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	Facial EMG	Within-Subjects Factorial Design
Ämnesområde	Socialpsykologi	Socialpsykologi
Familj	Process / pipeline	Process / pipeline
Ursprungsår	1986	2004
Upphovsperson	John Cacioppo, Richard Petty and colleagues	Experimental-design tradition (widely used in social psychology)
Typ	Psychophysiological affect-measurement method	Experimental design framework
Ursprungskälla	Cacioppo, J. T., Petty, R. E., Losch, M. E., & Kim, H. S. (1986). Electromyographic activity over facial muscle regions can differentiate the valence and intensity of affective reactions. Journal of Personality and Social Psychology, 50(2), 260-268.	Kahneman, D., Krueger, A. B., Schkade, D. A., Schwarz, N., & Stone, A. A. (2004). A survey method for characterizing daily life experience: The Day Reconstruction Method. Science, 306(5702), 1776-1780.
Alias	Facial Electromyography, EMG Affect Measurement, Corrugator-Zygomaticus EMG	Repeated-Measures Factorial Design, Within-Participants Factorial, Crossed Within-Subjects Design
Närliggande	3	2
Sammanfattning	Facial electromyography (EMG) measures affect by recording the tiny electrical signals produced by facial muscles, providing an objective, continuous index of emotional valence and intensity that can detect reactions too subtle or fleeting to produce a visible expression. Cacioppo, Petty, Losch, and Kim showed in 1986 that activity over two muscle regions differentiates affect: the corrugator supercilii (the brow muscle that furrows in frowning) increases with negative affect, while the zygomaticus major (the cheek muscle that pulls in smiling) increases with positive affect, and amplitudes scale with the intensity of the reaction. Because surface electrodes capture muscle activity even when no overt expression occurs, facial EMG offers a sensitive, hard-to-fake measure of evaluative responses widely used in research on attitudes, emotion, persuasion, and social perception, often paired with reaction-time and self-report measures.	The within-subjects factorial design is an experimental framework in which each participant is exposed to every combination of two or more manipulated factors, allowing researchers to test the main effect of each factor and their interactions while using each person as their own control. Because the same individuals experience all conditions, between-subject differences are removed from the error term, giving within-subjects factorial designs substantially greater statistical power and efficiency than between-subjects designs for the same number of participants. This makes them a workhorse of experimental social psychology, especially for reaction-time, judgment, and affect studies where many trials per person are feasible. The design's power comes with the need to control order and carryover effects through counterbalancing, and to analyze the data with repeated-measures or mixed-effects models that respect the non-independence of observations from the same person.