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Patterns of Actor and Partner Effects
David A. Kenny
February 17, 2013
You need to know the Actor Partner Interdependence
Model!
2
APIM
APIM Patterns: Couple Model
• Model– Equal actor and partner effects: a = p– e.g., my depressive symptoms has the
same effect on my quality of life as does my partner’s depressive symptoms on my quality of life
• Average or sum as the predictor– Although measured individually, the predictor
variable is a “dyadic” variable, not an individual one
3
APIM Patterns: Contrast
• Model – Actor plus partner effects equals zero: a – p =
0– Klumb et al. (2006): time spent doing
household labor on stress levels • The more household labor I do, the more stressed
I feel.• The more household labor my partner does, the
less stress I feel.
• Difference score (actor X minus partner X) as the predictor
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APIM Patterns: Actor or Partner Only
• Actor Only – Actor present but no partner effect– Fix the partner effect to zero.
• Partner Only – Partner present but no partner effect– Fix the actor effect to zero.– Relatively rare.
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Testing Patterns
• Multilevel Modeling– Sum and difference approach
• Structural Equation Modeling– Setting coefficients equal– Use of phantom variables
• General approach to patterns: k
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Sum and DifferenceApproach
• Remove the actor and partner variables from the model.
• Add to the model the Sum and the Difference score as predictors.
• If Sum is present, but not the Difference, you have a couple model.
• If Sum is not present, but the Difference is, you have a contrast model.
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Acitelli Example• Distinguishable
– Husbands• Sum: 0.392, p < .001• Difference: 0.131, p = .088
– Wives• Sum: 0.373, p < .001• Difference: 0.001, p = .986
• Indistinguishable– Sum: 0.344, p < .001– Difference: 0.056, p = .052
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Testing the Couple Model Using SEM
• Actor effect equal to the partner effect.• Can be done by setting paths equal.• Distinguishable dyads
a1 = p12 and a2 = p21
• Indistinguishable dyadsa = p
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Acitelli Example• Distinguishable
–Husbands: 0.346–Wives: 0.347–Test: c2(2) = 4.491, p = .106
• Indistinguishable–Effect: 0.344–Test: c2(1) = 3.803, p = .051
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Testing the Contrast Model Using SEM
• Actor effect equal to the partner effect times minus 1.
• Can be done by using a phantom variable.• Phantom variable
– No conceptual meaning– Forces a constraint– Latent variable– No disturbance
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X1
X2
Y1
Y2
E1
E2
1
1
a1
a2
P1
a1
-1
P2
a2
-1
Contrast Constraint Forced by Phantom Variables (P1 and P2)
• Now the indirect effect from X2 to Y1, p12 equals (-1)a1 12
Acitelli Example
c2(2) = 69.791, p < .00113
ConclusionUsing patterns can link the APIM to theory and simplify the model.
The k parameter is a general way to measure and test patterns
Readings
pp. 147-149, in Dyadic Data Analysis by Kenny, Kashy, and Cook
Kenny & Cook, (1999), Personal Relationships, 6, pp. 433-448.
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