1. A method comprising: tracking user behavior across multiple modalities for interacting with a device; storing representations of the user behavior in a log as descriptors, each descriptor associated with a modality, the descriptors comprising a first descriptor associated with a first modality and a second descriptor associated with a second modality, wherein the first modality and the second modality are distinct modalities; normalizing the descriptors, wherein the first descriptor and the second descriptor are normalized based on: (1) the first modality, (2) the second modality, (3) the device, and (4) a format associated with the device, to yield normalized descriptors; merging the normalized descriptors into a unified click stream; generating a behavioral model by analyzing the unified click stream; and upon receiving user input associated with modifying a presentation of search results associated with a search, dynamically modifying the presentation by using the behavioral model to generate the search results.