On Locality and Length Generalization in Visual Reasoning
Summary
This paper shows that state-of-the-art vision-language models fail at length generalization in visual reasoning due to 'global shortcuts', and demonstrates that combining local foveated perception with recurrence enables robust out-of-distribution generalization.
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Paper page - On Locality and Length Generalization in Visual Reasoning
Source: https://huggingface.co/papers/2607.09061 Your eyes don’t see a whole scene at once — they dart around in a sequence of foveated glimpses. Modern vision models take in the whole image in one shot. That difference decides if a model can generalize to scenarios that are out-of-distribution.
We built simple visual puzzles (e.g. “read these switches, navigate, track the state”) and made them longer at test time than in training. SOTA VLMs — GPT-5.4, Claude Sonnet 4.6, Qwen — ace the short ones… then fall off a cliff the moment the puzzle gets longer. A tiny recurrent agent (green) extrapolates the performance at test time. Even with task-specific training, the global model (Qwen) still breaks out-of-distribution.
The failure has a name:global shortcuts. When a model sees the whole image at once, it can memorize a parallel “trick” that works for the lengths it saw — but doesn’t actually implement the step-by-step computation. So it breaks out-of-distribution. Same thing happens to LLMs on parity/state-tracking. We show vision has the same problem.
You might think making the model recurrent (giving it a memory that updates step by step) is the fix. It isn’t — on its own. Same recurrent LSTM, three ways ofseeingthe image:
- Global— sees the whole image at once → collapses
- Local + Global— adds small high-res crops but keeps the global view → still collapses
- Foveated— only small local glimpses, no global view → generalized out-of-distribution. Hand a recurrent net the whole image and itstillmemorizes a shortcut.Locality is a necessary ingredient.
Now flip it: fix thelocalglimpses, swap only the backbone. Strict recurrent nets (LSTM/GRU/RNN) generalize. Transformers, Mamba, xLSTM — all degrade. So the recipe isboth: local perception + recurrence. Neither alone is enough. Together they’re sufficient. 🔑
There’s a real trade-off. Small/low-res glimpses → generalize but slow to explore. Big/high-res glimpses → easy to explore but invite shortcuts. With the right glimpse settings, we show that FoveAgentLSTM holds its accuracy at resolutions well beyond training — a global model only works in/near the resolution it was trained at.
But locality + recurrence isn’t a free win everywhere — and knowingwhenit helps is the point. On arecalltask the global VLMwinsand our local agent lags. State-tracking wants recurrence + locality. Pure retrieval doesn’t. The two split exactly like they do in language models.
The synthetic tasks isolate the mechanism. Does it carry over to a real task? We tested reasoning over math plots — finding a function’s roots. At thesame visual-compute budget, a foveated Qwen adds**+29 pts (~100%)**of accuracy over the global baseline. Uniformly cranking resolution 10× buys almost nothing (+3.8 pts). Same lesson as the synthetic tasks: locality + recurrence beats brute-force scaling. How you spend visual compute > how much visual compute you throw at it.
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