1. A method for automatically analyzing a category in a physical space based on video-based behavior analysis of a plurality of persons with regard to said category in the physical space, comprising the following steps of: a) capturing a plurality of input images of said plurality of persons by a plurality of means for capturing images in the area with regard to said category, wherein the means for capturing images includes at least a camera, b) processing said plurality of input images in order to process a video-based behavior analysis of each person in said plurality of persons using at least a computer that executes computer vision algorithms for said plurality of input images, wherein the computer vision algorithms include algorithms for person tracking, hand motion detection, and demographic classification, c) analyzing the category based on the accumulation of said video-based behavior analysis for said plurality of persons, and d) measuring the effect after making a change at the category level, whereby the analysis of said category facilitates an analysis of level of engagement and decision process at the category level, and whereby said change comprises change in the quantity, price, and position of certain products in said category.