Title: Language Modulated Detection and Detection Modulated Language Grounding in 2D and 3D Scenes. Abstract: To localize an object referent, humans attend to different locations in the scene and visual cues depending on the utterance.   Existing language and vision systems often model such task-driven attention using object proposal bottlenecks:  a pre-trained detector proposes objects in the scene, and the model is trained to selectively process those proposals and then predict the answer without attending to the original image.  Object detectors are typically trained on a fixed vocabulary of objects and attributes that is often too restrictive for open-domain language grounding, where the language utterance may refer to visual entities in various levels of abstraction, such as a cat, the leg of a cat, or the stain on the front leg of the chair. This paper proposes a model that reconciles language grounding and object detection with two main contributions: i) Architectures that exhibit iterative attention across the language stream, the pixel stream, and object detection proposals.In this way, the model learns to condition on easy-to-detect objects (e.g., “table”) and language hints (e.g.  “on the table”) to detect harder objects (e.g., “mugs”)mentioned in the utterance.  ii) Optimization objectives that treat object detection as language grounding of a large predefined set of object categories.  In this way,cheap object annotations are used to supervise our model, which results in performance improvements over models that are not co-trained across both referential grounding  and  object  detection.   Our  model  has  a  much  lighter  computational footprint,  achieves  faster  convergence  and  has  shown  on  par  or  higher  performance compared to both detection-bottlenecked and non-detection bottlenecked language-vision models on both 2D and 3D language grounding benchmarks.