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VLM Object Hallucination Lab: Decoding Vision-Language Models in 2D Phase Space

An interactive exploration of how vision-language models interpret visual evidence and linguistic context.

mysimulator teamUpdated June 2026≈ 3 min read▶ Open the simulation

What is VLM Object Hallucination Lab

The VLM Object Hallucination Lab provides a unique insight into how vision-language models (VLMs) decode visual inputs and linguistic cues. In this lab, each candidate object is represented as a dot in a 2D phase space, where the x-axis represents visual evidence and the y-axis represents language prior.

The size of each dot corresponds to its live softmax probability of being named next by the model, allowing us to visualize which objects are most likely to be hallucinated based on the current state of decoding.

Why It Matters

Understanding how VLMs interpret visual and linguistic data is crucial for developing more accurate and reliable models. By observing the dynamics in this 2D phase space, researchers can gain insights into the model's decision-making process and identify areas where improvements are needed.

This lab also helps in understanding the trade-offs between visual evidence and language prior, which can be critical in applications such as image captioning and visual question answering.

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How It Works

The lab uses a 2D phase space where each candidate object is represented by a dot. The position of the dot reflects the balance between visual evidence (how much the model believes in the presence of an object) and language prior (the influence of previous linguistic context).

The size of the dot represents the softmax probability, which indicates how likely it is for the model to name that object next. By adjusting sliders and buttons, users can manipulate these factors and observe their effects on the hallucination metric.

Real-World Applications

The insights gained from this lab have direct applications in improving VLM performance. For instance, understanding how to balance visual evidence and language prior can lead to more accurate image captions and better answers to visual questions.

Moreover, the ability to control factors like occlusion or sensor noise allows researchers to test robustness and adaptability of VLMs under different conditions.

Frequently asked questions

What is a hallucination in the context of VLMs?

In the context of VLMs, a hallucination refers to the model generating content that does not exist in the input image but is influenced by the language prior or other factors.

How do visual evidence and language prior interact in this lab?

Visual evidence represents what the model sees in the input image, while language prior reflects previous linguistic context. The interplay between these two factors determines which objects are most likely to be hallucinated by the model.

Why is it important to control visual evidence and language prior?

Controlling these factors helps researchers understand how VLMs make decisions and identify areas for improvement. It also allows testing the robustness of models under different conditions, such as occlusion or sensor noise.

What are some practical applications of this lab's findings?

Findings from this lab can be used to improve VLMs in various applications, including image captioning, visual question answering, and enhancing the robustness of models under different input conditions.

Try it live

Everything above runs in your browser — open VLM Object Hallucination Lab — Evidence/Prior Phase Plane (2D) and change the parameters while it is running. Nothing is installed, nothing is uploaded, the whole model lives in one tab.

▶ Open VLM Object Hallucination Lab — Evidence/Prior Phase Plane (2D) simulation

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