The monkey in the mirror: Hardly a stranger

de Waal et al. 10.1073/pnas.0503935102.

Supporting Information

Files in this Data Supplement:

Supporting Table 3
Supporting Table 4
Supporting Figure 6
Supporting Table 5
Supporting Figure 7
Supporting Table 6

Supporting Figure 6

Fig. 6. Mean (+ SEM) frequency of behavior per female subject combined for both tests per condition: familiar partner, mirror, and stranger. The graph shows only the behaviors for which significant differences between the conditions were found. For more details see Table 5.

Supporting Figure 7

Fig. 7. Mean (+ SEM) frequency of behavior per male subject combined for both tests per condition: familiar partner, mirror, and stranger. The graph shows only the behaviors for which significant differences between the conditions were found. For more details see Table 6.

Table 3. Eight female subjects and their female partners and 6 male subjects and their male partners

Subject name	Sex	Age in years (estimate)	Rank in own group	Familiar partner	Stranger	Accompanied by infant
Bias	F	16	medium	Star	Lulu	no
Goya	F	11	low	Sammie	Wilma	no
Lily	F	6	medium	Wilma	Sammie	yes
Lulu	F	19	medium	Nancy	Bias	yes
Nancy	F	18	alpha	Lulu	Star	yes
Sammie	F	7	medium	Goya	Lily	no
Star	F	(30)	alpha	Bias	Nancy	no
Wilma	F	6	low	Lily	Goya	yes
Bravo	M	11	beta	Drella	Ike	no
Drella	M	15	alpha	Bravo	Ozzie	no
Ike	M	30	beta	Ozzie	Bravo	no
Lucas	M	5	gamma	Ike	Mason	no
Mason	M	7	gamma	Bravo	Lucas	no
Ozzie	M	17	alpha	Ike	Drella	no

Familiar partners lived in the same group, whereas strangers lived in a physically and visually separate group. Subjects were paired such that age and dominance rank in their group were matched the best way possible. Subjects whose name starts with the same capital are kin, but kin pairs were never tested together.

Table 4. Definitions of coded behavior patterns

Avoid eye contact	neg	Partner and subject are close to making eye contact, but the subject abruptly looks away. In the case of a mirror reflection, the subject is in the process of inspecting the reflection’s face but quickly looks away when eye contact is about to be established.
Bunny sit	pos	Subject maintains a straight upright seated position while facing the partner, clutching both arms in towards the chest or reach with one hand out towards the partner while the other rubs the own chest.
Curling up	neg	Subject retracts arms and legs, often clutching the tail while laying on, or nearly on, its side. The arms are pulled in towards own chest.
Dismantling	neg	Great physical exertion aimed at destroying or opening the test chamber (shaking doors, pushing whole body across the chamber) except in relation to the partition between subjects (see partition manipulation).
Elevation	neg	Climbing up so that feet and tail do not touch the test chamber floor.
Eyebrow raise	pos	Subject raises the eyebrows and retracts the scalp for more than 1 sec without opening its mouth or baring its teeth.
Glancing	neg	A back-and-forth look in which the subject briefly glances in the direction of the partner, looks away, and then quickly looks back again within 1 sec. The partner does not need to be looking at the subject.
Friendly sway	pos	The subject rhythmically tilts its head from side to side while facing the partner, commonly accompanied by gentle swaying of the upper-body.
Lip smacking	pos	Subject orients towards the partner and often leans in towards the partner’s face. The subject’s lips and jaw rapidly move open and shut while making an audible "smacking" sound.
Make eye contact	pos	Subject engages in direct mutual contact with the eyes of the partner or the own reflection for more than 2 sec.
Observing partner	¾	The subject visually inspects (i.e. takes an intent look at) any part of the partner's or reflection's body (other than face) at close range. Only taken for females, since males were never at close range.
Partition manipulation	¾	Touching, hitting, or scraping the transparent or mirror partition with face or hands.
Self-directed behavior	¾	Auto-grooming and self-scratching, such as calm or frantic scratching motions with hands or feet over the own body for more than 1 sec, not necessarily while orienting to the mirror.
Silent bared teeth	neg	Baring of upper and lower teeth with jaws closed and without accompanying vocalizations.
Squealing	neg	High-pitched vocalizations ranging from chirping to squealing usually with baring of the teeth.
Threat display	neg	Subject stares at other while opening its mouth baring the canines and usually also incisors. The mouth may be closed and reopened. The eyebrows may be raised and the skin around the ears retracted, and the head of the subject may move from side to side, sometimes with sideways movement of the entire upper-body (lateral sway).

Behavior followed by "pos" is treated as socially positive, behavior followed by "neg" is treated as negative (i.e., threatening or indicative of anxiety). Remaining patterns were considered neutral.

Table 5. Individual means (± SD) for eight female subjects for behavior patterns with a total frequency among all subjects of n ≥ 10

Behavior	Familiar	Mirror	Stranger	*F_2,14*	P	Mir/Str
Avoid eye contact	0.13 ± 0.35	1.00 ± 1.51	7.25 ± 8.12	5.34	*	NS
Bunny sit	0.00 ± 0.00	1.25 ± 2.19	0.00 ± 0.00	2.61	NS	¾
Eyebrow raise	0.00 ± 0.00	9.13 ± 16.67	0.13 ± 0.35	2.41	NS	¾
Glancing	0.38 ± 0.52	9.38 ± 8.94	19.13 ± 11.32	9.76	**	NS
Friendly sway	0.00 ± 0.00	4.00 ± 4.69	0.00 ± 0.00	5.82	*	*
Lip smacking	0.00 ± 0.00	1.38 ± 1.77	0.13 ± 0.35	5.08	*	*
Make eye contact	0.50 ± 0.93	28.50 ± 19.89	0.75 ± 1.49	16.47	*******	**
Observing partner	12.88 ± 10.02	13.63 ± 6.61	14.75 ± 6.69	0.12	NS	¾
Partition manipulation	25.63 ± 15.48	34.63 ± 23.31	11.75 ± 8.07	7.14	**	*
Self-directed behavior	8.13 ± 5.64	9.88 ± 10.37	6.00 ± 7.27	1.76	NS	¾
Threat display	0.25 ± 0.71	3.25 ± 4.74	4.00 ± 3.25	3.01	NS	¾

Frequencies in the table are combined for both 15 min tests per condition. F values refer to repeated-measures ANOVAs using condition (n = 3) and test order (n = 2) as within subject variables. For significant ANOVA outcomes, the contrast between mirror and stranger condition was further evaluated. Asterisks mark significance: *, P < 0.05; **, P < 0.01; ***, P < 0.001.

Table 6. Individual means (± SD) for six male subjects for behavior patterns with a total frequency among all subjects of n ≥ 10

Behavior	Familiar	Mirror	Stranger	*F_2,10*	P	Mir/Str
Avoid eye contact	0.17 ± 0.41	10.83 ± 17.15	6.83 ± 5.63	1.61	NS	¾
Bunny sit	0.00 ± 0.00	7.83 ± 8.26	0.83 ± 1.17	4.58	*	NS
Curling up	0.00 ± 0.00	4.67 ± 5.65	0.67 ± 1.21	4.15	*	NS
Eyebrow raise	10.00 ± 8.99	21.33 ± 19.91	43.33 ± 33.18	5.69	*	NS
Dismantling	7.83 ± 7.60	12.33 ± 13.41	8.00 ± 6.42	0.74	NS	¾
Elevation	1.00 ± 1.55	2.17 ± 3.49	5.00 ± 11.30	0.71	NS	¾
Glancing	1.33 ± 1.97	3.83 ± 4.62	2.17 ± 1.72	1.62	NS	¾
Friendly sway	0.00 ± 0.00	5.50 ± 6.69	0.00 ± 0.00	4.06	*	NS
Make eye contact	0.67 ± 0.82	26.67 ± 10.75	2.33 ± 1.75	30.68	*******	**
Partition manipulation	54.83 ± 22.85	69.00 ± 32.97	42.83 ± 21.22	2.30	NS	¾
Self-directed behavior	7.00 ± 6.75	5.33 ± 3.56	3.00 ± 2.76	1.16	NS	¾
Squealing	0.00 ± 0.00	5.00 ± 4.69	0.33 ± 0.52	6.94	*	*
Threat display	4.67 ± 4.76	10.17 ± 20.12	40.17 ± 28.91	10.46	**	**

Frequencies in the table are combined for both 15 min tests per condition. F values refer to repeated-measures ANOVAs using condition (n = 3) and test order (n = 2) as within subject variables. For significant ANOVA outcomes, the contrast between Mirror and Stranger condition was further evaluated. Asterisks mark significance: *, P < 0.05; **, P < 0.01; ***, P < 0.001.