Method and system for testing cognition by processing a subject's response to a stimulus

Abstract

A system for processing the response of a human or animal subject to sensory stimuli is disclosed. The system includes: means for emitting these stimuli towards the subject; means for detecting the response of the subject to these stimuli; means for subjecting the subject to instructions for responding to these stimuli in response to instructions previously taught to the subject, the instructions having increasing or decreasing complexity according to at least three difficulty levels; means for measuring the reaction time to simple stimuli corresponding to a first difficulty level and means for measuring the reaction time to stimuli corresponding to a second difficulty level associated with a choice regarding categorization; and means for measuring the reaction time associated with a third difficulty level, the third difficulty level including a task in which the subject must perform two categorizations of the same stimulus simultaneously.

Description

Technical Field

[0001] The present invention relates to a system for testing cognition by processing a subject's response to a stimulus. The present invention also relates to a method implemented in the system. The method and system relate to the fields of neuropsychology and neuroscience and enable certain cognitive abilities involved in the user's response to difficulty to be tested in order to assist in the assessment of cognitive function, which is related to visual-motor decision-making ability and includes attention and executive function, as well as the response to difficulty. Background Art

[0002] According to the prior art, the patent application WO2009137663 A1 is known, which relates to visual and cognitive testing and / or learning under stress conditions. In this case, the visual and cognitive abilities of a subject can be analyzed and / or trained by providing visual stimuli to the subject. More particularly, when the subject is under stress conditions, they can be evaluated and / or trained to determine the effect of the stress conditions (such as physical stress or cognitive stress) on the subject's visual and sensory abilities.

[0003] The document WO2003015059 A1 discloses a system and method that enables the occurrence of intellectual disability to be diagnosed and the development of intellectual disability to be monitored. The method may include performing one or more psychological tests and teaching rules to the subject that enable a response to one or more tests without providing cultural signals (such as those found in language-based learning techniques). Appropriate responses to the tests can be simulated during a learning phase prior to the test phase. Devices, systems, and methods for controlling cognitive function can be implemented in a computerized system.

[0004] According to the prior art, the US Patent US6632174B1 is also known, which relates to a method for testing and / or evaluating cognitive abilities. Based on the results, the cognitive level can then be divided into different cognitive abilities, and one or more tasks can be created, each task being associated with each of the different cognitive abilities.

[0005] In another patent application US20090287064A1, a method for cognitive testing is implemented by a computer, particularly for diseases associated with dementia. The method is implemented in a web-based interactive format on a computer workstation and examines the cognitive abilities of a patient. The method enables an indication of dementia (including Alzheimer's disease and other cognitive problems) to be given. The method does not require implementation by a qualified professional, but is implemented in a web browser, using a server and workstation via the Internet, or on a local workstation.

[0006] According to the prior art, the U.S. Patent US6280198B1 is also known, which relates to a computer-implemented method that uses a computer network including separate computers to administer and remotely monitor cognitive tests on a person. The computer-implemented method includes administering a set of basic cognitive tests to a person. The method further includes: repeatedly administering a set of cognitive tests, obtaining the person's performance responses to the tests, and downloading test information via the computer network. A database can be constructed starting from the performance responses of multiple persons. The computer-implemented method includes using at least two computers to administer, with at least one computer being local and the other computers being remote.

[0007] Finally, in the prior art, the Canadian Patent CA 2683728 relates to the visual, cognitive, and coordination abilities of a subject, which can be tested and / or trained by providing the subject with a variety of stimuli. Responses can be received from the subject, and the appropriateness of these responses can depend on the combination of stimuli provided to the subject. A touchscreen display device can be used to both provide stimuli and receive the subject's responses. Any type of output device and input device for receiving responses can be used. Information related to behavior, as well as other data related to the subject's performance, can be recorded. The rating can be based on speed, accuracy, and other aspects of the subject's performance.

[0008] The document US 2005 / 0192513 A1 discloses a method for psychological testing of a subject, which is performed by the following steps: presenting a test having an output device such as a computer monitor and an input device such as a keyboard, and providing the subject with instructions to play a test simulation so that the subject can learn from the simulation how to perform the test. Thus, the test is independent of the subject's language ability or oral instructions provided by an administrator.

[0009] The literature "The 3RT Test: Three reaction time tasks for IBM PC computers" published by Evelyn Lee Teng in Behavior Research Methods, Instruments, & Computers on January 1, 1990 (1990-01-01), pages 389-392, XP5569775 describes a test consisting of simple tasks, choices, and conditional reaction time (ET). These three tasks involve "comparable" but not strictly identical visual stimuli, because in the third task, two symbols appear instead of a single symbol (right arrow or left arrow) in the first two tasks. The tasks require "the same" manual responses, where the subject presses two buttons corresponding to the right and left, but they differ in the complexity of the cognitive processing required. The third task is a conditional reaction time task, where the subject will respond right or left according to the second symbol that appears laterally; this response is conditional on the indication given by the second symbol that appears next to the arrow. Non-verbal (visual) stimuli convey "commonly known" meanings, namely, arrows and "+", "-", or "=" symbols. Responses can be made on a keyboard connected to the computer's serial port or on response buttons.

[0010] Known methods do not disclose more reliable measures of brain function because they do not involve greater mobilization of the patient's attention in response to strictly identical stimuli and also have strictly identical motor responses. Thus, there are biases due to variations (unreliability) in reaction time. Moreover, the prior art does not include filtering that enables distinguishing, among the patient's responses, those associated with the reaction to difficulty and those associated with attention and executive cognitive states.

[0011] The prior art mainly uses simple or choice-based measures of reaction time, or separate tests that calculate "global" metrics to measure specific functions. Subsequently, multiple sets of tests are performed, and it should be understood that most tests are culture-linked.

[0012] To evaluate attention and executive difficulty (involving visual-motor decision-making ability), it is necessary to evaluate the cognitive aspects and the reaction to difficulty. This requires a long series of tests. Most existing tests are not related to recent neuroscience models, are linked to a given culture or language, and thus cannot be used for all populations and do not have a learning effect (retest effect), which prevents them from being reused on the same person until several months or even years later.

[0013] The object of the present invention is to propose a novel method for measuring visual-motor decision-making abilities (including attention, executive function, inhibition, and response to difficulty), which is faster, more international (not linked to the language or culture of the subject), and repeated at intervals of several days (which can be used for follow-up monitoring), and is in line with the latest developments in neuroscience. Summary of the Invention

[0014] This object is achieved by a system for processing the response of a human or animal subject to sensory stimuli, the system comprising:

[0015] - means for emitting these stimuli towards the subject, and means for detecting the response of the subject to these stimuli,

[0016] - means for subjecting the subject to instructions for responding to these stimuli, the instructions having increasing or decreasing complexity according to at least three difficulty levels,

[0017] - means for measuring the reaction time to a simple stimulus corresponding to a first difficulty level,

[0018] - means for measuring the reaction time to a stimulus corresponding to a second difficulty level associated with a choice regarding classification in response to instructions previously taught to the subject.

[0019] According to the invention, the processing system further comprises means for measuring the reaction time associated with a third difficulty level, the third difficulty level comprising the subject having to perform two simultaneous classification tasks on the same stimulus.

[0020] Moreover, the processing system according to the invention can advantageously implement a common stimulus library for all difficulty levels.

[0021] The system may further comprise: a database for storing the detected responses, and means for extracting information about the cognitive and psychological functions of the subject from the database.

[0022] Advantageously, the database is intended to store the historical performance of each subject. The database may include animal images according to different color gradients, and / or object images according to different color gradients.

[0023] The means for emitting sensory stimuli towards the subject may include a screen or headphones, or a sound-emitting device.

[0024] A device for detecting a response may be configured to receive pressure continuously applied by a subject or gaze-fixing, and to detect the release of the pressure or the fixation, which release is interpreted as a response to the stimulus.

[0025] A device for detecting a response configured to permanently receive pressure applied by a subject or gaze-fixing and to detect the release of the pressure or the fixation may include, for example, a computer mouse, or a joystick, or a touch screen, or a device for sensing the direction of gaze, or any accessory that can sense pressure or the direction of gaze.

[0026] According to another aspect of the present invention, there is provided a method of processing a response of a human or animal subject to a sensory stimulus implemented in a processing method according to the present invention, the method comprising: a step of emitting the stimulus towards the subject, a step of detecting the response of the subject to the stimulus, a step of processing the response thus detected, the step of emitting the stimulus being arranged to subject the subject to an instruction to respond to the stimulus, the instruction having an increasing or decreasing complexity according to at least three difficulty levels, the processing step comprising:

[0027] - a step of measuring the reaction time to a simple stimulus corresponding to a first difficulty level, and a step of measuring the reaction time to a stimulus corresponding to a second difficulty level associated with a choice regarding categorization in response to an instruction previously taught to the subject.

[0028] According to the present invention, the processing step further comprises a step of measuring the reaction time associated with a third difficulty level, the third difficulty level comprising a task in which the subject must perform two simultaneous categorizations of the same stimulus.

[0029] The set of emitted stimuli may be configured to distinguish at least two choices, each choice involving two mutually exclusive categories.

[0030] Moreover, the method according to the present invention may include the following steps: processing the reaction times corresponding to the first difficulty level, the second difficulty level, and the third difficulty level, including:

[0031] - identifying errors caused by incorrect selection and / or premature response and / or failure to make a selection,

[0032] - identifying errors caused by incorrect selection and / or premature response and / or overly slow response,

[0033] - accessing the processing time of the difficulty associated with the categorization instruction for the subject, which processing time has had their simple reaction times corresponding to visual detection and motor response removed for each subject, to convey the average execution reaction time,

[0034] - Map the measurement results corresponding to the subject on multiple axes, the multiple axes including a first axis (S) representing the average execution reaction time, and a second axis (Δ) representing the subject's reaction to the difficulty of the stimulus.

[0035] "Average execution reaction time" refers to the reaction time associated with classification, that is, excluding the visual-motor response time.

[0036] The processing method according to the present invention may further include the following steps: placing the execution times of tasks with different difficulty levels on the same scale so as to be able to compare them.

[0037] The step of detecting the response to the stimulus may include: detecting the release of an action that was previously initiated and continuously applied until the stimulus arrives. Description of the Drawings

[0038] The present invention will be better understood with reference to the following drawings:

[0039] Figure 1 Shows a practical example of a set of tests (A, B, C) performed in the method according to the present invention, and the fact that there is a stage of learning the tasks before each group of tests.

[0040] Figure 2 Shows a specific embodiment of the response to a stimulus with attentional motor engagement (the pressure of the test);

[0041] Figure 3 Shows the steps associated with test section A - measuring the reaction time of the subject;

[0042] Figure 4 Shows an embodiment of a database without color and with pure colors;

[0043] Figure 5 Shows the steps associated with test section B - measuring the reaction time associated with the selection of a category;

[0044] Figure 6 Shows the steps associated with test section C - measuring the reaction time associated with the selection of two categories;

[0045] Figure 7 Is an example of the mapping of a set of measurement control item data collected in the test method according to the present invention;

[0046] Figure 8 Shows an example of a correlation table between the collected data;

[0047] Figure 9Shows the results of the control group and a graphical representation of the observed axis of symmetry, with the data represented having a 45-degree rotation about the axis of symmetry; and

[0048] Figure 10 Schematically shows the various measurement results, errors, and times that are identified, and the mathematical processing steps performed based on the measurement results. Detailed Description of the Invention

[0049] Now, with reference to Figures 1 to 6 , an actual embodiment of the test method according to the present invention will be described, which includes three parts A, B, and C with increasing difficulty, each part including 16 tests and learning tasks before these tests. The subject is placed in front of a computer screen and responds to stimuli via a mouse connected to the computer. The number and complexity of the images are the same under all conditions. The subject is invited to identify the target differences under each condition.

[0050] This test makes it possible to show two axes of cognition independent of executive function on the same data.

[0051] Using a mouse is an example, and another object can achieve the same function, such as a touch screen, keyboard, joystick, pedal, stylus, and more generally, any object that senses pressure on a target or remains stationary and then changes, such as a gaze direction sensor.

[0052] For example, the present invention can use various devices to test a wide range of motor skills, such as moving an object (changing position); and / or complex / continuous motor skills, such as positioning (acting according to commands with discrete states) or control. The present invention can also measure movement time, movement regularity, complex hand-eye coordination, hand-hand coordination, and foot-eye coordination.

[0053] The system can include software and combinations of software and hardware: specially adapted joysticks, pedals, microphones, etc. Moreover, the system can be configured to act as an autonomous module located in the user's home, medical center, institution, treatment center, or any other suitable location. The system can also include an interconnection system of one or more workstations. The system can include an adaptive computer program that can be accessed by a computer / workstation via a CD, USB stick, Internet, intranet, or any other means that allows information transmission.

[0054] The measurement of reaction time is actually performed using the internal computing device of the computer used to execute the test, but it can also be provided to use an external timing device connected to the computer.

[0055] With reference to Figure 2, The test method according to the present invention includes a basic interrogation sequence, which includes: pressing on the device, indicating the engagement of the subject's attention, a waiting time, the emission of a stimulus, and the subject's response by maintaining or releasing the press. The stimulus can be visual (image) or auditory (sound), and has common attributes (same visual load, duration, frequency, same volume, etc.). These stimuli each conform to or do not conform to the instruction criteria (e.g., gray or white, object or creature, low or high tone). If the stimulus meets all the instruction criteria (whether simple or complex), the instruction causes the subject to release the press.

[0056] The response is verified or not verified, depending on whether the stimulus meets the instruction criteria. In the case of a correct response, as in the case of an incorrect response, the time separating the emission of the stimulus from the response is measured.

[0057] In this embodiment, the test is performed by means of a computer and is based on the response after verifying the engagement of attention by moving a finger on the mouse or "lifting the finger from the mouse". The movements of the subject are measured in order to evaluate the speed of brain function in the case where the motor elements are removed from the response.

[0058] Part A of the test according to the present invention is dedicated to measuring the simple reaction time of the subject. Refer to Figure 3 , First, a white screen is displayed for 0.2 seconds, and then an invitation to perform a click action on the mouse appears for 2 seconds. A white screen is displayed for an arbitrary duration between 2 seconds and 7 seconds. If the subject responds by releasing their finger during this sequence, the response will be interpreted as an impulsive error. After the white screen for an arbitrary duration, a test image is displayed for 3 seconds. Failure to respond to the stimulus is interpreted as an omission error.

[0059] Figure 4 Shows an example of the test image displayed among 16 images for test part A, B, or C, with 4 different images for each category. These images are randomly extracted from a database and there are no duplicate images.

[0060] In test part B, as Figure 5 shown, the aim is to measure the reaction time and category selection (e.g., white / grey). The selection criteria are randomized. The criterion is, for example, that the subject only releases their click when the image is grey. In this test part B according to the present invention, in response to the instructions previously taught to the subject, the stimulus reaction time corresponding to the second difficulty level and associated with the selection regarding categorization is measured.

[0061] If the image is white, the basic sequence for inviting the release of the clicked part B is, for example: continuously displaying a white screen for 0.2 seconds, inviting a click on the mouse for 2 seconds, a random white screen for 2 to 7 seconds, followed by a gray image or a white image for 3 seconds. An incorrect choice by the subject (in this case, releasing the pressure when the gray image appears) will be considered a selection error.

[0062] As Figure 6 shown, the test part C according to the present invention is dedicated to measuring the reaction time and collecting two choices (white / grey, and biological / non-biological). The criteria for the white / grey choice are the opposite of those in condition B, and the criteria for choosing biological / non-biological or an object are randomized, for example, inviting the release of the click only when the image is both grey and biological. In this third test part C according to the present invention, the subject is subjected to a third difficulty level including such a task: in this task, the subject must perform two simultaneous categorizations regarding the same stimulus.

[0063] Now, an example of the processing of the data collected by the test method according to the present invention will be described with particular reference to Figures 7 to 10 .

[0064] The test method according to the present invention includes the following part: this part aims to help understand the cognitive function of the subject by post-processing the data of the subject, with the aim of isolating two possible components of slowdown in the subject. Thus, it is the case that the decision-making process of the subject is understood by decomposing their cognition according to a set of potential indicators of their cognitive function.

[0065] Data processing is performed on the normalized response time by removing the response time of the simplest experiment from other response times, so as to eliminate the stimulus perception and the action implementation part of the response from the response time.

[0066] With reference to Figure 7 and Figure 8 , a correlation matrix was established between the characteristics / practices of 84 subjects considered normal and who had served as controls in the first calibration and the processing of the data collected for three series of tests A, B, and C.

[0067] Based on the data of the normalized response time of experiments with increasing analysis difficulty, a two-factor analysis is performed, and the factors are denoted as S and Δ. These two factors have been proven to be independent of each other. The first factor S represents the overall slowdown of the average speed of the subject associated with the subject's attention to the task, placed on a scale independent of the difficulty level, and the second factor Δ represents the excessive or reduced slowdown in the case of increasing difficulty. These two factors can be used to characterize cognitive functions. Then, these elements can be used for neurological characterization and follow-up, for the screening and follow-up of cognitive problems, especially for decision-making and attention or alertness problems, for understanding the difficulties in people's daily lives, so as to implement effective assistance strategies especially in daily life.

[0068] It characterizes the cognitive functions of the subjects and the cognitive and psychological aspects associated with their decision-making, which enables the localization of the subjects' attention and executive functions statistically relative to norms. In addition to these two factors, the analysis also includes other factors based on the analysis of the error rate and error type generated and the variance of the response time of each individual. This is because the purpose of the test is to observe whether each of these factors deviates statistically from the norms.

[0069] Now, with reference to Figure 9 and Figure 10 , an example of determining the difficulty coefficient of a task is described. The principle is to place the execution times of tasks with different difficulty levels on the same scale so that they can be compared.

[0070] For the reaction time A, it has been observed that this time has small fluctuations. It has been decided to subtract the time A that is considered to be the "motor (perception of the item and decision-making and execution of the motor response)" time base because what is concerned is the "brain" extra time specifically associated with the difficulty analysis.

[0071] By means of this method, the times of different difficulty levels are placed on the same scale by means of a multiplication coefficient so that the times can be compared. This scale change is performed after subtracting the reaction time A. The coefficient 1.61 (non-limiting) has been established based on the data of 84 control subjects used for calibration, and the coefficient will be gradually adjusted as the calibration basis increases, especially according to the age and other parameters of the subjects. The coefficient is calculated as the ratio of the average value of C - A (on the control group) to the average value of B - A.

[0072] The reaction time A has been subtracted from two other cases including additional difficulty:

[0073] B' = B - A and C' = (C - A) / coefficient

[0074] Thus, the means have been aligned (B' and C' have the same mean on the control group). Thus, it has also been observed that the difference between the two distributions is no longer visible. The standard deviations have become the same.

[0075] From a scientific point of view, this would seem to imply that the remaining response time (the additional time required for the brain to analyze the difficulty) is a linear variable of the difficulty.

[0076] The two distributions are then compared, and it has been observed that it is not possible to statistically reject the hypothesis that they are the same.

[0077] In a 2D graph where the X-axis is B' = B - A and the Y-axis is C' = (C - A) / coefficient, since B' and C' have the same distribution, the graph of the 2D distribution is substantially symmetric. From here on, coordinates that conform to the said symmetry are sought. New coordinates S and Δ are thus defined, which are the directions of the principal components themselves.

[0078] Whenever the data is symmetric, the axis corresponding to that symmetry is chosen. In the test method according to the invention, the change of axis is thus carried out. This is merely a different representation without loss of information. Relying on this symmetry, the semi-sum and the semi-difference can be observed, since it is known that they are decorrelated mathematically (this is because it has been observed that B' and C' have the same standard deviation).

[0079] For S, the reaction time (RT) of the subject is obtained, which is independent of the difficulty and is thus specific to the individual subject being tested. A representation of the attention function specific to each subject is obtained.

[0080] In contrast, for Δ, it is associated with the concept of increasing difficulty and represents the way the subject responds to the increase in difficulty.

[0081] -S is the average attention time and corresponds to the average executive slowdown of a person. In a scale independent of the task difficulty level;

[0082] -Δ is the change in the response time associated with the increase in task difficulty, is an indicator of the response to difficulty (including the response to difficulty), but is also an indicator of the adaptability to difficulty.

[0083] For example, as Figure 10 shown, the variables S and Δ can be calculated as follows:

[0084] Δ = (C' - B') / 2 = 0.38A - B + 0.62C

[0085] S = t' BC = (C' + B') / 2

[0086] where t' BC represents the average execution response time of the test subjects who have undergone the test, which is independent of the difficulty and thus specific to the test subject.

[0087] The present invention can also be implemented on a separate workstation or a plurality of workstations connected to a network in a nursing home and a community or a health club.

[0088] The present invention can also include a database that can store responses and optionally store the historical performance of individual users. The database can be local or remote and can be accessed via the Internet, or can be fully or partially available in the user's facility. In one embodiment, the database can be managed by an organization and can accumulate the history and responses of multiple individuals, thereby allowing the ultimate creation of a general standard value database. The database can be used to compare the stored responses with the responses of the current user in order to facilitate cross-validation of the user's test results against the standard values.

[0089] In this way, the deviation of the current user from the normal can be characterized and optionally used to help practitioners determine cognitive impairments associated with conditions such as post-traumatic disorder (after a stroke or head injury), Alzheimer's disease, Parkinson's disease (particularly but not exclusively).

[0090] Therefore, the tool for determining cognitive function will constitute such an element: the element is used to help evaluate behavioral problems, such as attention deficit hyperactivity disorder and attention deficit disorder (particularly but not exclusively, using a set of tests related to attention ability); or learning difficulties, such as dyslexia, dysgraphia or dyscalculia (mainly but not exclusively, using fluency measurement and naming tests). The use of the database is not limited to these applications, and other applications of the database are included in the principles of the present invention.

[0091] It should be noted that the present invention can be utilized starting from a mobile storage device (such as a CD or a USB stick), or can be accessed from a central computer or via a public communication network (such as the Internet). Moreover, the present invention can actually be implemented by a single person or organization, and the database can be centralized, local and / or maintained by an internal or external organization.

[0092] Of course, the present invention is not limited to the above embodiments, and many developments can be made to the embodiments without departing from the scope of the present invention. Moreover, various features, types, variants and embodiments of the present invention can be related to each other according to various combinations as long as they are not mutually incompatible or exclusive.

Claims

1. A system for processing the response of a human or animal subject to sensory stimuli, the system comprising: - means for emitting these stimuli towards the subject, and means for detecting the response of the subject to these stimuli, - means for subjecting the subject to instructions for responding to these stimuli, the instructions having an increasing or decreasing complexity according to at least three difficulty levels, - means for measuring a reaction time A to a simple stimulus corresponding to a first difficulty level, - means for measuring a reaction time B to a stimulus corresponding to a second difficulty level associated with a choice of classification in response to instructions previously taught to the subject, - means for measuring a reaction time C associated with a third difficulty level, the third difficulty level comprising two simultaneous classification tasks that the subject must perform on the same stimulus, - means for processing the measured reaction times A, B, C in response to the stimuli, characterized in that the means for processing the measured reaction times A, B, C in response to the stimuli are configured to: - determine a normalized reaction time by subtracting the reaction time to the simple stimulus from the reaction times to the stimuli associated with a choice and to the stimuli associated with two simultaneous classifications, - calculate a difficulty coefficient of the task as the ratio of the average of the difference (C - A) between the reaction time C and the reaction time A to the average of the difference (B - A) between the reaction time B and the reaction time A, wherein the processed reaction times B', C' are: B' = B - A and C' = (C - A) / coefficient - analyze the normalized reaction time according to two independent factors (S, Δ), the two independent factors respectively representing (i) an average execution reaction time and (ii) the reaction of the subject to the difficulty of the stimuli, wherein: S = (C' + B') / 2 and Δ = (C' - B') / 2.

2. The system according to claim 1, characterized in that, The system implements a common stimulus library for all difficulty levels.

3. The system according to claim 1 or 2, characterized in that, The system further comprises: a database for storing the detected responses; and means for extracting information about the cognitive and psychological functions of the subject from the database.

4. The system according to claim 3, wherein The database is intended to store the historical performance of each subject.

5. The system according to claim 4, wherein The database includes animal images according to different color gradients.

6. The system according to claim 3, wherein The database further includes object images according to different color gradients.

7. The system according to claim 1 or 2, characterized in that, The means for emitting sensory stimuli towards the subject includes a screen or headphones.

8. The system according to claim 1 or 2, characterized in that, The means for detecting the response of the subject to these stimuli is intended to receive the pressure continuously applied by the subject or the fixation of the gaze, and is intended to detect the release of the pressure or the fixation, the release being interpreted as a response to the stimulus.

9. The system according to claim 8, wherein The means for detecting the response of the subject to these stimuli, which is intended to permanently receive the pressure applied by the subject or the fixation of the gaze and detect the release of the pressure or the fixation, includes a computer mouse, or a joystick, or a touch screen, or a means for sensing the direction of the gaze.

10. A method for processing the response of a human or animal subject to a sensory stimulus implemented in the system according to any one of claims 1 to 9, the method comprising: - a step of emitting the stimulus towards the subject, the step being arranged to subject the subject to an instruction to respond to the stimulus, the instruction having increasing or decreasing complexity according to at least three difficulty levels, - a step of measuring the response time of the subject to the stimulus, the step comprising: - a step of measuring the reaction time to a simple stimulus corresponding to a first difficulty level, - a step of measuring the reaction time to a stimulus corresponding to a second difficulty level associated with a choice regarding classification in response to an instruction previously taught to the subject, - a step of measuring the reaction time associated with a third difficulty level, the third difficulty level comprising two simultaneous classification tasks that the subject must perform on the same stimulus, - a step of processing the thus measured response times, characterized in that the step of processing the thus measured response times comprises: - a step of generating a normalized reaction time by subtracting the response time to the simple stimulus from the reaction times to the stimuli associated with the choice and to the stimuli associated with two simultaneous classifications, - a step of calculating the difficulty coefficient of the task as the ratio of the average of the differences (C - A) between the reaction time C and the reaction time A to the average of the differences (B - A) between the reaction time B and the reaction time A, where: B’ = B - A and C’ = (C - A) / coefficient - a step of analyzing the normalized reaction time according to two independent factors (S, Δ), the two independent factors respectively representing (i) the average execution reaction time and (ii) the reaction of the subject to the difficulty of the stimulus, where: S = (C’ + B’) / 2 and Δ = (C’ - B’) / 2.

11. The method according to claim 10, wherein The set of emitted stimuli is intended to distinguish at least two choices, each choice involving two mutually exclusive categories.

12. The method according to claim 11, wherein The processing of the reaction times corresponding to the first difficulty level, the second difficulty level, and the third difficulty level comprises: - identifying errors caused by incorrect choices and / or premature reactions and / or failure to make a choice, - identifying errors caused by incorrect choices and / or premature reactions and / or overly slow reactions, - accessing the processing time of the difficulty associated with the classification instruction of the subject, the processing time having had the simple reaction times corresponding to their visual detection and motor response removed for each subject to convey the average execution reaction time, - mapping the measurement results corresponding to the subject on multiple axes, the multiple axes including a first axis (S) representing the average execution reaction time and a second axis (Δ) representing the reaction of the subject to the difficulty of the stimulus.

13. The method according to claim 12, wherein The method further comprises the step of placing the execution times of tasks with different difficulty levels on the same scale so as to be able to compare the execution times.

14. The method according to any one of claims 10 to 13, characterized in that, The stimulus includes an image.

15. The method according to any one of claims 10 to 13, characterized in that The stimulus includes a sound.

16. The method according to any one of claims 10 to 13, characterized in that, The step of detecting a response to a stimulus includes: detecting the release of an action that was previously initiated and continuously applied until the stimulus arrives.

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