the lower point of the compasses along the base line until the upper point touches the male or female trace, as the cise may be ; then read off the grade at which the lower point Htan'ls on the base line. .Suppose it to be 35 ; wc thereby learn that 35 jicr cent, of Ihe same ses have more wDsilivity than the pernon tested, and that 65 per cent, have le»<. .Similarly for any other value.

It would, I think, lie well worth the while of an inquirer to repeal these tests, to revise my result*, and to pursue the subject m ' ' " ' '■ rr- should feel ilisposed to do so, I would

«i;. ikc his measurements with the cheap

for - .. , - - , in common nse by carpenters. The

legs arc connected not by a joint, but by a spring which tends to separate them, and they arc brought together to any desired

interval by turning a screw with the finger and thumb, whidi I overcomes the spring. The interval between the points could < ea-ily be measured on a separate scale ; all the more easily, if ] there were a slight depression at the zero point of the scale, in - which one leg luight be securely rested.

Francis Gaiton.

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