For
happy expressions, we selected the same three regions (around the eyes, mouth, and noninformative hair region) and ran the ANOVA as before. We found no significant main effect of participants' age group,
F(1, 32) = 0.52,
p = 0.48,
Display Formula\(\eta \)p2 = 0.016, or significant interaction,
F < 1.4,
p > 0.2,
Display Formula\(\eta \)p2 < 0.043, beyond a marginal trend to interact with facial feature,
F(2, 64) = 2.3,
p = 0.11,
Display Formula\(\eta \)p2 = 0.066, driven by a trend for more use of the mouth by older adults than younger,
t(32) = 1.7,
p = 0.09,
d = 0.59, with no difference in the eyes or hair region,
t < 0.7,
p > 0.5,
d < 0.24. As expected we again found main effects of feature,
F(2, 52) = 183,
p < 0.001,
Display Formula\(\eta \)p2 = 0.85, and scale,
F(2.27, 72.6) = 52.4,
p < 0.001,
Display Formula\(\eta \)p2 = 0.62, and a significant two-way interaction,
F(3.5, 111.8) = 39,
p < 0.001,
Display Formula\(\eta \)p2 = 0.55, which did not interact further with participant age or model age (
Fs < 1.55,
ps> 0.16,
Display Formula\(\eta \)p2 < 0.046). The main effect of feature confirmed significantly more use of the mouth than either the eyes,
t(33) = 15.7,
p < 0.001,
d = 3.81, or the hair region,
t(33) = 16.5,
p < 0.001,
d = 4.01, with the eyes more useful than the hair,
t(33) = 4.1,
p < 0.001,
d = 0.99. The interaction mediated these effects by indicating that for the highest two spatial scales (SF Bands 1 and 2), the eyes are not any more useful than the control hair region. Finally, we observed a significant interaction of stimulus age and facial feature,
F(4, 128) = 3.6,
p = 0.008,
Display Formula\(\eta \)p2 = 0.12, which was driven by significantly less use of the eyes than the hair region for middle aged faces in the first SF scale,
t(33) = −3.6, 0.001,
d = 0.87.