1. An image recognition system for detecting and tracking at least an image portion associated with a predefined object from a moving picture, wherein the image recognition system is configured to be able to perform: an object detection processing step of detecting the object from the moving picture; a tracking point specification processing step of specifying at least a predetermined point associated with the object as a tracking point; a tracking target recognition processing step of recognizing an actual tracking target based on the tracking point; a tracking processing step of tracking the tracking target; and a determination processing step of determining the type of the tracking target's behavior based on a result of the tracking processing step, wherein the tracking point specification processing step and the determination processing step are implemented by software, while the object detection processing step, the tracking target recognition processing step, and the tracking processing step are implemented by hardware, the object detector performing the object detection processing step includes at least a feature quantity calculating unit, a plurality of posterior event memories storing posterior events, a posterior event updater, and a score calculating unit, the feature quantity calculating unit calculates a feature quantity based on the moving picture, the posterior event memories store at least both of a posterior event in an object image and a posterior event in a non-object image, the posterior event updater updates the posterior event in the object image and the posterior event in the non-object image in accordance with a pattern of the feature quantity, and the score calculating unit retrieves, from the posterior event memories, a posterior event corresponding to an arbitrary pattern of the feature quantity obtained from the feature quantity calculating unit, and calculates a score corresponding to the arbitrary pattern of the feature quantity.