Motion modeling in biological and computer vision systems is divided into two categories: Intensity-based schemes and feature-matching schemes. Some models from each category are discussed. Intensity-based models are further subdivided into global and local models. Moreover, a new motion detection model that belongs to the family of intensity-based schemes is introduced. The model operates on the same basic structure as the Reichardt’s correlation model does, that is, a nonlinear asymmetric interaction between signals from two adjacent channels. However, the new model differs from that of Reichardt in the nature and origin of the nonlinear interaction: It is of the inhibitory type originating from the biophysical mechanism of shunting inhibition. Our model detects fairly well motion of objects like edges and bars. Furthermore, its mean response to a moving grating of low contrast is equivalent to that of the Reichardt correlation model. © 1989 SPIE.