Attention

• The state of attention is the difference between attended and unattended processing. Attention facilitates perception and any further processing (e.g memory) for relevant stimuli
• There are two types of attention: involuntary - driven by information in the environment. voluntary - driven by internal factors
• Selective attention: in visual processing, we are often unable to process all the information present in a visual scene, even if we wanted to. selective attention is the process by which relevant information is selected for further processing, and irrelevant information is discarded. It is often investigated by measuring the influence of ignored information on performance. If the nature of the irrelevant information affects performance, then it follows that the irrelevant information wasn't fully ignored. e.g stroop effect where coloured words are written as an incorrect colour - i.e "yellow" is written in red ink - the participant must name the ink colour. The irrelevant information which is the written word is not completely ignored, and affects performance - the participant will want to say the written word.
• Cocktail party effect (Cherry 1953): the phenomenon of being able to focus auditory attention on a particular stimulus while filtering out a range of other stimuli (like in the same way a partygoer focuses on a single conversation whilst filtering out other noise around them).

The Flanker task is a set of response inhibition tests used to assess the ability to suppress responses that are inappropriate in a particular context. The target is flanked by non-target stimuli which correspond either to the same directional response as the target (congruent flankers), to the opposite response (incongruent flankers) or to neither (neutral flankers). A directional response is assigned to a central target stimulus.

When subjects participate in the Flanker task, the anterior cingulate cortex, or ACC, is activated. The ACC is a frontal brain structure responsible for a wide variety of autonomic functions. It's observed to be more active in response to processing incongruent stimuli than congruent stimuli.

Various forms of the task are used to measure information processing and selective attention.

Broadbent (1958) argued that information from all of the stimuli presented at any given time first enters a sensory buffer. One of the inputs is then selected on the basis of its physical characteristics for further processing by being allowed to pass through a filter. Because we only have a limited capacity to process information, this filter is designed to prevent the information-processing system from being overloaded.
The inputs not initially selected by the filter remain briefly in the sensory buffer, and if they are not attended to and processed, they decay rapidly. Broadbent assumed that the filter rejected the non-shadowed or unattended message at an early stage of processing.
Broadbent wanted to see how people could selectively attend like this, so he conducted studies where he deliberately overloaded them with stimuli. He did this through dichotic listening tasks; participants were simultaneously sent one message to their right ear and a different message to their left ear. They were asked to listen to both messages at the same time and repeat what they heard. Broadbent found that people made fewer mistakes when reporting back what was heard in one ear, followed by the other ear. Broadbent thus concluded that we can pay attention to only one channel at a time.
So, you can only pay attention to the message in one ear at a time, the message in the other ear is lost, though you may be able to repeat back a few items from the unattended ear.

Broadbent thought that the filter, which selects one channel for attention, does this only on the basis of physical characteristics of the information coming in, e.g which ear the information was coming to, or the type of voice.

According to Broadbent, the meaning of any of the message is not taken into account at all by the filter. All semantic processing is carried out after the filter has selected the channel to pay attention to.

Selective attention requires that stimuli are filtered so that attention is directed. Broadbent's model suggests that the selection of material to attend to (i.e filtering) is made early, before semantic analyis.
Triesman's (1964) model retains this early filter which works on physical features of the message only. The crucial difference is that Treisman's filter attenuates rather than eliminates the unattended material. Attenuation is like turning down the volume so that if you have 4 sources of sound in one room, you can turn down or attentuate 3 in order to attend to the fourth.
The result is almost the same as turning them off, the unattended material appears lost. But, if a non-attended channel includes your name for example, there is a chance you will hear it because the material is still there.
Treisman agreed with Broadbent that there was a bottleneck, but disagreed with the location. Treisman carried out experiments using the speech shadowing method, where participants were asked to simultaneously repeat aloud speech played into one ear whilst another message is spoken to the other ear. In one shadowing experiment, identical messages were presented to 2 ears but with a slight delay between them. If this delay was too long, participants didn't notice that the same material was played to both ears.

When the unattended message was ahead of the shadowed message by up to 2 seconds, participants noticed the similarity. If it's assumed the unattended material is held in a temporary buffer store, then these results would indicate that the duration of material held in the sensory buffer store is about 2 seconds.
In an experiment with bilingual participants, Treisman presented the attended message in English and the unattended message in a French translation. When the French version lagged only slightly behind the English version, participants could report that both messages had the same meaning. 
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, couldn't explain these findings. The evidence suggests Broadbent's filter model isn't adequate.
It will often happen that there is insufficient processing capacity to permit a full analyis of unattended stimuli. In that case, later analyses will be omitted. This theory predicts that it will usually be the physical characteristics of unattended inputs which are remembered, rather than their meaning
To be analysed, items have to reach a certain threshold of intensity. All the attended/selected material will reach this threshold, but only some of the attenuated items.

The early selection model of attention was proposed by Broadbent. It posits that stimuli are filtered, or selected to be attended to, at an early stage during processing.
A filter can be regarded as the selector of relevant information based on basic features such as colour, pitch, or direction of stimuli.
After stimuli are presented, the information is temporarily held in a preattentive store. Information with similar characteristics pass through the filter and is attended so it can be processed for meaning; irrelevant attention is filtered out. The basic idea is that perception of the stimulus is not required prior to selecting its relevance
Broadbent showed evidence of early selection using a split-span technique. Participants were presented with a different list of digits in each ear. When asked to report the digits they heard, participants tended to report ear by ear (the numbers from one ear followed by the numbers from the next) regardless of the order in which the digits were presented. When asked to report the digits they heard in the order they were presented, accuracy dropped. This study suggested that information is filtered according to basic characteristics of the stimuli (e.g the ear in which it was presented). Participants first reported the information from one ear and then switched filters in order to report the digits presented to the 2nd ear. Therefore, when required to report the digits in the order they were presented, participants had to continuously switch filters, which impacted accuracy

Late selection models argue that information is selected after it has been processed for meaning, as opposed to during the earlier stages of processing. According to these models, all information is attended to, whether intentionally or unintentionally. Information inputs are processed equivalently, until semantic encoding and analyis can be performed. The filter merely acts as an information attentuator; it intensifies the pertinent information and attenuates the intensity of the stimuli deemed to be unimportant.

Gray and Wedderburn showed evidence of late selection using a split-span technique similar to Broadbent. Participants heard a mixture of numbers and words presented to each ear (e.g "Dear - 7 - Jane" and "9 - Aunt - 6"), and were asked to report back what they heard. According to the early selection model, participants should have reported all items presented to one ear first, and then the items presented to the other ear second. However, participants reported hearing "Dear, Aunt, Jane" and "9, 7, 6" - suggesting that stimuli aren't selected based on physical characteristics, but by meaning, as participants grouped words and then numbers into 2 groups, processing them for meaning.

Perceptual load theory stipulates that both early and late selection occur, depending on the processing demans of the task. It states that perception has limited cepacity, but operates in an automated, involuntary manner. If information doesn't exceed the brain's processing capacity, it will be perceived.

In tasks involving a large amount of information, in other words high perceptual load, capacity is fully exhausted by the processing of the task-relevant stimuli. This results in no perception of task-irrelevant information (early selection). In contrast, in tasks of low perceptual load, not all processing capacity is used up by the task. This results in the spare processing capacity that can then be used in the perception of task-irrelvant information (late selection).

In summary, the theory resolves the early and late selection attention debate by explaining that tasks of low perceptual load result in late selection, whereas tasks of high perceptual load result in early selection attention effects.

Visual spatial attention is a form of visual attention that involves directing attention to a location in space

Spatial attention allows us to selectively process visual information through prioritisation of an area within the visual field. A region of space within the visual field is selected for attention and the information within this region then receives further processing. Research shows that when spatial attention is evoked, an observer is typically faster and more accurate at detecting a target that appears in an expected location compared to an unexpected location

Posner: cueing the location of a next target allows attention to shift there earlier

Posner & Peterson (1990): 3 components of spatial attention: Disengagement of attention from a given visual stimulus. Shifting of attention from one target stimulus to another. Engaging or locking attention on a new visual stimulus.

Visual attention can operate at the level of spatial locations as well as objects