Face Trust Study
Laterality and Dimorphism in Facial Trustworthiness Judgments
An original Applied Psychology practicum study by Christopher M. Vetrano at Fielding Graduate University, supervised by Barbara Colombo, Ph.D.
What this study examined
Does the side of a face perceived as more feminine receive higher trustworthiness ratings? Does that relationship change when someone sees the whole face rather than one half? These are questions about the observer’s impression, not the actual trustworthiness of the person pictured.
The study examined naturally occurring facial differences using left-half, right-half, and whole-face views. Left and right refer to the observer’s view. Masculinity and femininity were rated separately rather than treated as opposite ends of one scale.
Key finding
Full faces received higher perceived trustworthiness ratings than either half-face view. Mean ratings were 5.28 for full faces, 5.03 for left hemifaces, and 4.98 for right hemifaces on a nine-point scale.
Both full-face comparisons were statistically significant (Bonferroni-adjusted p < .001). Left and right hemifaces did not differ significantly (p = .575). This supports a whole-face advantage in this task, not a reliable left-versus-right trust bias.
What participants were asked to do
Sixty adults recruited through Prolific evaluated 35 face identities from the Chicago Face Database. Participants were aged 19–63; most lived in the United Kingdom, with others from the United States, Ireland, Nigeria, and other countries. The median task duration was 39 minutes.
Participants toggled between left and right hemifaces, rating trustworthiness and emotional expression on nine-point scales and making separate masculinity and femininity comparisons. They then rated the full face. Full-face images were unchanged; half-face images were cropped at the vertical midline.
The personality and general-trust questionnaires were completed at the end, but their responses were not saved because of a technical error and were unavailable for analysis. The report states that the primary face-rating data were retained.
Mean Trust Ratings by Face Version
Other results and interpretation
The overall effect of face version was significant: F(2, 118) = 29.45, p < .001, partial η² = .33. The report describes a whole-face advantage that remained after accounting for perceived emotion.
Perceived femininity did not independently predict trust ratings in the full-face model (b = −0.042, p = .27). The exploratory femininity-by-version interaction was significant for the left hemiface (p = .044) but not conventionally significant for the right (p = .052). This exploratory pattern needs cautious interpretation and replication.
Limitations
These were appearance ratings, not tests of honesty, character, or actual trusting behavior. Cropped half-faces are an artificial presentation, and whole faces always followed the half-face views, so the design does not isolate presentation order from the whole-face comparison.
The online task was self-paced and limited to English-speaking Prolific participants. Its longer-than-expected duration may have affected attention or fatigue. Missing questionnaire responses prevented the planned personality and general-trust analyses.
Approval and reporting status
Fielding Graduate University’s Institutional Review Board approved study 25-0803 on August 15, 2025, under minimal-risk expedited review.
Connection to Zero Point
For Zero Point, the relevant question is how to distinguish an initial impression from evidence about another person. Noticing a judgment gives someone an opportunity to question it and consider behavior and context before acting.
That is an application of the framework, not a study result or evidence that Zero Point itself has been validated by this research.
Sources for this summary
Vetrano, Christopher. Laterality and Dimorphism in Facial Trustworthiness Judgments. Fielding Graduate University, PSY-686C: Practicum, October 31, 2025. Results: Trust Ratings, Table 1, and Table 3. Approval history: Fielding Graduate University IRB letter, August 15, 2025, study 25-0803.
This educational summary does not reproduce participant materials or research face images. It should not be used to judge, diagnose, screen, or make decisions about a person based on appearance.