Experimental variables and ways to control them. What is the dependent variable

Independent variable (IV)– an influencing factor that causes changes.

An independent variable (book definition) is an experimental effect or an experimental factor - controlled, i.e. a variable actively changed by the researcher, in other words, a functionally controlled variable; presented on two or more levels. In the experimental hypothesis it is understood as a causal factor.

Dependent Variable (DP)– what we consider as the effect of the influence of the independent variable.

Dependent variable (book definition) is a “response”, or a variable measured in an experiment, the changes in which are causally determined by the action of the independent variable (IV). In psychological research, it is represented by indicators of the subject’s activity, any forms of assessment of his subjective judgments and reports, psychophysiological parameters, etc.

Side variable – it is any factor, perceived or actual, that may influence changes in the dependent variable. There can be many such factors; the experimenter’s task is to control the impact of these factors.

It is important to note that when conducting any experiment we are interested in causality. - investigative connection. Establishing a fact in a study is not sufficient; the reason and method of verification must be established.

9. External ( they are side effects) variables. Ways to control variables.

External or additional variables(DP) is a concomitant stimulation of the subject that influences his response. The set of DP consists, as a rule, of two groups: external conditions of experience and internal factors. Accordingly, they are usually called external and internal DPs. TO external DP refers to the physical environment of the experiment (illumination, temperature regime, sound background, spatial characteristics of the room), parameters of equipment and equipment (design measuring instruments, operating noise, etc.), time parameters of the experiment (start time, duration, etc.), personality of the experimenter. TO internal DP includes the mood and motivation of the subjects, their attitude towards the experimenter and the experiments, their psychological attitudes, inclinations, knowledge, abilities, skills and experience in this type of activity, level of fatigue, well-being, etc.

Ideally, the researcher strives to reduce all additional variables to nothing or at least to a minimum in order to highlight “in pure form» relationship between independent and dependent variables. There are several main ways to control the influence of external DP: 1) elimination of external influences; 2) constancy of conditions; 3) balancing; 4) counterbalancing.

1) Elimination of external influences consists of complete exclusion from external environment any external DP.

2) Creation of constant conditions. The essence of this method is to make the effects of DP constant and identical for all subjects throughout the experiment.

3) In cases where it is not possible to create and maintain constant conditions throughout the experiment, they resort to the balancing method. This method is used, for example, in a situation where the external DP cannot be identified. In this case, balancing will consist of using a control group. The study of the control and experimental groups is carried out under the same conditions with the only difference being that in the control group there is no effect of the independent variable.

4) Counterbalancing as a way to control external DP is most often practiced when the experiment includes several series. The subject finds himself in different conditions sequentially, but previous conditions can change the effect of subsequent ones. To eliminate the “sequence effect” that arises in this case, experimental conditions are presented to different groups of subjects in different orders.

Types of experimental designs.

It is customary to distinguish the following Basic experimental designs: plans with one independent variable, with two independent variables and factorial designs.

Designs with one independent variable:

The design of this experiment should have the following features:

1) using one of the strategies for creating equivalent groups, most often randomization;

2) the presence of an experimental and at least one control group;

3) completion of the experiment by testing and comparing the behavior of the group that received the experimental intervention (X1) with the group that did not receive the intervention (X0).

If it is necessary to use more than 1 level of exposure, then plans with several experimental groups (according to the number of exposure levels) and one control group are used.

Using a 2 randomized group design with post-exposure testing allows for major sources of internal validity (as defined by Campbell) to be controlled. The plan allows you to control the influence of group composition, spontaneous attrition, the influence of background and natural development, and the interaction of group composition with other factors.

Two randomized group design with preliminary and final testing. This design is widespread in social and clinical experiments (for example, the Stanford prison experiment).

In the study of mental processes, such a plan, as a rule, is not used, since preliminary testing affects the internal validity of the experiment by setting certain settings.

Factorial experiments are used when it is necessary to test complex hypotheses about the relationships between variables. General form a similar hypothesis: “If A1, A2, .... A, then B.” Such hypotheses are called complex, combined, etc. In this case, there can be various relationships between the independent variables: conjunctions, disjunctions, linear independence, additive or multiplicative, etc. Factorial experiments are a special case of multivariate research, during which they try to establish relationships between several independent and several dependent variables. In a factorial experiment, as a rule, two types of hypotheses are tested simultaneously:

1) hypotheses about the separate influence of each of the independent variables;

2) hypotheses about the interaction of variables, namely, how the presence of one of the independent variables affects the effect on the other.

A factorial experiment is based on a factorial design. Factorial design of an experiment involves combining all levels of independent variables with each other. The number of experimental groups, as a rule, is equal to the number of combinations of levels of all independent variables.

Dependent Variable

Parameter name	Meaning
Article topic:	Dependent Variable
Rubric (thematic category)	Psychology

What can the experimenter vary?

Firstly, these are the physical parameters of the situation: the location of the equipment, appearance rooms, lighting, sounds and noises, temperature, placement of furniture, painting of walls, time of experiment (time of day, duration, etc.). That is, all the physical parameters of the situation that are not stimuli.

Secondly, these are socio-psychological parameters: isolation - work in the presence of an experimenter, work alone - work with a group, etc.

Third, these are the features of communication and interaction between the subject(s) and the experimenter.

Judging by publications in scientific journals, for last years There has been a sharp increase in the number of experimental studies that involve varying external conditions.

TO ʼʼorganismal variablesʼʼ, or uncontrollable characteristics of subjects, include:

* physical,

* biological,

* psychological,

* socio-psychological and

*social characteristics.

Traditionally, they are classified as “variables,” although most are constant or relatively constant throughout life. The influence of differential psychological, demographic and other constant parameters on an individual’s behavior is studied in correlation studies. At the same time, the authors of most textbooks on the theory of psychological method, for example M. Matlin, classify these parameters as independent variables of the experiment.

As a rule, in modern experimental research, differential psychological characteristics individuals, such as intelligence, gender, age, social position (status), etc., are taken into account as additional variables that are controlled by the experimenter in general psychological experiment. But these variables can turn into a “second main variable” in differential psychological research, and then a factorial design is used.

Psychologists deal with the behavior of the subject, in connection with this, parameters are selected as the dependent variable verbal and non-verbal behavior.

These include:

*number of mistakes the rat made while running through the maze;

*time spent by the subject in solving the problem, changing his facial expressions when watching an erotic film;

*motor reaction time sound signal etc.

The choice of behavioral parameter is determined by the initial experimental hypothesis. The researcher must specify it as much as possible, that is, ensure that the dependent variable is operationalized - amenable to registration during the experiment.

Behavior parameters can be divided into formal-dynamic and substantive. Formal-dynamic (or spatio-temporal) parameters are quite easy to record with hardware.

Let's give examples of these parameters.

1. Accuracy . The most frequently recorded parameter.
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Since most of the tasks presented to the subject in psychological experiments are achievement tasks, then accuracy or the opposite parameter - the error of actions - will be the main recorded parameter of behavior.

2. Latency . Mental processes occur hidden from the outside observer. The time from the moment the signal is presented to the choice of response is usually called latent time. In some cases, latent time is the most important characteristic of the process, for example, when solving mental problems.

3. Duration , or speed, execution . It is a characteristic of executive action. The time between the selection of an action and the end of its execution is called the speed of action (as opposed to latent time).

4. Pace, or frequency of actions . The most important characteristic, especially when studying the simplest forms of behavior.

5. Productivity . The ratio of the number of errors or the quality of execution of actions to the execution time. Serves the most important characteristic in the study of learning, cognitive processes, decision-making processes, etc.

Recognizing various forms of behavior is the job of specially trained experts or observers. It takes considerable experience to characterize one act as a manifestation of submission, and another as a manifestation of servility.

The problem of recording qualitative characteristics of behavior is solved by:

a) training observers and developing observation maps;

b) measuring formal dynamic characteristics of behavior using tests.

The dependent variable must be valid and reliable. The reliability of a variable is manifested in the stability of its recordability when experimental conditions change over time. The validity of a dependent variable is determined only under specific experimental conditions and in relation to a specific hypothesis.

Three types of dependent variables can be distinguished:

1) simultaneous;

2) multidimensional;

3) fundamental.

In the first case only one parameter is recorded, and it is this that is considered a manifestation of the dependent variable (there is a functional linear relationship between them), as, for example, when studying the time of a simple sensorimotor reaction.

In the second case the dependent variable is multidimensional. For example, the level of intellectual productivity is manifested in the time it takes to solve a problem, its quality, and the difficulty of the problem solved. These parameters can be fixed independently.

In the third case when the relationship between individual parameters multidimensional dependent variable, the parameters are considered as arguments, and the dependent variable itself is considered as a function. For example, a fundamental measurement of the level of aggression F(a) is considered as a function of its individual manifestations (a.) facial expressions, pantomimes, swearing, assault, etc.

F(a) = f/(a r a 2 ,..,a n).

There is one more important property dependent variable, namely - sensitivity(sensitivity) of the dependent variable to changes in the independent one. The point is that manipulation of the independent variable affects the change in the dependent variable. If we manipulate the independent variable, but the dependent variable does not change, then the dependent variable is non-positive with respect to the independent one. Two variants of manifestation of non-positivity of the dependent variable are called "ceiling effect" and "floor effect".

First case occurs when the task presented is so simple that the level of its implementation is much higher than all levels of the independent variable.

The second effect on the contrary, it occurs when the task is so difficult that the level of its implementation is below all levels of the independent variable.

So, like other components psychological research, the dependent variable must be valid, reliable, and sensitive to changes in the level of the independent variable.

Exist two basic techniques for recording changes in the dependent variable.

First used most often in experiments involving one subject. Changes in the dependent variable are recorded during the experiment following changes in the level of the independent variable. Example is to record the results in learning experiments. The learning curve is a classic trend - changes in the success of completing tasks based on the number of trials (time of the experiment). To process such data, the statistical apparatus of trend analysis is used.

Second The technique of recording changes in the level of an independent variable is called delayed measurement. A certain period of time passes between the impact and the effect; its duration is determined by the time of distance between the effect and the cause. For example, taking a dose of alcohol increases the time of the sensorimotor reaction not immediately, but after a certain time. The same can be said about the effect of memorizing a specific number of foreign words on the success of translating a text into a rare language: the effect does not appear immediately (if it does).

Dependent variable - concept and types. Classification and features of the category "Dependent Variable" 2017, 2018.

Specifics of a psychological experiment. Psychological understanding of causation. Causal inference in a psychological experiment and subjective variables. (In contrast to other methods. Activity, reliability, organization. Features of the hypothesis. Adequacy and unambiguity of objectification of experimentally induced mental phenomena. Conditions of causality according to Campbell, cause and correlation, artifacts.)

Experiment is one of the main methods of scientific research. In general scientific terms, an experiment is defined as a special research method aimed at testing scientific and applied hypotheses, requiring strict logic of proof and based on reliable facts. In an experiment, an (experimental) situation is always created, the causes of the phenomena being studied are identified, the consequences of the actions of these causes are strictly controlled and evaluated, and the connections between the phenomena being studied are clarified.

An experiment as a method of psychological research corresponds to the above definition, but has some specifics. V.N. Druzhinin identifies the “subjectivity of the object” of research as a feature of a psychological experiment. Man, as an object of knowledge, has activity, consciousness, and thus can influence both the process of his study and its result.

The task of a psychological experiment is to make an internal mental phenomenon accessible to objective observation. In this case, the phenomenon under study must be adequately and unambiguously manifested in external behavior, which is achieved through targeted control of the conditions of its occurrence and occurrence.

Validity and reliability of the experiment

The following concepts are used to design and evaluate experimental procedures: ideal experiment, perfect compliance experiment, and infinite experiment.

D. Campbell identifies the following factors that threaten the internal validity of an experiment: background factor, natural development factor, testing factor, measurement error, statistical regression, non-random selection, screening. If they are not controlled, they lead to the appearance of corresponding effects.

Correlation studies

The theory of correlation research was developed by the English mathematician K. Pearson. Correlational research is a study conducted to confirm or refute a hypothesis about a statistical relationship between several (two or more) variables. In psychology, mental properties, processes, states, etc. can act as variables.

The problem of interpreting psychological causation is closely related to the theoretical attitudes and methodological positions of the authors in relation to the construction of a psychological explanation. In educational and methodological literature on an introduction to the experimental method, it is usually emphasized that testing causal hypotheses is the prerogative of experimental research. At least two topics in such manuals are mandatory, although in reality the authors pay unequal attention to them: the problem of understanding causality in psychological theories and hypotheses and the problem of competing hypotheses. Establishing the direction of the relationship between variables is the third topic when discussing the specifics of psychological causation.

The conditions for causal inference are built on the basis of an understanding of physical causality, which presupposes the influence of some material conditions (or factors) on others. Assumptions about laws reflected in generalized or so-called universal statements serve as an equally important basis for causal interpretations. In the literature summarizing the standards of experimental reasoning, the question is specifically discussed with what the causal inference is primarily associated with: with an appeal to these laws or to conditions controlled by the experimenter. Psychological laws as deductively posited generalizations and empirically presented (identified by one method or another) patterns as a manifestation of the action of laws relate to different realities - the world of theories and the world of empirical realities (psychological reality). For a number of authors, this difference serves as the basis for statements about the inapplicability of the experimental method in psychology on the grounds that the mental world - as a subjective reality - is unique and there are no general laws in it, that control influences from the outside are not applicable to it, etc. Another twist on this topic is the search for differences, i.e. the specifics of psychological laws as dynamic, statistical (as opposed to deterministic statements with a physicalist understanding of causality), as laws of development, etc.

This problem is partially solved by pointing out the need to distinguish between the levels of hypotheses tested in a psychological experiment. An experimental hypothesis always relates to empirically established patterns. However, behind it there is another – a theoretical hypothesis that establishes the principle of explanation based on the provisions of one or another psychological theory.

18. Types of variables during verification experimental hypothesis: independent variable, dependent variable, additional variables. (Their types and requirements for them)

Variables- a reality parameter that can and/or changes in experimental research. There are: independent variables - changed by the experimenter; dependent variables - those that change under the influence of changes in the independent variable; external (side) - inaccessible to control, but affecting the dependent, source of error; latent - inaccessible to direct measurement, fixed by analyzing the joint variation of the dependent variables; additional - external variables taken into account in the experiment, etc.

The researcher should strive to operate only on the independent variable in the experiment. An experiment where this condition is met is called a pure experiment. But more often than not, during an experiment, by varying one variable, the experimenter also changes a number of others. This change can be caused by the action of the experimenter and is due to the relationship between two variables.

For example, in an experiment on developing a simple motor skill, he punishes the subject for failures electric shock. The size of the punishment can act as an independent variable, and the speed of skill development can act as a dependent variable. Punishment not only reinforces the appropriate reactions in the subject, but also gives rise to situational anxiety in him, which affects the results - it increases the number of errors and reduces the speed of skill development.

The central problem in conducting experimental research- identification of an independent variable and its isolation from other variables.

The independent variables in a psychological experiment can be:

1) characteristics of tasks;

2) features of the situation ( external conditions);

3) controlled characteristics (states) of the subject.

The latter are often called “organism variables.”

4) Sometimes a fourth type of variable is identified - constant characteristics of the subject (intelligence, gender, age, etc.), but, in my opinion, they belong to additional variables, since they cannot be influenced, but can only be taken into account when forming experimental and control groups.

The characteristics of the task are something that the experimenter can manipulate more or less freely.

The experimenter can vary the stimuli or task material, change the type of response of the subject (verbal or nonverbal response), change the rating scale, etc. He can vary the instructions, changing the goals that the subject must achieve during the task. The experimenter can vary the means that the subject has to solve the problem and put obstacles in front of him. He can change the system of rewards and punishments during the task, etc.

The features of the situation include those variables that are not directly included in the structure of the experimental task performed by the subject. This could be the temperature in the room, the environment, the presence of an external observer, etc.

What can the experimenter vary?

Firstly, these are the physical parameters of the situation: the location of the equipment, the appearance of the room, lighting, sounds and noises, temperature, placement of furniture, painting of the walls, time of the experiment (time of day, duration, etc.). That is, all the physical parameters of the situation that are not stimuli.

Secondly, these are socio-psychological parameters: isolation - work in the presence of an experimenter, work alone - work with a group, etc.

Thirdly, these are the features of communication and interaction between the subject(s) and the experimenter.

“Organismal variables,” or uncontrollable characteristics of the subjects, include physical, biological, psychological, socio-psychological and social characteristics. They are traditionally referred to as “variables,” although most are constant or relatively constant throughout life. The influence of differential psychological, demographic and other constant parameters on an individual’s behavior is studied in correlation studies.

As a rule, in modern experimental research, the differential psychological characteristics of individuals, such as intelligence, gender, age, social status(status), etc., are taken into account as additional variables that are controlled by the experimenter in a general psychological experiment. But these variables can turn into a “second main variable” in differential psychological research, and then a factorial design is used.

For example, in an experiment on developing a simple motor skill, he punishes the subject for failure with an electric shock. The size of the punishment can act as an independent variable, and the speed of skill development can act as a dependent variable. Punishment not only reinforces the appropriate reactions in the subject, but also gives rise to situational anxiety in him, which affects the results - it increases the number of errors and reduces the speed of skill development.

The central problem in conducting experimental research is identifying the independent variable and isolating it from other variables.

As independent variables in a psychological experiment may act:

1) characteristics of tasks;

2) features of the situation (external conditions);

3) controlled characteristics (states) of the subject.

The latter are often called “organism variables.” Sometimes isolated fourth type variables - constant characteristics test subject (intelligence, gender, age, etc.), but, in my opinion, they belong to additional variables, since they cannot be influenced, but can only take into account their level when forming experimental and control groups.

The characteristics of the task are something that the experimenter can manipulate more or less freely. According to the tradition coming from behaviorism, it is believed that the experimenter varies only the characteristics of the stimuli ( stimulus variables), but he has much more options at his disposal.

The experimenter can:

* vary stimuli or task material,

*change the type of response of the subject (verbal or non-verbal response),

* change the rating scale, etc.

*He can vary the instructions, changing the goals that the subject must achieve during the task.

*The experimenter can vary the means that the subject has to solve the problem and put obstacles in front of him.

*He can change the system of rewards and punishments during the task, etc.

Example. Experiments on identifying the effect of social facilitation (gains) were carried out according to the following scheme: The subject was given some sensorimotor or intellectual task. He first performed it alone, and then in the presence of another person or several people (the sequence, of course, changed depending on different groups). The change in the productivity of the subjects was assessed. In this case, the subject’s task remained unchanged, only the external conditions of the experiment changed.

What can the experimenter vary?

Firstly, these are the physical parameters of the situation: the location of the equipment, the appearance of the room, lighting, sounds and noises, temperature, placement of furniture, painting of the walls, time of the experiment (time of day, duration, etc.). That is, all the physical parameters of the situation that are not stimuli.

Secondly, these are socio-psychological parameters: isolation - work in the presence of an experimenter, work alone - work with a group, etc.

Third, these are the features of communication and interaction between the subject(s) and the experimenter.

Judging by publications in scientific journals, in recent years there has been a sharp increase in the number of experimental studies that use varying environmental conditions.

TO "organismal variables", or uncontrollable characteristics of the subjects, include:

* physical,

* biological,

* psychological,

* socio-psychological and

*social characteristics.

They are traditionally referred to as “variables,” although most are constant or relatively constant throughout life. The influence of differential psychological, demographic and other constant parameters on an individual’s behavior is studied in correlation studies. However, the authors of most textbooks on the theory of psychological method, for example M. Matlin, classify these parameters as independent variables of the experiment.

As a rule, in modern experimental research, the differential psychological characteristics of individuals, such as intelligence, gender, age, social position (status), etc., are taken into account as additional variables that are controlled by the experimenter in a general psychological experiment. But these variables can turn into a “second main variable” in differential psychological research, and then a factorial design is used.

The first thing you need to decide when planning an experiment is how many levels of the independent variable there will be and what they will be. The levels of an independent variable are its specific values. They can be specified in any measuring scale, i.e. can be both quantitative and qualitative.

An independent variable must have at least two levels that reflect the characteristics of its impact on the dependent variable. Otherwise, it simply ceases to be a variable. In the problem solving example, the independent variable has two quality level, specified in the scale of names: 1 - stuffy room; 2 - ventilated room. If a researcher wants to trace more detailed, quantitative relationships between how much oxygen is saturated in the air in a room and the level of intellectual activity of the subjects, he can express his independent variable on a stronger scale, determining, for example, different values of oxygen content per 1 m 3 of air.

If a researcher finds a difference in the success of solving problems in a stuffy and ventilated room, then he has some reason to believe that stuffiness affects the quality of problem solving. In any case, the first two conditions of causal inference are satisfied. In other words, a change in the dependent variable in accordance with a change in the independent variable allows us to talk about the influence of the independent variable on the dependent variable.

Experimental designs with an independent variable that have two levels are called single-level designs, probably because one of the levels of the independent variable reflects a normal, usual state of affairs, which is characterized by the absence of exposure (in our example, this state corresponds to a ventilated room). The impact on the subjects, leading to a deterioration in problem solving, is exerted by another level of the independent variable, reflecting the abnormal state of affairs (in our example, a stuffy room).

An independent variable can have more than two levels. Experimental designs in which the independent variable has more than two levels are called multilevel. For example, if we are interested in whether who a child walks with on the playground influences what games the child prefers to play, then in this case the researcher controls one independent variable with four levels: 1 - walks alone, 2 with a nanny , 3 - with parents, 4 with friends. And if, for example, a child walking with a nanny prefers to play catch (rather than other games) much longer, then the researcher has reason to believe that this factor determines the child’s interests in preferring this game.

Note that if the experimenter’s task is not just to note the influence of one variable on another, but also to find out the nature of such a relationship, he must use multi-level independent variables. Otherwise, the nature of the connection will not be established. For example, a researcher studying the psychophysical relationships between various concentrations of an odorous substance and the corresponding sensations must take several such concentrations in order to understand whether the desired relationship is described by a logarithmic or power law. A single-tier plan will not give him this opportunity.

When planning an experiment, the researcher must clearly determine how many levels the independent variable has and exactly how, according to his hypothesis, they influence the dependent variable. After this, he will be faced with the question of how to most reliably distinguish different levels variables from each other. The better the different levels of the independent variable are separated, i.e. The more clearly their differences are recorded, the more obvious their influence on the dependent variable will be. If the levels of the independent variable can hardly be distinguished from each other, then their influence on the dependent variable will be less noticeable. In this case, the researcher risks missing a result that is important for confirming the hypothesis and passing by his discovery.

In addition, the researcher must decide how many independent variables he will use in his study. If there is only one independent variable, we speak of single-factor experimental designs. Depending on the number of levels of the independent variable, univariate designs can be either single-level or multi-level.

When a researcher uses two or more independent variables that together influence the same dependent variable, such designs are called multivariate designs. Multivariate designs can include either single-level or multilevel independent variables. For example, a researcher tests the hypothesis that approximately the same success of boys and girls in performing an intelligence test is associated with the fact that boys are significantly better at solving arithmetic tasks, and girls are significantly better at anagrams. This would be an example of a multivariate design in which the first variable (gender) has two levels (boys and girls), and the second variable (task type) also has two levels (arithmetic problems and anagrams).

If a researcher is interested in how the quality of problem solving changes in people with different mode day (“night owls” and “larks”), then he will construct an experiment with one single-level and one multi-level variable: the first variable (day mode) has two levels (“owls” and “larks”), the second variable (time of day) has four levels (morning, afternoon, evening and night). In this case, the dependent variable in both cases will be the quality of problem solving.

Thus, the independent variable plays key role in planning an experimental study, and even before starting practical actions, the researcher must clearly understand how many independent variables there will be in his study, which ones, how many levels each will have, and how he will record these levels in the study.