Table 2.

Overview of studies referenced.

Moderationa	Study	Measurementb	Time per stimulusc	Measurement periodd	Stimulie	Expressionsf	Sourceg	Sitesh	Nh
Social inter-action; gender	Hess and Bourgeois, 2010 (Study 1)	EMG	30–625 s (M = 183 s)	15 s time bins	Live interaction	ha, an	n/a	Zyg, Corr, Orb, Lev	96 same sex dyads (48 f)
Social inter-action; gender	Hess and Bourgeois, 2010 (Study 2)	EMG	30–856 s (M = 185 s)	15 s time bins	Live interaction	ha, an	n/a	Zyg, Corr, Orb, (Lev)	72 mixed sex dyads
Social inter-action; gender	Hinsz and Tomhave, 1991	Direct coding	n/a	Relative frequencies	Live interaction	ha, an, ne	Own	KJ79	1095 (483 m, 612 f)
Social interaction	Heerey and Crossley, 2013 (Study 1)	FACES	300 s	300 s	Live interaction	Genuine and polite smiles	n/a	KS07	48 same sex dyads (24 f)
Social interaction	Heerey and Crossley, 2013 (Study 2)	EMG	4 s	2 s/2 s	Static	Genuine and polite smiles	Own	Zyg, Corr, Orb	35 (85% f, 15% m)
Cognitive load	Cannon et al. (2009)	EMG	1 s	300–1000 ms	Static	ha, an	MBFSS	Zyg, Corr	46 f
Cognitive load	Hess et al., 1998 (Study 1)	EMG	10 s	10 s	Static	ha, an, dis	JACFEE	Zyg, Corr	48 f
Cognitive load	Hess et al., 1998 (Study 2a+2b)	EMG	10 s	10 s	Static	ha, an, dis	JACFEE	Zyg, Corr, Orb, (Lev)	90 f
Empathy	Sonnby-Borgström, 2002	EMG	17 ms–6 s	Not specified	Static	ha, an	EF1	Zyg, Corr	43 (21 m, 22 f)
Empathy	Sonnby-Borgström et al., 2003	EMG	17, 56, 2350 ms	2.5 s	Static	ha, an	EF1	Zyg, Corr	61 (33 m, 28 f)
Empathy	Dimberg et al., 2011	EMG	5 s	5 s	Static	ha, an	EF2	Zyg, Corr	144 (72 m, 72 f)
Empathy; current state	Hermans et al., 2006	EMG	6 s	6 s; 500 ms time bins	Morph	ha, an, ne	EF2/KDEF	Zyg, Corr	20 f
Attachment style	Sonnby-Borgström and Jönsson, 2004	EMG	17–2350 ms	2.5 s	Static	ha, an	EF1	Zyg, Corr	62 (33 m, 28 f)
Social anxiety	Dimberg and Christmanson, 1991	EMG	8 s	8 s	Static	ha, an, ne	EF2	Zyg, Corr	30 (gender unspecified)
Social anxiety	Dimberg, 1997	EMG	8 s	8 s	Static	ha, an	EF2	Zyg, Corr	16 f
Social anxiety	Dimberg and Thunberg, 2007	EMG	1 s	1 s; 500 ms time bins	Static	ha, an	EF2	Zyg, Corr	56 f
Social anxiety; gender	Vrana and Gross, 2004	EMG	8 s	8 s	Static	ha, an, ne	EF2	Zyg, Corr	19
Gender	Dimberg and Lundquist, 1990	EMG	8 s	8 s	Static	ha, an	EF2	Zyg, Corr	48 (24 m, 24 f)
Gender; eye gaze	Soussignan et al., 2013	EMG	2 s	2 s; 100 ms time bins	Morph	ha, an, fe, sad, ne	Poser	Zyg, Corr, Front, Dep	31 (17 f, 14 m)
Age	Bailey et al., 2009	EMG	5 s	200–500 ms; 500–800 ms	Static	ha, an, ne	EF2	Corr	35 younger, 35 older
Age	Bailey and Henry, 2009	EMG	14/42 ms (young/older adults)	200–800 ms	Static	ha, an, ne	EF1	Zyg, Corr	46 younger, 40 older
Age	Hühnel et al., 2014	EMG	20 s	20 s; 1 s time bins	Video	ha, an, sad, dis	Own	Zyg, Corr, Orb, Lev	39 older f, 39 younger f
Age; ingroup vs. outgroup	Ardizzi et al., 2014	EMG	4+1 s	5 s; 500 ms time bins	Dynamic + static	ha, an, fe, sad, ne	Own	Zyg, Corr	20 teenagers; 20 adults
Current mood state	Moody et al., 2007 (Study 1)	EMG	1 s	1 s in 100 ms epochs	Static	an, fe, ne	EF2	Corr, Front	48 (6 m, 42 f)
Current mood state	Moody et al., 2007 (Study 2)	EMG	1 s	500–1000 ms	Static	an, fe, ne	EF2	Corr, Front	39 (12 m, 27 f)
Current mood state	Likowski et al., 2011b	EMG	6 s	6 s	Static	ha, an, sad, ne	Poser	Zyg, Corr, Front	60 f
Eye gaze	Rychlowska et al., 2012, Study 3	EMG	8 s	500–1500 ms	Static	ha, ne	Own	Zyg	27 f
Current state	Harrison et al., 2010	EMG	≥1 s	500–1000 ms	Static	ha, sad, an	KDEF	Zyg, Corr	40 (26 m, 14 f)
Eye gaze; gender	Schrammel et al., 2009	EMG	3 s morph, 5.5 s total	500–1000 ms after apex	Morph	ha, an, ne	Poser	Zyg, Corr	44 (22 m, 22 f)
Dynamic expressions	Rymarczyk et al., 2011	EMG	1.5 s	1,5 s; 500 ms time bins	Static/morph	ha, an	MSFDE	Zyg, Corr	27 (12 m, 15 f)
Dynamic expressions	Sato and Yoshikawa, 2007	FACS	1520 ms	2.5 s	Static/morph	ha, an	Own	AU4, 12	18 (9 m, 9 f)
Dynamic expressions	Sato et al., 2008	EMG	1520 ms	2.5 s	Static/morph	ha, an	Own	Zyg, Corr	29 (11 m, 18 f)
Dynamic expressions	Weyers et al., 2006	EMG	1 s	1.5 s; 500 ms time bins	Static/morph	ha, an, ne	Poser	Zyg, Corr	48 f
Familiarity	Fischer et al., 2012	FACS	n/a	n/a	Live setting	dis, pride	n/a	AU 4, 9, 10, 12, 43	112 f (56 dyads)
Familiarity	Häfner and Ijzerman, 2011 (Study 1)	EMG	2 s	2 s; 1 s time bins	Static (averaged)	ha, an	KDEF; Own	Zyg, Corr	23 dyads
Attitudes	Likowski et al., 2008	EMG	6 s	6 s	Static	ha, sad, ne	Poser	Zyg, Corr	25 f
Attitudes; empathy	Sims et al., 2012	EMG	4 s (apex at 2–3 s)	2000–4000 ms	Video	ha, an	TIGTE	Zyg, Corr	33 (7 m, 26 f)
Attitudes; empathy	Aguado et al., 2013	EMG	1 s	1 s; 100 ms time bins	Static	ha, an, ne	KDEF	Zyg, Corr	57 (9 m, 48 f)
Cooperation/competition empathy	Likowski et al., 2011a	EMG	6 s	6 s	Static	ha, an, sad, ne	Poser	Zyg, Corr, Orb	77 f
Cooperation/competition	Seibt et al., 2013	EMG	6 s	6 s	Static	ha, an, sad, ne	Poser	Zyg, Corr, Orb	84 f
Cooperation/competition	Weyers et al., 2009	EMG	8 s	8 s; 1 s time bins	Static	ha, sad, ne	Poser	Zyg, Corr	49 f
Fairness	Hofman et al., 2012	EMG	2/4 s	Bl 1+3: 4 s; Bl 2: 2 s	Morph + static	ha, an	EF2	Zyg, Corr	30 f
Power relationships	Carr et al., 2014	EMG	5 s	5 s; 500 ms time bins	Video	ha, an	MMI	Zyg, Corr	55 (82% f)
Ingroup vs. outgroup	McHugo et al., 1991	EMG	32–40 s	First 30 s	Video	ha, an, ne	Own	Zyg, Corr, Orb	100 (46 m, 54 f)
Ingroup vs. outgroup	McHugo et al., 1985	EMG	37–74 s	First (after 5 s) and last 15 s	Video	ha, an, fe, ne	Own	Zyg, Corr	40 (31 m, 9 f)
Ingroup vs. outgroup	Bourgeois and Hess, 2008 (Study 1)	EMG	M = 13.2 s	M = 13.2 s	Video	ha, an	Own	Zyg, Corr, Orb	54 (19 m, 25 f, 10?)
Ingroup vs. outgroup	Bourgeois and Hess, 2008 (Study 2)	EMG	Not specified	Not specified	Static	ha, an, sad	MSFDE	Zyg, Corr, Orb, Lev	60 m
Ingroup vs. outgroup	Mondillon et al., 2007 (Study 1)	RPA	400–1600 ms	n/a	Static	an, ne	MSFDE	n/a	47 f
Ingroup vs. outgroup	Mondillon et al., 2007 (Study 2)	RPA	400–1600 ms	n/a	Static	an, ne	MSFDE	n/a	41 f
Ingroup vs. outgroup	van der Schalk et al., 2011 (Study 1)	EMG	5 s	5 s	Static	ha, an, fe	Not specified	Corr, Orb	42 f
Ingroup vs. outgroup	van der Schalk et al., 2011 (Study 2)	FACS	~5 s (apex at 1 s)	~ 5 s	Video	ha, an, fe	Not specified	AU 4, 5, 6, 10, 12	153, (gender unspecified)
Social exclusion	(Kawamoto et al., 2014)	EMG, ERP	1 s	1 s	Static	ha, dis, ne	ATR	Zyg, Corr	42 (22 m, 20 f)

^aThe first keyword refers to the section where the study is mainly discussed, the second keyword to another mention within the review.

^bEMG, Electromyogram; FACES, Facial Expression Coding System (Kring and Sloan, 2007); FACS, Facial Action Coding System (Ekman and Friesen, 1978a); RPA, response prediction accuracy; ERP, event related potential.

^cper expression (where suitable time at apex of expression).

^dtotal period of facial response measurement, if applicable, length of individual measurement bins. Ranges refer to time after stimulus onset (e.g., 300–1000 ms means measurement started 300 ms after stimulus onset and went on for 700 ms).

^emorph: dynamic transition, usually from neutral to emotional expression, with first and last frame taken from photos or generated by the researcher, and transitional frames generated by the software.

^fha, happy; an, angry; ne, neutral; fe, fearful; dis, disgusted.

^gName of the stimulus set or software to generate the stimuli. Own, stimulus material created by the authors; MBFSS, MacBrain Face Stimulus Set (http://www.macbrain.org/resources.htm); JACFEE, Japanese and Caucasian Facial Expressions of Emotion (Matsumoto and Ekman, 1988); EF1, Unmasking the Face (Ekman and Friesen, 1978b); EF2, Pictures of Facial Affect (Ekman and Friesen, 1976); KDEF, Karolinska Directed Emotional Faces (Lundqvist et al., 1998); Poser, computer generated faces (Poser software, Curious Labs, Santa Cruz, CA); MSFDE, Montreal Set of Facial Displays of Emotion (Beaupré and Hess, 2005); TIGTE, Mindreading: The Interactive Guide to Emotions (Baron-Cohen et al., 2004); MMI, Facial Expression Database (Pantic et al., 2005); ATR, Facial Expression Database (DB99, ATR Promotions, Kyoto, Japan).

^hSites for EMG electrodes; Action units for FACS coding: Zyg, Zygomaticus major; Corr, Corrugator; Orb, Orbicularis Oculi; Dep, Depressor anguli oris, Lev, Levator labii; Front, Frontalis; KS07, Coding according to Kring and Sloan (2007); KJ79, response scoring according to Kraut and Johnston (1979).