using functional magnetic resonance imaging. Models of attention Not all the information presented to us can be processed. In theory, the selection of what to pay attention to can be random or nonrandom. For example, when driving, drivers are able to focus on the traffic lights rather than on other stimuli present in the scene. In such cases it is mandatory to select which portion of presented stimuli is important. A basic question in psychology is when this selection occurs. This issue has developed into the early versus late selection controversy. The basis for this controversy can be found in the Cherry dichotic listening experiments. Participants were able to notice physical changes, like pitch or change in gender of the speaker, and stimuli, like their own name, in the unattended channel. This brought about the question of whether the meaning, semantics, of the unattended message was processed before selection. In an early selection attention model very little information is processed before selection occurs. In late selection attention models more information, like semantics, is processed before selection occurs. Broadbent The earliest work in exploring mechanisms of early selective attention was performed by Donald Broadbent, who proposed a theory that came to be known as the filter model. This model was established using the dichotic listening task. His research showed that most participants were accurate in recalling information that they actively attended to, but were far less accurate in recalling information that they had not attended to. This led Broadbent to the conclusion that there must be a "filter" mechanism in the brain that could block out information that was not selectively attended to. The filter model was hypothesized to work in the following way: as information enters the brain through sensory organs (in this case, the ears) it is stored in sensory memory, a buffer memory system that hosts an incoming stream of information long enough for us to pay attention to it. Before information is processed further, the filter mechanism allows only attended information to pass through. The selected attention is then passed into working memory, the set of mechanisms that underlies short-term memory and communicates with long-term memory. In this model, auditory information can be selectively attended to on the basis of its physical characteristics, such as location and volume. Others suggest that information can be attended to on the basis of Gestalt features, including continuity and closure. For