5 Steps to a 5 AP Psychology, 2010-2011 Edition (37 page)

Figure 11.1 Atkinson–Shiffrin three-stage model of memory.

Short-term memory
(STM) can hold a limited amount of information for about 30 seconds unless it is processed further. Experiments by George Miller demonstrated that the capacity of STM is approximately seven (plus or minus two) unrelated bits of information at one time. STM lasts just long enough for us to input a seven-digit phone number after looking it up in a telephone directory. Then the number disappears from our memory. How can we get around these limitations of STM? We can hold our memory longer in STM if we
rehearse
the new information, consciously repeat it. The more time we spend learning new information, the more we retain of it. Even after we’ve learned information, more rehearsal increases our retention. The additional rehearsal is called
overlearning
. While rehearsal is usually verbal, it can be visual or spatial. People with a photographic or eidetic memory can “see” an image of something they are no longer looking at. We can increase the capacity of STM by
chunking,
grouping information into meaningful units. A chunk can be a word rather than individual letters, or a date rather than individual numbers, for example.

Although working memory is often used as a synonym for STM, Alan Baddeley’s working memory model involves much more than chunking, rehearsal, and passive storage of
information. Baddeley’s
working memory model
is an active three-part memory system that temporarily holds information and consists of a phonological loop, visuospatial working memory, and the central executive. The phonological loop briefly stores information about language sounds with an acoustic code from sensory memory and a rehearsal function that lets us repeat words in the loop. Visuospatial working memory briefly stores visual and spatial information from sensory memory, including
imagery,
or mental pictures. The central executive actively integrates information from the phonological loop, visuospatial working memory, and long-term memory as we associate old and new information, solve problems, and perform other cognitive tasks. Working memory accounts for our ability to carry on a conversation (using the phonological loop), while exercising (using visuospatial working memory) at the same time. Most of the information transferred into long-term memory seems to be semantically encoded.

Long-term memory
is the relatively permanent and practically unlimited capacity memory system into which information from short-term memory may pass. LTM is subdivided into explicit memory and implicit memory.
Explicit memory,
also called
declarative memory,
is our LTM of facts and experiences we consciously know and can verbalize. Explicit memory is further divided into
semantic memory
of facts and general knowledge, and
episodic memory
of personally experienced events.
Implicit memory,
also called
nondeclarative memory,
is our long-term memory for skills and procedures to do things affected by previous experience without that experience being consciously recalled. Implicit memory is further divided into
procedural memory
of motor and cognitive skills, and classical and operant conditioning effects, such as automatic associations between stimuli. Procedural memories are tasks that we perform automatically without thinking, such as tying our shoelaces or swimming.

How is information in long-term memory organized? Four major models account for organization of LTM: hierarchies, semantic networks, schemas, and connectionist networks.
Hierarchies
are systems in which concepts are arranged from more general to more specific classes.
Concepts,
mental representations of related things, may represent physical objects, events, organisms, attributes, or even abstractions. Concepts can be simple or complex. Many concepts have
prototypes,
which are the most typical examples of the concept. For example, a robin is a prototype for the concept bird; but penguin, emu, and ostrich are not. The basic level in the hierarchy, such as bird in our example, gives us as much detail as we normally need. Superordinate concepts include clusters of basic concepts, such as the concept vertebrates, which includes birds. Subordinate concepts are instances of basic concepts.
Semantic networks
are more irregular and distorted systems than strict hierarchies, with multiple links from one concept to others. Elements of semantic networks are not limited to particular aspects of items. For example, in a semantic network, the concept of bird can be linked to fly, feathers, wings, animals, vertebrate, robin, canary, and others, which can be linked to many other concepts. We build mental maps that organize and connect concepts to let us process complex experiences. Dr. Steve Kosslyn showed that we seem to scan a visual image of a picture (mental map) in our mind when asked questions.
Schemas
are preexisting mental frameworks that start as basic operations, then get more and more complex as we gain additional information. These frameworks enable us to organize and interpret new information, and can be easily expanded. These large knowledge structures influence the way we encode, make inferences about, and recall information. A
script
is a schema for an event. For example, because we have a script for elementary school, even if we’ve never been to a particular elementary school, we expect it to have teachers, young students,
a principal, classrooms with desks and chairs, etc.
Connectionism
theory states that memory is stored throughout the brain in connections between neurons, many of which work together to process a single memory. Changes in the strength of synaptic connections are the basis of memory. Cognitive psychologists and computer scientists interested in
artificial intelligence
(AI) have designed the
neural network
or
parallel processing model
that emphasizes the simultaneous processing of information, which occurs automatically and without our awareness. Neural network computer models are based on neuron-like systems, which are biological rather than artificially contrived computer codes; they can learn, adapt to new situations, and deal with imprecise and incomplete information.

According to neuroscientists, learning involves strengthening of neural connections at the synapses, called
long-term potentiation
(or LTP). LTP involves an increase in the efficiency with which signals are sent across the synapses within neural networks of long-term memories. This requires fewer neurotransmitter molecules to make neurons fire and an increase in receptor sites. Where were you when you heard about the 9/11 disaster? Like a camera with a flashbulb that captures a picture of an event, you may have captured that event in your memory. A
flashbulb memory,
a vivid memory of an emotionally arousing event, is associated with an increase of adrenal hormones triggering release of energy for neural processes and activation of the amygdala and hippocampus involved in emotional memories. Although memory is distributed throughout the brain, specific regions are more actively involved in both short-term and long-term memories. The role of the
thalamus
in memory seems to involve the encoding of sensory memory into short-term memory. STM seems to be located primarily in the prefrontal cortex and temporal lobes. The
hippocampus
, frontal and temporal lobes of the cerebral cortex, and other regions of the limbic system are involved in
explicit
long-term memory. Destruction of the hippocampus results in
anterograde amnesia,
the inability to put new information into explicit memory; no new semantic memories are formed. Another type of amnesia,
retrograde amnesia,
involves memory loss for a segment of the past, usually around the time of an accident, such as a blow to the head. This may result from disruption of the process of long-term potentiation. Studies using fMRI indicate that the hippocampus and left frontal lobe are especially active in encoding new information into memory, and the right frontal lobe is more active when we retrieve information. A person with damage to the hippocampus can develop skills and learn new procedures. The
cerebellum
is involved in
implicit
memory of skills.

Retrieval
is the process of getting information out of memory storage. Whenever we take tests, we retrieve information from memory in answering multiple-choice, fill-in, and essay questions. Multiple-choice questions require
recognition,
identification of learned items when they are presented. Fill-in and essay questions require
recall,
retrieval of previously learned information. Often the information we try to remember has missing pieces, which results in
reconstruction,
retrieval of memories that can be distorted by adding, dropping, or changing details to fit a schema.

Hermann Ebbinghaus experimentally investigated the properties of human memory using lists of meaningless syllables. He practiced lists by repeating the syllables and keeping records of his attempts at mastering them. He drew a
learning curve
. Keeping careful records, he then tested to see how long it took to forget a list. He drew a
forgetting curve
that declined rapidly before slowing. He found that recognition was sometimes easier than recall to measure forgetting. A method he used to measure retention of information was the
savings
method
, the amount of repetitions required to relearn the list compared to the amount of repetitions it took to learn the list originally. Ebbinghaus also found that if he continued to practice a list after memorizing it well, the information was more resistant to forgetting. He called this the
overlearning effect
. When we try to retrieve a long list of words, we usually recall the last words and the first words best, forgetting the words in the middle. This is called the
serial position effect.
The
primacy effect
refers to better recall of the first items, thought to result from greater rehearsal; the
recency effect
refers to better recall of the last items. Immediately after learning, the last items may still be in working memory, accounting for the recency effect. We may remember words from the beginning of the list days later because rehearsal moved the words into our LTM.

What helps us remember?
Retrieval cues,
reminders associated with information we are trying to get out of memory, aid us in remembering. Retrieval cues can be other words or phrases in a specific hierarchy or semantic network, context, and mood or emotions.
Priming
is activating specific associations in memory either consciously or unconsciously. Retrieval cues prime our memories.

Cramming for a test does not help us remember as well as studying for the same total amount of time in shorter sessions on different occasions. Numerous studies have shown that
distributed practice,
spreading out the memorization of information or the learning of skills over several sessions, facilitates remembering better than
massed practice,
cramming the memorization of information or the learning of skills into one session.

If we use
mnemonic devices
or memory tricks when encoding information, these devices will help us retrieve concepts, for example acronyms such as ROY G. BIV (red, orange, yellow, green, blue, indigo, violet) or sayings such as, “My very educated mother just served us “noodles” (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Neptune). Another mnemonic, the
method of loci,
uses association of words on a list with visualization of places on a familiar path. For example, to remember ten items on a grocery list (chicken, corn, bread, etc.), we associate each with a place in our house (a chicken pecking at the front door, corn making a yellow mess smashed into the foyer, etc.). At the grocery store, we mentally take a tour of our house and retrieve each of the items. Another mnemonic to help us remember lists, the
peg word mnemonic,
requires us to first memorize a scheme such as “One is a bun, two is a shoe,” and so on, then mentally picture using the chicken in the bun, the corn in the shoe, etc. These images help both to encode items into LTM and later to retrieve it back into our working memory.

Successful retrieval often depends on the match between the way information is encoded in our brains and the way it is retrieved. The context that we are in when we experience an event, the mood we are in, and our internal state all affect our memory of an event. Our recall is often better when we try to recall information in the same physical setting in which we encoded it, possibly because along with the information, the environment is part of the memory trace; a process called
context-dependent memory.
Taking a test in the same room where we learned information can result in greater recall and higher grades.
Mood congruence
aids retrieval. We recall experiences better that are consistent with our mood at retrieval; we remember information of other happy times when we are happy, and information of other sad times when we are unhappy. Finally, memory of an event can be
state-dependent;
things we learn in one internal state are more easily recalled when in the same state again. Although memory of anything learned when people are drunk is not good, if someone was drunk when he or she hid a gift, he or she might recall where the gift was hidden when he or she was drunk again.