Observers accurately judge children's degree of kinship given facial photographs (Dal Martello & Maloney, VSS2002). We report two experiments intended to determine where in the face the cues signalling kinship fall. Since the upper face changes less than the lower during development (Enlow & Hans, 1996), we hypothesized that observers would rely on age-invariant features in the upper face. Stimuli:30 pairs of photographs, each photograph portraying a child's face with background removed. Half were of siblings, half, unrelated. The children's ages spanned 14 years. Observers: 220 observers judged each pair as siblings or not. We summarized performance in each condition by signal detection d' estimates. Experiment 1 Conditions: Full Face visible (FF); Upper Half face visible (UH); Lower Half face visible (LH). Different observers participated in each condition. Results: Performance in FF (d' = 1.19) and in UH condition (d''=1.12) did not differ significantly (p = n.s.). Performance in LH (d' = 0.41) was significantly lower (p < 0.0001) than that in other conditions.

Experiment 2 Conditions: Full Face visible (FF); face visible except for a small mask over the eye region (ME); face visible except for the masked mouth (MM). Results: Performance in the masked conditions (ME d' = 0.82; MM d' = 1.11) was not significantly different from that found in FF (d' = 1.02).

Conclusion: Observers (correctly) use kinship cues in the upper half face but, surprisingly, the eye region either provides little information or cues available in that region are redundant with other facial cues.