Experimental Design
We conduct dictator game experiments in the following seven conditions:
A) Anonymous: A recipient is anonymous for an allocator.
B) Japanese mask wearers: A recipient wears a mask. The recipient nationality is Japanese.
C) Japanese non-mask wearers: A recipient does not wear a mask. The recipient nationality is Japanese.
D) East Asian mask wearers: A recipient wears a mask. The recipient nationality is non-Japanese and East Asian.
E) East Asian non-mask wearers: A recipient does not wear a mask. The recipient nationality is non-Japanese and East Asian.
F) Non-East Asian mask wearers: A recipient wears a mask. The recipient nationality is non-Japanese and non-East Asian.
G) Non-East Asian non-mask wearers: A recipient does not wear a mask. The recipient nationality is non-Japanese and non-East Asian.
Each participant in the five dictator game experiments as an allocator. We randomly set the order of the above conditions to create seven groups in each of the mask wearers and non-mask wearers samples. The order of five dictator games as follows:
Group 1. A⇒A⇒A⇒A⇒A
Group 2. A⇒B⇒C⇒F⇒G
Group 3. A⇒C⇒B⇒E⇒D
Group 4. A⇒D⇒E⇒B⇒C
Group 5. A⇒E⇒D⇒C⇒B
Group 6. A⇒F⇒G⇒B⇒C
Group 7. A⇒G⇒F⇒C⇒B
First, we set up six groups: the Japanese condition (B and C), the East Asian condition (D and E) and the Non-East Asian condition (F and G). In all groups, the first among the five games is played in the anonymous condition (A). In the second and third games, for each nationality condition, we randomly set either the in-group condition (B, D and F) or the out-group condition (C, E and G). In Groups 2 and 3, the fourth and fifth games will be played in the East Asian or Non-East Asian condition. In Groups 4, 5, 6 and 7, the fourth and fifth games are played in the Japanese condition. The order of the in-group and out-group conditions is set to correspond to the order of the in-group and out-group conditions in the second and third games. Consequently, each of the mask wearing and non-wearing samples have six groups. Furthermore, we create Group 1 as a control group, where we present the anonymous condition (A) five times, to address potential order effects caused by successive participation in the dictator games. Totally, each of the mask wearing and non-wearing samples have seven groups, including the control group.
We conduct the between-analysis to test the existence of ingroup favoritism, ingroup bias, and outgroup bias in each of face mask wearers and non-mask wearers. We also investigate whether the mask wearers’ ingroup favoritism change between when the nationality of the recipient pair is Japanese and when the nationality of the recipient pair is non-Japanese. Our experimental design allows for both between- and within-individual comparisons. We further conduct the within-analysis to check the robustness of the between-analysis.
We explain more details in the attachment of the pre-analysis plan.