Morning Edition · Thursday, July 23, 2026Published at 2:03 AM EDT · New York

Study Finds Supervised Fine-Tuning Collapses Behavioral Diversity in Sequential Decisions

In controlled game-play suites, fine-tuned models narrow toward a few moves, a failure mode that reasoning traces can worsen rather than fix.

A new paper, When Reasoning Narrows the Move, studies how supervised fine-tuning (SFT) affects behavioral diversity in sequential decision-making. Using a controlled suite of games, the authors document what they call diversity collapse: af…