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7 Multifactorial Design.doc

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David Nussbaum

Chapter 7: Multifactorial Design -How can emotions be manipulated in the laboratory?And would these laboratory manipulations provide a realistic depiction of true emotional experience? -study design that is ideally suited to disentangle both direct and interactive influences on measured responses: -complex experimental design: used when a researcher seeks to manipulate 2 or more IV at the same time --> referred to as factorial designs --> more realistic, b/c if allows researcher to examine how IVs interact with each other --> more efficient since it isnt limited to one at a time variable manipulation -factor is another name for IV -multifactorial is term used for exp that vary two or more IV and will provide direct test of the main effects of each IV as well as interaction b/w and among IVs -can vary IVs between subjects, others can vary them within subjects and some can combine Multifactorial Designs -compared to single factor experiment where there is only one IV and you can just keep adding conditions/levels -a new IV is devised and incorporated into research design -impt to understand difference b/w adding a level to an existing IV as done in single factor vs. Devising an entirely new and dindinct IV altogether as done in multifactorial -How do you add a 2 IV? -ie. Two IVs: mood induction and cognitive exercises –qualitatively different from each other -two distinct IV, one mood, and other cognition that are each manipulated within the same multifactorial experiment, each with two levels -idea: how emotion (mood induction) might influence thinking and whether particular mood state might be better for performing a particular cognitive exercise -similar to single factor, each IV can be studied either b/w subjects or within subjects -Between subjects multifactorial research design: = Need four groups of participants, each randomly assigned to one of the 4 exp conditions (1) happy mood/verbal (2) happy mood/visual (3) sad/verbal (4) sad/visual -Within-subjects multifactorial experiment: =all participants would be run through each of the four experimental conditions =so you would not need 4 different groups you would just need 1 =same participants would receive the happy mood induction followed by verbal task and then the visual task =it would be necessary to counterbalance the order of tasks between moods and in between participants Advantages to multifactorial design: -more complex, provides more realistic model of rich psychological phenomena -offers an economical and efficient design to evaluate and to test separate and joint influences of one or more IVs on a DV -ie. Mood induction differed depending upon the level of the second IV -had we studied the IVs separately using single factor, the interaction of mood and cognition would not have been discovered Notations and Terms -simplest multifactorial design= 2 IVs, each with 2 levels/values “2 x 2” -identified by numbering notation -”3x 4” has two IVs, one with 3 levels and another with 4 levels - number of numbers tells how many factors of the IV there are -number values tell how many levels of IV -order of numbers makes no differences = 3 x 4 can be 4 x 3 -every level of each IV is combined= 3 levels of IV combined with 4 levels of IV2 = 12 levels/treatments -number of treatment groups calculated by multiplying number notation Theory and Experimentation -theory guides how an experiment is designed, how IVs are developed and manipulated, how Dvs are measured and what hypotheses are tested. -complex multifactorial: role of theory may be more prominent than for single factor AComplex Within-Subjects Experiment --Adams and Kleck 2003 -theorized that eye-gaze detection and facial expressions represent two distinct isolable features which may be impt in conveying social information -understood in terms of approach-avoidance motivation – confrontation or fight -theory proposed that facial expressions of emotions and gaze direction operate as a social signaling system that governs our basic evolved behavioural tendencies for approach or avoidance -direct gaze and angry face ==angry at observer Decoding Facial Expressions of Emotion -Adams and Kleck conceptualized perceptions of facial displays of affect as represented by dynamic interplay of countenance expression and eye gaze Devising IVs -investigated 2 aspects of face: (a) facial muscle contractions that form diff emotional expressions (2)gaze direction such as direct or averted eyes -Two-prong hypothesis: (a) Anger faces with direct gaze would be more readily perceived than anger faces with averted gaze (b) Fear faces with averted gaze would be more readily perceived than fear faces with direct gaze 1. Created experimental stimuli, constructed facial stimuli that varied in expression and gaze direction =Four types of faces: angry/direct, angry/averted, fear/direct, fear/averted 2. Organize four types of faces into an experimental task for participants to perform =participants shown photo and then asked to make speedy judgement by clicking anger or fear and asked to label as quickly as possible 3. Last step was to use either a within-subject or between subject design = chose within-subject design --> all participants received all 4 types of faces = allowed for comparison of participants' response times in emotional judgement -individual differences that could figure very prominently in processing emotions are automatically controlled = people may vary in response to diff faces -Advantage: each particiapnt serves as his/her own control = differences are held constant -more economical than between-subjects: fewer participants needed to perform the task BUT, fewer participants require you to collect more observations/data PER participants -reliability of a test can be increased by simply adding more items -Adams and Kleck had 32 participants but experimental task had 240 slides of faces -large number of items/slides provided sufficient number of observations to reliably measure emotional perception The 2 x 2 Design -experiment manipulated 2 var: emotional expression and gaze direction -each IV had two levels (a) emotional expression: anger and fear (b) gaze direction: direct and averted -design provided four combinations of conditions -dependent measure was response time in milliseconds for judging faces as expressions of either anger/fear -column means: average the numbers in the two left cells and find average response time as well as average numbers in two right cells and find avg response -calculated by averaging columns of table -shows us that faces with direct gaze were responded to as quickly as faces with averted gaze -row means: calculated by averaging the rows of the table -looking at row means show us that anger faces were responded to more quickly than were fear faces Main Effects -What effect does gaze direction have on mean responses times? -What effect does type of emotional expression on the face have on mean response times? -Main effect of IV: the effects of each IV on a DV -can be calculated for EACH IV = done by column means and row means -ie. Column means were nearly identical, hence gaze direction of faces did not significantly influence the DV of response time Interactions -Before interpreting main effect of emotional expression, must first look to
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