Attention is viewed as the process of selecting some of the many available inputs. There are certain theories proposed by different psychologists on how this selection takes place. In this session we are going to learn about Treisman’s Attenuation theory.

Anne Treisman, in 1964, proposed an attenuation theory of attention in which the processing of unattended information is attenuated. An ‘attenuator’ is an electronic device that reduces the amplitude or power of a signal without appreciably distorting its waveform. This means, according to Treisman, instead of completely blocking out the unattended message, it gets attenuated or weakened. Treisman believed that some meaningful information in unattended messages might still be available, but may be hard to recover. She compared this theory to volume control in saying that our "volume" can be turned "down." The attenuation model therefore proposes that there is a decrease in the perceived loudness of an unattended message.

Treisman carried out experiments to prove the validity of  Attenuation Theory,  using the 'speech shadowing method'. Participants were presented with two auditory messages, one to each ear via a set of headphones. They were required to attend to one message while ignoring the other message. To be sure that participants were attending to the message they were asked to repeat aloud the message they hear (shadowing). Typically, the messages presented were spoken words or sentences. Treisman was interested to know how much and what type of information the participant can hear from the non-attended message (the ‘unshadowed' message). Findings suggested that some information, such as one's own name, the gender of the speaker and other features could be detected in the unshadowed message.

In one of her experiments, identical messages were played into both ears but with a slight delay between them. If the delay was too long, the participants were unable to realize that the same material was played into both ears. When the unattended message was ahead of the shadowed message by up to 2 seconds, participants noticed the similarity.

In an experiment with bilingual participants, Treisman presented the attended message in English and the unattended message in French. When the French translation lagged only slightly behind the English translation, participants could report that both messages had the same meaning. Clearly then, the unattended message was being processed for meaning.

This led Treisman to develop her attenuation theory of attention. She stated that stimulus processing proceeds systematically. It starts with analysis based on physical characteristics (location, pitch, gender etc.) syllabic pattern, and individual words. After that, grammatical structure and meaning are processed. When the unattended messages yield no useful or important information, those messages are attenuated; they are weakened in their importance to ongoing processing.

Why did that happened? Mitesh could not hear the entire conversation but he could hear his name. Treisman explains that different words have different chances of making it through the unattended channel, due to a threshold effect. A threshold is the minimum amount of activation required to produce conscious awareness of a stimulus. Stimuli having low threshold easily make their way into awareness. Those with high threshold do not. A word’s meaning determines its threshold. Important words and those with personal relevance, such as our names or that signal danger (someone shouting the words fire or watch out), have a lower threshold for recognition and make it past the filter. In simple words, meaningful units, such as words or phrases, are processed quite easily. They are easily recognizable at lower volumes. Less important words have higher threshold and get filtered out.

The dictionary unit at Treisman’s model contains words, each of which has a threshold for being detected.