definitely in mind I retested Y on D. 105 as she lay on her mother's knee resting in an interval of feeding.

This curious phenomenon of the blinking in response to seen claps, when claps only heard were not blinked at, seems only explicable to me on the assumption that this reflex sometimes works as the result of a summation of two stimuli when it may not in response to one alone. It is to be remarked that this phenomenon was only noticed at a period when the eye-blink response to an object seen approaching had developed.

The next record on B is D. 164 when "pretended hand clap produced blinking, three or four times; then did not. Made hand claps where he could not see, and blinks recurred each time. Then claps renewed in his sight and blinks occurred. Now pretended claps produced blinks again two or three times and then failed again: renewed claps in sight, then again pretended ones, produced blinks, but for a shorter time-only once or twice, then failed."

This tendency remained at least as late as D. 200, the last note, when "he still blinks at a seen clap and at first pretended clap, but not at second or third. He still blinks at a clap noise when hands not seen."

Here again we seem to have definite evidence of a transference, in the course of the development in early infancy, of the reflex response to some stimulus (seen movement usually associated with sound of clap) associated with the primary essential 'appropriate' stimulus, viz. the loud sound of a clap. It may be compared with the fact discovered by Pavlow, that when a horn was repeatedly blown at the same time as an acid was placed in the mouth of a dog the increased flow of saliva due to the acid could eventually be obtained by the blowing of the horn alone, when it had become associated with the acid1. And further, it affords an example of 'co-ordination' by a common path to use Sherrington's phrase. "The ramifications," he writes, "of the central neurones attached to these (distance) receptors are so extensive and the reactions they excite are so far spreading in the organism that their

1 Pavlow, Scientific Investigation of the Psychical Faculties or Processes in Animals, Huxley Lecture, 1906.

association with the reactions and central mechanisms of other receptors is especially frequent and wide1."

THE INSTABILITY OF A REFLEX.

The variability of the eye-blink reflex in response to sound was so marked, and so great was the difficulty of making certain that it was not due to varying strength of stimuli that I carried out with Y a rather long series of experiments with a standardized sound stimulus. This was produced by dropping a stone weighing about 1 lb. on to a small tin tray turned upside down on the floor at a distance of 6 feet from the infant. The stone was dropped at first from a height of 1 foot, which was then raised to 2, then to 3 feet, and finally to 4 feet. The experiments were only done when the child was lying happy and contented on her mother's knee, usually resting in the middle of a meal, or at the end. Except in earlier cases specially indicated, the intervals between the bangs was as on D. 115 timed at about 15 seconds and on and after D. 116 at about 20 seconds, the time required for me to turn and write down the result of the previous bang, pick up the stone and measure the correct height again. For the first 3 days the intervals were about 5 to 7 seconds. I lengthened the intervals to lessen the chance of fatigue influences.

In the table below the score 1 means a complete blink, means a slight blink but not a complete shutting of the eyes. Any special occurrence is noted below.

This experiment clearly illustrates the extreme instability of the blink reflex at this stage. It was certainly suggested at one sitting that some other happening beside the sound, as for example the diversion of attention by the face of a visitor, might inhibit the reflex: but on many occasions no such variations in surroundings occurred: the reflex, indeed, seemed to appear or not in a most arbitrary fashion. Table I shows more clearly than we have done so far, how cautious we must be in interpreting the absence of a reflex response on one or two given occasions as showing that the requisite mechanism has not yet matured. There was no response to any of the twelve tests in the morning of D. 195, but the reflex revealed itself again in the evening.

1 Op. cit. p. 351.

Day

111 112 114 115 116 117 118 119 120 131

Table I. Showing Variability of Eye-blink response to loud sound.

195 195 196 a.m. p.m.

15"

15"

15"

1

1

0

1

Ob

le

0

N.B. The mark 1 indicates a complete blink; indicates a partial blink.

At the same moment as the bang, door opened and E came into the room. ? Summation of stimuli. Had just turned away from looking at me when the 9th bang took place; and at the 11th she was

in the act of so turning.

4 was now within sight and Y interested in gazing at him. This day (117) she was tested when

ready for her meal and at bang No. 12 she was turning towards E making food grunts.

e

On D. 118 she was held by her nurse and was gazing all the time at her mother's face.

Looking smiling at me.

On D. 120 after No. 1, I was feeding continuously during the experiment. At every bang, after the 2nd, whether there was a blink or not, she took her face away from the breast and looked up.

* For 6th and following tests Y was placed on bed instead of on mother's knee but it was impossible to place her where she could not see one of us and yet be where her eye-blink could be seen. She was in a most jovial exuberant mood at the time of this test, laughing and crowing. A drop of 5 feet was tried for No. 12 without avail.

A slight frown occurred: in cases 5 and 12 there was a delay of a fraction of a second.

THE VARIABILITY OF A REFLEX UNDER VARYING
GENERAL CONDITIONS.

In view of the great instability of the blink-reflex without any apparent variation of external conditions to account for it, we are more prepared to find that varying bodily conditions, emotional states, etc., may affect markedly the happening of a reflex. I often observed with B that crying at a strange sound and other 'fear' reactions were less likely to take place when the baby was nursing than at other times. Similarly Miss Shinn noted that the eye-blink, which took place at the ringing of a bell, did not do so when the child was nursing1. In the case of reflexes which are associated with emotional states (for example, blushing, paling and starting), it is not surprising that a special condition

1 Notes on the Development of a Child, p. 107.

of the whole organism may inhibit the emotion normally produced and so the reflex associated with it.

In view of the known central interference or facilitation of reflexes, of the general influence of the cortex on reflexes (both by way of unconscious inhibition and in some cases of the voluntary initiation of the usual reflex action), and of the effect of fatigue on reflexes, one would expect a priori that varying conditions of the central nervous system and especially strong instinctive impulses and emotional states would have their influence on the appearance in infancy, even of those reflexes not usually considered to be specially related to emotions or instincts.

The neglect of this possibility has led to a failure to interpret aright the variability of some reflexes in individual cases. No doubt individuals vary as to the strength and fixity of certain reflexes, and the relative maturity of the child at birth may have its influence on the date of the appearance of some reflexes. But some differences in the results of tests on different children are almost certainly due to the influences of the general psychophysical conditions of the children at the moment.

THE FINGER-GRASP REFLEX.

A good example of this may be found in some observations I made on the finger-grasp reflex. Very varying reports have been made on this reflex. Dearborn noted it in his daughter on D. 1, "strong and quick," and found it "notably less vigorous" on the 10th day. Preyer mentions a marked difference between his two children, and on D. 12 A's finger-grasp was not nearly so strong as B's at the same period. But the reports on B and Y are suggestive of the effect on the reflex. of emotional influences. They are, on B:

D. 1: "Grasped my little finger with left hand, but not strongly." D. 3: "When held on back, preparatory to bath, groped vigorously with hands and arms, as though for something to hold. When his father's head was offered he grasped the hair and tugged vigorously: his hand had to be unclasped."

There was of course no deliberate groping at this stage. There appeared to be simply more vigorous and sustained spontaneous movements than usual under the stimulus of excitement through vague feeling of insecurity due to suspension in the air.

In the little girl Y the finger-grasp was weak on D. 3 as she lay comfortably on her nurse's knee. When at my request she was held aloft rather insecurely on the nurse's hands the grasp was much stronger,

till the arm was stretched fully out: though it would not support the weight.

Of B I noted again on

D. 8: "Finger grasp not shown to-day."

D. 10: "No grasp of my hair when put to his hands which were groping and feeling about."

These were but two of frequent tests of the kind giving negative results.

The next record indicates the presence of the reflex during sleep when inhibitory central influence, if developed at this early stage, would be at rest or lessened, an observation, therefore, not strictly comparable with the earlier and later ones. Finally, on D. 20, when B was in his bath, which judging from facial expression invariably caused "a combination of pleasure and rather fearsome excitement," the reflex was noted again. "In his bath to-day he had my head presented to his clutching hands. He took a firm grasp of my hair with his right hand— quite painful. I raised my head slowly, but he held on, being raised almost out of the bath (with some support of nurse). Then his hold gave way and he dropped a little with a very short, sharp cry."

In these early days then, a strong finger-grasp reflex was noticed in B and Y only under conditions of some excitement. It may be remarked that the remarkable consistency of strong finger-grasp found by J. B. Watson was obtained when the children were entirely suspended by and dependent for support on the grasp1.

It would be useful if a sensitive dynamometer could be made suitable for testing the strength of a baby's hand grasp. The difficulty is to get something thin enough for the tiny fingers to enclose. With Y I endeavoured to do this by attaching a round pencil with wire to the hook of the nurse's sensitive spring balance made for the purpose of weighing babies. Two observations I made with this on Y are germane to our present topic.

D. 25: "Took the opportunity of nurse cleaning Y's nose (to wake her when she fell asleep too soon in feeding) to test finger-grasp with balance. Got the handle with difficulty into her left hand-very gentle grip: thumb went round very readily (boy's grip). When nurse inserted cotton wad in nostril, grip greatly increased and registered 2 lbs. pressure. Then I tried right-hand grasp: even slacker at start and thumb would not be placed in 'opposed position.' Insertion of wad in nose led to greatly increased grip, 1 lb. registered before it lapsed."

1 Psychology from the Standpoint of a Behaviorist, p. 262.