Fig. 3

The time-course of the average change in oxy-, deoxy-, and total-Hb concentrations The time-course of the average change in oxy-Hb, deoxy-Hb, and total-Hb concentrations in the boys during the familiar face and unfamiliar face conditions. Zero on the horizontal axis represents the beginning of the test period and 10 represents the end of the test period. The areas in red and blue represent the zones for statistical analysis, i.e., the early phase (3–10 s) of the test period and late phase (10–17 s) after the test period