PraCha, home

Personality-Aligned Vision-Language Model

People describe the same image differently depending on how they think. This aligns a vision-language model to specific personality styles, then tests whether that consistency makes it a better coaching assistant.

buildsettledscience · engineering

A group of blind monks crowd around a white elephant, each touching a different part, its trunk, ear, tusk or leg, and each making something different of it.
Blind Monks Examining an Elephant, Hanabusa Itchō (1652–1724), woodblock print published 1888, after Itchō's painting. Library of Congress, Prints and Photographs Division (cph.3g08725). Public domain.

Motivation

Vision-language models describe images in a generic, averaged-out voice. Human visual description is not generic — an introvert notices different things than an extrovert; a sensing type anchors to concrete details while an intuitive type reaches for patterns. Can RLHF-style fine-tuning produce VLMs that adapt description style to personality dimensions?

Approach

Starting from LLaVA-1.6, I construct a preference dataset by:

  1. Generating N candidate image descriptions per input
  2. Scoring them against personality-keyed rubrics (MBTI dimensions: IE, SN, TF, JP)
  3. Forming preference pairs (chosen, rejected) per dimension
  4. Fine-tuning with DPO (Direct Preference Optimization) via TRL

PEFT (LoRA) adapters are trained per personality dimension, enabling runtime mixing via linear adapter combination.

Evaluation

Automatic: BERTScore between generated descriptions and personality-keyed reference descriptions. Human: pairwise preference study on AMT with MBTI-tested annotators. Downstream: VQA accuracy across personality-aligned vs. generic descriptions on COCO-QA.

Status

Dataset construction complete. DPO training done for IE and SN dimensions. TF and JP in progress. Human evaluation planned for Q2 2026.

Settled · 2025–26

If you'd have built it another way, I'd like to know how. Write to mepc3197@columbia.edu · the title goes in the subject line

Related

Sent through Substack, which will ask you to confirm. Your email is used for these letters and nothing else. Subscribe on Substack instead.