Attention : Notes.

Attention and perception syllabus :
Attention - factors, influencing attention including set and characteristics of stimulus. Sensation-concepts of threshold, absolute and difference thresholds, signal detection and vigilance. Definition and concept of perception, biological factors in perception. Perceptual organisation-influence of past experiences, Perceptual defence-factors influencing. Space and depth perception, size estimation and perceptual readiness.

Summary :

1. The auditory system is able to process sounds in such a way that, although several may be present simultaneously, it is possible to focus upon the message of interest. However, in experiments on auditory attention, there have been contradictory results concerning the fate of the unattended material:

. The auditory system processes mixed sounds in such a way that it is possible to
focus upon a single wanted message.

. Unattended material appears not to be processed:
– The listener is normally unable to report significant details concerning the unattended information.

– Only the most recent unattended material is available, while still preserved in the echoic memory.

. These results suggest parallel acquisition of all available information, followed by serial processing to determine meaning for one attended message.

. Although there is little conscious awareness of unattended material, it may receive more processing than the above results imply:
– Words presented to the unattended ear can produce priming and physiological effects.

– Participants trying to ‘shadow’ one ear will follow the message to the other ear.

. These results imply that processing takes place in parallel, to the extent that meaning is extracted even from unattended material.


2. The results of the visual attention experiments we have considered can be interpreted as follows.
. Attention can be directed selectively towards different areas of the visual field,without the need to re-focus.The inability to report much detail from brief, masked visual displays appears to be linked to the need to assemble the various information components.
. The visual information is captured in parallel, but assembly is a serial process.
. Episodic detail (e.g. colour, position) is vulnerable to the passage of time, or to ‘overwriting’ by a mask.
. Semantic information (i.e. identity/meaning) is relatively enduring, but does not reach conscious awareness unless bound to the episodic information.
. Attention, in this context, is the process of binding the information about an item’s identity to its particular episodic characteristics.
. ‘Unbound’ semantic activation can be detected by priming and electrophysiological techniques.


3. When consciously perceiving complex material, such as when looking for a particular letter of a particular colour:

. Perception requires attention.

. The attention has to be focused upon one item at a time, thus ...

. processing is serial.

. Some parallel processing may take place, but ...

. it is detected indirectly, such as by the influence of one word upon another.



4. We have seen that attentive processes will ‘work hard’ to unite information into a coherent whole.
. Even spatially separate visual and auditory stimuli can be joined if they appear to be synchronous (the ventriloquism effect).
. When stimuli are not synchronous the system attempts to order the segments of the stimuli independently, resulting in distraction and lost information.
. It is a ‘bottleneck’ in the ordering process that results in one stream of information interfering with the processing of another.



Attention has a role to play in dealing with competition. The early researchers believed that attention was vital, because the brain would be able to deal with only one signal at a time; a ‘winning’ signal had to be picked from among the competitors. Although we have shown that a good deal of analysis can actually take place in parallel, there are also results which suggest that more complex analysis is largely serial, thus requiring a mechanism to select from the competing stimuli. Often, the parallel processes have to be demonstrated rather obliquely, since their results do not become consciously available. Thus attention has to do with what reaches conscious
awareness. Why should this be so? Why should we not be equally aware of several items imultaneously?
Allport (1987) offered an answer that suggests yet another role for attention: it is to direct actions. Although we might, in principle, be able to perceive many things at once, there are situations where it would be counterproductive to attempt to do more than one thing. Allport gave fruit-gathering as an example. When we look at a bush of berries we need to focus attention upon one at a time, since that is how they have to be picked. If animals had not evolved this ability to select, if all the food items remained equally salient, they would starve as they hovered over them all, unable to move toward any one! From this perspective, attention is the process that saves us from trying to carry out incompatible actions simultaneously. However, everyday experience reminds us that the issue of consciousness remains relevant. For example, novice drivers experience considerable difficulty in trying simultaneously to perform all the actions needed to control a vehicle; in Allport’s view they are trying to ‘attend-for-action’ to more than one thing at a time. However, this could be restated as an attempt to be conscious of more than one thing at a time. Once the driver has become more skilful, the difficulty of combining actions disappears, but so too does the driver’s conscious awareness of performing them: they have become automatic.

One might well ask how the term ‘attention’ has come to be applied to so many roles and processes; it might have been better to use different labels to distinguish between them. To use one word with so many aspects certainly makes a unitary definition very difficult to formulate. I suspect that the single term has stuck because ultimately all these facets of attention do lead to one result: conscious awareness. Even in so-called altered states of consciousness, such as hypnosis, attention appears to be a vital component.
Attention is the process which gives rise to conscious awareness.