Treisman (1964) agrees with Broadbent's theory of an early bottleneck filter. However, the difference is that Treisman's filter attenuates rather than eliminates the unattended material.

Criticisms leading to a theory of attenuation

As noted above, the filter model of attention runs into difficulty when attempting to explain how it is that we come to extract meaning from an event that we 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.

       For two messages identical in content, it has been shown that by varying the time interval between the onset of the irrelevant message in relation to the attended message, participants may notice the message duplicity.

       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.

       Participants with training or practice can more effectively perceive content from the unattended channel while attending to another.

       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 is like turning down the volume so that if you have 4 sources of sound in one room (TV, radio, people talking, baby crying) you can turn down or attenuate 3 in order to attend to the fourth.

This means that people can still process the meaning of the attended message(s).

treisman attenuaton model of attention

In her experiments, Treisman demonstrated that participants were still able to identify the contents of an unattended message, indicating that they were able to process the meaning of both the attended and unattended messages.

Treisman carried out dichotic listening tasks using the speech shadowing method.  Typically, in this method participants are asked to simultaneously repeat aloud speech played into one ear (called the attended ear) whilst another message is spoken to the other ear.

For example, participants asked to shadow "I saw the girl furniture over" and ignore "me that bird green jumping fee", reported hearing "I saw the girl jumping over"

Clearly, then, the unattended message was being processed for meaning and Broadbent's Filter Model, where the filter extracted on the basis of physical characteristics only, could not explain these findings.  The evidence suggests that Broadbent's Filter Model is not adequate, it does not allow for meaning being taken into account.

Evaluation of Treisman's Model

1. Treisman's Model overcomes some of the problems associated with Broadbent's Filter Model, e.g. the Attenuation Model can account for the 'Cocktail Party Syndrome'.

2. Treisman's model does not explain how exactly semantic analysis works.

3. The nature of the attenuation process has never been precisely specified.

4. A problem with all dichotic listening experiments is that you can never be sure that the participants have not actually switched attention to the so called unattended channel.