REBUS

Recent advances in large language models have led to the development of multimodal LLMs
(MLLMs), which take both image data and text as an input. Virtually all of these models
have been announced within the past year, leading to a significant need for benchmarks
evaluating the abilities of these models to reason truthfully and accurately on a diverse set
of tasks. When Google announced Gemini (Gemini Team et al., 2023), they showcased its
ability to solve rebuses—wordplay puzzles which involve creatively adding and subtracting
letters from words derived from text and images. The diversity of rebuses allows for a
broad evaluation of multimodal reasoning capabilities, including image recognition, multi-
step reasoning, and understanding the human creator’s intent.
We present REBUS: a collection of 333 hand-crafted rebuses spanning 13 diverse cate-
gories, including hand-drawn and digital images created by nine contributors. Samples are
presented in Table 1. Notably, GPT-4V, the most powerful model we evaluated, answered
only 24% of puzzles correctly, highlighting the poor capabilities of MLLMs in new and unex-
pected domains to which human reasoning generalizes with comparative ease. Open-source
models perform even worse, with a median accuracy below 1%. We notice that models
often give faithless explanations, fail to change their minds after an initial approach doesn’t
work, and remain highly uncalibrated on their own abilities.