Just as in the time of Lamark, Goethe, Haeckel and Darwin the problem of man's origin, or of how “man became man” ranks first among the problems of the day. However, the preponderant part in its solution now belongs to one of the youngest branches of science — namely to zoopsychology. And we believe that the remarkable researches of a number of distinguished scientists (Bingham, Hobhouse, Kinnaman, Koehler, Révész, Shepherd, Thorndike, Yerkes, Watson) devoted to the investigation of apes and monkeys are called upon to pronounce themselves ultimately upon the subject.

The present work is merely a modest contribution towards the elaboration of these problems and it chiefly endeavours to bring to light certain new correlations purporting on these items:

An answer to these two general problems should be largely based upon two other more particular points viz. 1) the scope of a monkey's adaptive motor habits when overcoming different artificial handicaps on the way to freedom and food, 2) which distinguishing features, does the motor labour of a monkey's hands possess and 3) how the psychological characteristics of a monkey are outlined on the ground of manual behaviour.

A sexually mature and semi-tame female Macacus Rhesus (Photo D.1) (Simia rhesus Audeb.) was selected for the purposes of our experiment. The method employed was the well known puzzle box method devised by American zoopsychologists. The only variations adopted consisted in some changes in the structural units of the box and the locking devices.

The front wall of the experimental cage (Figure E.1, “Experimental cage”) consisted of a framework with grooves for inserting movable (compact wooden or transparent network) frames with doors cut in, these doors being easily closed from either inside or outside by means of different closing contrivances. The number of frames corresponded to the number of unlocking tasks.

The mechanically closed doors could be opened either outward or inward, but were never arranged to fall down; wherefore the animal was always bound to bring its hands into active motion when opening them. This circumstance enabled us to ascertain the degree to which the animal became assimilated with the device and to get a comprehensive idea of the completeness of the work performed. All the locking contrivances were selected from the implements of human daily routine. The variations incorporated in the different devices were reduced to altering the following items:

The main types of devices, made use of, number eleven:

For unlocking these devices twenty finger movements differing in form, six differing in direction ^[335] and three differing in force application ^[336] were required: taking off, drawing aside, pulling aside, pushing back, turning, rotation, pulling out, extraction, attraction, throwing backward, unscrewing, unwinding, tearing, untying, pressing, pushing, lifting, dropping, raising, throwing down.

The chief aggregate devices comprised the following:

The factors that stimulated the animal towards the performance of the task were only of an encouraging or pleasant nature. The animal, hungry after the night, was stimulated by food; the satiated monkey obtained some sweetmeat (the food being placed within the cage); in case the food was placed outside the cage, the animal was not only given food, but also liberty, entertainment, such as swinging (see Photo D.6, fig. 2). Punishing methods were totally obviated.

The picture-film performance developed in accordance with the following successive stages:

As an extra reward, the process of swinging the macaque was also used. Fig. 1 of Photo D.6 represents the moment when the whole posture of the animal expresses his eagerness to indulge in that entertainment. His aerial evolutions (represented in fig. 2 of Photo D.6), however vague and illusory the resemblance, still recall to the beast his familiar mode of locomotion amongst the tree branches and pliant lianas of the jungle.

The experiments were recorded with an almost stenographical accuracy. Besides a quantitative timing of each item of work completed, a qualitative account of the experiments was set down. The records of time are represented by the curves of the performance (see Equation F.1, “Hooks A₁, A₂, A₃, Б, E₁”— Equation F.36, “2 door straps, pawl, padlock, key (d₀З₁d₂)”); the main data obtained during the work with serial sets are to be found in summarized tables.

The analysis of the summarized results of the experiments was carried out from several viewpoints, viz.:

All that part of the investigation, that deals with minute analysis, is set down in detail in the Russian text. It allows to set forth the following summarized statements.

From all devices offered, i. e. 60 unit devices and 33 aggregates, two devices only have proved to present unsurmountable difficulties to the macaque, who did not succeed in unlocking them; these were a tightly inserted though simply modelled hook (Figure E.4, “Hook E₁ horizontal to left”) and a freely suspended padlock locked by an unattached key (see Photo D.22, Photo D.23); the latter device having greater mobility in secondary parts than the mobility at the point of force application.

Failure in the above two cases may be accounted for as follows: in the first case, i. e. that of the hook, the macaque does not apply a sufficient muscular effort when unlocking the device; in the second instance the monkey follows a blind avenue; he clutches at the most movable part of the device — the padlock — while totally neglecting the key which presents a less yielding point of force application. Even so many as 26 repeated experiments, taking on the whole 3531 sec., do not teach him to master the task.

Thus, the macaque nearly equals man in the variety of the minute mоvements of his fingers, though the force of these movements is obviously inferior to that exerted by man.

The vast majority of separate devices (82%) and the predominant amount of aggregates (79%) are mastered by the monkey without any foreign assistance. As regards the rest of the devices, the monkey receives help on the part of the experimenter who either sets an example of unlocking or points out the obstacle or, finally, aids the animal by half-unlocking the device.

The macaque cannot grasp without assistance the working of the following contrivances: the first hook offered А₁ (Figure E.2, “Hook А₁ inclined to right (1-st)”); the first bolt with a novel method of unlocking P (Figure E.14, “Sliding bolt P horizontal to right”); devices possessing considerable resistance at the point of force applicatoin (E₂, O, G, X₂, Z₂ Figure E.4, “Hook E₁ horizontal to left”, Figure E.13, “Sliding bolt O horizontal to right”, Figure E.18, “Sliding bolt G horizontal to right with stud bolt”, Figure E.27, “Complex sliding bolt X₂ vertical upwards”, Figure E.37, “Centre-handle turning-lock Z₂ with spring act. to left”), contrivances whose parts of secondary importance possess greater mobility than does the centre of force application, viz.: chain C₁ (Figure E.43, “Chain inclined C₁ to right”) and padlock (З₁ Photo D.23 fig. 1, 2); devices with centre of force application masked or disguised (Y) (Figure E.21, “Sliding bolt Y horizontal to left (with concealed stud bolt)”); aggregates containing new items which-being out of sight cannot be detected by the monkey and are therefore to be pointed out to him (Z₃Z₄, OIP, V₁W₁X₂Y₁, ROYP, KM, KNM, IP). Figure E.40, “Combination of 2 latches, 2 centre-handle turning-locks KMZ₃Z₄”, Figure E.29, “Combination of 4 complex slid.-bolts: V₁, W₁, X₂, Y₁”, Figure E.25, “Combination of 4 sliding-bolts ROIP”, Figure E.11, “Combination of 4 latches K, L, M, N”.

Thus, the macaque displays certain self-activity in finding the means of unlocking, develops energy in action and exhibits self-initiative in performing different tasks but exclusively within narrow limits — a confined scope of activity as well as conditions of its display.

A casual ^[338] success in apprehending the means of unlocking separate devices is met with comparatively rarely (in 17 % of all cases). With aggregates this occurs oftener (in 35% of cases). When separate devices are operated a casual success of unlocking happens when the centre of force application may be particularly easily set into motion. In case of serial contrivances such success happens without any rational accountability.

In the vast majority of cases (72%) the monkey discovers, as soon as in the first experiment, the point of force application whereupon he carries out the first successful unlocking. He requires 2 to 10 repeated experiments to grasp the method of unlocking only with regard to 24% of separate devices, — those which present particular difficulties, e. g. novel design; great resistance; change in position as compared with that of previous devices; difficulty in detecting the point of force application; mobility of parts of secondary importance which diverts the monkey's attention from the right spot, etc.

When confronting aggregates, the monkey the sooner surmounts the first successful unlocking, the closer the components are concentrated in the field of his vision, the smaller they are in number, and the more accustomed he is to operate the individual contrivances that constitute the whole aggregate.

In detecting the main points of hinderance as well as in finding the means of unlocking, the monkey is chiefly, if not exclusively, guided by kinaesthetic but not by visual perception. The motor reactions of the monkey the sooner result in the fulfilment of the object i. e. release, — the more reduced the field of their application is, for actions which are developed in a narrow field exhibit greater progress in their variety, improvement and perseverance superior to that obtained in a vast field.

The first initial trick in which the macaque effects the unlocking is in most (80%) cases overloaded with superfluous, essaying movements (from 1 to 30); it is in 16— 19% of all cases only that he acts in a precise and simplified way. These essaying movements vary in number depending on the following factors: degree to which the monkey is accustomed to the method of unlocking an individual device; the intricacy and novelty of the latter with regard to the method of unlocking; the extent to which the. number of component units is increased; intricacy of the qualitative composition of the aggregate.

In most cases (72 %) the ultimate wау of unlocking individual devices becomes, now sooner, now later, — it depends on the intricacy of the device — modified to such a stage as to contain but strictly indispensable movements. The ultimate method of work remains complicated — “monkey-like” — only with regard to considerably resistive devices, to contrivances presenting but little resistance in secondary parts, and finally to those whose unlocking the monkey has insufficiently rehearsed.

In case of aggregates no such standardizing of method is observed; “ideal” experiments (those which record no superfluous movements) usually alternate with unsuccessful ones and though the former prevail in number during the middle and final stages of the work, they do not survive up to the last experiment of the series.

Of course, these superfluous movements require extra time and in individual experiments it amounts to 16 times the normal value.

The macaque grasps the unlocking of novel devices in the process of numerous and varied groping kinetic attempts, but he misuses this experimenting — he applies it in operation with combined devices consisting of units whose working has already been learnt. This means that here the experimenting both takes the place of exасt reсоlleсtion of kinetic habits in familiar situations and fills the deficiencies of ingeniousness in novel situations.

The analysis of the quantitative data which express the duration of individual, especially important experiments (1-st, last, longest and shortest), allows to infer the following summarized conclusions.

The first experiment of unlocking an individual device is at the same time the most lengthy one in the whole series of experiments dealing with that device; if, however the work is performed with an aggregate, the first experiment often does not prove to be the longest one; this may be accounted for as follows: in the first instance the most serious difficulties arise at the outset as the macaque has not yet grasped the most essential part of the task — the very idea of unlocking; on the other hand, in the second case the embarassment is due to casual circumstances, as fatigue, distraction, forgetfulness with regard to various obstacles etc. The length of the first experiment depends on the intricacy of the contrivance. The most serious trouble is met with in case of single devices, that are novel in the method of unlocking, resistive at the point of force application and those with particularly mobile parts of secondary importance; similar difficulty is presented by aggregates consisting of numerous separate devices of complicated design. It as a rule does nof occur that a series of experiments with a particular device should comprise two experiments of the same maximum length: as a rule, there usually exists but one moment of the work, culminant in regard of embarassment; this moment necessarily takes place either in the first or in one of the five earliest experiments of the series. The maximum value of the length does not coincide with the first experiment in the following two opposite cases: that of a considerably resistive device (then it may be explained by fatigue) and that of an easily yielding contrivance, in which case the value of maximum length is inconsiderable and no constant ways of unlocking are assumed. The complication of design embarasses the monkey more than does the extension of the number of unit components (the culminant value of the maximum of single devices^[339] considerably exceeds that of aggregates^[340].

According to the diversity of figures which the value of the maximum assumes, the articles of human daily routine when offered to the monkey confront him with difficulties whose degree varies within a very wide range; but in most cases of average difficulty the operation of these articles is fulfilled in 1 to 5 minutes at the worst.

The most successful, i. e. the most rapidly fulfilled tasks are to be assigned to the final period of the performance with unit contrivances and usually coincide with the last experiment of the series. When dealing with aggregates, this climax appears in the middle period and often does not survive it.

The macaque does not fail to exhibit a manifest progress in gradually shortening the time required for the fulfilment of tasks. The rapidity of approaching the stage of the shortest experiment, depends upon the intricacy of the contrivance ^[341] while the degree of perfection (rapidity of operation) hinges on the amount of preceding exercise, though both the usual hastiness of the macaque and his eagerness about getting an edible reward are the chief factors tending to promote his activity. Generally, at the final stage of the training, the monkey succeeds in operating-devices of most varied intricacy with an uniform perfection.

The monkey displays a very ununiform progress when working with different devices. The improvement of his skill is more considerable in the operation of single contrivances as opposed to aggregates; it is greater in case of the qualitative complication of conditions than it is when the components of the set are developed in number. According to the lines of the maximum downfalls of the curves (see Equation F.1, “Hooks A₁, A₂, A₃, Б, E₁”— Equation F.36, “2 door straps, pawl, padlock, key (d₀З₁d₂)”), the climax of efficiency coincides, in most cases with the initial period of work, more rarely with the middle period and still more rarely with the last one.

According to the lines of the maximum upheavals of the curves (see Equation F.1, “Hooks A₁, A₂, A₃, Б, E₁”— Equation F.36, “2 door straps, pawl, padlock, key (d₀З₁d₂)”) the efficiency is most unsteady in the initial and the middle periods to which periods the maximum upheavals of the curves expressing the deterioration of the efficiency are sometimes also to be assigned. In the last period the efficiency is most perfect and uniform.

The analysis of the curves leads to the conclusion that the macaque supplies three different types of efficiency curves:

The first two types are met with in case of insufficient practice of unlocking.

The third type with prevailing progress is most peculiar to the macaque.

The analysis of the tempo of the work, both with each device, throughout a whole series and with different devices along periods similar in the order of succession, was effected in the following way:

The whole series of experiments on each device was divided into tetrads, comprising four experiments each. The average duration of experiments was calculated for each tetrad respectively. Next a comparison was made between such values obtained respectively for a series of tetrads referring to the same device. A similar comparison was drawn between the average durations of different devices for corresponding tetrads.

A scrupulous investigation of the tempo of performance infers a conclusion to the effect of the extreme “jerkiness” of tempo: periods of high efficiency alternate with those of slackened unsuccessful activity. The former last twice as long (in the course of 2 tetrads) as the latter (for 1 tetrad). The jerks of the curve appear just in the middle and final stages of the work: with single devices they come about later (after 40 experiments) and with aggregates — sooner (after 24 experiments).

Thus, the appreciation of the tempo of performance of the macaque with regard to different contrivances throughout the whole period of experiments suggests the conclusion that, in case of lengthy work, periods of high efficiency alternate with periods of depression — quick performance is intersected by periods of slackening, outbursts of energetic work occasionally give way to languidness.

This means that the psycho-physiological condition of the monkey undergoes changes during the whole period of experimenting — the macaque now exhibits high efficiency and now appears to indulge in repose. Energetic, perfect, efficient work is displayed by the monkey at the initial stage when he is full of fresh energy supply. Work with alternating efficiency begins at the middle stage and extends over the last period. When the monkey is busy with single devices the “jerks” appear later than it occurs in case of aggregates which latter fatigue the macaque apparently sooner.

As has already been mentioned, the efficiency of the monkey is usually of a progressive nature, the regressive character being met with more rarely and in a less pronounced form.

In the initial period ^[342] the work of the monkey is of most varied character. At this stage, single devices, which present the qualitative difficulties in design, are to be classified either as the most difficult or as the easiest ones in operation, whereas serial sets presenting but quantitative complications are usually of middle difficulty. The most difficult of unit contrivances are those which are novel to the macaque, those whose unlocking requires a considerable muscular effort, and those with unlimited mobility of parts. As regards serial contrivances, the difficulty of operation depends upon both qualitative and quantitative intricacy.

In the course of training, the macaque manifestly improves his achievements in respect of efficiency, the tempo and the degree of this improvement being greater in case of single devices than is the case with aggregates.

The computation of the average rapidity of performance (which rapidity is calculated as the mean value of each series of experiments on a particular device) reveals that, on the whole the articles of human daily use are very ununiform in regard of the difficulty they present to the macaque (in most cases they are of middle difficulty). The most troublesome devices are those which do not admit quick and easy kinetic manipulations in a narrow field of action.

On classifying all contrivances into groups according to the average rapidity of unlocking, it appears that the prevailing percentage of devices, both single and combined, take from 10 sec. to 1 min. to be unlocked; most of the remaining single devices may be assigned to the group of easily unlocked contrivances (taking 1 to 10 sec.) and most aggregates to the difficult group (taking 1 do 5 min.); as an exception only it occurs that single devices are to be found in the difficult group and aggregates in the easy one.

This classification confirms the idea that though at the initial stage of work single devices present to the macaque difficulties, both more material and more multiform than those involved in aggregates, — the monkey succeeds in overcoming them with greater ease than he does in mastering the unlocking of aggregates, though the latter are presented later.

The consideration of the composition of devices in groups differing in degree of facility, again brings forth the conclusion' that the conditions favourable for the rapidity of work with single devices are the following:

For aggregates the conditions securing the fulfilment of the task are the same as for single devices, but here it is necessary to take into account also the number of unit devices that constitute the combination (naturally, this number is in most cases directly proportional to the time required for operation).

The conditions hampering the work are opposite to those above mentioned, which fact may be proved by a series of negative arguments.

In each series of different devices (e. g. hooks, bolts, latches etc.) the first novel types offered, especially the very first absolutely novel devices ^[343] take a longer time for unlocking than do those presented subsequently ^[344].

Among newly presented devices those proved the most troublesome whose secondary parts were more movable than the main parts (first padlock З₀, chain, C₁ tope), also devices with little give-in (a tight hook “E₂” and tight sliding bolt, “O”), springing devices, devices complicated by additional parts (pawls locks), those presenting a great temptation to indulge in superfluous kinetic manipulations and finally aggregates, intricate both in respect of composition and number of components.

Within each series of uniform devices (as either hooks, or latches, or sliding bolts) the same relationship is also observed.

The first mechanisms of a given series presented, with tightly fitted point of force application, with springs (automatically locking) take the greatest time for unlocking; on the other hand, those whose method of unlocking is familiar to the macaque and those with easily movable centre of force application, are unlocked most rapidly.

Devices partly familiar and possessing an average difficulty give-in are to be assigned to the group taking middle time for unlocking.

Thus, ceteris paribus, the average rapidity and skill in performing work is defined by a series of factors:

In the first place (and partly) by the sequence in which the devices are submitted to the animal (the first devices presented — 1-st hook, 1-st sliding bolt are unlocked slower than are the subsequent devices of the same series). This emphasises the importance of the degree to which the monkey becomes accustomed to a device and points to the fact that he makes use of experience acquired in preceding experiments. But this is observed at the stage of initial orientation, or first acquaintance with devices (I-st hook, А₁; 1-st bolt, P; door strap, d₁) or in operation of specific contrivances (first chain, C₁, first padlock, З₀).

In the second place by the type of device and the respective method of unlocking.

In case the type of device be altered, the most marked alteration in the rate of performance comes about when a device of the first type, the hook (А_i) is supplanted by one of the second type (latch K), then when a device more movable in its secondary parts as compared with the principal ones (З₀) is introduced. Less marked is the change in the rate of performance ^[345] when a device of the type of sliding bolt (P) is introduced, since it calls for the now movement of pushing aside; the same holds true when a chain device with easily moving secondary parts (C₁) is made use of.

Should we now follow the graph of average experimental time required for mastering the different devices, and accordingly tabulate them in order of decreasing rate of performance we shall readily see ^[346] that the greatest initial difficulty is presented by the padlock which is mobile in its secondary parts as compared to the main portion, further always in decreasing order, follow sliding bolt, chain, tape, key, centre-handle turning lock, excentre handle turning lock, door strap, latch and latches.

Hence the following conclusions may be made:

As regards the increasing order of difficulty the main types of the monkey's movements may be classed as follows: pulling out, sotting aside, attraction, lowering, turning, rotation, unwinding, setting aside and extraction, pushing aside.

The third factor that influences the rate of unlocking is to be found in complication of design, when additional parts, such as pawls or locks are introduced, or when greater mobility of accessories is imparted, or still when the centre of force application is disguised or the path of its motion lengthened. These intricacies, as well as the introduction of self-locking or spring devices in the stead of ordinary ones, exert a considerable resistance to the efforts of the macaque ^[347]. And naturally, as a result, the average experimental time is extended and the moment of unlocking delayed.

As regards rotating motions the “lowering” movement is more easily performed than that of turning 90º; this latter movement with greater ease than turning 180º; this turning 180º — with a limited direction of motion — is again easier performed than the same movement with unlimited motion — that is to say — all rotating movements are fulfilled the easier, the more limited in respect of mobility and the shorter the angle of revolution, the more support the double armed lever gives to the fingers.

The fourth factor is whether or not the centre of ferece application should be easily yielding. In case of its greater resistance in motion the average time is again prolonged.

This influence is more considerable when the centre of force application assumes a straight-line motion (hooks or sliding bolts being operated with) and decreases with rotary motion turning-locks (centre and tape being used).

This points to the fact that a monkey seems more accustomed to obstructed movements that require greater muscular effort when following a curve than when proceeding along a straight line.

The fifth factor, namely when the device is transferred from right to left similarly increases the average duration of the experiment.

The work of the monkey is performed with greater celerity when manipulating with a device where the centre of force application is checked over to the right-hand side.

The influence hereat exerted becomes especially marked in respect of pushing away and ratation as contrasted with taking off and lifting, which induces us to think that when the performance involves considerable friction and consequently requires great muscular effort, a transposition of the centre of force application in right-hand direction is effected with greater ease than when made to the left. This circumstance gives evidence to the effect that the right hand of an ape seems more developed and endowed with greater strength than the heft one.

The sixth factor — viz. when the device is arranged vertically instead of horizontally involves the conclusion that devices located vertically (i. e. with axis of force application vertically located) are in most cases somewhat easier unlocked, than devices of similar design but with horizontal attachment — thus, the monkey performs with greater facility such movements as setting aside, extracting, attracting, lasy upward pushing, similar forward pushing (that is in the vortical plane) as compared to moving to right or left (that is in the horizontal plane).

Whatever change might be introduced into the plane in which the centre of force application is situated, no influence of this factor can be traced in the setting aside motion.

This means that the monkey is naturally more apt to develop his motions making use of vertically located supports, transposing them in the vertical plane.

The seventh factor — habituation or the degree to which the animal becomes familiarized with the direction any transposition in the; centre of force application is to evolve along, exerts a marked positive influence upon the average rate of performance. The animal acquires stable kinetic habits and makes successful use of these under analogous circumstances notwithstanding any new changes in the structural units of the device.

Now, which of the said seven factors may be said crucial as regards influencing the average rate of performance?

An examination of the 7 tables drawn up with a view to each of the 7 problems raised (see page 191— page 197) with due account taken of the maximum coefficient changes in average performance rate helps us to visualize that when the course of the experiment is altered by any of the seven possible factors affecting the rate of performance, the most considerable influence seems in all cases to be exerted by greater intricacy of design. Next follow: change in the give-in of the centre of force application and alteration of the very type of device.

The duration of the experiment is to a lesser degree influenced by such factors as previosly acquired habit, the sequence in which the devices are offered to the macaque, habituation in respect of the very unlocking and finally transposition of device from right to left.

The transposition of the device from the vertical to the hоrizоntal plane has the least influence of all.

And finally, colour, form and size may be said to play no part whatsoever as regards the results of work ^[348].

When operating with a combination of devices, we may state that the chief rules established for unit devices hold good also in this connection. This statement need however be supplemented by the following remarks: As a rule, the average rate of performance is, with aggregates, less than the sum of average performance rates with the unit parts of the aggregate. This means that work conducted with serial sets is on the whole easier than with separate units. As it is. aggregates present more complications of quantity than quality, though, naturally enough, every increase in the number of separate devices and any new variety in their selection increase the experimental time.

Comparative Rate of Performance in Unlocking Different Aggregates. 

Thus it stands to reason that the average rate of performance with aggregates is determined by the type of constituent units.

A change in the type of devices constituting an aggregate thus affects the rate of performance: A combination of hooks, latches and excentre handle turning locks is unlocked easier than a combination of centre handle turning locks and sliding bolts; an aggregate of homogenous devices is unlocked with greater facility than a set comprising different components.

Hоw long does a monkey retain the motor habits he has acquired?

This can be estimated by confronting performance rates in crucial experiments (the first, the longest, the last, the shortest) and average rates in experiments before and after interruption in work.

Thence it will appear that any interruption in performances with units (the interims lasting from half a day to 180 days) exerts no detrimental influence upon the main features of the work, since the values of the first and last, most and least successful experiments, just as the average duration of task completion not only do not increase but often even dwindle down.

There has only been recorded a greater duration of the first experiment after interruption as compared with the last before; this points to the fact that the monkey, when lacking exercise, temporarily loses the once acquired mastery and perfection in executing the given task. Skill, dexterity and quickness have gone, but even when reproducing the task for the first time after the interval, the animal shows no sign of complete oblivion; while, in the subsequent, the monkey not only easily restores the once acquired mastery but progresses further in new accomplishments.

It is only when comparing the evidence obtained after interims of varying duration, that there is reason to say that a long interim in work with the same device (an interim of 45 to 180 days) exercises a markedly slowing down influence upon all the aspects of the work. A short interim (from half a day to 30 days) only delays the first experiment after interruption as compared to the last one before, but in all other respects the performance may be said to proceed without any change, or, in some cases, even with improved results. This tends to support the conclusion that in individual cases the perfection of the performance undoubtedly hinges on the amount of exercise, or, to put it otherwise, the longer the period of inactivity, the slower the rate at which the motor habits already acquired are put into practice.

However, the value for this loss differs for different devices and even for one given contrivance it is not apt to affect the different aspects of performance in the same way. The thus acquired kinetic habits of the monkey are characterized by considerable stability the means of acting is well memorized, but the rapidity and ease of fulfilment greatly depend on existing exercise and become easily forgotten when such is lacking.

Now, the performance of the monkey dealing with unit sets and his work in connection with aggregates develop along altogether different lines (in most cases the first type is rationally conditioned, the second not — having an irrational way of its own). The first type is rich in positive characteristics, the second in negative ones.

For the sake of convenience we shall place the distinct characteristic features of work with units on the left hand side and those of work with aggregates on the right.

When working with serial sets some important negative features stand out with particular prominence.

The macaque has no tendency towards sparing either his movement or strength, or time, he has no will-control over his actions (he produces an exhorbitant percent of extra, unnecessary movements, gives a minimum percent of “ideal” experiment, he spends an enormous amount of time on wasteful work).

When accounting for all the number of wasteful motions performed during all the while of experimenting with serial sets, we find that the percent of unnecessary movements never falls below 12 even when the combination is at its simplest (an aggregate of 2 elements) while this percent rises to 77% when the set becomes more complex containing from 3 to 4 elements. On the whole with 82% combinations we find 50% wasteful movements, i. e. in the overwhelming majority of cases the performance is encumbered by one half unnecessary movements.

During individual especially unlucky experiments the macaque performed 54 movements instead of the requisite 3, consequently 51 surplus. Sometimes the monkey goes so far as to produce 17 times more motion than required.

When working out individual motor habits the monkey manifestly progresses in his actions, and his performance takes the least time, while, when evolving serial habits such progress cannot be traced, and this is apparently due to the macaque well and thoroughly remembering individual successful tricks, but being unable to memorize and reproduce exactly a whole series of such motor habits.

It should also be emphasized that, besides these unnecessary motions, the macaque also performs a number of altogether wasteful gropings about the controls of the door, which the animal endeavours to fling open much before time and with which he begins to manipulate long before this is necessary. These superfluous tacklings of the control have been observed with all combinations, while at individual experiments their number assumes 11 (instead of the just one necessary movement). They were not only met in quantity at the early stages of experimentation, when the animal had not yet become sufficiently familiarized with the unlocking devices, but we encountered them in the later experiments (up to experiment 46 inclusive); at times, after having reverted to the device all the same be his attempt being fruitful or not, the monkey again and again starts controling the door in the hope of gaining freedom; it seems that there is nothing but this control to signal out to the monkey that the work is completed — for, without tactual perception the monkey is not able to ascertain the completion of his task only after the appearance of the locks or according to the course of his actions.

There is therefore no wonder that both the percentage of superfluous movements controlling the door and that of experiments containing such movements are very high (in 26% of combinations it reaches 75%), and that the number of experiments with superfluous controlling movements is greater than the number of “ideal” experiments, free of such movements.

It is observed that the greatest percentage of superfluous movements spent on controlling refers in most cases to aggregates which, though numbering but few component units, sometimes contain devices with novel specific methods of unlocking. This means that the fewer are the unit devices within sight, the oftener the door is looked upon as the cause of hindrance; the more difficult the method of unlocking of a device, the oftener the appreciation of unlocked state is effected through opening the door. The appreciation of the unlocked state reaches the macaque consciousness indirectly.

That is the reason why the fewest superfluous movements at the door may be assigned to aggregates forming simple but quantitatively developed combinations because superfluous movements in controlling concerns the mechanisms and not the door.

On adding the percentage of superfluous door-controlling movements to the general waste of movements it will be evident that 66,6% of aggregates are operated with a total waste of movements amounting to 50% and up to 77% the amount of superfluous movements thus exceeding that of necessary ones.

This gives an idea of the waste of time which the macaque spends on such aimless work thus confining his efficiency to very low limits.

What are then the reasons for this imperfection? They are several:

The first reason is lack of system, better to say utter disorderliness of unlocking: the macaque does not control his serial actions, he developes them at random, without any rational purport.

In regard of 17 devices forming an aggregate and comprising 4 types of units classified according to topographical distribution ^[349], there have been observed 14 different orders, according to which the monkey passed from device to device. There exists some system in proceeding from unit to unit of the aggregate but only at the very outset (1-st and 2-nd tests) as well as at the end of the work (last test), whereas the middle period is characterized by totally irrelevant behaviour in these proceedings. Should the intermediate tests be taken into consideration it would result that the multiformity of the system of unlocking is still greater.

This suggests the idea that the macaque has no plan whatever in performing and developing his actions.

Some system concerning the order of proceeding from device to device is to be found in the fact that the monkey starts in most cases from devices situated in the middle part of the aggregate and those closest to himself in his field of vision; he ends the process with unlocking the uppermost device. So he begins the work at the nearest and easiest point and therefore often forgets the existence of excentrically situated (the uppermost and the lowermost) devices; he leaves them unnoticed and finally finds them when he has already become exhausted.

Should the unlocking be systematic, both the superfluous aimless proceedings and the forgetting of remote obstacles would become reduced as well as the waste of muscular efforts.

Another drawback of the macaque's behaviour, which involves the imperfection of his work, consists in the following deficiencies: the neglecting of the useful auxiliary role of vision; want of rational utilization of natural means; inability or unwillingness to decide according to the outward appearance whether or not the contrivance is unlocked; want of understanding of the purpose of unlocking. When operating with new devices the macaque does not appreciate at the right time the success of his trick and the degree to which the task is completed: even after successful experiments the outward appearance of a device does not give him any idea as to whether it is unlocked; he persistently performs the senseless locking of a device just unconsciously unfastened by him; after many successfully performed tasks he unexpectedly takes to unlocking a device already unlocked; he wastes energy in a direction irrelevant with regard to the ultimate purpose as he aimlessly handles various parts of complex devices such as pawl or tape.

The macaque finds a means of overcoming new intricacies in unlocking the device and he estimates the completeness of the work chiefly, if not solely, by means of kinetic tests and not through visual perception.

So, the low efficiency of the monkey is due to the fact that with him visual appreciation is wholly substituted by kinaesthetic perception which is more imperfect and slow.

The monkey takes much time to grasp the relationship between the components of an aggregate (as between key and padlock, pawl and door-strap).

Even as he obviously appreciates through eye-sight the fact that the unlocking is fulfilled, he neglects this fact owing to the hurried, disorderly, inert groping which constitutes his operations.

The monkey does not appreciate the natural consequences of his actions; he ascertains that the task is fulfilled in an indirect and more troublesome way of pushing the door instead of merely judging by his own actions.

The macaque acts unconsciously: he does not understand the purpose of unlocking and often locks the device instead of unlocking it.

The developement of his actions has two opposite tendencies:

The work of the monkey is characterized by very considerable automatism; this statement finds corroboration in a series of data. The shifting of either the type or the position of the locking device does not at once induce the monkey to alter his way of unlocking; the monkey persists in using the now familiar pattern trick for a long time, though he gets many an opportunity to judge of the uselessness of this method.

When facing two unlocked devices — the old and new ones — the animal in the first place directs his attention to the old one which he operates at considerable length; only after many vain attempts of unlocking does he proceed to the new device.

One might ascribe this to the fact that the macaque is inclined to save his energy in the task of unlocking. This is particularly manifest when he operates resistive, spring devices whose unlocking he effects at several resumptions; but on closer examination it was ascertained that though he actually saves muscular effort, he does not abstain from superfluous attempts which causes him to spend time and energy more than is absolutely necessary.

The spendthriftiness of the monkey in spending his quick light movements finds its counterpart only in his lavishness at mess when he destroys and scatters more food than he actually eats. This implies the idea that when the saving of energy apparently takes place, it actually is nothing but sheer hurriedness.

This hastiness causes the monkey to change just at random the butts of his blind unaccomplished attempts of unlocking, to cling to the point of the greatest give-in and to abandon the task as soon as he meets the first hint of resistance. These changes as well as interruption of work not only occur in case of some resistance but also in case of no resistance at all with no perceptible reason to explain such behaviour.

It is the same inborn, fussiness and hastiness of the monkey, now moreover stimulated by eagerness for food and desire to escape from the cage that encourage him to begin repeatedly pushing the door, this last barrier to freedom, — wasteful and unnecessary as all these motions are.

The dissipation and lack of concentration on the part of the monkey also interrupt the regular completion of the work set and impede the solution of the task.

The impatience of the animal causes more or less lasting but frequent moments of dissipation and the longer the preceding lapse of fruitless attempts, the more frequent are and the longer do these dissipations last.

In some cases the animal drops his work altogether and has to be artificially stimulated (by some sweatmeat or practical demonstration of unlocking).

In the worst case this impatience becomes apparent after 40 seconds of uninterrupted performance, at best it is evident after 23 minutes, but never does the monkey's patience extends over half an hour, after which term he always stops his work for good.

Further, even the slightest obstacle makes the monkey interrupt his work — so minimal is the volition of the animal.

It appears that the field of vision which the macaque possesses is in no harmony whatever with his kinetic perceptual range. Even within the restricted confines of experimental space, is his sphere of perception limited, his field of kinetic actions — minimal and attention — inconsiderable, both in respect of volume and constancy of fixation. Very often, the monkey does not notice a new device or he forgets a peripherally located old one, or still he takes into no account all the handicapping items (when operating with aggregates). And the monkey's sphere of investigation becomes extended only after some concrete trial-and-error attempts to control the door and in result of acquiring kinetic habits of rightaway unlocking or still it is due to hints on the part of the experimenter.

So very restricted is the monky's field of attention that he fails to distinguish devices located at no more than 15 inches from the centre.

The widely spread opinion respecting the greatly developed imitative faculty of monkeys seems greatly exagerated. Demonstrative unlocking of the device by the experimenter does not teach the monkey anything, but only stimulates him in the performance of his task and shows him a definite spot where some kind of work is to be fulfilled.

The monkey often neglects all indications of the experimenter^[350] tending to point out a forgotten device and it frequently occurs that he unlocks the contrivances in a sequence differing from that followed by the experimenter when locking them.

Thus, there has been found no exact imitation of specimen procedure, as shown by the experimenter.

When attempting an intrinsic classification of the aboveoutlined characteristics, the following three points are brought to light:

Why then does the monkey leave aside or perhaps lose altogether the well tested regular principles of action?

In fact, this really gives us food for thought. What is the matter? How is this contradiction to be accounted for?

It seems that we could understand this only if taking our starting-point in the presumption that the negative characteristics of the macaque are in the ultimate result counterbalanced and annulled by positive ones when the performance is carried on in a very limited sphere of activities and with very limited alternates of choice. Under these conditions, the macaque stimulated by his hastiness and helped by reiterated exercise automatically memorizes individual successful tricks and finally acquires the maximum perfection in respect of quickness and ease for the performance of individual actions.

Under conditions of greater freedom for the choice of his actions and a more considerable range of kinetic display (as this is the case with aggregates) the negative characteristics are more freely exhibited and become predominant in their influence upon the eventual result.

In this case the monkey's memory, limited in scope as it is, totally deserts him. He is unable to memorize a series of casual lucky hittings and he is under the obligation of experimenting in groping attempts to solve the problem.

But, on account of the narrowness of his perception he is limited in kinetic investigations — wherefore the more distantly located devices remain outside the sphere of his activities. His vision does not help him in pointing out handicaps, since he usually ignores the auxiliary assistance rendered by eyesight, and should lie even throw a casual glance upon the locking devices, he fails to perceive their being locked or open, therefore his eyes do not save him from wasteful manipulations and afford no economy in endless stray gropings.

These useless motions could have been considerably reduced in number, they might have saved a stupendous waste of energy and forces, if the macaque had only had the slightest glimpse at the possibilities of controling or regulating his actions, making them more orderly, or imparting them with a certain plan, — but not a single of these features is traceable; nothing but chaos and haphazard reign in the macaque's performance; his actions spring up and die away independently of any rational determinate.

These superfluos tacklings might of course be replaced by more effective movements, if the monkey would have made use of imitation, following the example of the experimenter in the cases when he is confronted with a particular difficulty.

But it appears that the imitative powers of the monkey are exceedingly limited in scope and they do not come to the rescue even when they would seem to have the best chance to be exercised, namely when actions which under the circumstances are by all means worth duplication insistently arise before his eyes. Even when the favourable, ultimate result appears plain and manifest the monkey will not avail himself of the example set.

True, even these random actions would have sooner brought to the desired end of liberation, if each of them were only brought to its ultimate end, but the extreme fussiness, lack of concentration and distraction of the monkey — especially in the case of any resistance in the free display of his motions — at every moment interfere with a well begun task; it would seem that something was every moment throwing the monkey from place to place, from just begun to always new starting points.

Of course should the animal possess a determinate volition in estimating and developing his actions, there would be no doubt that even when confronted with considerable resistance or when coming across failure, he would again double his efforts in one point, make a successful trial, then pass to the second point and so on to ultimate triumph without having to recur for a second time to the stages already gone through.

But here another handicap presents itself on the way: all the while of the work the monkey is unconscious of the natural consequences of his very own actions. He fails even to realize the moment of accomplishment or achieved task. It is only indirectly — namely by means of pushing the door — that he becomes aware of it and never otherwise.

Moreover he is not conscious (does not understand the value) of the central— in so far as he is concerned — fact, namely that of unlocking. It frequently happens that the animal repeatedly locks the devices that he himself has just unfastened.

Hence, it follows that the monkey has not the slightest idea of the purport of his actions, wherefore he is naturally unable to foresee their consequences.

This description as visualized on the ground of experimental data is suggestive of some broader conclusions and generalizations with respect to the much discussed problem, reference to which has already been made above: we mean the problem of “labour processes” in the “development of ape into man”.

Now, inasmuch as every labour process is in the first place an act tending toward a clearly realized goal, which is moreover governed by attention and reasoning will, under whose influence all actions are subjected to conscious estimation and control, involving not only the imediate but also the more remote consequences of our doings — we must say on the ground of the present research mainly devoted to the monkey's manual labour (which labour, in fact underlies every working process) — that the monkey, such as it is to-day, is incapable of work.

If even in the limited confines of the experimental cage the monkey loses his modest assets, whenever the scope of his activities is, be it even so little, increased, — how much more must he become bewildered under natural conditions where unlimited possibilities present themselves at every moment and where there is no experimenter to stimulate, force or offer an example to the beast.

The monkey as we know him now has, strictly speaking, no labour.

But here again a new question arises: perhaps the positive characteristics of the monkey are only oriments that are to develop into more perfect properties?

Just give them a new, free and vast field of application and they will increase manyfold, grow in importance and ultimately give a mighty blossom!

May this be so? And what can we predict with respect to the monkey's onward development?

Any oriments, with a future before them, must in the first place be vastly positive adaptive.

But as our experiments show it to be the case, they are narrowly and specially limited both as regards sphere of application and range of action.

When broader or altered propositions are set forth, they not only do not increase in their positive value, but on the contrary, turn into their antipodes — negative characteristics.

It would seem that they have so much differentiated, crystallized in the narrow and limited part they are called upon to play, that they no more deserve to be called oriments but rudiments.

And similarly to morphological rudiments — these concrete witnesses of long ago lost complex structures and truthful heralds of a terminated stage of regress, — are not also perhaps the monkey's psychic rudiments a kind a faint echo, a weak call from a consonant but much more powerful and harmonious psychic counterpart of the remote ancestors of the actually now existing lower primates.

And just like an old withered portrait, does not perhaps the semi-human image of the monkey remind us of his more human and perfect ancestor, — some of whose features though but remotely resembling the original still live, while others have become so changed as to be entirely lost in oblivion.

Through this assumption we come to the recognition of a regressive evolution process of the monkey down from better developed ancestors.

And now we arrive at unveiling the mystery of the monkey's psychology and his place in the scheme of organic development. We believe that his double face is a reflection of the twofold position occupied by the macaque. More than that. It is perhaps even a temporary station on the path of losing the more human face and acquiring the countenance of real animal.

It would seem that the upper portion of the monkeys body — his human eyes, his look and his hands — send a last farewell to man, while his lower portion with tow in opposition is again within the realm of mere beast.

And however much his head resembles the human one, however uplifted may be his look, the monkey's body keeps him in downward posture and bends him towards the lowlands of earth.

And no one can tell the end of the regressive trend of this creature, as on the other end of the scale it is impossible to find a limit to the progressive evolution of man-genus homo, who leaving his semi-beast ancestors far behind in the triumphant march of progressing philogeny has advanced in stupendous onward strides to the conquest of material and spiritual culture.