Perception Tokens Enhance Visual Reasoning in Multimodal Language Models
Authors: name: Mahtab Bigverdi, name: Zelun Luo, name: Cheng-Yu Hsieh, name: Ethan Shen, name: Dongping Chen, name: Linda G. Shapiro, name: Ranjay Krishna

Multimodal language models (MLMs) still face challenges in fundamental visual
perception tasks where specialized models excel. Tasks requiring reasoning
about 3D structures benefit from depth estimation, and reasoning about 2D
object instances benefits from object detection. Yet, MLMs can not produce
intermediate depth or boxes to reason over. Finetuning MLMs on relevant data
doesn't generalize well and outsourcing computation to specialized vision tools
is too compute-intensive and memory-inefficient. To address this, we introduce
Perception Tokens, intrinsic image representations designed to assist reasoning
tasks where language is insufficient. Perception tokens act as auxiliary
reasoning tokens, akin to chain-of-thought prompts in language models. For
example, in a depth-related task, an MLM augmented with perception tokens can
reason by generating a depth map as tokens, enabling it to solve the problem
effectively. We propose AURORA, a training method that augments MLMs with
perception tokens for improved reasoning over visual inputs. AURORA leverages a
VQVAE to transform intermediate image representations, such as depth maps into
a tokenized format and bounding box tokens, which is then used in a multi-task
training framework. AURORA achieves notable improvements across counting
benchmarks: +10.8% on BLINK, +11.3% on CVBench, and +8.3% on SEED-Bench,
outperforming finetuning approaches in generalization across datasets. It also
improves on relative depth: over +6% on BLINK. With perception tokens, AURORA
expands the scope of MLMs beyond language-based reasoning, paving the way for
more effective visual reasoning capabilities.