Psychology
Chapter 9
Memory and attention

Overview: an information-processing model of the mind

Information-processing theories are built on a set of assumptions concerning how humans acquire, store and retrieve information.
Key assumptions:

• An individual has limited mental resources in processing information.
• Information moves through a system of stores. Information this brought into the mind by way of the sensory systems, and then it can be manipulated in various ways, placed into long-term storage, and retrieved when needed to solve a problem.

The model we use to portray the mind as containing three types of memory stores.

• Sensory memory
• Short-term (or working) memory
• Long-term memory

Each store is characterized by its function, its capacity and its duration.
In addition to the stores, the model specifies a set of control processes.

• Attention
• Rehearsal
• Encoding
• Retrieval

Those govern the processing of information within stores and the movement of information from one store to another.

Sensory memory: the brief prolongation of sensory experience

This trace is called sensory memory.
A separate sensory-memory store is believed to exist for each sensory system (like vision, hearing, touch, smell and taste), but only those for vision and hearing have been studied extensively.
Each sensory store is presumed to hold, very briefly, all the sensory input that enters that sensory system, whether or not the person is paying attention to that input.
The function of the store, presumably, is to hold on to sensory information, in its original sensory form, long enough for it to be analyzed by unconscious mental processes and for a decision to be made about whether or not to bring that information into the short-term store.
Most of the information in our sensory store does not enter into our consciousness.
We become conscious only of those items that are transformed, by the selective process of attention, into working memory.

The short-term store: conscious perception and thought

Information in the sensory store that is attended to moves into the short-term store.
Each item fades quickly and is lost within seconds when it is no longer actively attended to or thought about.
This is conceived of as the major workplace of the mind (working memory).
Working memory has been used to refer to the process of storing and transforming information being held in the short-term store. It is the seat of conscious thought.

Information can enter the short-term store form both the sensory-memory store and the long-term-memory store.

Both the sensory store and long-term store contribute to the continuous flow of conscious thought that constitutes the content of the short-term store.
The momentary capacity of the short-term memory is very small. Only a few items of information can be perceived or thought about at once.

Long-term memory: The mind’s library of information

Once an item has passed from sensory memory into the short-term store, it may or may not then be encoded into long-term memory.
Long-term memory is the stored representation of all that a person knows.
We are not conscious of the items of information in our long-term store except when they have been activated and moved into the short-term store.

Long-term memory is passive and short-term memory is active.
Long-term memory has essentially unlimited capacity and a long duration (some a lifetime)

Control processes: the mind’s information transportation systems

The movements of information from one store to another is regulated by the control processes of:

• Attention
  The process that controls the flow of information from the sensory store into the short-term store. Because the capacity of sensory memory is large and that of the short-term store is small, attention must restrict the flow of information form the first into the second.
• Encoding
  Controls movements from the short-term store into the long-term store.
  Mostly it occurs not deliberate, but as a side effect of the special interest that you devote to certain items of information.
• Retrieval
  Controls the flow of information from the long-term store to the short-term store. Remembering or recalling.
  It can be deliberate or automatic.

Any control process can be viewed as requiring a certain proportion of the system’s limited capacity for its execution. One way of thinking about this is to ask how much mental energy any particular process takes. Research has shown that glucose consumption in brain areas associated with cognitive processing is greater when executing more difficult tasks relative to those that are easier.

Individual mental operations can be placed on a continuum with respect to how much of one’s limited capacity each requires for its execution.

• Effortful processes
  Require the use of mental resources for their successful completion.
• Automatic processes
  Require little or none of the short-term store’s limited capacity.

In addition to not requiring any mental effort, truly automatic processes are hypothesized to:

• Occur without intention and without conscious awareness
• Not to interfere with the execution of other processes
• Not to improve with practice
• Not to be influenced by individual differences in intelligence, motivation and education.

Effortful processes are hypothesized to:

• Be available to consciousness
• Interfere with the execution of other effortful processes
• Improve with practice
• Be influenced by individual differences in intelligence, motivation and education.

Some operations are at first very effortful and require your full attention, but with practice are done effortlessly.
Everyday cognition involves a constant combination of automatic and effortful processes.

Attention: the portal to consciousness

Natural selection endowed us with mechanisms of attention that can meet two competing needs.

• To focus mental resources on the task at hand and not to be distracted by irrelevant stimuli.
• To monitor stimuli that are irrelevant to the task at hand and to shift attention immediately to anything that signals some danger or benefit that outweighs that task.

All information that is picked up by the senses enters briefly into sensory memory and is analyzed to determine its relevance to the ongoing task and its potential significance for the person’s survival or well-being. That analysis occurs at an unconscious level and is referred to as prattentive processing.
Such processing must involve some comparison of the sensory input to information already stored in short-term or long-term memory.
The portions of the brain that are involved in preattentive processing must somehow operate on the attention gate to help determine what items of information will be allowed to pass into the limited-capacity, conscious, short-term compartment at any given moment.

The ability to focus attention and ignore the irrelevant

Selective listening

Selective viewing

Inattentional blindness

The ability to shift attention to significant stimuli

There are limits to inattentional blindness.
We can shift attention. We are good at screening out irrelevant stimuli when we need to focus intently on a task, but we are also good at shifting our attention to stimuli that signal danger or benefit or are otherwise significant to us.

Our ability to shift attention appears to depend, in part, on our capacity to listen or look backwards in time and ‘hear’ or ‘see’ stimuli that where recorded a moment earlier in sensory memory.
A major function of sensory memory is to hold on to fleeting, unattended stimuli long enough to allow us to turn our attention to them and bring them into consciousness if they prove to be significant.

Shifting attention to meaningful information in auditory sensory memory

Auditory sensory memory is also called echoic memory.
The brief memory trace for a specific sound is called an echo. The echo fades over a seconds and vanishes within at most 10 seconds.

Shifting attention to meaningful information in visual sensory memory

Visual sensory memory is also called iconic memory.
Icon: the brief memory trace for a specific visual stimulus.
When images containing rows of letters were flashed for one twentieth of a second, people could read the letters, as if they were still physically present.
Memory store must hold visually presented information, in essentially its original form, for about a third of a second beyond
the termination of the physical stimulus.
People who are attending to one set of visual stimuli and successfully ignoring the other set will tend to notice stimuli in the ignored set that have special meaning to them.

Effect of practice on attentional capacity

Only a few items of information cross through the gate between sensory memory and the short-term memory at any given instant.

Training can enhance attentional capacity. (Multitasking generally does not result in getting more things accomplished efficiently, but rather actually impairs performance).

Unconscious, automatic processing of stimulus input

There are unconscious effects of sensory input.
Sensory input can alter behavior and conscious thought without itself becoming conscious to the person.
One means by with it can do this is called priming.

Unconscious priming of mental concepts

Priming: the activation, by sensory input, of information that is already stored in long-term memory.
The activated information then becomes more available to the person, altering the person’s perception or chain of thought.
The activation is not experienced consciously, yet it influences consciousness.
Such activation can occur even when the priming stimulus is not consciously perceived.

In everyday life, priming provides a means by which contextual information that we are not attending to can help us make sense of information that we are attending to.
Priming also helps us retrieve memories from our long-term store at times when those memories are most useful.

Automatic, obligatory processing of stimuli

An adaptive characteristic of the mind is its capacity to perform routine tasks automatically, which frees its limited, effortful, conscious working memory for more creative purposes or dealing with emergencies.
This depends at least partly on the mind’s ability to process relevant stimuli preattentively (unconsciously) and to use the results of that processing to guide behavior.

The stroop interference effect.
Green written in red (for example).
This effect depends on people’s inability to prevent themselves from reading the color words.
The preattentive processes that involved in reading are so automatic that we cannot consciously stop them from occurring when we are looking at a word. We find it impossible not to read a color name that we are looking at, and that interferes with our ability to think of and say quickly the ink color name then the two are different.

Brain mechanisms of preattentive processing and attention

Three general conclusions:

1. Stimuli that are not attended to nevertheless activate sensory and perceptual areas of the brain.
   The unconscious preattentive analysis of stimuli for meaning involves many of the same brain mechanisms that are involved in the analysis of consciously perceived stimuli.
2. Attention magnifies the activity that task-relevant stimuli produce in sensory and perceptual areas of the brain, and it diminishes the activity that task-irrelevant stimuli produce.
   Attention, at the neural level, seems to be a process that temporarily sensitizes the relevant neurons in sensory and perceptual areas of the brain, increasing their responsiveness to the stimuli that they are designed to analyze, while having the opposite effect on neurons whose responses are irrelevant to the task.
3. Neural mechanisms in anterior (forward) portions of the cortex are responsible for control of attention.
   Areas in the frontal lobe and in anterior portions of the temporal and parietal lobe become active at moments when shifts in attention occur.
   The prefrontal cortex is especially active during tasks, such as the Stroop task, that require intense concentration on relevant stimuli and screening out of irrelevant stimuli.
   These anterior regions control attention by acting top-down on sensory and perceptual areas farther back in the cerebral cortex.

Spatial neglect: individuals being unable to ‘see’ things in the contralateral visual field (the side opposite the brain injury).

Working memory: The active conscious mind

The working memory is the part of the mind that thinks, makes decisions and controls such processes as attention and retrieval of information.
It is the center of conscious perception and thought.
Refers to the process of storing and transforming information being held by the short-term store.

Working memory is divided into a number of separate but interacting components

• Phonological loop
  Holding verbal information
• Visuospatioal sketchpad
  Holding visual and spatial information
• Central executive
  Coordinating the mind’s activities and bringing new information into the working memory from the sensory and long-term stores.

Verbal working memory: The phonological loop

Digit span: the number of digits that a person can keep in mind for a brief period and report back accurately.
Short-term memory span (or just memory span): the number of pronounceable items that a person can keep in mind and report back accurately after a brief delay.

The memory span depends on how rapidly the person can pronounce the items to be remembered.
Generally, people can keep in working memory about as much verbal material as they can state aloud in 2 seconds.
Any manipulation that interferes with a person’s ability to articulate the words to be remembered interferes with verbal short-term memory.

The working-memory span

Depending on the information one is working with, an average adult can keep between five and nine items active in consciousness.
The memory span increases over childhood and decreases in old age.

A better measure for assessing cognitive abilities is to examine how many items a person can keep in mind while performing some ‘work’.

The working-memory span is typically about two items shorter than memory span. It also shows improvements over childhood and declines in old age.

Working-memory span tasks are more strongly associated with important higher-level abilities.

One way of demonstrating the importance of working memory task performance is to examine when someone tries multitasking.
Although both tasks can be highly developed and automatic skills, they each consume a portion of working memory, and so performing one interferes with performing the other.

Executive functions

Working memory is part of executive functions.
Relatively basic and general-purpose information-processing mechanisms that, together, are important in planning, regulating behavior and performing complex cognitive tasks.

Executive functions consist of three related components:

• Working memory or updating
  Monitoring and rapidly adding/ deleting the contents of working memory.
• Switching
  Shifting flexibly between different tasks or mind-sets
• Inhibition
  Preventing a cognitive or behavioral response, op keeping unwanted information out of mind.

Individual differences in executive functions are related to performance on other cognitive tasks such as IQ, reasoning, school grates and socioemotional phenomena.

Four general conclusions about executive functions

• Executive functions show both unity and diversity.
  Performance on the various types of executive functions all correlate with one another.
• There is a substantial genetic component to executive functions.
  It can also be altered by experience.
  Bi- and multilingual people have better executive-function abilities than monolinguals.
• Executive functions are related to and predictive of important clinical and societal outcomes.
  Executive functions are related to the ability to regulate one’s behavior and emotions, beginning in early childhood through adulthood.
• There is substantial developmental stability of executive function abilities.

Executive functions can be thought of as a set of low-level cognitive abilities that, in combination, make it possible for people to regulate their thoughts, emotions and behavior. These abilities improve with age, decline in old age and at all stages are associated with psychological functioning.

Neurological basis of executive functions

Research has found correlates of executive functions with brain function and structure, especially in the prefrontal cortex.
There is no single area of the brain that is responsible for the various components of executive functions, but the prefrontal cortex has been identified as a critical area for the control of thought and behavior. It appears to be the neural hub for executive functions.
The prefrontal cortex is the part of the brain that somehow organizes the efforts of the other portions of the brain and keeps them focused on the task. It receives information from the sensory cortex and is connected to structures in the motor system, the limbic system and the basal ganglia.

Memory as the representation of knowledge

Memory: all of the information in a person’s mind and the mind’s capacity to store and retrieve that information.

Explicit and implicit memory

Explicit memory: the type of memory that can be brought into a person’s consciousness. It provides the content of conscious thought, and it is highly flexible. It is assessed through explicit tests, what do you remember explicit about a situation? The information can be declared in words.

• Episodic memory
• Semantic memory (words, meanings, facts, general knowledge)

Implicit memory: the type of memory that cannot be verbalized. It consist of all the nonverbal and unconscious means through which previous experiences can influence a person’s actions and thoughts. The memory is not reported directly but is inferred from behavioral responses. It exert its effects automatically in the context of the specific stimuli, tasks, or problems to which they pertain.

• Classical conditioning
• Procedural memory
• Priming

Varieties of explicit memory: episodic and semantic

Explicit memory is divisible into two subclasses

• Episodic (or autobiographical memories)
  Memory of one’s own past experiences.
• Explicit memory that is not tied mentally to a particular past experience.
  Knowledge that constitute one’s general understanding of the world and knowledge of oneself that is not mentally tied to the re-experiencing of a particular episode in one’s life. The information had to have been acquired through past experiences, but your memory of the information does not depend on remembering those experiences.
  It is in the domain of temporarily and contextually unspecific pieces of information. Just knowing.

Network models of memory organization.

The mind’s storehouse of knowledge is a vast network of mental concepts linked by associations.

The spreading-activation model proposes that the activation of any one concept initiates a spread of activity to nearby concepts in the network, which primes those concepts so they become temporarily more retrievable than they were before.
The spreading activity declines with distance, so concepts that are closely linked within the active concept receive more priming than those who are more distantly linked.

Memories for concepts are stored in overlapping neural circuits in the cerebral cortex.
Some of the neurons are part of the circuit for one concept are part of the circuit for other concepts as well. The more overlap there is between the circuits for two concepts, the more closely they are associated in the person’s mind.
Priming occurs (according to those theories) because the activation of the circuit for one concept literally does activate part of the circuit for another, making that whole circuit more easily activated than it was before.

Varieties of implicit memory

Implicit memory can be divided in subclasses.

• The memories resulting from classical conditioning
• Procedural memory
  Includes motor skills, habits and unconsciously learned rules.
• Priming
  As the activation, by sensory input, of information that is already stored in long-term memory.
  This activation is not experienced consciously, yet it influences subsequent conscious perception and thought and thus provides a link between implicit and explicit memory.
  It helps us keep our stream of thought running along consistent, logical lines.
  It occurs independently of the person’s conscious memory for the priming stimulus.

Neuropsychological evidence for separate memory systems

Brain damage can destroy one kind of memory while leaving another kind intact.

A loss of long-term memory, usually resulting from some sort of physical disruption or injury to the brain, is called amnesia.
The areas of destruction most strongly correlated with it are: the hippocampus and cortical and subcortical structures closely connected with the hippocampus in both halves of the brain.
BUT: implicit memories remain intact. The implicit memory is manifested even when the subjects with amnesia cannot consciously remember anything at all about the learning experience.

The activity in the hippocampus is essential for the formation of at least some types of long-term memories.

Semantic memory without memory in some patients with amnesia

The most extreme differentiation between episodic and semantic memory is found in patients who suffer from a rare disorder called developmental amnesia.
These people have bilateral damage to the hippocampus, but not to structures surrounding it.
This is caused by temporary loss of blood flow to the brain at the time of birth or in early childhood.
This patients serve deficits of episodic memory, but develop verbal capacities in normal range. They also remember facts.

The hippocampus is essential for episodic-memory encoding, but not for semantic-memory encoding.

Patients with amnesia who lose the ability to encode new semantic as well as episodic memories, have damage to the hippocampus and to other portions of the temporal lobes.

Other evidence of semantic memory without episodic memory

In old age, the capacity to form new episodic memories generally declines more rapidly than does the capacity to form new semantic memories.
Young children also show excellent semantic memory and poor episodic memory. So the ability for episodic memory encoding develops more slowly and unravels more quickly than that for semantic-memory encoding.

Infantile amnesia: the inability to remember events from infancy and early childhood.

Most people who have recollections from infancy and early childhood can be explained as a reconstruction based on what one heard, experienced or imagined later.

Infantile amnesia reflects important changes that occur during early childhood, changes that permit autobiographical memory and that separate our species from all others.

The relatively poor episodic memory at both ends of the life span may be related to prefrontal cortical functioning.
The prefrontal cortex develops more slowly in childhood and tends to suffer more damage in old age than does the rest of the brain. People with prefrontal cortical damage typically experience a much greater loss in episodic-memory encoding than in semantic-memory encoding.

Memory as the process of remembering

Memory is also the process of encoding, storing and retrieving information.

Encoding information into long-term memory

There are two kinds of rehearsal:

• Maintenance rehearsal
  The process by which a person holds information in working memory for a period of time.
• Encoding rehearsal
  The process by which a person encodes information into the long-term store.

The activities that are effective for maintenance are not necessarily effective for encoding.
Some of the most effective activities for encoding are:

• Elaboration
• Organization
• Visualization

Elaboration promotes encoding

The immediate goal of elaboration is not to memorize, but to understand. This is perhaps the most effective of all ways to encode information into long-term memory.

Thinking about meaning promotes long-term memory.

Organization promotes encoding

Organization can improve memory by revealing or creating links among items that would otherwise be perceived as separate.

Chunking: to group adjacent items that are at first perceived as separate, thus making them a single item. It decreases the number of items to be remembered and increases the amount of information in each item.

We are much better at forming long-term memories for information that is within rather than outside our realm of expertise.

Long-term working memory:
This is a memory for the interrelated set of items that is crucial for solving the problem or completing the task at hand.
Such memories are encoded into long-term storage in a manner that makes the entire structure of information easily accessible to working memory, at least until the problem is solved or the task is finished.
Such memories are not lost as a result of interruptions so they allow the person to go back to a previous task after time spent on another task.
In order to form such a memory, a person must already have in long-term storage a great deal of well-established information about possible and likely ways that such items might be arranged.
This knowledge provides a foundation for the efficient chunking of new items of information.

The most useful format for organizing some kind of information is the hierarchy.
Related items are clustered together to form categories, related categories are clustered to form larger categories and so on.

Visualization promotes encoding

Visualization may provide a distinct visual memory trace to supplement the verbal memory trace, thereby increasing the chance that the memory will be recalled in the future.
It may also provide an efficient way to chunk several verbally presented ideas together.

Memory consolidation

Retrograde amnesia as evidence for gradual consolidation of long-term memories

Anterograde amnesia: the loss of capacity to form long-term memories of events that occur after the injury.

Retrograde amnesia: the loss of memories of events that occurred before the injury.
Generally time graded. It is the greatest for memories acquired just before the injury and least for those acquired long before.
This suggest that long-term memories are encoded in the brain in at least two forms:

• A labile, easily disrupted form
• A stable, not easily disrupted form.

Then, gradually over time, they are either re-encoded in the stable form or lost.

Consolidation: the process in which the labile memory form is converted into the stable form.

A prominent theory is that:
The labile form of long-term memory involves neural connections in the hippocampus and that the stable form involves neural connections in various parts of the cerebral cortex, without dependence on the hippocampus.
When people recall memories that were acquired relatively recently, neural activity in the hippocampus increases. But when they recall memories that were first acquired many years earlier, increased activity occurs in parts of the cerebral cortex and not in the hippocampus.

Role of retrieval in memory consolidation and modification

Nobody knows just how memory consolidation occurs, though it apparently involves modification of existing synaptic connections and growth of new synaptic connections in the brain.

There is evidence that memories that are recalled and used repeatedly, over relatively long time periods, are the ones most likely to be consolidated into a form that resist disruptions.

Every time a memory is recalled and put to use, the neural trace for that memory enters temporarily into a new labile stage, a stage when it ca be modified. Depending on what happens when the memory is recalled, the memory may be strengthened, weakened, or changed by the addition of some new content to it.

The role of sleep in memory consolidation

Sleep, shortly after learning, helps to consolidate newly acquired memories, making them more easily retrievable and less susceptible to disruption than they were before sleep.
A similar period of wakefulness does not have this effect.
It does not matter what time of the day the sleep occurs, as long as it occurs within a few hours after the learning experience.

For paired-associate tasks and other tasks involving conscious recall, the type of sleep that seems most valuable is slow-wave, non-REM sleep.
The hippocampus becomes activated at various times during slow-wave sleep.
The hippocampus activity represents activation of the memory trace, which allows consolidation of the memory into a new, more stable form.

Sleep may also improve, next to the durability, the quality of new memories, in a manner that helps to achieve new insights.

Retrieving information form long-term memory

The long-term-memory store of your brain contains vast quantities of information, which is useful only to the degree that we can call information forth at the moment we need it.

In the human mind, long-term memories are stored in networks in which each item is linked to many others through associations.

A stimulus or thought that primes a particular memory is a retrieval cue.

Mental associations as foundations for retrieval

Association by contiguity
Some concepts are associated because they have occurred together in the person’s previous experience.

Association by similarity
Items that share one or more properties in common are linked in memory whether or not they were ever experienced together.

Why elaborative rehearsal creates easily retrievable memories

The more mental associations you create in learning a new item of information, the more ways will be available for you to retrieve it later.

Contextual stimuli as retrieval cues

The environmental context that we find ourselves in at any given moment provides retrieval cues that prime our memories for our past experiences in that context.

Memory construction as a source of distortion

Remembering is an active, inferential process guided by a person’s general knowledge and intuitions about the world and by cues in the present environment.
A memory is a construction built and rebuilt form various sources. This ability is adaptive because it allows us to make logical and useful sense of our incompletely encoded experiences. But the process can also lead to distortions.

Effects of pre-existing beliefs: fitting memories to schemas and scripts

Schema: one’s generalized mental representation, or concept of any given class of objects, scenes or events.
Especially in relation to concepts that may vary from culture to culture and that involve spatial or temporal relationships among the individual units of the object, scene or event. (Like a schema of a living room).

Scripts: schemas that involve the organization of events in time (rather than of objects in space).

Schema and scripts affect the way we remember things.
We fill gaps in our memory for specific scenes and events with information drawn from our more general schema and scripts.

False eyewitness memories: effects of suggestion

Memory construction is affected not just by pre-existing schemas, but also by events that occur after the event being remembered was encoded.

Hypnosis is a state of high suggestibility, false memories can be created relatively easily through suggestions or encouragement made in that state. His can also happen without hypnosis.
Leading questions for example.

False memories of childhood experiences: effects of suggestion and imagination

False-memory construction can be abetted by imagination.
Imagery alone, even without misleading suggestions, can create false memories.

Source confusion and social pressure as causes of false-memory construction

The basic cause of most false-memory construction is source confusion.
We acquire information from various sources and our minds reorganize the information in ways that may be meaningful but that obscure the ties between each item and its original source. Events that are conceptually linked but came from different sources may become confounded in memory.

Social pressure figures into many cases of false memory.
A person who feels pressured to come up with a memory is more likely than an unpressured person to identify a vague, possible memory as an actual memory. The more often the memory is repeated, and the more praise the person receives for recalling it, the more confident the person becomes that the memory is true. The opposite is probably true also.

Prospective memory and mental time travel

Retrospective memory: remembering things in the past

Prospective memory: remember to do things in the future
A type of episodic memory, but future intent
Two types:

• Event-based
  Remembering to perform a particular action when cued by a target event.
• Time-based
  Remembering to execute an intended action after the passage of a certain amount of time or at a specific moment

Prospective memory is relatively poor in children and declines in older adults.
Three phases in prospective memory

• A subject forms an intention
• The intention must be maintained
• There must be a ‘switch’ from the ongoing task to execute the intention

The executive functioning account of prospective memory proposes that each phase requires using a limited pool of cognitive resources in an effective way.

Having to remember to do something in the future reduces performance on a simultaneous task.