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Reduction of the psychology of visual perception to the neurophysiology of vision is not possible in the sense of inferring the properties of perception from the properties of neurophysiology: one cannot deduce what a monkey sees from knowledge of which cells are firing and how they are firing. Nevertheless, with the aid of linking hypotheses it is possible to demonstrate surprising and compelling relationships between neural events and behavioural responses. For example, orientation- and direction-selective cells in the first cortical visual area (VI), first studied systematically by Hubel and Wiesel, respond separately to the components of a complex pattern; but some cells in a higher area (V5 or MT) respond to the pattern and not to the individual components. Human observers cannot see the components either, which suggests that the “percept” arises beyond VI and possibly in MT, although a feedback loop cannot be ruled out In recent years, experiments have been reported in which an animal performs a behavioural task while the experimenter simultaneously records from and/or stimulates single cortical cells. These experiments strongly implicate certain extrastriate areas of visual cortex in the process of perception. The experiments also suggest likely outcomes of psychophysical experiments with human observers and some of these experiments are described.