CAPACITY AND ITS CONSEQUENCES FOR PROCESSING INFORMATION
Selectivity: we choose from many inputs which to attend to--if there are
too many things to attend to something suffers.
Mental Effort or "Concentration": energy or effort expended in processing
1. General arousal
2. Automatic vs Deliberate processing
3. Single vs Multiple Resource Theory: two tasks may
tap same or different resource pools.
There are two major categories of theories:
filter or bottleneck theories, and capacity theories.
for Early Filter Models
Placement of an attention filter--need
to select which incoming stimuli are attended to and which are ignored.
Early Selection Theory: Selective filter
prior to abstract STM (prior to Central Processing Unit, CPU) e.g., Broadbent,
1957; Triesman, 1960. Target stimuli are processed more fully because there
is perceptual suppression of nontarget stimuli.
Multiple inputs are registered and
held briefly but only one message is analyzed perceptually--perceptual
analysis requires attention, which is limited to one input at a time.
ATTENTION IS A BOTTLENECK (the point
at which information overload is reached) THAT LIMITS PERCEPTION.
Broadbent (1957): subjects attend to
only one ear--they perform well, but remember little about what they heard
in the other ear.
Selective filter occurs prior to abstract
STM. Subjects can tell sensory characteristics from the unattended ear:
male/female voice; music/ noise/speech--no semantic processing
A second example is the split span
experiment: (why not use 7?)
Numbers are presented simultaneously
to both ears, rapidly. Subjects can attend well to one ear at a time and
must hold the information from the other ear in a buffer memory.
If subjects are asked to recall the
digits ear by ear they will do well, but if asked to recall the digits
by pairs they do poorly.
This is the ‘funnel’ model in which
movement of a flap (1) uses energy; and (2) takes time--so with pair by
pair retrieval the buffer decays because the flap moves more times than
with ear by ear retrieval.
Thus, the amount of information that
can be attended to at any given time is limited. If information exceeds
capacity it is filtered out; only that which gets past the filter can be
analyzed for meaning.
Broadbent's theory of strict serial
processing explains apparent parallel processing (watching TV and eating
popcorn at the same time) as time-sharing or multiplexing--two
or more tasks are done by simply switching attention back and forth between
VS CONTROLLED (DELIBERATE) PROCESSING
Norman, 1969: Interrupted subjects
periodically during a shadowing task.
Found subjects were able to recall
the last 1-2 words from the unattended ear.
Therefore all the information was processed
to some extent--
Filter had to occur after abstract
Gray & Wedderburn (1960) found
that if you give the following:
Thus, it seems that messages from both
ears get into sensory memory, and subjects choose certain features, including
semantic, for selecting what to attend to in sensory memory.
This suggests the information in the
unattended ear is processed somewhere and leads to:
Late Selection Theory: selective filter
after abstract STM; e.g., Deutsch & Deutsch, 1963; Norman, 1969.
The differential processing accorded
to target and nontarget stimuli is thought to be nonperceptual in nature.
According to this model all perceptual
information enters the system, but only that which is selected by
the special attention mechanism reaches higher processing
The basic difference between early
and late selection theories lies in their view of the processing stage
at which unimportant aspects of information or stimuli are screened out.
Early-selection theories propose that
certain stimuli are never processed due to perceptual suppression of nontarget
Late-selection theories propose that
the unimportant information enters the system but simply is not chosen
for further processing.
Triesman, 1969: suggested the filter
can occur at several places.
It is selective across a whole continuum
of input characteristics, and its tuning at any moment is determined by
the character of the information that has most recently entered consciousness.
The filter never completely blocks
any incoming stimulation; it simply attenuates (lessens in intensity) it,
making is more or less perceptible.
Capacity Allocation Theories - There is thought to be a pool of resources
which can be brought to bear and a central allocation mechanism which dumps
resources in one direction.
The more complex the stimuli, the more
complicated the processing and, therefore, more resources are required.
Example: walking and talking: if you
become interested in the conversation walking slows.
1.) Single-Resource Theory - one large single pool
of processing capacity (i.e. Kahneman, 1973).
2.) Multiple-Resource Theory - different pools
for different tasks (e.g., Navon & Gopher, 1979)--i.e., hemispheres
& dual tasks.
Kahneman’s model: suggested real world tasks require concurrent operation
of perceptual and cognitive processes.
Core Assumption: mental processes compete
for a single, limited pool of resources, or capacity.
He assumes there is also an allocation
policy which is affected by enduring dispositions
(individual differences in selection), momentary
intentions (temporally-tied selection), and evaluation
of demands on capacity (subjective decision) and this is all modulated
Multimode Theory: Johnston & Heinz (1978)
Suggested both filter and capacity
models may contribute to actual attention processes.
We adapt to mode of attention best
suited to current task demands.
Paradigm: dual task methodology with
Group One: shadow one ear based on
pitch of voice (male/female)--early filter task.
Group Two: shadow words based on category
membership--late filter task.
Concurrently press a button whenever
a light comes on.
Shadowing based on pitch takes less
effort and dual task will show relatively fast RTs.
Shadowing based on semantic process
takes more effort and dual task will show relatively slower RTs.
Attention requires capacity.
Capacity requirements increase from
early to late filter placement.
effects for automatic and effortful processing
Schneider & Shiffrin, 1977 investigated the ways which subjects scan
a visual display.
Two conditions: same-category,
wherein letters were scanned for on a field of letters, and different-category,
wherein a number was scanned for on a field of letters.
The same category condition was more
difficult for subjects--they required more time and made more errors.
S & S argued that before coming
into the lab subjects were well practiced at detecting a number among letters
so that this process was automatic.
In contrast, when subjects had to identify
a letter among letters deliberate processing was needed. Subjects had to
attend to each letter in each frame.
In the different category condition
all items could be checked simultaneously because the detection process
In a second experiment they used the
same pool of letters as targets (e.g., b, c, d, f, g, h, j, k, l) and the
same pool of letters as distractors (q, r, s, t, v, w, x, y, z).
With practice subjects were able to
learn to learn this discrimination to the point where their performance
became automatic. Attention no longer needed to be devoted to scanning
each individual letter sequentially.
Similarly, LaBerge & Samuels (1974)
taught subjects to discriminate real letters and artificial letters. Across
time, subjects were able to discriminate mirror-image from identical letters.
Posner & Snyder (1975) concluded that automatic processes:
Occur without intention.
Require little attention.
Complete themselves without conscious
Lower level processes are more likely
to become automatic than are later, more cognitive processes.
Do not interfere with one another.
Hasher & Zacks (1979, 1984) provided evidence we automatically encode
In a series of studies across several
age groups they showed that information for frequency of occurrence of
an event, for its spatial features, and for temporal information is all
automatically encoded along with the target information.
Intentional versus incidental learning:
Effect of instructions and practice:
Both improve performance
Depression or high arousal:
Decreased performance in young children or elderly
SPECIFIC APPROACH: PRACTICAL APPLICATION
Current models of attention fail to
adequately address the clinical phenomena of attention deficits, or their
The process specific approach views
attention as the capacity to focus on particular stimuli over time and
to flexibly manipulate the information.
Attention is conceptualized as a multi-dimensional
cognitive capacity fundamental to information processing.
Deficits in memory and learning are
often a consequence of impaired attentional processing.
Within this model there are four levels
or components of attention. These are:
Sustained Attention - Vigilance
The ability to maintain a consistent
behavioral response during continuous or repetitive activity.
The ability to simultaneously respond
to multiple tasks.
Selective Attention - Focused
Ability to maintain a cognitive set--requires
activation and inhibition of responses dependent upon discrimination of
stimuli--includes the ability to screen out extraneous visual or auditory
Alternating Attention - Switching
The capacity for mental flexibility
which allows for moving between tasks having different cognitive requirements.