1. A method for detecting a pedestrian moving in an environmental region of a motor vehicle relatively to the motor vehicle based on temporal sequence of images of the environmental region, which are provided by a camera of the motor vehicle, the method comprising: extracting characteristic features from the images; determining a plurality of optical flow vectors to the characteristic features of at least two consecutively captured images of the sequence by an image processing device of the motor vehicle, wherein the plurality of optical flow vectors indicate a movement of the respective characteristic features over the sequence; determining several confidence metrics for detecting the pedestrian, based on the characteristic features and the optical flow vectors, and based on the confidence metrics; and examining whether a preset plausibility check criterion required for the detection of the pedestrian is satisfied, wherein the pedestrian is detected when the plausibility check criterion with respect to the confidence metrics is satisfied.