Attenuation theory
Treisman proposed attenuation theory as a means to explain how unattended stimuli sometimes came to be processed in a more rigorous manner than what Broadbent's filter model could account for.
[6] Dichotic listening is an experimental procedure used to demonstrate the selective filtering of auditory inputs, and was primarily utilized by Broadbent.
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.
[2] Due to its live rehearsal characteristic, shadowing is a more versatile testing procedure because manipulations to channels and their immediate results can be witnessed in real time.
[9] Broadbent proposed the idea that the mind could only work with so much sensory input at any given time, and as a result, there must be a filter that allows us to selectively attend to things while blocking others out.
[9] The second stage was claimed to be of limited capacity, and so this is where the selective filter was believed to reside in order to protect from a sensory processing overload.
[9] Based upon the physical properties extracted at the initial stage, the filter would allow only those stimuli possessing certain criterion features (e.g., pitch, loudness, location) to pass through.
As noted above, the filter model of attention runs into difficulty when attempting to explain how it is that people come to extract meaning from an event that they should be otherwise unaware of.
For this reason, and as illustrated by the examples below, Treisman proposed attenuation theory as a means to explain how unattended stimuli sometimes came to be processed in a more rigorous manner than what Broadbent's filter model could account for.
[1] Treisman further elaborated upon this model by introducing the concept of a threshold to explain how some words came to be heard in the unattended channel with greater frequency than others.
[1] The crucial aspect of attenuation theory is that attended inputs will always undergo full processing, whereas irrelevant stimuli often lack a sufficiently low threshold to be fully analyzed, resulting in only physical qualities being remembered rather than semantics.
[16] Context plays a key role in reducing the threshold required to recognize stimuli by creating an expectancy for related information.
[9] Context acts by a mechanism of priming, wherein related information becomes momentarily more pertinent and accessible – lowering the threshold for recognition in the process.
[17] On the other hand, some words are more variable in their individual meaning, and rely upon their frequency of use, context, and continuity with the attended message in order to be perceived.
[1] The hierarchical analysis process is characterized by a serial nature, yielding a unique result for each word or piece of data analyzed.
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.
It was found that if these words were later presented in the absence of shock, participants would respond automatically with a galvanic skin response (GSR) even when played in the unattended ear.
[21] 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.
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.
