Serial bottleneck
- The point in the path from perception to action at which people cannot process all the information in parallel (and information is lost)
- When you have to make sense of experiences (interpretation)
How much earlier bottlenecks occur?
- Early-selection theories
- Late-selection theories
- -Auditory attention
- -Visual attention
Early-selection Theories
The filter theory (Broadbent, 1958)
Dichotic listening task
-A task in which subjects are presented with two messages over headphones, one to each ear, and are instructed to shadow one
Filter theory
- Sensory information comes through the system
- Some bottleneck is reached
- Person chooses which message to process on the basis of some physical characteristic
- Person filters out the other information
- -We attend based on physical characteristics ( such as the speaker’s voice)
- Cocktail party effect: being able to focus one’s attention on a particular stimulus while filtering out a range of other stimuli
- -But we attend based on semantic content too (if someone in another conversation says your name)
The Attenuation Theory (Tresiman 1964)\
Treisman 1960 experiment:
- Based on cocktail party effect & how we attend based on semantic content too
- Participants were instructed to shadow a -particular ear
- Participants can shadow a message on the basis of meaning rather than on the basis of what each ear physically hears
Attenuation Theory
- A modification of the Broadbent model
- Certain messages could be weakened but not filtered out entirely on the basis of their physical properties
- Some relevant (meaningful) information passes through the attentional filter
Late-selection Theories
Deutch & Deutch 1963:
- Assumes that the filter occurs after the perceptual stimulus has undergone analysis for verbal content (meaningful analysis)
- Hypothesis: the capacity limitation in in the response system, not the perceptual
- We can perceive multiple messages but that they can shadow only one message at a time
SERIAL BOTTLENECK
Early vs Late- selection theories
There is neural evidence for a version of the attenuation theory that asserts that there is both enhancement of the signal coming from the attended ear & attenuation of the signal coming from the unattended ear
Visual attention: spotlight metaphor
Serial bottleneck in auditory perception
-Dichotic listening task
The spotlight metaphor
Neisser & Becklen (1975)
-Visual analog of the auditory shadowing task
Becklen & Cervone (1983)
-The focus of attention is analogous to the bean of spotlight: the moveable spotlight is directed at one location & everything within its bean is attended & processed, while info outside the beam is unattended
Visual attention
We must focus attention on a stimulus before we can synthesize its features into a pattern
blindness
Inattentional blindness
-Failure to notice a fully-visible, but unexpected object because attention was engaged on another task, event or object
Change blindness
-When a change in a visual stimulus goes unnoticed by the observer
Motion induced blindness
-We ignore what seems irrelevant based on motion
Evidence of the no ability to overlap tasks
Byrne & Anderson, 2001
-Participants in this experiment saw a string of three digits, such as 3,4,7. There were two tasks they might be asked to do:
- -Task 1: Judge if the first digits add up to the third & press a key with the right index finger if they do & another key with the left index finger if they do not
- -Task 2: Report verbally the product of the first and third numbers. In this case the answer is 21 since 3*7=21
- Single task: asked participants to solve one task, the the other
- Dual task: asked participants to solve both tasks simultaneously
Evidence of the ability to overlap tasks
Schumacher et al (2001): perfect time-sharing
Participants simultaneously saw a single letter on a screen (left center or right position) & heard a tone. As in the first experiment, they had to perform two tasks
- -Task 1: Press a left, middle, or right key according to whether the letter occurred on the left, middle or right .
- -Task 2: Report one, two or three according to whether the tone was low, middle, or high in frequency
- Single task: asked participants to solve one task, the the other
- Dual task: asked participants to solve both tasks simultaneously
There are many differences between these tasks:
- Complexity of tasks
- Practice
- Different sensory modality
Explanation based on the central bottleneck
Although all these streams can go on in parallel, within each stream only one thing can happen at a time
Automaticity
-Performance of a skill that has been practiced repeatedly that eventually is executed with little or no direct attention.
- -Occurs when practice eliminates most of the need for central cognition
- -The general effect of practice is to reduce the central cognitive component of information processing
- -Automaticity is a matter of degree
Stroop effect
The task requires participants to say the ink color in which words are printed
-Comparing: word reading and color naming
