Attenuation theory

Selective attention theories are aimed at explaining why and how individuals tend to process only certain parts of the world surrounding them, while ignoring others. Given that sensory information is constantly besieging us from the five sensory modalities, it was of interest to not only pinpoint where selection of attention took place, but also explain how people prioritize and process sensory inputs. Early theories of attention such as those proposed by Broadbent and Treisman took a bottleneck perspective. That is, they inferred that it was impossible to attend to all the sensory information available at any one time due to limited processing capacity. As a result of this limited capacity to process sensory information, there was believed to be a filter that would prevent overload by reducing the amount of information passed on for processing. Methodology Early research came from an era primarily focused upon audition and explaining phenomena such as the cocktail party effect. From this stemmed interest about how people can pick and choose to attend to certain sounds in our surroundings, and at a deeper level, how the processing of attended speech signals differ from those not attended to. Auditory attention is often described as the selection of a channel, message, ear, stimulus, or in the more general phrasing used by Treisman, the "selection between inputs". As audition became the preferred way of examining selective attention, so too did the testing procedures of dichotic listening and shadowing. Shadowing Shadowing can be seen as an elaboration upon dichotic listening. In shadowing, participants go through largely the same process, only this time they are tasked with repeating aloud information heard in the attended ear as it is being presented. This recitation of information is carried out so that the experimenters can verify participants are attending to the correct channel, and the number of words perceived (recited) correctly can be scored for later use as a dependent variable. It is also favored for being more accurate since shadowing is less dependent upon participants' ability to recall words heard correctly. • When participants were presented with the message "you may now stop" in the unattended ear, a significant number do so. • In a classic demonstration of the cocktail party phenomenon, participants who had their own name presented to them via the unattended ear often remark about having heard it. • Semantic processing of unattended stimuli has been demonstrated by altering the contextual relevance of words presented to the unattended ear. Participants heard words from the unattended ear more regularly if they were high in contextual relevance to the attended message. ==Attenuation model of selective attention==

How attenuation occurs Treisman's attenuation model of selective attention retains both the idea of an early selection process, as well as the mechanism by which physical cues are used as the primary point of discrimination. Recognition threshold The operation of the recognition threshold is simple: for every possible input, an individual has a certain threshold or "amount of activation required" in order to perceive it. The lower this threshold, the more easily and likely an input is to be perceived, even after undergoing attenuation. Threshold affectors Context and priming Context plays a key role in reducing the threshold required to recognize stimuli by creating an expectancy for related information. Hierarchy of analyzers The hierarchical system of analysis is one of maximal economy: while facilitating the potential for important, unexpected, or unattended stimuli to be perceived, it ensures that those messages sufficiently attenuated do not get through much more than the earliest stages of analysis, preventing an overburden on sensory processing capacity. If attentional demands (and subsequent processing demands) are low, full hierarchy processing takes place. If demands are high, attenuation becomes more aggressive, and only allows important or relevant information from the unattended message to be processed. The hierarchical analysis process is characterized by a serial nature, yielding a unique result for each word or piece of data analyzed. Attenuated information passes through all the analyzers only if the threshold has been lowered in their favor, if not, information only passes insofar as its threshold allows. The nervous system sequentially analyzes an input, starting with the general physical features such as pitch and loudness, followed by identifications of words and meaning (e.g., syllables, words, grammar and semantics). The hierarchical process also serves an essential purpose if inputs are identical in terms of voice, amplitude, and spatial cues. Should all of these physical characteristics be identical between messages, then attenuation can not effectively take place at an early level based on these properties. Instead, attenuation will occur during the identification of words and meaning, and this is where the capacity to handle information can be scarce. ==Evidence==

Following messages to the unattended ear During shadowing experiments, Treisman would present a unique stream of prosaic stimuli to each ear. Sometime during shadowing, the stimuli would then swap over to the opposite side so that the formerly shadowed message was now presented to the unattended ear. Participants would often "follow" the message over to the unattended ear before realizing their mistake, Event-related potentials of irrelevant stimuli Von Voorhis and Hillyard (1977) used an EEG to observe event-related potentials (ERPs) of visual stimuli. Participants were asked to attend to, or disregard specific stimuli presented. Results demonstrated that when attending to visual stimuli, the amount of voltage fluctuation was greater at occipital sites for attended stimuli when compared to unattended stimuli. Voltage modulations were observed after 100ms of stimuli onset, consistent with what would be predicted by attenuation of irrelevant inputs. Effects of attentional demand on brain activity In a functional magnetic resonance imaging (fMRI) study that examined if meaning was implicitly extracted from unattended words, or if the extraction of meaning could be avoided by simultaneously presenting distracting stimuli; it was found that when competing stimuli create sufficient attentional demand, no brain activity was observed in response to the unattended words, even when directly fixated upon. These results are in keeping with what would be predicted by an attenuation style of selection and run contrary to classical late selection theory. ==Competing theories==

In 1963, Deutsch and Deutsch proposed a late selection model of how selective attention operates. They proposed all stimuli get processed in full, with the crucial difference being a filter placed later in the information processing routine, just before the entrance into working memory. The late selection process supposedly operated on the semantic characteristics of a message, barring inputs from memory and subsequent awareness if they did not possess desired content. According to this model, the depreciated awareness of unattended stimuli came from denial into working memory and the controlled generation of responses to it. A criticism of both the original Deutsch and Deutsch model, as well as the revised Deutsch–Norman selection model is that all stimuli, including those deemed irrelevant, are processed fully. ==See also==