Unpacking the Validity of Open-Ended Personality Assessments Using Fine-Tuned Large Language Models

Alternative approaches to personality measurement, such as open-ended narrative-based assessments, have potential advantages for organizational research and practice. In this research, we investigate factors that affect valid application of natural language processing (NLP) for scoring open-ended personality assessments and when, how, and why such assessments capture personality-related variance. Using a large sample of responses to open-ended assessments, convergence between NLP scores and self-report target scores increased as the degree of customization and the sophistication of the underlying model increased, with the worst psychometric performance occurring for zero-shot large language model (LLM) scores and the best for fine-tuned LLM scores. However, all scoring methods exhibited evidence of validity. Additionally, when trained to predict direct evaluations of the narrative responses, correlations with target scores were large (M = .83). NLP scores also exhibited discriminant and criterion-related validity evidence. However, validity was contingent upon the methodological rigor employed in developing writing prompts. Prompts designed to elicit trait-relevant information outperformed generic prompts, and this occurred because trait-specific prompts increased the amount of trait-relevant information (i.e., narrative units), which was associated with enhanced convergence with target scores.