Table 4.

Ethogram of behaviors coded during the Human Intruder Test.

Behavior	Operational definition
Vigilant	Subject's gaze is not directed toward human intruder
Freeze	Tense body posture with no movement and no vocalization
Locomotion	Active behavior resulting in movement from original location (e.g., moving across cage)
Stationary	Focal individual sitting quietly, not engaged in other behavior
Stereotypical behavior	Repetitive behavior with no apparent purpose
Vocalizations	Includes coo and shriek
Yawn	Subject opens mouth very wide, baring upper teeth
Self-directed anxiety behavior	Subject scratches or shakes (quick action of rotating head and top of shoulders back and forth)