CA1151865A - Equipment for measuring the reaction time - Google Patents

Abstract

ABSTRACT
The invention relates to equipment having a digital display, for use in measuring reaction time. This equipment is suitable both for research and for routine testing procedures. The equipment includes a stimulus-transmitting device which permits the application of two different light stimuli, two acoustical stimuli, the application of a white noise or a covering stimulus played from a tape recorder at the same time. The equipment indicates whether a response took place with the right hand and/or foot. It displays the occurance of a faulty reaction and also measures the reaction time in such case. It is possible to couple to the equipment a special light-stimulus transmitter by means of which operational conditions may be simulated in a laboratory and the two cerebral hemispheres may be stimulated independently of each other.

Description

This invention relates to equipment for measuring reaction time, and in particular to a digital reaction time chronometer.
Measurement of reaction time is a procedure that has been used for more than a century in the field of psychology and medical science. During this period measurement has been accomplished in several ways and by using different devices. Previously, time measuring devices based on mecha~ical principles were used, but with the development of electronics and the accompanying increase in the accuracy and reliability of such measurements measuring equipment other than electronic equipment, has been completely supplanted~ Today measurements are obtained almost exclusively by use of electronic equipment.
Of the different stimuli the use of light and sound stimuli have been most widely used. Tactile stimuli and application of electrical shock are not normally applied. To produce a light-stimulus,lamps of different colours are used, particularly lamps which are capable of blinking on and off at a high frequency. Accordingly such lamps do not use a heating fila-ment which cause delays in switching on and off but rather gas-filled tubes and light emitting diodes ~LED) are used. To produce acoustical stimuli, clear sounds of different frequency and intensity are used within the limits of audibility.
Measurements of reaction times are mostly used in psychological laboratories, as a basic measuring method. In the field of medical science and therapy such measurements are used to study the effect of medicaments.
Measurement of reaction time has been applied in all special branches of psychology, in the field of psychology of labour for performing tests of fitness, in the field of sport psychology for measuring the con-nections between practice, motivation and performancc, in the field of clini-cal psychology for testing the psychical condition of the person being examined.
In the field of the psychology of labour, measuring of reaction '".-` ! 1- ~

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time is yielding essential basic infoTmation in the course of fitness tests and the testing of the actual condition of drivers and operators. Testing reaction time is of utmost importance, when installing new signalling systems, in the course of designing new operational mining plants or in the course of supervision to avoid accident hazards or to ensure continuity of work in existing plants. Presently all drivers and operators are regularly tested ~not only when accepted and when deciding fitness), and measurement of reac-tion forms the basis of such tests.
Measurement of reaction time performs a similarly important role in the field of medicine. When testing the effect of the different pharm-aceutical products, particularly that o:E sedatives and tranquillants, measure-ment of reaction time performs indispensable function. The application o:E
reaction time measurement in the course of psychiatric treatment and neurological testing is also wide-spread.
From the foregoing it is apparent that the extremely wide scope of application of reaction time measurement results in considerably different requirements in relation to the measuring instruments.
In general, current instruments for the measuring reaction time, consist of four principal parts:
2G ~1) stimulus transmitting equipment ~2) responsing equipment ~3) time measuring and control equipment ~4) data recording equipment.
The different tests applied differ mostly in the mode of trans-mitting the stimulus. These differences lie partly in relation to the spatial arrangement of the light-stimuli and partly in the frequency and loudness of the acoustical stimuli.
The responsing equipment may be controlled by the hands or by the fee~ ~e.g. when testing drivers or operators of machines) of the person being tested. It is the task of the time measuring and controlling equipment to 1~L5~5 control the manner in which measuring of reaction time takes place for example whether simple reaction time or selective reaction is measured, whether the beginning or the end of the stimuli should be responded to, what kind of iterative sequence is followed etc.
In general, the equipment which records the data is a digital printer, arranged to record the results on a strip of paper. In order to facilitate further calculations, it is a routine procedure to print the results of serial measurement at the end of the measuring procedure.
The rapid development of psychology renders it difficult to anticipate the requirements which must be met by new measuring devices.
The essence o these requirements is that the equipment should have the capability to carry out all meas~lring methods including those which are not presently used in course of routine procedures and should also be capable of being adapted and expanded to meet future testing procedures.
In general, existing reaction time measuring devices reproduce laboratory conditions. An important deficiency of such devices is that they do not provide for the reproduction of noises in conformity with practical conditions (e.g. operational noise, noise in mines, etc.), even though these loading factors considerably influence reaction time and fatigue, as well as other capacities of persons.
Another deficiency of known equipment is that in applying acoustical stimuli, the frequency response of the human ear is partly dis-regarded (the curve of M. Fletcher and A. Munson). Accordingly, no attention is paid to the fact, that reaction time depends to a considerable extent on the intensity of the stimulus. The longest reaction time occur when the stimuli are in the region of the threshold level of audibility, while the shortest occur at acoustical stimuli which is louder by 100 dB than the threshold level.
With stimuli in the region of the threshold level an average reaction time of ~00 msec has been measured, while at a sound 100 dB louder ,,~ ~

3~ 5~ 5 an average reaction time of 110 msec has been measured (Sorbonne Laboratory, Chocholle, 1945). When using two or more stimuli, the frequency of the stimuli should preferably be chosen so that they are of approximately the same subjective loudness. ~Taking the Fletcher-Munson curve into consider-ation.) Thus there is a further requirement that the device regulating the intensity of the stimulus should have a dB scale by the aid of which an accurate value of audible stimulus can be adjusted for every single measuring process.
In general a disturbing effect on measurements of reaction time may occur if the switching on of the sound does not take place at the point of zero transition, as a result of transient occuring in the earphone or the loudspeaker. This inconvenient accompanying phenomenon which influences the results of the tests, should be eliminated by synchronizing the commencement of the stimulus with the occurrance of the zero-transition of the sinusoidal sound used. In this case the sound will be emitted free from any disturbing effect, with the result a more accurate measurement is possible.
One of the fundamental faults of available commercial equipment is that they do not register and record the quality nor the duration nor the quantity of faults committed by the person being tested. This deficiency is disturbing in the performance of serial measurements and in the course of the evaluation of the results. One of the most frequently occurring faults is the anticipated response, that is when the person tested is answering and starting the motorized reaction of the response, respectively, prior to the occurrance of the stimulus, i.e. duration of the response lies within the range between 0 and 100 msec. When calculating the average value, these values must not be considered.
A further significant fault occurs, when in course of measuring selective reaction time the person to be tested is instructed to answer one of the stimuli by means of one hand or foot, and the other stimulus with the other hand or foot, but contrary to such instructions - the response is given ~L~5~8~S~

with the incorrect limb. In such case it is relevant to record the time of the faulty response, simultaneously lndicating the wrongness of the response.
It seems to be useflll to measure the time, so much the more as several psychical characteristics exist, which can be recognized just from said data.
A third possible fault, which may occur mainly in the course of serial measurements, is that the person to be tested leaves one of the stimuli ~manswered. It is o:E utmost importance to know when several responses are omitted in course of serial measurements, thus it is imperative to immediately record the missing responses on the recording paper strip, at the time of their occurrence.
The equipment for achieving the objects of this invention will now be described in further detail.
The present invention is adapted for use in current psychological testing with the objective that it be suitable not only for research but also for routine procedures. The invention is particularly suited for testing in the field of labour psychology. Modern production is tending more and more to the use of mechanized, semi-automatized and fully automatized machines.
Thus the selection of suitable persons for handling and managing these machines represents an important task of the psychological laboratories of the plants. By the introduction of the new, up-to-date machines in mining which replace the work of several men, the selection of the personnel to operate these machines became a cardinal problem. The proper selection is necessitated not only by the inevitable increase of productivity but also by the need to avoid accidents which can endanger the life of several men in the special situation of the mining industry. At the same time significant financial damages may also be involved. Accordingly, it is of utmost impor-tance, that the operators be tested by up-to-date devices and modern methods in order to be able to ascertain their fitness for such new requirements.
As previously mentioned measurement of reaction time is one of the most important fundamental testing methods. However~ tests of aptitude do 1~5~8~

not measure simple reaction time, that is the measurement of the period be-tween the lighting of a lamp and the response consisting of the pressing of a response-button. It is of importance to simulate under laboratory conditions all the circumstances prevailing in the given enviroment of a working place and for this purpose to provide expediently designed stimulus transmitting equipment. The present invention provides the ability to select any variation of two optical stimuli of different colours, a visual stimulus transmitted from a tachystoscope, and two acoustical stimuli. Simultaneously with the transmission of the stimuli, a white noise or any kind of cover noise may be transmitted by means of a tape recorder for further loading.
The application of a cover stimulus may be of importance from the point of view of representing the burdening effects of the conditions pre-vailing in the working place. The ability to couple a stimulus from a tachistoscope provides an advantageous testing method that can be of particular importance in relation to certain work areas. By using this method, not only general abilities may be tested, but it is possible to differentiate particular abilities.
The apparatus for transmission of the light-stimulus permits two light-tubes to be located at an adjustable distance, to the left and to the right of a fixed point. The cm-scale to the left and -to the right of the fixed point enables the tubes to be reset at their original positions. In both light-tubes there are red and green LED light-sources which provide illuminatiOn at a poSition through a simple system of lenses. Thus it is possible that a red or green light-stimulus can appear at the same place.
The box containing the light sources may be mounted on a stand in such a manner that it could be swiveled by 90 about the point of attachment.
Accordingly, the stimuli can be projected in a horizontal direction as well as in a vertical direction. At the same time the distance between the tubes may be also altered.

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This permits the testing of the optimum spatial location of different signalling systemsJ e.g. how are the signalling units on a switch-board should be positioned to be most promptly answered, and how are those to be positioned to which an operator is permltted to delay answering.
The stimulus transmitting unit may emit two kinds of acoustical stimuli. The acoustical stimuli used, are of frequencies that take into account the physiological features of the ear, speciflcally the relationship of the frequencies of the stimuli are such that their subjective loudnesses are identical. Based on the Fletcher-Munson curve, their frequencies must lie in the ranges between 400 Hz and 800 Hz and 1800 Hz and 2500 Hz, re-spectively. The frequencies 500 and 2000 Hz are used in the present invention.
The intensity of the acoustical stimuli may be altered by means of a regulator provided with a dB-scale having a range between the threshold of audibility and 100 dB. The occurrance of the acoustical stimuli takes place at the sinus-zero-transition only in order to avoid inconvenient transient effects.
This permits the use of a wide range of sound intensities without the adverse effect on the measuring process that occurs if the commencement of the stimulus does not coincide with the zero transition point.
Both the acoustical stimuli and light and visual stimuli can be applied simultaneously with a white noise background. The amplifier of the white noise is provided with a dB-scale in order to be able to recreate identical testing conditions. In order to provide for the application of a special white noise, the apparatus has been provided with means for connection to a tape recorder.
Accordingly, the unit transmitting the stimulus permits the choice of stimuli ~depending on the tests being conducted) which may consist of the variation of two kinds of light, two kinds of sound and a visual stimulus.
All the variations are synchronized with a chronometer, thus a measuring accuracy of ~ 1 msec has been ensured.
The chronometer consists of the following principal parts: ;
- a quartz oscillator providing an accurate t;me bases through the appropriate dividing circuits;
Preferably the time-base of the measuring process is 1 msec.
- counters with digital displays for measuring and displaying the time - an automatic unit, to provide accurate measurement of the period between the transmission of the stimuli and the response, as well as the automatic random transmission of stimuli;
- a circuit to sense and display faulty answers;
- a Ullit to measure the complete testing period, measuring the time from the beginning of testing till the end of the same.
This process is of significance in course of testing monotony tolerance;
- a digital printer for recording the results on a paper strip.
~xperience has shown, that when there is a constant interval be-tween the stimuli, an anticipated response of the person tested or a very short time of reaction is observed. This is due to the fact that the se-quence of stimuli has been learned. Objective and accurate tests require that the stimuli occur at random intervals.
Various types of the equipment for measuring reaction time are provided with devices for transmitting random stimuli. The most common deficiency of such devices is that the shortest interval between two stimuli is not controlled. Thus it may readily occur that a person being tested is unable to respond to a stimulus because it followed the previous response within too short a period. When evaluating correct and incorrect answers such devices yield erroneous results. In case of these equipments the average of the random intervals used to be indicated.
In the present invention this deEiciency has been eliminated by fixing 500 msec as the shortest duration of random intervals between stimuli.
On the basis of tests performed 500 msec represents a value which can be responded to with few faults by a person of average capacity. ~n order to achieve a new method of testing with the present invention, not .~

~L15~ ;5 only are the intervals between the single stimuli changing at random, but also the duration of the stimuli. The various operational modes of the present equipment not only enable the examination of simple reaction times and selective reaction times, but also permits testing of reactions to simultaneous stimuli. In this mode of operation two stimuli appear at random and alternatingly, and at random and simultaneously; the task is for the person being tested to give an answer only when both stimuli occur simultaneously (at once). The simultaneous stimuli may be two lights, or one light, one sound or two sounds.
This form of measuring could not be obtained using previously known equipment. For the purpose of modern testing it is of importance to be able to ascertain whether a person being tested is able to select the correct (simultaneous) stimuli from monotonously changing stimuli. Such ability represents an important psychical characteristic of operators of machines, dispatchers of process controlling equipment, and its testing is therefore important.
The random intervals are produced by selecting the signals of the white noise generator being present anyway in the equipment by the aid of a comparator of defined amplitudes. The different durations of time are produced by dividing circuits. The minimum interval of 500 msec is provided by use of a comparator that controls a monostable multivibrator having a period of 500 msec. This signal is applied to the input of the dividing counters. The random program of the transmission of stimuli is produced by means of a built-in program-generator.
The stimulus-program was stored in a programmable read-only-memory circuit (PROM). The steps of the program (50 steps) cannot be learned even during repeated tests, accordingly it is unnecessary to provide for changing the program. It goes without saying, that several read-only-memory circuits (ROM) may be buil~-in and in -this case one can choose from several kinds of selective programs.

~5~8~5 The advantage of said R~M circuit is that the program steps for measurement of simple reaction time, selective reaction tlme and reaction time for simultaneous stimuli, are contained in one single circuit ~by means of a switch the appropriate mode of operation may be selected). The present apparatus makes it possible to measure the time of reaction upon the occurrence of a stimulus in any mode of operation, or when a reaction follow-ing a cessation of a stimulus is required, such reaction time may be measured also.
It is often the case, that the operator of a machine, a driver or a technician controlling a process, must intervene promptly upon the cessation of some particular condition. If it is desired to test this abil-ity and to determine the promptness of the reaction, the mode of operation of the test apparatus should measure the reaction to the cessation of the stimulus.
Modern test requirements may be, such that the answer should not be given by pressing a button by the hands or feet, but rather a response in the form of a verbal answer may be required.
This method uses the transmission of stimuli coupled with a tachistoscope, and the promptness of any response can be tested and the answer given may be positive or negative. For the purpose of such a type of testing, the present invention is provided with a connection for a tape recorder, whereby the answer given through the microphone is substituted for operation of the push-button. In this method of measuring the stimulus is transmitted from the tachistoscope and the person to be tested is required to give a negative or a positive answer. The tachistoscope starts the chronometer, while the signal of the microphone operates to stop and block the tachistoscope.
Accordingly, the response may be given by operation of switches through movement of a hand or foot, or verbally, via a microphone. In all cases it is imperative to indicate faulty answers. All answers deviating ~lS~S

from the instruction are to be considered as faulty (the equipmen-t should be always adjusted according to the instruction in relation to the mode of operation, transmittance of the stimuli etc.).
Being influenced by the state of nerves, by age, profession, etc.
the value of an anticipated answer may be different. It seems to be ex-pedient, that answers between the limits 0 and 150 msec be qualified as anticipated answers and that the equipment declare all such answers as faulty.
An answer is also to be considered as faulty, when in course of the selective reaction time measurement, the person being tested gives an answer with a hand or foot which is contrary to instructions. From the point of view of the diagnosis or evaluation it is useful to know the times of the respo~se wllicll took place in course of committing the faults. The present invention is adapted to measure reaction time in such situation also, but the answer is indicated on a digital printer and beside the value displayed. The information indicated is that: the person being tested gave the answer with the incorrect hand or foot.
When simultaneous stimuli are used, it may be considered as faulty, that the person being tested has responded to one stimulus only.
The present equipment is adapted to determine such a kind of answer as being faulty and to provide an indication of such for consideration in course of evaluation of the test results.
In the case of random transmission of stimuli, the successive stimuli may occur at a high rate with intervals of not more than 500 msec.
In such cases the person being tested may be lmable to respond to every stimuli. Such faults are indicated and recorded with the present equipment.
A very important parameter is the time, at which the responses occur in course of the tests. In the present equipment a digital chronometer measures the time from the beginning of the testing and with each response printed the actual time is indicated on the paper strip of the digital printer. Thus measuring of fatigue or monotony tolerance is possible through the recording of the time of the occurrence of faults.
In accordance with the present invention, there is provided equlpment for measuring reaction time, comprising a logic control circuit, a quartz time-base generator and scaling circuit connected to said control circuit through a time measuring and display circuit, a circuit for select-ing the mode of operation connected to said logic control circuit, audio-frequency oscillators connected through a selector, said selector adapted to permit an operator to select light- and sound stimuli, a random time-base signal generator connected to said selector through a progr~m producing circuit, and a null detector connected between the audio-frequency oscilla-tors and the selector, sound-signalling units connected to a dB scaler, light-signalling units are connected directly to the selector, a responder connected to an input of the logic control circuit, and the logic control circuit is connected through a circuit adapted to sense faulty reactions, to a display adapted to indicate faulty reactions.
The equipment according to the invention for measuring time will be described in detail by means of preferred embodiments cmd with the aid of the accompanying drawings wherein;
Figure 1 is a schematic block diagram of equipment for measuring reaction time according to the present invention;
Figure 2 illustrates a simplified embodiment of the equipment shown in Figure l;
Figure 3 illustrates in more detail the circuits for generation of the white noise and random program of the equipment;
Figure 4 illustrates the single signal forms appearing at cer-tain points of the circuit according to Figure 3;
Figure S illustrates an embodiment of the stimulus transmitting device according to the invention.
Referring to Figure 1, the apparatus for measuring reaction time according to the present invention: includes a quartz generator time-basis .

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-~15:1 ~355 and scaling circuit 1 for scaling the signal (of e.g. 100 kllz) genera*ed by the quart~-controlled oscillator. The built-in scaling circuits of the co~mters provide 100 msec and 1 sec pulses, respectively, for the control of the counters measuring the program time. The generated pulsc having the period 10 ~Isec ensures the synchronized operation of logic circuits. In order to provide an accurate evaluation, responses given by the left limbs are measured by the left time-measuring counters 3a, while the answers given by the right limbs are measured by the right counters 3b. This facilitates the evaluation and avoids the changing of the push-buttons in course of the change of the stimuli, and the possible adverse affects of such on the person being tested. From the stand point of direct comparison oE the left-side responses with the right-side responses this arrangement is very suit-able, since the left-answers are always to be found on the left side, while the right ones appear always on the right side of the paper strip of the digital printer 27. Preferably the counters count in four decades, thus making it possible to use the equipment in clinical practice where reactions surpassing 1 sec are also frequent due to organic diseases (Parkinson's Disease) or to the influence of medicines.
The program-chronometer 4 measures the time which has passed from the beginning of the test until its end. This is of particular impor-tance, when pre-loading with white noise is used and the reaction time of the person being tested is measured afterwards. Use of this program chron-ometer ensures that all persons being tested are subjected to the same pre-loading. Another important function is the measurement of the duration of the testing procedure. Since in case of random transmission of stimuli, this is the sole source of information concerning the total duration of the test, which could be an important parameter in the test results.
The chronometer 4 preferably includes a four-decade counter and by using a lsec time-basis, the chronometer may be used for measurement of periods of 2.5 hours. Thus it is possible to measure reaction time as a ~_"

~S~Ll36~ii function of fatigue.
The logic circuits 5 and 6 - which are composed of for example of integrated circuit elements or microprocessors, ensure that between the occurrence of the stimuli and the commencement of operation of the counters ~the beginning of the measuring procedure) deadtime should not occur with *he result that synchronized operation is obtained. They also ensure that synchronized counting and transmission of the stimuli take place in accor-dance with the selected operational mode, i.e. depending on the mode of operation either the beginning of the stimulus ~the leading edge) or the cessation of the stimulus ~trailing edge) controls the counter. Furthermore, these circuits sense the reaction through the responders 8 and immediately terminate operation of the counters.
By means of selector 7, the desired mode of testing is selected.
One may choose whether the reaction time is to be measured fromthe appearance of the stimulus or from the cessation of the same. The measurement of simple reaction time takes place, when the person being tested responds to the stimulus by using one of his limbs or verbally, by means of a microphone.
"Selective reaction time" may occur in two forms:
The first is version RI-l, in which two kinds of stimuli appear at random (light-light, light-sound or sound-sound), and one stimulus is answered by one hand or foot and the other stimulus by using the other hand and other foot.
In the other mode, RI-2, the two stimuli appear alternating ~at random) and only one of them is required to be answered by using one hand or one foo~ previously determined.
Measurement of reaction times for simultaneous appearance of stimuli yields a new testing capability. In such measuring procedure the two stimuli occur alternatively and a response is required only upon the simultaneous appearance of both stimuli.
~n control boards for automatic processes, signalling systems ~5~ S

may be used in which individually displayed signals and simultaneous appear-ing signals may have different meanings. Often only those signals appearing simultaneously require a reaction. When selecting operators for such apparatus, the value of reaction time for simultaneously appearing stimuli and the number of failures represent important psychological characteristics.
In the design of control boards the means by which a reaction may be readily obtained by the operator is significant, i.e. it seems to be advan-tageous to choose the arrangement and shape of the signalling systems on basis of ergonomical examinations.
This relatively complicated testing method is playing a consider-able role in the examination of different organic diseases of the nerve system or psychological disorders, as a result of the influence of pharma-ceutical products.
Both the measuring of the reaction times RI-l and RI-2, as well as of the reaction time of simultaneous stimuli, yield important information through examination of the coordination of sensing by sight or hearing and the subjects reaction thereto.
During -the course of the tests important information may be ob-tained by observing the number and occurrence of faulty answers during the measuring procedure. The circuits 9 which sense the faulty answers indicate a number of kinds of faults. A fairly frequently occurring fault is the so-called anticipated answer, in which the person being tested starts the reaction prior to the appearance of the stimulus. In such case, the answer is either given before the measuring procedure of the counters, or immediate-ly after the appearance of the stimulus, and thus an extremely short reaction of about between O and 100 msec time would be registered. The present equipment senses the anticipated character of such a reaction, and calls it to the attention of the person performing evaluation by applying the designation "H" beside the measured value.
Another frequently occurring fault, which may occur in all modes ~ ,~

11S~L8~i of operation takes place when the stimuli follow each other in a rapid se-quence, and the person being tested misses one or more, e.g. he does not answer at all. Upon such occurrences the present equipment indicates the faults by applying a particular designation, beside the measured value of the subsequent marking, e.g. "E" will appear beside the numerical data dis--played, or the marking "Ex" on the paper strip of the printer. This means that the person being tested has not reacted to the previous stimulus.
In the course of selective reaction time tests~ when one of the stimuli should be answered by a particular hand or foot and the other stimulus by using the other hand or foot, it may happen, that the answer is given by an incorrect hand or foot. In such case the present invention indicates the fault, and measures the time of response. This provides important informa-tion to be used for the purpose of evaluation as it is desirable to know the reaction time for the faulty answer. Current measuring equipment for measuring reaction time indicates the occurrence of the fault but does not measure the reaction time.
The equipment for measuring reaction time in accordance with the invention may be coupled with a tachistoscope as an external stimulus source.
As a result a new testing method is possible in that, in case of the fault ~0 described above, the time is also measured. In the two channels of a double tachistoscope the verbal stimuli occur alternatively, and according to the instructions given, the person to be tested must give a negative or positive answer. The person being tested must determine, while time is being measured, whether a positive or negative answer complies with the instructions and, must push the appropriate button with the left or right hand.
In an other type of selective reaction measurement when two stimuli are appearing alternatively, but only one of them need be answered~
a faulty result often occurs by reason of the fact that the person being tested does not answer the relevant stimulus.
In such case a fault will be indicated by the equipment, marking ~L5~3 Ei5 the incorrect answers. This kind of fault may occur in measuring reaction times for simultaneous stimuli, needless to say, that in this mode of opera-tion the fault is indicated by the equipment.
Beside the fact that display o:E the faulty answers takes place and a high level of accuracy of measuring is possible, the invention provides the capability of performing an extensive qualitative analysis. Information concerning the physical condition of the person being tested may be obtained through the recording by the program-time-measuring feature of the invention of the time at which the fault occurred in relation to the beginning of the measuring procedure.
l~he selector lO for selecting the program of light-and sound stimuli includes switches and related circuits, by means of whic'n it there can be selected the particular stimulus or variation of stimuli for perform-ing measurements, and for specifying which stimulus is to be answered by which of the limbs in accordance with the measuring instructi~ns ~e.g. red lamp; right hand, a sound of 800 Hz: left foot). The capability of select-ing the side of the response, facilitates and lends safety to the evaluation.
For example in the following digital display the first four digits show the reading of the program-time-measuring chron-ometer in seconds, the second four digits the value of the response given by the left hand or left foot in msec and the third four digits give the value of the answer given by the right hand or right foot, in msec. As it is to be seen from the foregoing example, left and right reaction time values always appear in separate columns. Accordingly comparison may be performed by simple glance and further mathematical analyses is facilitated. Needless to say the selected program, the stimulus~ as well as the expected response must be part of the instructions given to the person being tested before the beginning of the measuring procedure. For example, he may be instructed ~lS~ 5 that he should answer the red lamp using his right hand and upon a sound of 800 ~Iz ~which should be presented as a trial) a reaction with the left foot is required. Prcferably a trial before testing should be given by means of the manually controlled stimulus transmitter 2~ (a press-but-ton). In course of a manually performed stimulus transmission the person giving the test may better observe whether the person to be tested is giving his answers according to the instructions ~whether he has understood the instructions).
The light-slgnalling unit 11 includes light-emitting diodes mounted in a tube (e.g. two colours, red and green). The position o:E the tubes can be altered both in vertical and horizontal directions. The cap-ability of adjustment (e.g. on a scale with a cm-scaling) can be important, because when testing drivers, it seems to be advantageous to adjust the stimulus transmitters in accordance with the actual conditions. For example in case of the operators of mine elevators, therey are required to intently observe a given point, where the elevator is stopped and simultaneously visual signals appear at different distances from the positioning point, horizontally displaced. Similar situations may occur on other working places and accordingly the capability of spatial displacement of the stimulus transmitter is necessary.
The sound-signalling units 12 or loud-speakers, which are located in the testing area may consist of earphones, preferably stereoearphones which enable the simultaneous but separate stimulation of the ears. Selec-tion of the acoustic stimulus is performed by means of the selector 18.
The selected acoustic stimulus may be a white noise, ~00-800 Hz or 1800-2000 ~Iz, or any covering noise played from a tape recorder. The possible varia-tions are as follows:
left channel right channel stimulus stimulus white noise stimulus stimulus white noise white noise white noise t~pe recorder stimulus stimulus tape recorder tape recorder tape recorder The acoustic stimuli from the end-amplifier 17 are conducted to the selector 18 which serves to select the required acoustic stimulus which is transmitted to the sound signalling unit 12. The dB-scaler 16 situated before the end-amplifier 17 provides for the adjustment of the pro-per sound intensity. The signal from the oscillator 14 (400-800 Hz) and the oscillator 15 (1800-2500 Hz) arrives at the dB-scaler 16 through the zero-crossing detector 13. The zero-crossing detector 13 functions in such a manner that at zero-crossing the sinusoidal sound frequency activates a comparator, which is connected to the input of two monostable multivibrators.
One of the monostable multivibrators produces a signal at the transition from the negative into the positive, while the other at the transition -from the positive to the negative. The outputs of the monostable multivibrators are connected to the inputs of an OR-gate, while the output of the OR-gate emits the signal permitting the appearance of the stimulus (acoustical stimulus), but only after the transition of the sinusoidal signal through the zero-crossing detector. The sinusoidal stimulus signal of the frequency of 400 to 800 Hz and 1800 to 2500 Hz, is connected through the gated ampli-fier to the dB-scaler 16. The stimulus signals may pass the gated amplifier only then, when in accordance with the program the acoustical stimulus is due and the zero-crossing detector is giving the enabling signal. The occur-rence of the acoustic stimulus and starting of the coun~ers takes place in a synchronized manner.
Due to the fact that the oscillator 14 (400 to 800 llz) and the oscillator 15 ~1800 to 2500 Hz) are connected to a common dB-scaler 16, as well as to the common end-amplifier 17, identical intensities of both acoustical stimuli may be obtained. The frequencies of the oscillators ~400 ~, .

~51~5 to 800 and 1800 to 2500 Hz) have been chosen with the purpose of enabling the person being tested to hear frequencies of identical intensities , i.e.
they should fall onto identical intensity curves on the Fletcher-~unson curve. This avoids measurement of differing reaction times for the two acoustical stimuli employed owing to differences in their intensities. By comparing our experimental results to well-known curves for identical inten-sities, the frequencies 400 to 800 Hz and 1800 to 2500 Hz have been chosen for forming the stimulus signals.
The psychological factor which results in the intensity of an audio stimulus influencing reaction time, mai<es it necessary to ~1) eliminate measuring uncertainties resulting from the transient phenomena accompanying switching-on of the stimuli, and (2) to ensure the audibility of the fre-quency of the stimuli employed with an equal intensity.
The white noise generator 21 is connected to dB-scaler 20 and to the end-amplifier 19, and finally by way of the switch 18 for selecting the acoustical stimuli, it is connected to the sound signalling unit 12. In the course of the test the white noise serves partly to load and partly to produce a cover-stimulus effect. The use of the dB-scaler 20 is important in order to adjust the white noise to a proper intensity.
~ selected amplitude of the white noise generator 21, provides with the aid of a comparator the required signal for the random time-basis 22. The output of the comparator controls a monostable multivibrator having a period of 500 msec. By this arrangement signals which follow each other in short intervals cannot overlap and even between the most rapidly occurring random stimuli there should be an interval of at least 500 msec. The output of the monostable multivibrator is connected to the input of the scaling circuit, whereby the double, fivefold, ten-fold and fiftyfold recurrence time of the stimuli may be selected by means of a switch. The scaled time-base signal is connected to one of -the inputs of gate NAND-l and the time-base signal is connected to the other input of the NAND-l gate. The signal appear-~15~Li36~i ing on the output of the NAND-l gate is connected to the input o a stepping-type counter 23 producing the automatic random program. The stepping-type counters control the ROM circuits containing the program steps. On two of the outputs of the ROM circuits the two stimulus signals appear in a random sequence, and on the third output the random signal of the simultaneous stimuli will appear.
In order for the duration of the stimulus signal ~when the two stimuli alternately occur) to change at random, and in order that no two stimuli should occur without an interval between them, the output of the ROM
circuit is connected to the input of the NAND-gates while the other input of the NAND-gates are connected to the output Q of the bistable multivibrator ~Figure 3). The stimulation signals appear at the output of the NAND-gates.
The maximum duration of the stimuli is 1 msec, which is twice the minimum period of random reoccurence of stimulus signals (500 msec). By means of this circuit arrangement the stimuli occur at statistically controlled intervals and for statistically controlled durations and are statistically terminated, whether the person being tested has given an answer or not.
Accordingly a program may be produced in which two stimuli occur alternat-ingly, at random, but only one of them is to be responded to it may also produce a program, in which two stimuli occur alternating at random, with both occurring simultaneously at random, and the person being tested in regard to response, when both stimuli occur simultaneously. The measurement of reaction time only for termination of the stimulus can take place in such a manner.
In the device according to the present invention a ROM circuit having eight outputs has been used and accordingly two different programs containing 50 steps each may be stored. The required program may be select-ed from two programs ~program 1~ program 2) by means of a swltch. By this means the person tested can be prevented from learning the first few steps of the program and using this knowledge to influence his reaction. The ,...,.~
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possibility of the subject learning the sequence occurs when the same pro-gram is used in course of tests performed one after the other in immediate succession. The variability of the two programs excludes the risk of such recognition occurring.
~ xternal control signal circuit 25 enables the equipment to be coupled to other stimulus-sources for measuring reaction time. The most important of these sources is the tachistoscope Th, which provides an accur-ate testing of reaction times for verbal and visual stimuli. With such arrangement the starting signal of the tachistoscope starts the counters and answers given whether by means of a press-button, or verbally, through a microphone, stop the counters. Psychologists are able to evaluate data as to the correlation between certain phenomena and the physical responses based on consideration of the statistical relationship of the measured results. It is important that measurements are performed with the highest possible accuracy and the conditions of measurement closely are controlled.
The digital printer 27, which records the results of the measuring procedure, the fault signals and the values of the program time on the paper strip permits correct processing of test data.
The digital printer is controlled by the control circuit 26, which stores the data and generates the signals for the transfer of data.
Figure 2 represents a simplified arrangement of the invention illustrated in Figure 1. The circuit of Figure 2 represents apparatus which meets minimum re~uirements for measurement of reaction time.
From the stand point of stimulus and reaction the following test-ing methods may be selected using the equipment of Figure 2.
1/ Simple reaction time measuring, in course of which the selected light-or sound stimulus is to be answered by the person to be tested by using his hadn or foot. In this measuring method a stimulus e.g. a light (red or green) or an acousti.cal stimulus ~400 to 800 or 1800 to 2500 Hz) may be chosen by means of the push-buttons situated on the operator's control panel.

~151~ S

If the person to be tested does not answer or answers prior to the occur~
rence of the stlmulus, the equipment displays the fault. The test may be performed by a manually controlled stimulus or by an automatically control-led stimulus. In the latter case the sequence of the stimuli takes place at random, and the durations of the stimulus is also random.

2/ Disj~mctive or selective reaction time measurement ~RI-l), wherein two stimuli are used (two lights, two sounds or one sound, one light) and one of the stimuli is to be answered with one hand or one foot, and the other stimulus is to be answered with the other hand and the other foot. If the person being tested does not answer at all or if the answer occurs prior to the occurrence of the stimulus, or if he does not react with the limb speci-fied in the instructions, the equipment senses the faulty answer. The test may be performed by means of a manually controlled stimulus with the intervals between the stimuli and duration of the stimuli being randomly-controlled.

3/ Disjunctive or selective reaction time measuring (RI-2), wherein two stimuli are applied (two lights, two sound~ one light, one sound) and only one of the stimuli is to be answered according to the instructions. The two stimuli appear alternating at random. If the person -to be tested does not answer at all, or the answer is given prior to the occurrence of the stimulus, or an incorrect stimulus is answered, the equipment senses the faulty reaction. The test may be performed by means of a manually controlled stimulus Gr by automatically controlled stimulus. In the latter mode of operation alternating appearance of the stimuli, the interval between the stimuli, and duration of the stimuli are random-controlled.

4/ Measuring reaction time with simuitaneously appearing stimuli. In course of this mode of measurement two stimuli appear alternating and from time to time both occur at once. The person to be tested must react to the simul-taneous appearance of the stimuli only (two lights, two sounds or one light and one sound may be selected). If the person being tested does not answer ~S~ i5 at all or if a premature answer is given, or if he reacts upon the occurrence of only one stimulus, the equipment senses the faulty answer. The test can be performed in an automatic mode only, because simultaneous ~synchron-ized) appearance of the two stimuli cannot be obtained with manual control.
The alternating appearance of the stimuli, the interval between them and the duration of the stimuli is random-controlled.
The accuracy of the reaction time for the stimulus is provided by the quartz oscillator and a scaling circuit of the quartz time-base l.
The time between the transmission of the stimuli and the answer is measured by the counter 2, the result may be read on the display. The operation o:E
the equipment in accordance with the different modes of operation can be selected by the selector 7, while the reaction is measured by the logical circuits 6 and the response 8. The faulty answers are sensed by the cir-cuits 9. Faulty answers are also displayed ~in form of codes or numbers) while they appear on the display 28. Light stimuli are produced by means of the light-signalling devices ll positioned in boxes arranged on separate stands. The position of the light-stimuli can be changed mutually in relation to the point of fixation ~the lamp). The sound-signa.ling device 12 produces the signal through a loudspeaker or headphones. The acoustical stimuli are produced by the oscillator 14 ~400 to 800 Hz frequency) and the oscillator 15 ~1800 to 2500 Hz) at frequencies having approximately identi-cal subjective loudness. The absence of transients in the stimulus is achieved by means of the zero-crossing detector 13. Adjustment of the sound intensity needed for the tests may be provided by means of -the dB-scaler 16.
The absence of transientsin the acoustical stimulus is of particular impor-tance in application of higher intensities ~over 40 d~) in order to avoid any startle reaction of the person being tested which might adversely in-fluence the accuracy of the measurement. Measuring may be performed either by manual control 24 or automatically through a circuit 23 producing the random automatic program ~with the exception of measuring the reaction upon _ ~4 -~15~ 5 simultaneous stimuli J since this can be performed by automaticaL control only). The occurrence of stimuli in the manual operational mode is initiated by means of push-buttons. Automatic control o:E the random program produces alternating occurrence of the stimuli at random at the same time random-intervals are also produced which is important for preventing anticipated reactions. The equipment also produces change in the duration of the stimuli, also in a random manner. The circuit producing the random program ensures that two stimuli do not follow each ot~ner within a period being shorter than 500 msec. By means of the switch a multiple of said average time ~i.e. the twofold, ivefold, tenfold and fiftyfold) can be selected. The program control contains 20 or 50 program steps making it suitable for serial measurements. The program is adapted for uses where not every stimulus is to be answered, that is for the disjunctive "2" and simultaneous stimulus reaction. In such modes out of fifty stimuli, twenty-five will be of a first type of light- or sound stimulus and the other twenty-five will be of a second type of light or sound stimulus. In the mode of operation for simul-taneous stimuli twenty-five such stimuli will be simultaneous.
The random time-base circuit 22 for controlling the occurrence of the random stimulus and for controlling the stimulus duration and the circuits 23 for producing the automatic random program are illustrated in Figure 3. From the signals produced by the circuit 22 which generates the white noise, an amplitude value is selected by means of the comparator 22b.
This signal controls a monostable multivibrator 22c having a period of 125 msec. The signals of the monostable multivibrator 22c, which are used as a timing pulse are scaled by means of the scaling circuits 22d in ratios of 1: 2, 1: 5, 1: 10 and 1: 50 (the scaling proportion may be adjusted by a switch). The scaled random signal is fed to the timing input of a master-slave flip-flop 23a, having outputs Q and Q. The output Q and the scaled random signal are applied to the inputs of the NAND-l gate 23b, and the program storing signal is obtained at the output of the NAND-l gate. The ~YJ

8~5 circuit 23c control~ing the program storing unit steps the EPROM circuit 23d (ROM pr~gram may be extinguished by means of W -radiation), and here occurs at the OlltpUts out-l, out-2 and out-3 the random stimulus control signals in accordance with the program. The outputs out~l and out-2 provide for the random change of the two stimuli, while the output out-3 controls the occurrence of the simultaneous stimuli. The random duration of the stimuli is obtained by the NAND-2 gate 23e and NAND-3 gate 23f the inputs of which are connected to the outputs out-l and out-2~ as well as to the output Q
of the flip-flop 23a. The output out-3 and the output Q of the flip-flop 23a are connected to the inputs of the NAND-6 gate 23kJ the output of which is connected to the inputs of the NAND-4 gate 23g and NAND-5 gate 23h thro-ugh the mode of operation switch k. This provides Eor the occurrence of two stimuli signals Ing-l and Ing-2 in the simultaneous stimuli reaction time measurement mode. The functional signals of the circuits are illus-trated in Figure 4.
The 500 msec minimum time for recurrence of the stimuli signals is produced by double scaling ~in a proportion of 1 : 2) the signal of the monostable multivibrator (125 msec). The termination of the program is controlled by the program preset circuit 23i.
Where a light stimulus is usedl there is a relationship between the intensity of the light and the reaction of the subject being tested.
At higher intensities faster reaction times, at lower intensities slower reaction times have been measured. However, it is not sufficient to ad-just the stimulus transmitting light sources to a given intensity as it is also necessary to keep the background illumination at a predetermined con-stant level. This requirement can be hardly met in most of psychological laboratories and coordination of the illuminating level of the different laboratories is impossible. In a situation in which a special measuring situation occurs (e.g. testing of operators in mines or testing sportsmen on sports grounds etc.), where background illumination cannot be , ~ s ~

controlled, the results produced by such measurements cannot be compared with the rcsults of measuring procedures performed in laboratories. In many cases comparison would be of significance, but in the absence of proper measuring conditions such tests cannot be performed (e.g. to the drivers, when the driver has been on the road for several days and drives alternating with his colleague, it would be useful to know the extent of his Eatigue by measuring reaction time). Such tests ought to be performed at different hours of the day and under different illumination conditions. In such case results of measuring could be compared only if it were possible to control the constancy of background illumination conditions.
The equipment for measuring reaction time in accordance with the present invention is suitable for the performance of such tests, when using the light-stimulus transmitter which will now be described.
The light-sources of the light-stimulus transmitter are adapted to be attached to the subject's head, in front of his eyes. They are situated in a light tight box along with a light-source which produces a constant level of illumination. The light of the stimulus-transmitters is transmitted to both eyes by means of an optical system which provides that the same distance- and light impression can be reproduced in different laboratories. By use of such a stimulus-transmitter results of measurements performed anywhere and under any illumination circumstances can be compared.
This provides new possibilities in the field of quantitative analysis of test results.
The application of tile new-type stimulus-transmitter makes it possible to measure the fusion frequence which being also characteristic for fatigue, without faults which arise from differences in illumination.
An embodiment of the light stimulus-transmitter is illustrated in Figure 5.
The light stimulus-transmitter 31 consists of light tight tubes ~0 provided with flanges 38 excluding outer illumination and having been S

designed in such a manner that it can be attached to the head of the person being tested ~y means of straps 39. The spacing of the light-tight tubes 40 can be adjusted by means of a hinged construction 37 in accordance with the request of the wearer. The tubes contain constant intensity light-sources 35 emitting diffused white light illumination through a matte glass 32 and through abducent optics. The light-sources 33 and 34 are mounted in a light-proof cylinder 36 in front of the matte glass 32. The color of the stimulus light-sources 33 and 34 differs from that of the illuminating source emitting the diffused light (e.g. it may be red or green).
Abducent optics ensure for the eye the most advantageous distance-feeling ~in relation to the light-sources) and projects the stimulus in a distance corresponding to clairvoyance.
The light-sources are connected to the control unit by means of connecting cables 41.
Various alternative embodiments of the invention are possible.
By use of a prismatic optical system or by use of fibre-optics identical background light-sources for both eyes may be provided. In such case identical light-sources should be used for the stimuli ~in case of two different stimuli).
A further alternative is that by using the stimulus-transmitter according to the invention, retinal stimulation of both cerebral hemis-pheres - independent of each other - can be performed. In such case two parallelly controlled stimulus light-sources are built-in, which transmit the stimulating light through an optical system to the area of the retina of both eyes connected to the identical cerebral hemisphere.

-.

Claims (9)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Equipment for measuring reaction time, comprising a logic control circuit, a quartz time-base generator and scaling circuit connected to said control circuit through a time measuring and display circuit, a circuit for selecting the mode of operation connected to said logic control circuit, audio-frequency oscillators connected through a selector, said selector adapted to permit an operator to select light- and sound stimuli, a random time-base sig-nal generator connected to said selector through a program producing circuit, and a null detector connected between the audio-frequency oscillators and the selector, sound-signalling units connected to a dB scaler, light-signalling units are connected directly to the selector, a responder connected to an in-put of the logic control circuit, and the logic control circuit is connected through a circuit adapted to sense faulty reactions, to a display adapted to indicate faulty reactions.

2. Equipment as claimed in claim 1, including a manual control having an output connected to the selector.

3. Equipment as claimed in claim 1, characterized in that the logic circuit is divided into a left-side circuit and a right-side circuit and a left time measuring counter is connected to said left circuit and a right time measuring counter is connected to said right circuit.

4. Equipment as claimed in any of claims 1, 2 or 3, characterized in that the selector for selecting the mode of operation is provided with means for adjustment of the equipment for measurement of simple reaction time, two kinds of selective reaction time, reaction time of simultaneous stimuli, and reaction times responsive to the beginning or the end of the stimuli.

5. Equipment as claimed in any of claims 1, 2 or 3, characterized in that the audio frequency oscillators are adapted to generate signals having frequencies in the ranges 400 to 800 Hz, and 1800-2500 Hz.

6. Equipment as claimed in any of claims 1 to 3, characterized in that the program producing circuit is connected to the random time-base signal gen-erator, said program producing circuit comprising a flip-flop, said first out-put of said flip-flop upon being rendered negative is connected through a first NAND-gate to a first ROM control-circuit, said first ROM control-circuit hav-ing an output thereof connected to inputs of a second ROM circuit, said second ROM circuit having first and second outputs connected to a first input of a second and of a third NAND-gate respectively, said second and third NAND-gates having second inputs thereof connected to said second output of the flip-flop, said second and third NAND-gates having outputs connected to a first input of a fourth, and fifth NAND-gate respectively, said fourth and fifth NAND-gates having second inputs thereof connected through a switch to the output of a sixth NAND-gate, said sixth NAND-gate having a first input thereof connected to the second output of the flip-flop, and having a second input thereof con-nected to a third output of the second ROM circuit, a fourth output of the ROM
circuit is connected to a third input of the first NAND-gate through a program preset circuit, a second input of the first NAND-gate is connected to the out-put of the random time-base signal generator and the input of the flip-flop.

7. Equipment as claimed in claim 1, including light-stimulus transmitter having flanges thereon adapted to exclude extrinsic light, attachment elements for holding the transmitter in place on a user's head, light-tight tubes in which are situated at least one light source of constant intensity, and at least one stimulus light-source - the colour of which differs from that of the light-source of constant intensity.

8. Equipment as claimed in claim 7, characterized in that separate light-sources are provided for each eye of a user, the light-sources for one of the eyes being of different colours.

9. Equipment as claimed in claim 7 or 8, characterized in that for both eyes there are at least two stimulus light-sources provided with abducent optices connected to common control source and formed for deflecting the light directed to the nasal retina-half of one of the eyes and to the lateral retina-half of the other eye.