Researching Cause and Effect          Chapter 2 – Second Slideshow
As a psychologist, when I hear people state a belief, I immediately start thinking in terms of variables.I realize that mo...
A variable is any quantity or quality that can take on  different values. Here are two random examples.               The ...
Perhaps these two variables are related. Maybe people who are more interested in the scientific method will be more likely...
Each person watching this slideshow can place themselves          along the continuum of each variable.1. The degree to wh...
Here is an example of one student, Phil.Phil finds this to be a great slideshow. Philalso loves science.1. The degree to w...
Here is another example. This is where                          James ranks himself on both variables.1. The degree to whi...
We could ask a large group of students to mark where they fall on both variables.Perhaps we might start to see a pattern. ...
It is very tempting to start fitting these findings into a   story. Maybe people who like science are more   curious and p...
Maybe one’s attitudes toward science causes them to like or dislike this slideshow.
How do we research Cause and Effect relationships in                   Psychology?
Establishing Cause and Effect   John Stuart Mill    David Hume       Immanuel KantPhilosophers have a lot to say about how...
Establishing Cause and EffectConditions to establish Cause and Effect.1. The variables are correlated.2. The cause comes b...
Establishing Cause and EffectNote that the first step is to establish a correlation.Correlation is a fancy term for “relat...
Establishing Cause and Effect                A                  BIt is very easy to think about how one thing may cause   ...
Correlation examplesDoes having a nice teacher cause students to learn more? Here are the two variables:                  ...
Correlation examplesIf the variables are related, then we should see nicer   teachers have classes that perform better. Pr...
Correlation examplesIf the variables are related, then we also should see   teachers who are not nice have classes that pe...
Two Sides to a CorrelationThis is the hard part. Correlations have two sides, or ends. People usually only think about one...
Two Sides to a CorrelationIf you believe a nice teacher causes a class to do   better then you are also saying that not be...
More Examples – Two Sides of CorrelationIf you believe that giving someone flowers will make   them like you, then you als...
More Examples – Two Sides of CorrelationIf you believe that spanking a child causes the child to   behave better, then you...
Each of these is a proposed correlation. It can be difficult to think about these, but practicing this can help you think ...
Correlational MethodsMost correlational research methods involve collecting data on at least two variables.               ...
Correlational MethodsHowever, we usually cannot determine cause and effect just from simple correlational studies.
Establishing Cause and EffectThe problems are the second and third conditionsConditions to Establish Cause and Effect 1.  ...
Problem    2. The Cause comes before the EffectUsually, in correlational studies, we observe both variables at the same ti...
Problem    2. The Cause comes before the EffectFor the example with Mr. Carter and Ms. Stark, this is a problem. The idea ...
Problem    2. The Cause comes before the EffectThe opposite direction is also possible. Some teachers may respond to their...
Problem    2. The Cause comes before the EffectFor every correlation you observe, be sure to consider both possible direct...
But those aren’t the only possibilities…
Establishing Cause and EffectThe third condition also has to be met.Conditions to Establish Cause and Effect 1.   The Vari...
Problem  3. Are there other variables to explain the effect?In correlational research, even if we observe a  correlation a...
Problem  3. Are there other variables to explain the effect?The problem is that correlational research observes variables ...
Problem  3. Are there other variables to explain the effect?In the real world, there are countless other variables.  Some ...
Problem  3. Are there other variables to explain the effect?In the most simple form, this is called the third-variable  pr...
Problem  3. Are there other variables to explain the effect?For our teaching example, pretend that we found a correlation ...
Problem  3. Are there other variables to explain the effect?Next, pretend that we establish that the teacher’s niceness co...
Problem  3. Are there other variables to explain the effect?We still would not be able to say for certain that another var...
Problem  3. Are there other variables to explain the effect?For example, maybe the resources available to the school affec...
Problem  3. Are there other variables to explain the effect?Let’s look at another example. There is a correlation between ...
Don’t worry, this correlation is meaningless.     It is explained by a third variable.
Problem  3. Are there other variables to explain the effect?There is a simple third variable: Population of the City. The ...
Review   Correlational research is a valuable tool.   There are many ways to collect correlational data.
Review   Correlation is a first step in the search for causes.    To establish cause, we need all three of the following ...
Review   Simply observing a correlation does not tell us that    one variable causes the other.       The direction of c...
Establishing Cause and Effect        Through Experiments
The Experimental MethodThe experimental method is a researcher’s strongest tool for establishing cause and effect relation...
The Experimental MethodConditions to Establish Cause and Effect1.   The Variables are Correlated.2.   The Cause comes befo...
The Experimental Method1.   The experimenter looks for a relationship between     one variable that is a cause and another...
The Experimental MethodThe two variables have special names.Independent variable – the   variable manipulated by   the res...
The Experimental Method                Independent VariablesTypically, independent variables describe what is  different b...
The Experimental Method               Independent VariablesPerhaps the hardest part of conducting an experiment is making ...
The Experimental Method          Independent Variables, ExampleWe could use an experiment to study the effect of teacher n...
The Experimental Method       Independent Variables, Example        Experimental Group – Students assigned            a te...
The Experimental Method           Independent Variables, ExampleThe hard part is making sure that the only thing that diff...
The Experimental Method       Ways to Eliminate Extraneous VariablesAn extraneous variable is a variable other than the in...
The Experimental Method        Ways to Eliminate Extraneous VariablesThere are two main ways to eliminate Extraneous  Vari...
SummaryGive yourself ample time to master these ideas and the terminology. You should be able to define all of the followi...
Limits of the Experimental MethodNot every variable can be manipulated. Remember the first example of two correlated varia...
Limits of the Experimental MethodWe hypothesized that a person’s interest in science will affect how useful they think thi...
Limits of the Experimental MethodHow would you manipulate people’s “interest in science” for an experiment, making some pe...
Limits of the Experimental MethodEven if we could come up with a creative way to manipulate “interest in science,” would i...
Limits of the Experimental MethodOther variables cannot be manipulated without causing harm or other problems.
Limits of the Experimental Method                     SummarySome variables are impractical to manipulate.Experiments can ...
Review   Practice turning explanations or stories into    hypotheses about the relationship between two    variables.   ...
ReviewConditions to establish Cause and Effect.1. The variables are correlated.2. The cause comes before the effect.3. The...
Review   Correlational Research Methods can identify    relations between variables that you measure.   Correlational Re...
Review   Correlations have several possible causal    explanations    1.   The direction of cause could go either way.   ...
Review   The Experimental Method allows us to establish    cause and effect relationships by manipulating an    independe...
These are the foundational ideas to help you think about research more critically.There are many more details in your book...
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Researching cause and effect

  1. 1. Researching Cause and Effect Chapter 2 – Second Slideshow
  2. 2. As a psychologist, when I hear people state a belief, I immediately start thinking in terms of variables.I realize that most people do not do this, but this is ultimately the evidence we can collect and evaluate.
  3. 3. A variable is any quantity or quality that can take on different values. Here are two random examples. The Degree to which this Slideshow is Helpful. Not at all Helpful Very Helpful A Person’s Interest in Scientific Research Not at all Interested Extremely Interested
  4. 4. Perhaps these two variables are related. Maybe people who are more interested in the scientific method will be more likely to find this slideshow to be helpful.
  5. 5. Each person watching this slideshow can place themselves along the continuum of each variable.1. The degree to which this slideshow is helpful. Not at all Helpful Very Helpful2. A person’s interest in scientific research. Not at all Interested Extremely Interested
  6. 6. Here is an example of one student, Phil.Phil finds this to be a great slideshow. Philalso loves science.1. The degree to which this slideshow is helpful. Phil Not at all Helpful Very Helpful2. A person’s interest in scientific research. Phil Not at all Interested Extremely Interested
  7. 7. Here is another example. This is where James ranks himself on both variables.1. The degree to which this slideshow is helpful. James Not at all Helpful Very Helpful2. A person’s interest in scientific research. James Not at all Interested Extremely Interested
  8. 8. We could ask a large group of students to mark where they fall on both variables.Perhaps we might start to see a pattern. People who like science keep ranking this slideshow as helpful. People who do not like science rank it lower.
  9. 9. It is very tempting to start fitting these findings into a story. Maybe people who like science are more curious and patient. Maybe they find slideshows (which are, admittedly, kind of dull) to be more interesting.
  10. 10. Maybe one’s attitudes toward science causes them to like or dislike this slideshow.
  11. 11. How do we research Cause and Effect relationships in Psychology?
  12. 12. Establishing Cause and Effect John Stuart Mill David Hume Immanuel KantPhilosophers have a lot to say about how we determine if one thing causes another. We will skip that debate and focus on three characteristics to help us establish cause and effect.
  13. 13. Establishing Cause and EffectConditions to establish Cause and Effect.1. The variables are correlated.2. The cause comes before the effect.3. There are no other variables to explain the effect.
  14. 14. Establishing Cause and EffectNote that the first step is to establish a correlation.Correlation is a fancy term for “related.” To understand how psychologists study causes and effects, we need to understand correlation.
  15. 15. Establishing Cause and Effect A BIt is very easy to think about how one thing may cause another. However, it is not always easy to see how these ideas imply a correlation. Let’s look at examples.
  16. 16. Correlation examplesDoes having a nice teacher cause students to learn more? Here are the two variables: Teacher’s Niceness Not at all Nice Very Nice Student Learning Very Little Learning Mastery of Content
  17. 17. Correlation examplesIf the variables are related, then we should see nicer teachers have classes that perform better. Pretend we observed a teacher that fits this pattern, Mr. Carter. Teacher’s Niceness Mr. Carter Not at all Nice Very Nice Student Learning Mr. Carter’s Class Very Little Learning Mastery of Content
  18. 18. Correlation examplesIf the variables are related, then we also should see teachers who are not nice have classes that perform poorly. Pretend we observed a teacher like this, Ms. Stark. Teacher’s Niceness Ms. Stark Not at all Nice Very Nice Student Learning Ms. Stark’s Class Very Little Learning Mastery of Content
  19. 19. Two Sides to a CorrelationThis is the hard part. Correlations have two sides, or ends. People usually only think about one. In our case, we think about good teachers having good students (the high end).
  20. 20. Two Sides to a CorrelationIf you believe a nice teacher causes a class to do better then you are also saying that not being nice goes with students doing worse. This is the low end of the correlation. For a correlation to exist, we need to have both Mr. Carter and Ms. Stark!
  21. 21. More Examples – Two Sides of CorrelationIf you believe that giving someone flowers will make them like you, then you also should observe that people to whom you do not give flowers would like you less.
  22. 22. More Examples – Two Sides of CorrelationIf you believe that spanking a child causes the child to behave better, then you are also saying that not spanking should co-occur with worse behavior.
  23. 23. Each of these is a proposed correlation. It can be difficult to think about these, but practicing this can help you think about what type of observations you would need in order to see if two variables are correlated.
  24. 24. Correlational MethodsMost correlational research methods involve collecting data on at least two variables. Surveys /There are many ways to collect these data. Questionnaires See your text for those details. Archival Research Naturalistic Observation
  25. 25. Correlational MethodsHowever, we usually cannot determine cause and effect just from simple correlational studies.
  26. 26. Establishing Cause and EffectThe problems are the second and third conditionsConditions to Establish Cause and Effect 1. The Variables are Correlated. 2. The Cause comes before the Effect. 3. There are no other variables to explain the effect.
  27. 27. Problem 2. The Cause comes before the EffectUsually, in correlational studies, we observe both variables at the same time. It is not always possible to know which comes first.
  28. 28. Problem 2. The Cause comes before the EffectFor the example with Mr. Carter and Ms. Stark, this is a problem. The idea that a nice teacher causes a class to learn more is only one possible direction of cause between these variables. As you see below, this explanation hypothesizes that the niceness comes first. Teacher’s Causes Students’ Niceness Learning
  29. 29. Problem 2. The Cause comes before the EffectThe opposite direction is also possible. Some teachers may respond to their class’s performance. It feels great to have a class do well, and it can feel very defeating if your class is struggling and performing poorly. Teacher’s Causes Students’ Niceness Learning
  30. 30. Problem 2. The Cause comes before the EffectFor every correlation you observe, be sure to consider both possible directions of cause. Variable A Causes Variable B OR Variable A Causes Variable B
  31. 31. But those aren’t the only possibilities…
  32. 32. Establishing Cause and EffectThe third condition also has to be met.Conditions to Establish Cause and Effect 1. The Variables are Correlated. 2. The Cause comes before the Effect. 3. There are no other variables to explain the effect.
  33. 33. Problem 3. Are there other variables to explain the effect?In correlational research, even if we observe a correlation and establish that one variable happens before the other one… …we still do not know if there is a cause and effect relationship.
  34. 34. Problem 3. Are there other variables to explain the effect?The problem is that correlational research observes variables as they occur in the real world. Although valuable, this leaves many questions.
  35. 35. Problem 3. Are there other variables to explain the effect?In the real world, there are countless other variables. Some may also be recorded in our study, but others may vary without us knowing.
  36. 36. Problem 3. Are there other variables to explain the effect?In the most simple form, this is called the third-variable problem. Does some other variable, other than our two observed variables, cause the other two to be related? Third Variable Variable A Variable B
  37. 37. Problem 3. Are there other variables to explain the effect?For our teaching example, pretend that we found a correlation between teacher’s niceness and student learning (step 1 in our search for causes). Teacher’s Student Niceness Learning
  38. 38. Problem 3. Are there other variables to explain the effect?Next, pretend that we establish that the teacher’s niceness comes first (step 2 in our search for causes).
  39. 39. Problem 3. Are there other variables to explain the effect?We still would not be able to say for certain that another variable did not cause the observed correlation. Third Variable ? Teacher’s Student Niceness Learning
  40. 40. Problem 3. Are there other variables to explain the effect?For example, maybe the resources available to the school affects both of the other variables. School Resources Teacher’s Student Niceness Learning
  41. 41. Problem 3. Are there other variables to explain the effect?Let’s look at another example. There is a correlation between the number of churches in a city and the amount of crime. Cities with more churches have more crime. Yes, that’s right, more churches is associated with more crime! Number of Number of Churches in Violent Crimes City in City
  42. 42. Don’t worry, this correlation is meaningless. It is explained by a third variable.
  43. 43. Problem 3. Are there other variables to explain the effect?There is a simple third variable: Population of the City. The more people in a city, the more churches they build. The more people in a city, the more chances there are for crime. Population Size of City Number of Number of Churches in Violent Crimes City in City
  44. 44. Review Correlational research is a valuable tool. There are many ways to collect correlational data.
  45. 45. Review Correlation is a first step in the search for causes. To establish cause, we need all three of the following conditions: 1. The Variables are Correlated. 2. The Cause comes before the Effect. 3. There are no other variables to explain the effect.
  46. 46. Review Simply observing a correlation does not tell us that one variable causes the other.  The direction of cause could go either way.  There may be a third variable causing the observed variables to look correlated.
  47. 47. Establishing Cause and Effect Through Experiments
  48. 48. The Experimental MethodThe experimental method is a researcher’s strongest tool for establishing cause and effect relationships. A well-structured experiment meets all three criteria for establishing cause and effect.
  49. 49. The Experimental MethodConditions to Establish Cause and Effect1. The Variables are Correlated.2. The Cause comes before the Effect.3. There are no other variables to explain the effect.
  50. 50. The Experimental Method1. The experimenter looks for a relationship between one variable that is a cause and another variable that shows the effect.2. The experimenter manipulates the causal variable first and measures the effect variable later.3. By using manipulation and controls, the experimenter can rule out alternate explanations.
  51. 51. The Experimental MethodThe two variables have special names.Independent variable – the variable manipulated by the researcher to see if it is a cause.Dependent variable – the variable measured to see if there is an effect.
  52. 52. The Experimental Method Independent VariablesTypically, independent variables describe what is different between two groups: an experimental group and control group.
  53. 53. The Experimental Method Independent VariablesPerhaps the hardest part of conducting an experiment is making sure that the independent variable, and ONLY the independent variable, differs between the groups.
  54. 54. The Experimental Method Independent Variables, ExampleWe could use an experiment to study the effect of teacher niceness on student learning. We would need to create two groups of students:
  55. 55. The Experimental Method Independent Variables, Example Experimental Group – Students assigned a teacher who has instructions in specific ways to be nice in class. Control Group – Students assigned a teacher without instructions to be nice.
  56. 56. The Experimental Method Independent Variables, ExampleThe hard part is making sure that the only thing that differs systematically between these two groups is the niceness of the teacher.
  57. 57. The Experimental Method Ways to Eliminate Extraneous VariablesAn extraneous variable is a variable other than the independent variable that might be affecting the dependent variable.
  58. 58. The Experimental Method Ways to Eliminate Extraneous VariablesThere are two main ways to eliminate Extraneous Variables:1. Experimental Control – designing the study carefully to remove extraneous variables.2. Randomization – If an extraneous variable cannot be removed, it can be randomly distributed across experimental groups. That way it does not vary systematically with the independent variable.
  59. 59. SummaryGive yourself ample time to master these ideas and the terminology. You should be able to define all of the following terms, and describe how they relate to each other.Experiment Extraneous VariableIndependent Variable Experimental ControlDependent Variable RandomizationExperimental GroupControl Group
  60. 60. Limits of the Experimental MethodNot every variable can be manipulated. Remember the first example of two correlated variables: The Degree to which this Slideshow is Helpful. Not at all Helpful Very Helpful A Person’s Interest in Scientific Research Not at all Interested Extremely Interested
  61. 61. Limits of the Experimental MethodWe hypothesized that a person’s interest in science will affect how useful they think this slideshow is. Interest in Causes Perception of Scientific this Slideshow Research
  62. 62. Limits of the Experimental MethodHow would you manipulate people’s “interest in science” for an experiment, making some people very interested and others disinterested? ? ? Interest in Scientific Research
  63. 63. Limits of the Experimental MethodEven if we could come up with a creative way to manipulate “interest in science,” would it be the same thing as the interest people develop over a lifetime?
  64. 64. Limits of the Experimental MethodOther variables cannot be manipulated without causing harm or other problems.
  65. 65. Limits of the Experimental Method SummarySome variables are impractical to manipulate.Experiments can be artificial.Some experiments cannot be conducted ethically.
  66. 66. Review Practice turning explanations or stories into hypotheses about the relationship between two variables. When variables are correlated, think about both ends, or poles of the relationship: The high end, and the low end.
  67. 67. ReviewConditions to establish Cause and Effect.1. The variables are correlated.2. The cause comes before the effect.3. There are no other variables to explain the effect.
  68. 68. Review Correlational Research Methods can identify relations between variables that you measure. Correlational Research cannot offer strong evidence of cause and effect!
  69. 69. Review Correlations have several possible causal explanations 1. The direction of cause could go either way. 2. A third variable could cause both variables.
  70. 70. Review The Experimental Method allows us to establish cause and effect relationships by manipulating an independent variable in a controlled setting, then looking for its effect on a dependent variable.
  71. 71. These are the foundational ideas to help you think about research more critically.There are many more details in your book, which can help to improve your ability to evaluate evidence about causes and effects.
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