Fig 1. Frequency of occurrence of categorized behaviors during each day of mirror exposure for each dolphin.

The shaded sections represent the age when children first demonstrate self-directed behavior (light gray, 12–15 months) and mark-directed behavior (dark gray, 18–24 months). a, Although Bayley’s first instances of self-directed behavior at the mirror were observed at 5.5 months old (session 4), by 7 months old (session 9) her self-directed behavior was well established. b, Foster exhibited predominantly self-directed behavior on his first day of mirror exposure when he was 14.5 months.