Read the following so that I may ask some questions regarding it:

Attention and meaning 
Two undergraduates at Oxford, Gray and Wedderburn (1960), conducted an experiment. They said if attention is low level process and select early, then the meaning should not be important. And they demonstrated that subjects were quite successful in following a message that jumped back and forth between ears. Shadow meaningful messages that were given to the subjects were: 
Left Ear: John Eleven books
Right Ear: Eight writes Twenty
Instructed to shadow the meaningful message, subjects reported: John writes books. Thus, subjects are capable of shadowing a message on the basis of meaning rather than physical ear. 
Implications
In this experiment subjects switched some information and select meaningful words whether they were presented in left ear or right ear. So this experiment proved attention can use meaning that is a higher level process. Attention is probably not an early selector but a late selector. 
Triesman's experiment
Treisman (1960) conducted an experiment to know are the attention is early selector or late selector. In this experiment subjects are asked to shadow message in Left ear. The messages are: •In Left area: I was going there when/ China, smoke, lovely, chirping •In Right Ear: books, chairs, tables, elephant/ I saw a bright flash Many subjects switched ears to follow the meaningful message.
Attention models
1. Treisman's Model Trisemen gave early selection model according to his experiment. In this model at bottom there are shadow message that is to which attending and other message is other input. She said there is not filter there is attenuator. Attenuator weakened unattended signals. After attenuator information is processed in mental dictionary where some things are very important than other. Like our name is important rather than table or fire. This model explains selection on the basis of meaningful information. This all is showing in this figure.. 
2. Broadbent's experiment
He was working on how skill created. And information processing his model shows senses take information within their limited capacity. Then this information goes in short-term store. Short term store is limit less because all the information is retained that receives by senses but only for a very brief period. This short term store is sensory store. Then the selective filter tune out extra information and pass selected information. Then limited capacity channel pass the important information to other channels. One is going back toward short term store that is feedback loop. Limited-capacity channel pass information to the store of conditional probabilities of past events. This also moves again towards selective filter. Then information is going to system for varying output until some input is secured channel. And then depending on what is happening we move towards effectors. It means our physical response towards attention. The most important thing in Broadbent's model is selective filter is soon after short term store. This models does not select on the basis of meanings.
3. Norman's Model Another model is given by Norman. This model is not very popular. Norman tried to explain attention is late selector. He said we get all information that store in short term memory than in long term memory. In long term memory we check its relevance when relevance is done we select information and then pay attention. This is opposite model. 
There are two most important models: 1. Early selection model 2. Late selection model Early selection model also are of two types one uses filter that is given by Broadbent and other model uses attenuator that is given by Triesman. Filter model means filter some things are pass and some are stopped. Attenuator means some information is weakened and some strengthens. In Mental dictionary some things are very important for us. These things are strengthens bye attenuator. 

Capacity Models
Psychologists have become more interested in capacity Demands of different tasks (Kahneman, 1973). Like there is information coming in and then goes to filter and only relevant information is selected. Different tasks different demands attention diverted to one task to other task. Tasks require mental effort. People may have some control over where the bottleneck occurs (Johnston & Heinz, 1978)
Kahneman's Capacity Model
Attention and Effort" was a major work of kahneman (Kahneman, 1973). He shifted the focus from bottleneck to capacity. There is flexibility in attention, like we can change our attention from one thing to other thing. There is a lot of evidence that our bottle neck is actually adjustable and it can be move early to late. A general limit on a person's capacity to perform mental work. A person has considerable control over how this capacity is allocated.
Daniel Kahneman
He has been doing his work at Princeton University. He has been a pioneer of cognitive psychology not only in the area of attention but on other areas.
Kahneman's Capacity Model
In this model there are many miscellaneous determinants that impact sensory system. Something happens that trigger arousal. Arousal means some activity starts. Arousal has many manifestations. Available capacity of attention will be allocated depending on the state of arousals. So there is allocation policy. Then there are some possible activities. Like the amount of attention is paid on a task. At the same time there is a feedback loop. We evaluate how much attention is needed for the task. Then we readjust more capacity to that task. The factors that have impact on allocation policy are: Arousal A physiological state that influences the distribution of mental capacity in the various tasks. 
Enduring Disposition
An automatic influence where people direct their attention.
Monetary Intentions
A conscious decision to allocate attention to certain tasks or aspects of the environment. Example: World Trade Centre Boeing 707 flying in cloudy weather, at an altitude 200 feet below the top of the WTC was reported by the airport controller. Alarm buzzed in the airport control tower to signal the danger. The controller radioed the crew to turn around and climb up to 3000 feet. The controller was monitoring seven other planes at the time. His attention was diverted to other planes so he could not pay attention to that plane. So alarm diverted his attention toward that plane.
Bottleneck vs. Capacity Both models predict that simultaneous activities are likely to interfere with each other. They attribute the interference to different causes.
Bottleneck: According to this model same mechanism required to perform 2 incompatible tasks. It is specific. It says same mechanism id needed to those tasks.
Capacity: Demands of 2 activities exceed available capacity then there is problem. It is non- specific to the task. Total demands of the task, is an important variable. Both kinds of interference occur (specific and capacity, early selection and late selection.) Both kinds of theories are necessary. 
Capacity & Stage of Selection
All experiments are showing flexibility of attention. It means we can divert our attention from one task to other task. These are also showing an interaction between bottleneck &capacity theories (Johnston & Heinz, 1978). Listener has control over the location of the bottleneck. The location can vary from early mode of selection (before recognition) to late mode of selection (after semantic analysis means meaning analysis). There is a need to combine capacity model and stage of selection. 
Multimode Theory