 Psychologists attempting to produce a theory of attention in the nineteen sixties and seventies were highly influenced by Donald Broadbent’s picture of attention as corresponding to a bottleneck in information processing capacity resulting from the connection of two separate perceptual processing systems. The first piece of business for these psychologists was to locate this attentional bottleneck, by determining which sorts of processing are done by the large capacity, pre-bottleneck system, and which by the small capacity, post-bottleneck system. Debates between these psychologists gave rise to various theories in which the selectivity of attention was characterized with a claim about the location of this bottleneck.