A single session consisted of four trials of the neutral condition, followed by either the both-hands or one-hand condition.
Correlations among the averaged ratings of the three subtypes were calculated for one-hand and both-hands conditions, separately for the Japanese and non-Japanese groups.
The waveform measured in the neutral condition was obtained from the four trials just before the both-hands condition and the one-hand condition.
As shown in Figure 4, significantly greater oxyHb concentrations were observed when Japanese and non-Japanese participants observed the one-hand action, as compared to the both-hands action within the left superior temporal regions (left 18ch, t (34) = -2.
We analyzed the correlation between neural activation and the three subtypes of subjective ratings using the difference in oxy-Hb concentrations (subtracting the one-hand condition from the both-hands condition), separately for the Japanese and non-Japanese groups.
In the Japanese group, when the subjective rating of "easy to receive" using both-hands was high, oxy-Hb concentration in the inferior parietal cortex was also high.
Differences in reactions in the IFG to both-hands and one-hand conditions found in this study could be attributed to the interpretations of the both-hands movement necessitated, because it exceeds its functional goal of handing an item.
In contrast, the non-Japanese participants interpreted the functional and affective elements of both-hands handing independently.
Based on these results, it can be inferred that with the Japanese participants, oxy-Hb concentrations in the frontal lobe were greater in the both-hands handing condition than in the one-hand condition, indicating a reaction to affective, as well as functional elements.
One possible reason that little reaction was observed in the fronto-parietal mirror neuron system of the non-Japanese participants, in response to both-hands handing, could be because the purpose of deliberately handing an object with two hands, when it could be handed with just one hand, was unclear to them.
Additionally, with regard to the subjective ratings, functional ratings and positive affective ratings were found to correlate in the both-hands condition with the Japanese participants, but not with the non-Japanese participants.
drawing an arc) as an impolite action because all participants described the both-hands actions as polite and the one-hand action as impolite (see the method and the result sections).