Physiological recordings by Recanzone, Wurtz and Schwarz (1997), and other labs, indicate a decrease in the time-averaged response of directionally selective MT neurons to a stimulus moving in the preferred direction when that stimulus is paired with one moving in a non-preferred direction. Similarly, there is an increase in the response to an anti-preferred stimulus when it is paired with one moving in a non-preferred direction. In fact, the response to such complex stimuli is approximately the average of the responses to each of the moving components. We implemented a variant of the model by Simoncelli and Heeger (1998), in order to examine its responses to such stimuli. The model consists of two stages corresponding to visual areas V1 and MT, with each stage computing a weighted linear combination of inputs, followed by rectification and divisive normalization. The V1 stage contains directionally selective motion-energy neurons, and the MT stage selectively combines afferents of V1 neurons over a range of spatio-temporal orientations, to produce a velocity-selective response. In our model, the feedback normalization signal for each stage is computed by time-averaging and delaying the summed responses of all neurons in that stage. The model is able to replicate the averaging behavior described above, primarily as a result of the second stage of normalization. In addition, the time delay and low-pass filtering of the normalization signal produce transient temporal dynamics in the model which are qualitatively similar to those of MT responses.