<p>This study investigates the influence of the top and bottom facial cues on trustworthiness judgments and associated behaviors through two experiments: (1) a trustworthiness rating task assessing perceptual judgments, and (2) an investment game measuring behavioral trust (investment amounts) and trust expectations (expected returns). Using faces with high, moderate, and low initial trustworthiness, we compared responses to full faces, top halves, and bottom halves. Three main findings emerged: First, both tasks demonstrated that participants could distinguish between high- and low-trustworthiness faces using either top or bottom facial halves, confirming that partial facial information supports both judgments and behaviors. Second, while the top halves always preserved discrimination across all three trustworthiness levels in ratings and behaviors, the bottom halves failed to distinguish between moderate and low trustworthiness in either task. Third, responses to the top halves correlated more strongly with evaluations of the full face, especially for trustworthiness judgments and expected returns. These results reveal that although trustworthiness cues exist in both facial regions, the top half dominates in guiding social judgments and behavioral decisions. The findings enhance our understanding of trust evaluations in real-world situations where facial information is often incomplete.</p>