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Lecture 5 Notes

by: Rachel Onefater

Lecture 5 Notes 76884

Rachel Onefater
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About this Document

These notes cover the lecture from January 26th!
Dr. George Howe
Class Notes




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This 7 page Class Notes was uploaded by Rachel Onefater on Tuesday January 26, 2016. The Class Notes belongs to 76884 at George Washington University taught by Dr. George Howe in Spring 2016. Since its upload, it has received 65 views. For similar materials see PSYC4201W in Psychlogy at George Washington University.


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Date Created: 01/26/16
Causal Reasoning  We can infer that A influences B:   • When changes in A are ​followed by changes in B,   • given that absence of or differences in the pattern of change in A would have been followed by  absence of change in B,   • all other plausible causes being equal.   → In the chapter, Howe talks about “all other things being equal” is quite IMPOSSIBLE.  Ex​: giving you a medication to see how your heart responds and at exactly the same time, he  does not give you medication to see how your heart responds→ Does not happen in reality  → We can infer that something causes or influences something else.      What do we mean by “being equal”?   • Operating in the same way in both the factual and the counterfactual condition   • In experiments:   – There can be other things influencing B, but theycan’t diffe for the experimental and control  groups 4     Example: Williams et al   • Researcher assigned people to one of two conditions   – Verbal worry → Worry, but use words  – Imagery worry → Worry, but have images and pictures in your head  • Then measured attention bias towards threat words (dot probe task)   • Could other factors (personality, recent experiences) influence responses in dot probe task?   Answer​ : personality, recent experiences, and when they come into the study, it will influence  whether or not they were attentive to something.   → ​Ex​: saw car accident, ended a relationship, comes from an abusive household ro a volatile  household, someone has some sort of mental condition i.e. Asperger's Syndrome, inherent  sensitivity to stimuli     Selection?   • What if people had been allowed to choose​ their condition (verbal or imagery)?  → Would suggest that there are things we experience/something about who we are that could  influence that choice!   • What factors (personality, recent experiences) might influence their choice?   Answer​ : For young kids, boys tend to develop more slowly verbally than girls do, vision  problems might make imagery harder for that individual.         Selection effects   • Could any of the factors we just came up with also influence sensitivity to threat?   Answer​ : Sensitivity to contact, some people may be more sensitive to threat cues, verbal threat  cues may be more pushed away from the verbal condition, so you get more people from the  imagery from the imagery condition, and they become more sensitive to threat cues.   → Personality style pushes someone to select a certain style(imagery/verbal), and then affects  how they respond to threat cues.      Selection effects   • If yes, our groups are not meet the “all other plausible causes being equal” requirement   → People in them(groups), share the same set of causes!    A visual tool   • Directed graphs   • Labels are causes or effects   • Arrows indicate direction of cause   Mode of worry → Sensitivity to threat     Various possibilities   – (Possibility 1) The way I think it goes   Mode of worry → Sensitivity to threat      – (Possibility 2) The way I think it goes, but with selection factors influencing both     *NOTE:  Selection factor(influences both of the factors below)  Mode of worry→  Sensitivity to threat     – (Possibility 3) I’m wrong, and only selection factors are causal   Selection factor → Mode of worry   Selection factor → Sensitivity to threat      If groups differ on selection factors, which of these possibilities are ​ consistent with​ :   • Findings that those in the verbal condition show faster threat sensitivity than those in the  imagery condition?      Confounding   • Confounding occurs when some third factor:   – Is associated with my supposed cause   – Influences the supposed effect   • When confounding occurs, any observed association between supposed cause and effect could  be ​purious​(def.) wrong  → Faster in the verbal condition, and slower in the imagery condition, and by allowing people to  select in, experimenter has created  a confounding study. Any association between the two  variables could be incorrect, but there could be no way of knowing if you are wrong/right!     What if a person gets both conditions?   • Personality, recent conditions are all the same, and they can’t be confounds   – “A person acting as their own control”   • BUT: The problem of ​ spillover   – If I first use verbal worry, could it change the effects of later imagery worry?   *NOTE: When you are in the second condition, your history is no longer the same because you  were in the first condition first! (iwithin­subject study​).  • Example: Trials comparing two medications   – If someone gets both meds, need ​ washout​  period to be sure first med is out of the  system, and then have them come back after a time when you know it has washed out of  the system  → need to have prior theory, understanding, and studies, and may mean no longer  detectable levels in the blood stream, or other ways).   → Anesthetics have an effect up to a few months later, so this can be a complicated  method!    Can one person be the control for another?   • Juan does verbal worry(happy person), Jenny does imagery worry(angry person)   • Personality, recent conditions are very likely to be different  Answer​ : No! Not useful at all     Can one group be the control for another?   • Personality, recent conditions are more likely to be equivalent on average   → When you get larger groups, the average attitude, shifts toward the middle, and average  attitudes are going to be similar under certain conditions!     Experimental counterfactual: Average causal effect (picture on slide)  Intervention to Learn Stress management techniques:  Sleep quality (No treatment vs. Treatment)  Counterfactual assumption: Group averages equivalent on all other plausible causes   → Sensitivity to context, but you look at the measure of sensitivity context in group, they should  have pretty much equivalent average, group difference cannot account for the treatment effects  as long as you have an equivalence!    What research conditions support this assumption?   • Various research methods available for getting closer to equivalence on confounds   • Depends on type of confounding     Types of confounding   • Selection effects   – Some third factor influences selection into our supposed causal conditions, and also  influences our outcome   → Have been a very important for trials of intervention/programs (Example: very first study of  Head Start​  to see if it had an impact on kids development of educational skill).  • Chance effects   – People in our causal conditions differ by chance on some factor that influences the  outcome   • Induced confounding   – We think our conditions vary only on the feature of interest, but they also vary on some  other feature that influences the outcome.   → You create the confounding as you go along, and Prof ill ask us how to design our studies not  to do that!     How to eliminate selection effects?   • Use a selection method that can’t be biased (by either your participants or you)   → MAKE it completely chance!  – Random assignment​  (each person has equal probability of being in one group or the  other)   – When random assignment is used, groups will be ​ closer to equivalent​ even on  unknown or unobserved factors     Can groups differ on confounds by chance?   • Yes, even when using random assignment   – More likely with smaller samples   – Ways to improve on simple randomization   • Therefore, good to measure potential confounds and test whether groups are equivalent or not  – Can adjust statistically if differences are found     What if you can’t use random assignment?   • We often aren’t able to randomly assign people to causal conditions  1. Ex​ : Teen pregnancy on the development of a child at age 4→ cannot assign people to be  pregnant or not!  2. Ex​: EMT member are sent to a brutal tragic accident, and you can see if this affects later  PTSD  3. Ex​: Test people who smoke on Cancer development  4. Ex​: GENDER is a big one too! ​ If gender is a viable, alternate plausible reason for people  to respond to your measurement.   • Here, identifying, measuring, and testing potential confounds becomes the main method   • But, how do we know what factors to look at?      Plausibility   • Don Campbell​  : major methodologist in social scientist suggested that while there are many  possible confounds, what we are really interested in, is in those that are plausible  • Focus on plausible alternative causes of B that could also vary by A (i.e. confounds)     What is Plausible?   • How do we determine what is plausible?   – Common sense   – Prior research   – Theory   • Example: trait anxiety has been found to be associated with attention bias to threat   – So groups in Williams study need to be equivalent on average levels of trait anxiety, so  this was based on both theory and on prior research   • What is plausible can change as science in a specific area progressescan never prove anything  with 100% certainty!     Induced confounds   • In experiments, we create both factual(experimental) and counterfactual (control)  conditions­design materials that you expose people to.   •Within­subject​ example: using dot probe task to test whether threat words lead to faster  response than non­threat words   – Suppose we show someone 24 threat words and 24 non­threat words   – They respond with either the left or right hand, depending on the cue (one star or two)  → It is likely that a person is faster with one finger than the other finger(more often than not, this  is true).  – Words appear at the top and bottom of the screen    What if the threat words always appeared at the top?   What if the two star cue (right hand) was always associated with the threat word?   → You have now created a condition where location of the cue is mixed up with whether it is  threatening or not!     Induced confounding   • Creating conditions that differ on factors other than the ones we are interested in   → Words can differ in threat meaning, length, and how difficult they are   Ex: Hate and Supercalifragilisticexpialidocious, should not be compared to one another  • When those factors have some impact on the outcome of interest     How to reduce or eliminate induced confounding?   • Creating conditions that differ on factors other than the ones we are interested in   • When those factors have some impact on the outcome of interest      How to reduce or eliminate induced confounding?   • Design experimental and control conditions so they differ on your construct of interest, but not  on other factors that could ​plausibly​ influence the outcome   • Lab 2: you will be design both experimental and control conditions for a study:   – How your conditions vary   – How your conditions need to be similar      Example   • Experimental trial of yoga for stress reduction   – You believe the active ingredient is explicit training on how to gain mindful awareness of  muscle movement, position, and sensation   – Design a control group that is similar in terms of:   • Number and length of sessions   • Sequence of yoga poses in each session   • Level of stretching and strenuousness   – But differs in having no explicit mindfulness training​ , want to rule out as potential alternate  effects that you do not want to induce.   • Notice that this tests the influence of the mindfulness training, not yoga in general     How do we keep plausible causes equal?   • Experimental studies:   – Random assignment at various levels   – Constrain the stimuli or contexts we manipulate   → Cortisol a  stress hormone, but your body produces it all the time, and produces on a daily  fluctuation and as you wake up, system up, your cortisol pops up pretty fast! Depends on the  time of day you do something­level of cortisol changes at different points during the day for  different people.    • Any study:   – Observe plausible alternative causes of B   – Determine whether they differ for A   – Adjust statistically if they do 


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