Transcript A Model of Memory

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A Simplified Model of Memory
Rehearsal
Sensory
Stimuli
Working
Memory *
(STM)
Retrieval
• recall (for declarative memory only)
• recognition
Reference Memory (LTM)
(Consolidation)
•declarative (or explicit) *
 semantic (what & where)
 episodic (when)
•procedural (or implicit)
 motor learning (how)
 perceptual learning (what)
 nonassociative learning
 simple (S-R) conditioning
* accompanied by conscious awareness in humans as
evidence by verbal behavior.
(associative learning)
• classical (Pavlovian)
• instrumental (operant)
Working Memory(STM)
Working memory is commonly referred to as Short-Term Memory (STM). The
term STM implies a repository- a place for the temporary storage of facts.
Modern human cognitive research suggests that the “repository” view is much
too simple. The information in STM is not just held but actively processed,
worked on; hence working memory is a more appropriate label.
Working memory in people appears to consist of several components, a visual
information sketchpad (“seeing” things in our mind’s eye), a verbal information
area (when we mentally “talk to ourselves”), and a control processing area
(manipulating and thinking about visual & verbal information).
Working memory is temporary, lasting a relatively brief period of time
particularly if rehearsal is prevented.
When we are “recollecting” or “remembering” we are working on information
that has been retrieved from reference memory (or LTM) into our working
memory. Thus working memory is not possible without reference memory.
Working memory in people is accompanied by immediate conscious awareness.
Working Memory in Animals
Working Memory in Animals
It is not possible to determine if working memory in animals is accompanied
by conscious awareness, but there is plenty of evidence that animals use
working memory to solve problems set up by experimenters.
Several procedures have been developed to study working memory in
animals. In these procedures animals are first trained to perform a task (learn
rules of a game by storing them in reference memory). These rules stored in
reference memory are retrieved and used to process information in working
memory. For example to play a game of Poker you need to know the rules
(reference memory), but to win you also need to remember which cards have
recently been played (working memory).
Procedures used to study working memory in animals include:
•Delayed matching-to-sample
•Delayed nonmatching-to-sample
•Olton radial arm maze
Consolidation
Some cognitive behaviorists (scientists who explain learning from an information
processing approach) argue that information to be stored into reference memory must
be rehearsed in working memory immediately after it is presented. The rehearsal
process allows for the memory to be permanently stored in reference memory, this
process of rehearsal and storage is called consolidation. Failure to consolidate
memories is presumed to be a cause of forgetting.
Another view held by cognitive behaviorists is that the storage process occurs very
rapidly, without working memory or rehearsal. According to this view (called retrieval
theory) forgetting is presumed to be due to the failure to find or retrieve the information
stored in reference memory. Forgetting can be alleviated by providing retrieval cues.
Both views are probably correct. Most of us cannot memorize a new phone number
without rehearsing it several times. Yet there are times where we can remember a new
face or name after experiencing it only once, even when it was a very brief
presentation.
(ALSO SEE the discussion under recognition to address the differing
theoretical views in this area of research)
Acquisition
The term acquisition, which refers to the initial stage of learning, is used most often by
scientists who study animal learning in the laboratory. A characteristic of most studies of
acquisition in laboratory experiments is numerous learning trials. The subject is
presented with one or more stimului or a task over and over again until evidence of
learning emerges. Once a learned response is established the response is observed to
strengthen gradually with additional trials. The two most popular paradigms for studying
acquisition is classical conditioning and operant conditioning.
Ivan Pavlov was one of the first scientists to develop classical conditioning procedures to
study animal learning in the laboratory (he used dogs in his experiments). A modern
example of the acquisition of a classically conditioned response is sign tracking. A bird
is placed in a chamber with a small screen that can be illuminated and a food dispenser.
When first illuminated the bird spends little time responding to the screen. However, if
the illuminated screen is reliably followed by brief access to food, the bird begins to
approach and peck at the illuminated screen (indicating that the animal has associated the
illuminated screen with food). The pecking response towards the screen gradually
increases in frequency from trial to trial. This initial stage of learning is called
acquisition. When the animal’s behavior stabilizes (no further increases in responding)
learning is presumed to be complete.
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Acquisition continued
An example of the acquisition of an operantly conditioned response is barpressing
in rats- a procedure introduced by B.F. Skinner. A hungry rat is placed in a chamber
with a bar that can be manipulated by the rat. When first placed in the chamber the
rat will spend little time near the bar. However, if the rat receives a pellet of food
whenever it accidentally presses the bar, the rat begins to spend more time near the
bar and to manipulate it sufficiently to press it. The rat’s barpressing behavior
gradually increases in frequency and becomes more efficient with practice. The
initial stage of learning to barpress is called acquisition. When the animal’s
behavior stabilizes (no further change in the rate of barpressing) learning is
assumed to be complete.
Once acquisition is complete what the animal learned is presumed to be stored in
reference memory. The acquisition process leads to both declarative and
procedural memories, however most cognitive psychologists refer to the
consolidation of declarative memories rather than the acquisition of declarative
memories.
(ALSO SEE the discussion under recognition to address the differing theoretical
views in this area of research)
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Reference Memory (LTM)
Everything that you know and learned is in reference memory. There are two types of
reference memory:
declarative memory - Those things that you know and that you can declare verbally
(e.g., your name, the answers to “Who was the first president of the USA?” and “What
is the product of 6 X 6?).
procedural memory -Those things that you know, or do, (skills and preferences) but of
which you are not normally conscious.
Most often when people discuss memory they are referring to memories of which they
are consciously aware and are able to describe verbally. These memories consist of
information that is retrieved into working memory from declarative memory.
Many experimental psychologists who study the formation (acquisition) of reference
memory in animals typically don’t use the term “reference memory”, they prefer to use
the term learning. Asking how a human or animal forms reference memories is the
same as asking how it learns. When these same psychologists use the term memory, they
are referring to information being processed in working memory. They view memory as
not being possible without learning occurring first. This is why some text books have
titles referring to “Learning and Memory” as if they are separate entities.
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Reference Memory continued
Even when information in reference memory is not retrieved into
working memory it can affect our behavior and how we process our
working memories. Our skills (reading, writing, playing a musical
instrument) and our preferences (for foods, music, sexual partners) are
partly influenced by learning (information in reference memory).
How we process information in working memory is influenced by
reference memories of which we are not conscious. For example we use
our knowledge of the English language to construct sentences.
Nevertheless, when we construct sentences we are not consciously aware
of all the rules of the English language that we learned throughout our
lifetime.
Other terms for reference memory:
•long term memory (LTM)
•inactive memory
•secondary memory
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Retrieval
Most cognitive psychologists are comfortable with
the idea that there are two types of memories, a
relatively permanent and vast storehouse of
memories (reference memory) and a temporary or
short-term storage area with limited capacity used to
process new information and stored memories
(working memory). In order to process information
in working memory it must be retrieved from
reference memory. There are two major retrieval
mechanisms:
•recall
•recognition
Rehearsal
When we are recalling or recollecting we place information from our reference memory
into our working memory and repeatedly think about the information. This repetitive
process which maintains information in working memory is called rehearsal. Most
often rehearsal involves language- people silently verbalize the information they are
trying to remember. One way that researchers study the rehearsal process in people is to
prevent it by asking subjects to perform distracting tasks like counting backward.
Because animals do not have language it seems that they probably do not rehearse.
However, there is evidence that nonverbal rehearsal (such as the use of imagery) occurs
in humans and animals. Some learning theorists (Wagner, 1981) have developed models
of memory in animals that includes the rehearsal of information that is brought into
working memory (from reference memory) by stimuli they encounter in the environment.
These environmental stimuli, or retrieval cues, activate a process of recognition. Once
the information is recognized the animal keeps it in working memory by rehearsing.
Wagner, A.R. (1981.). SOP: A model of automatic memory processes in animal
behavior. In N.E. Spear & R.R. Miller (Eds.) Information processing in animals (pp.
5-47). Hillsdale, NJ: Erlbaum
recall
When most people speak of memory they are referring to recall- the ability to
produce information not currently in conscious experience (or the ability to
retrieve information from reference memory into working memory). What was
the name of the dog in the Wizard of Oz? If you answered Toto, you
successfully recalled information from your reference memory.
Is language necessary to recall a memory? Most likely not. What does an
octopus look like? In response to this question you most likely produced a
mental image of the animal in your mind. However, the only way for someone
to know what image you have in mind is for you to verbally describe the
mental image that you are experiencing. Although language may not be
necessary for recalling visual stimuli, language is necessary for another person
to know what it is that an individual is recalling. The requirement of language
to study recall is the reason that recall is not studied in animals. To study the
retrieval of memories in animals it is necessary to examine the process of
recognition.
recognition
When you recognize something (a name, place, or thing) some information that was
presented to you helped you gain access to your memory. A common example of a
test of recognition memory in people is the multiple choice question. Even if you
are unable to recall information you may be able to recognize the information when
it is provided among a list of several alternatives. People who have been out of high
school for 20 or more years cannot recall many of their classmates, but they can
recognize a large majority of their classmates’ pictures and names. Also, anytime
you perceive an object as familiar you are experiencing recognition memory. In
these examples the actual item that a person is being asked to remember is presented
to them either alone or with other items. The response to the item determines if the
subject remembered.
Recognition tests can also involve presentation of stimuli that are associated with
the information or item that is to be remembered. The item is remembered
(retrieved into working memory) because the associated stimulus serves as a
retrieval cue. A common request made by people trying to recall an answer to a
question is “Give me a hint”; this request can be rephrased “Give me a retrieval
cue”.
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recognition continued
Retrieval cues may include any stimulus that was present when the to-beremembered item was originally experienced (and therefore associated with the
item). A retrieval cue can also be the context where an item was experienced
and even emotions that were evoked at the time the original item was
experienced.
All tests of memory in animals are tests of recognition. In recognition tests a
previously experienced item or a stimulus associated with the item (a retrieval
cue) is presented. An animal’s response to the item (or the retrieval cue)
provides evidence of recognition by the animal.
Not all scientists that rely on recognition tasks to study animal learning and
behavior use the memory terminology covered here. It is possible, for example,
to read a text book on animal learning where the word “memory” rarely appears.
Instead of terms like memory, retrieval, and recognition, learned behavior is
described in terms of conditioning principles such as “classically conditioned
responding” and “stimulus control of operant behavior”. Radical behaviorists
(psychologists working within the tradition of B.F. Skinner), for example, do
not refer to memories in their theorizing. Why?
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recognition continued
The argument against the use of memory terms is that such terms are not needed to explain learning
and behavior. Radical behaviorists argue that to explain learning in animals (and humans) one must
first know the history of the subject’s experiences and then simply describe the relationship between
the current stimuli presented to the subject and the responses that occur. Learning theories based on
this view are sometimes called S-R theories.
Stimulus ----> Response
When”memory” is introduced into the equation it is presumed to occur between the stimulus and
response. Memory is an intervening variable- it intervenes between the stimulus and response.
Stimulus ------> Memory ------> Response
A stimulus is presented which in turn evokes a memory and which in turn determines the response
made by the subject. But unlike stimuli and responses, memories cannot be directly observed. They
can only be inferred from behavior (that is, the responses that are observed). Why then, ask the
radical behaviorists, introduce “memory” in our explanations? It should be sufficient to simply
describe the stimuli in the environment and the responses that are likely to follow. Because all tests
of “memory” in animals are recognition tests (a stimulus is always presented and a response is
measured), the radical behaviorsts have a point-- why not simply use the stimulus (and knowledge
of the animals previous experiences) to predict the response that will occur. Thus for radical
behaviorists animals learn through the acquisition of stimulus-response associations, not through the
consolidation of memories.
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recognition continued
The typical lay person sees the radical behaviorist’s explanation of learned behavior
in animals as unsatisfying. We know from our own subjective experiences that we
experience rich memories and that these memories often guide our behavior. Why
wouldn’t animals have similar memories? Recall that information retrieved into
working memory in humans is accompanied by consciousness- we are aware of our
memories. But it is difficult, if not impossible, to know if animals are ever conscious
of their experiences. It certainly seems like many animals (especially mammals and
birds) are at times conscious of their experiences, but unequivocal evidence is
difficult to come by. If what the lay person refers to as memory (and scientists refer to
as working memory) is always accompanied by consciousness, and evidence of
consciousness in animals still eludes us, then describing memory in animals may not
be necessary or at least is premature theorizing. (There has been a recent reemergence in an interest of animal consciousness especially in the field of Cognitive
Ethology. Developments in this field and others (e.g., neuroscience) are likely to
change our views of consciousness in animals- stay tuned.)
Cognitive behaviorists, scientists who study Animal Cognition, argue that the radical
behaviorists’ approach to animal learning is lacking in explanatory power. They see
value in using intervening variables such as memory to explain animal behavior
whether or not consciousness is involved. Like most psychologists, cognitive
behaviorists believe that the causes of behavior are understood
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recognition continued
when behavior can be reliably predicted. They argue that simply knowing about an
animal’s learning history and the current stimuli that the animal is exposed to is not
sufficient to reliably predict behavior. To improve prediction one must also assume that
animals actively process information in the form of mental representations. That is,
intervening variables that are inferred from stimulus and responses relationships improve
a scientist’s ability to predict the behavior of animals at any given time. Cognitive
behaviorists spend their days designing experiments that support their claims of the need
to infer cognitive processes such as memory in animals to better predict behavior. For
example, in one task called a delayed matching-to-sample procedure animals are
presented with a sample stimulus for a brief period (e.g., 5 sec). After a delay (e.g., 1
minute), in which no stimulus is available, the original stimulus is presented again along
with another stimulus. The animal must choose (that is, recognize) the stimulus that was
presented earlier. In order for the animal to choose the correct stimulus it must use
information(the sample stimulus) that is no longer available. Many species of animals
display accurate performance on this task as long as the delay interval is not too long. To
predict this accurate performance, argue cognitive behaviorists, one must infer that the
animals are maintaining a mental representation of the sample during the delay intervalthat is, they remember the original sample stimulus. The delayed matching-to- sample
procedure is an accepted measure of working memory in animals.
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recognition continued
I see merit with both the radical behaviorist and the cognitive behaviorist
arguments. Taking either position (S-R behaviorism and cognitive behaviorism)
to explain all animal learning is extreme and most certainly leads to erroneous
explanations.
For now I look at it in this way. Animal behavior is often (but not always)
influenced by what cognitive psychologists call reference memory. There are
two kids of reference memory: declarative memories and procedural memories.
Behaviors that involve the retrieval of declarative memories are more
appropriately explained by principles of animal cognition. However, behaviors
that involve procedural memories are more accurately explained by S-R
principles. Why, you may ask, refer to “procedural memories” as “memories”?
Why not drop the “memory” part of the term? Well… one reason is to maintain
some coherent level of organization. I see no problem with choosing the
terminology of a major approach, then analyzing the approach and pointing out
its merits and demerits. In time, the hope is that scientists with an interest in
animal learning and behavior from different disciplines and theoretical
backgrounds can agree on a common terminology that describes the complexity
and richness of the learning ability of animals.
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recognition continued
Deciding whether to classify learned behaviors as involving declarative or procedural
memories is not easy. Take, for example, a type of associative learning called
classical conditioning or Pavlovian conditioning (after the Russian physiologist Ivan
Pavlov). Some cognitive behaviorists assign classical conditioning to the category of
declarative memory. These scientists generally view the animal as obtaining
information about the relationships between important stimuli in the environment
(e.g., Pavlov’s dogs learned that a tone predicts the arrival of food); the animals are
presumed to process this information (think?) and to respond appropriate to the
situation. Other psychologists (usually those specializing in human learning) argue
that classical conditioning represents procedural memory (e.g., Pavlov’s dogs learned
to automatically salivate to tones that were previously paired with food). This latter
view presumes that animals learn to respond to stimuli in a mechanical, habit-like
and non-thinking manner.
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recognition continued
These two positions are extreme and overly simplified. It is best not to view classical
conditioning as a type of learning, but as an experimental procedure used by scientists
to study associative learning in the laboratory. Numerous variations of the standard
classical conditioning paradigm have been developed since the time of Pavlov. In some
instances evidence suggests that animals learn about the relationship between stimuli.
They learn that some stimuli are informative and predictive of important biological
stimuli such as food and predators. In these instances animals obtain knowledge that
establish expectations that help guide their behaviors. These qualify as declarative
memories.
On the other hand, evidence that classical conditioning procedures yield mechanical,
non-thinking behavior is also abundant. For example, associative learning occurs in
animals with very simple nervous systems (e.g., insects and other invertebrates).
Associative learning also occurs in people when they are unaware that they have
learned. In humans memories that are not accompanied with awareness are classified as
procedural memory. If humans learn without awareness, animals most certainly do too!
So it appears that classical conditioning most likely represents both declarative and
procedural memories. Very careful (and often difficult) experimental analysis is needed
to help classify the learning that occurs during a classical conditioning procedure.
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•declarative (or explicit) memory
One of the two types of memory classified by cognitive psychologists as
reference memory is declarative memory. Most text books describe this
form of memory as involving the memory of facts and events that can be
made explicit by the subject by verbalizing. In humans this form of
memory is always accompanied by conscious awareness (afterall, you can’t
speak about something that you are not aware).
What people typically refer to as their memory or recollection is what
psychologists call declarative memories. Declarative memories are further
divided into two types:
semantic memory - are all the facts that you accumulate throughout your
lifetime (vocabulary, cultural information, trivia)- and in the information age
in which we live there are plenty of facts to be obtained.
episodic memory - are personal memories, memories for specific events that
an individual personally experienced. Remembering the words to “the itsybitsy spider” involves semantic memory, but remembering precisely when
you first learned the children’s song involves episodic memory.
•semantic memory (what & where)
Semantic memory includes all of the practical information that we need in order to
survive in our environment. In humans this information is closely tied to languagewe are highly verbal creatures. When we recognize people, places, or things we
immediately attach words to them. For people language, thinking, and memory are
intimately related. The term semantic is used to stress the importance of language.
Animals also need to survive in complex environments, but they do not have
language. Does this mean that they do not have semantic memory? If they do not
have semantic memory then does this mean that they do not have the capability of
obtaining practical information to survive in their environment?
Animals do indeed have memories that can be classified as declarative, but because
they lack language there is no need to introduce the term semantic. Animals learn to
recognize objects (“what is it” memories) and the location of objects (“where is it”
memories) in their environment, practical knowledge that affords animals an
enormous advantage at surviving in their environment. In some cases the memorial
abilities of animals far exceeds the memorial abilities of humans. Some birds, for
example, can remember where they buried hundreds of seeds with incredible
accuracy.
• episodic (when)
Episodic memories are memories of personally experienced events. Case
studies of humans with brain damage suggest that semantic and episodic
memories are controlled by different brain structures. Patients with damage to
medial temporal lobe of the brain can learn new reference memories but fail
to remember when they personally learned the new information.
It is very difficult, if not impossible, to determine if animals experience
episodic memories. While it is very clear that an animal trained to press a bar
to get food remembers what to do, it is not possible to determine if the animal
remembers precisely when it learned to press a bar.
The issue of episodic memories in animals is controversial because it relates
to two very difficult issues to study experimentally:
• consciousness in animals
• self-awareness in animals
•procedural (or implicit) memory
Procedural memory is a type of reference memory that involves welllearned motor and cognitive skills, usually performed without conscious
awareness. Procedural memories are often described as automatic (very fast
and effortless processing of information) or habit (behaving without
thinking). Examples of the former include immediate recognition of letters,
words, and other visual stimuli (perceptual learning); examples of the latter
include writing, riding a bicycle, and playing a musical instrument (motor
learning). Simple conditioning procedures used to study learning in the
laboratory may also lead to the acquisition of procedural memories, as well
as repetitive exposure to a single stimulus (nonassociative learning).
Clinical case studies and animal experimentation provide strong evidence
that procedural memories are stored in brain structures that differ from
where declarative memories are stored.
Procedural memories involving motor skills are usually established
gradually through an acquisition process that involves repetition. ( How do
you get to Carnegie Hall? Practice, practice, practice…).
• motor learning (how)
Repetitive practice of a motor task leads to improved performance of the task. Learning
to write, to play the piano, and to expertly hit a tennis ball involves motor learning-learning how to do something. This type of learning is categorized as procedural
memory because behavior, once learned, occurs more or less automatically. In the
laboratory motor learning is studied by asking people to perform unfamiliar motor tasks.
In the mirror-drawing task, for example, subjects are asked to use a pencil to trace the
outline of a star-shaped figure by looking at the figure and hand through a mirror.
Departures from the outline are counted as errors. Initially many errors are made, but
with repetitive practice subjects become very proficient at the task.
Motor learning is not studied in animals as it is in humans because animals cannot be
instructed to practice a motor task. To get an animal to repeatedly perform a specific
behavior the experimenter must reinforce the animal with a desired item (e.g.food). This
reinforcement procedure is called instrumental or operant conditioning. Early theories of
instrumental conditioning described learning in these tasks as always involving
mechanistic (stimulus-response) performance, which suggests a kind of motor learning.
But modern research on instrumental conditioning suggests that instrumental
procedures can lead to different kinds of learning, some of which involve declarative
memory and other cognitive processes. Nevertheless, in some situations highly
practiced instrumental performance is likely to lead to motor learning.
• perceptual learning (what)
How we perceive and recognize what an object is is an
ancient question. Early philosophers believed that we
develop the ability to perceive objects as we gradually piece
together elementary units of sensation and perception
through learning. Modern research, however, revealed that
some aspects of form perception (object recognition) are a
result of innate mechanisms. Nevertheless, contemporary
theories of form perception presume that our perceptions are
strongly influenced by expectations and inferences of which
we are not consciously aware. These automatic cognitive
processes in perception are presumed to depend on
procedural memory.
• nonassociative learning
When an individual encounters a stimulus for the first time he is likely to respond to it in
some way. To a sudden loud noise the response is likely to be a startle. To a gentle
rustling the response may be subtle, like looking in the direction of the sound to spy a
possible cause (called an orienting response). But if the sound is continual or repeats
over and over again the response to it will most likely change. The change in behavior to a
repeating single stimulus is classified as nonassociative learning. If the stimulus is
innocuous or has no meaning to the individual responding is likely to decrease and
eventually disappear (stop startling or looking). This decline in the responsiveness to a
repeatedly occurring stimulus is called habituation. Habituation is very important type of
learning that is seen in all animals, even in single-celled animals.
Typical phrases that the lay person uses to describe habituation include “getting used to
it”, “learning to ignore it”, and in some cases, “boredom”. We are bombarded by stimuli
all the time. Imagine if, while trying to do a simple thing like reading, you were unable to
”ignore” or “get used to” the hum of the air conditioner, the chit-chat of all the people
around you, the sound of the distant traffic, or the beating of your heart. Without the
ability to habituate life would be very difficult. Fortunately habituation occurs frequently
and automatically, hence its classification as procedural memory.
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• nonassociative learning continued
Sensitization is a second type of behavior change that is often classified as nonassociative
learning. The change in responding in sensitization also occurs over time in reaction to a
single stimulus but it differs from habituation in that:
1. the stimulus causes an increase in responding
2. responding increases not only to the stimulus itself, if it reoccurs, but also to
all subsequent stimuli, even stimuli that normally evoke little or no
responding.
Imagine that an individual not particularly fond of scary movies attends one to placate her
friends. When she is back home alone she now startles to noises she normally ignores- the
creaking in the walls, the whistle of the wind entering through the crack in the window,
the shadows in her room . A single stimulus (the scary movie) intensified responses to all
stimuli-- this is sensitization.
The behavior change in sensitization is not typically long-lasting, eventually dissipating.
For this reason I wonder whether it should be classified as a type of nonassociative
learning (see definitions of learning). Nevertheless, sensitization is an important process
that is critical to all animals. Sudden, unexpected or potentially dangerous stimuli excite
the animal into a state of alert. This sensitized state of alert allows the animal to be
vigilant and to respond quickly to anything that may appear.
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•simple (S-R) conditioning
(associative learning)
Associative learning occurs when an individual’s response to a stimulus, or the meaning of a
stimulus, changes as a result of the stimulus being paired with (and therefore related to) a
second stimulus.
Associative learning is ubiquitous and it takes several forms. In some cases associative
learning is mechanistic, habit-like, and non-cognitive. Classical conditioning procedures are
used to study associative learning in which stimuli gain the power to automatically elicit
responses. Instrumental conditioning procedures are used to study associative learning in
which responses are emitted automatically in the presence of certain stimuli. These are the
situations that are categorized as simple or S-R conditioning. The behaviors that emerge
from S-R conditioning are classified as procedural memory because they are usually
acquired gradually and because they are automatic and do not involve the retrieval of
information into working memory.
In many instances associative learning is more complex, involving the learning of
relationships. An individual doesn’t just react to a stimulus or respond because of the
presence of a stimulus, but instead learns that the appearance of one stimulus predicts that a
second stimulus is likely to follow. The first stimulus sets up an expectation that the second
stimulus is likely to occur. How one responds depends on what the expected stimulus is and
the personal goal of the individual. Under these circumstances learning is more accurately
categorized as declarative memory.
• Classical (Pavlovian) conditioning
The Russian physiologist, Ivan Pavlov, was the first scientist to use classical
conditioning procedures in the laboratory to study associative learning in
animals. Pavlov showed that a dog will change its response to a stimulus if the
stimulus is paired with food. While a dog will salivate when food is placed in
its mouth, it will not salivate to the sound of a tone. However if the tone is
repeatedly followed by the appearance of food the animal’s response to the
tone will eventually change- the dog will begin to salivate reliably to the tone.
In general then, classical conditioning procedures involve the presentation of
two stimuli that are related (correlated) in some way but are independent of
the subject’s behavior (the stimuli will occur whether or not the animal
behaves). If the subject learns that the two stimuli are related it will become
evident in the subject’s behavior- the response to the first stimulus will
change. Salivating to a tone that reliably precedes food is evidence that the dog
has associated the tone with food.
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• Classical (Pavlovian) conditioning continued
What exactly did Pavlov’s dogs learn? Did they learn to expect that food will follow the
tone? This explanation assumes that the dogs learned the relationship between two events
and suggests that the animals are relying on their declarative memories. The tone reminds
the animal of food, thereby setting up an expectation that food will appear. An animal that
expects food will show its knowledge in its behavior-- it becomes restless, it approaches
the potential source of food (if not restrained), and it salivates.
Another possibility is that the animal’s digestive system learns. The digestive system, like
most systems of the body, is under the control of the nervous system. Classical
conditioning procedures involving food stimuli may cause the nervous system to alter its
control of the digestive system so as to reflect events in the environment. Thus, signals
that reliably precede food gain the power to elicit salivation in the mouth, gastric acid
secretion in the stomach, and the release of insulin by the pancreas. These responses
allow the digestive system to prepare for the arrival of food. They are automatic and, in
humans, do not require conscious awareness. Learned adjustments of in-born, functional
physiological systems represent procedural memories.
In humans classical conditioning procedures result in both declarative and procedural
memories, and modern research suggests that the same may be true for many non-human
vertebrate animals. But it is the procedural memories that arise from classical
conditioning procedures that are classified as simple or S-R conditioning.
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• Instrumental (operant) conditioning continued
Instrumental conditioning procedures are used by scientists to study a form of associative
learning whereby animal’s learn to control events in their environment. The experimenter
sets up a situation so that a response emitted by the animal is instrumental in causing
events in the local environment or so that a response can operate on the environment to
produce a change. (Compare with classical conditioning procedures.) The required
responses typically involve behaviors that already exist in the animal’s repertoire and the
change caused by the resposes often involve the delivery of a desirable consequence,
such as the appearance of food or the removal of a potentially dangerous stimulus.
Instrumental conditioning procedures are sometimes used by scientists to study the
“problem solving” ability of animals. The first instrumental conditioning experiments
were conducted by Thorndike in the late 1800s. His most famous experiments involved
placing hungry cats in what he called a puzzle box, with food available outside of the box.
The puzzle box was set up so that certain responses (pulling a string or stepping on a
platform) would cause the door to open, releasing the animal. The cats had no trouble
learning to escape the box. Since this pioneering work numerous laboratory experiments
have been published documenting the ability of a wide range of species, including ants
and the common fly, to learn during instrumental conditioning tasks. It is assumed that
these instrumental conditioning tasks recreate under controlled conditions the kinds of
things that animals need to learn to survive in their natural world.
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• Instrumental (operant) conditioning
What do the animals learn during these tasks? It seems reasonable to assume that
the animals learn about the consequences of their own behavior; that responding is
effective in causing change and in resulting in desired goals. This explanation of
instrumental conditioning suggests that declarative memories are involved. That is,
that the cats learn to “solve” the problem. They anticipate a goal (to escape the box
and eat the food) and they remember a way to achieve the goal (pull on the string to
open the door). Interestingly, Thorndike came to a different conclusion.
Thorndike suggested that the cats learned in a mechanical, S-R fashion. Such an
S-R conditioning explanation suggests that when a response leads to a desired
consequence, a stimulus-response connection (association) is strengthened.
Thorndike argued that the cats escaped because the sight of the string (the S) caused
the cat to pull the string (the R), nothing more. B.F. Skinner and many other
behaviorists studying rats, birds, and other animals, came to a similar conclusion -when responses are followed by desired consequences the likelihood that the
responses will be emitted in the presence of a given stimulus increases because of
the strengthening of S-R associations. Thorndike, Skinner, and other behaviorists
concluded that instrumental conditioning procedures lead to the establishment of
procedural memories, not declarative memories. (also see the discussion on
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retrieval through recognition. )
• Instrumental (operant) conditioning continued
Modern experimental research suggests that instrumental conditioning
procedures are very effective in changing the behavior of virtually every
species tested. However, research also has shown that these seemingly
simple instrumental conditioning procedures can lead to many different
types of learning. The type of learning that occurs is believed to depend
on many factors including the species, the details of the training
procedure, and the duration of the training. It is very difficult to
determine exactly what an animal learns during these procedures; careful
and time-consuming experimental manipulations are required, but rarely
done. Suffice it to say that, depending on the circumstances,
instrumental conditioning procedures can lead to anticipated goaldirected behavior and problem-solving (both involving declarative
memory) as well as automatic S-R responding involving procedural
memory . In humans the latter is usually described as habit and it may
include insignificant behaviors such as nail-biting or serious maladaptive
behaviors such as drug abuse.
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Definitions of learning
It may surprise you to learn that it has been notoriously difficult for scientists to
agree on a definition of learning. The reason is that scientists approach the study
of learning from very different theoretical positions. The definition of learning
that a scientist accepts provides clues to their theoretical background.
“Learning is the acquisition of new information or knowledge. Memory is
the retention of learned information. “
This definition suggests a cognitive (information processing ) approach.
Unfortunately, it seems to emphasize declarative memories over procedural
memories.
“Learning is a relatively permanent change in behavior resulting from
personal experience”.
This definition suggests a behavioral approach. But the emphasis on behavior
gives the impression that there is a greater emphasis on procedural memories
than on declarative memory.
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Definitions of learning continued
Perhaps the best way to define learning is in terms of its function. In terms of
why animals learn?
Learning is an individual’s ability to adapt (or adjust) to personally
experienced changes in the environment so as to ultimately improve its
chances of survival.
Animals adjust to subtle and significant changes in the environment- this is what
learning is all about. An animal that can adapt to a changing environment is more
likely to survive.
How an animal learns is multifarious, but it always involves changes in the
nervous system. These changes may give animals immediate advantages or they
may be latent, providing an advantage later when a specific environmental
situation presents itself. The changes can be complex (involving cognitive
processes) or it can be simple (involving simple reflex systems). Any animal with
a nervous system learns. The more complex the nervous system the more varied
the mechanisms of learning that the animal is likely to have at its disposal.
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Conscious Awareness
Over 100 years ago a concern with the conscious content of the mind of humans and
animals was common among philosophers and scientists with an interest in
psychology. From the 1920s and through the 1960’s the dominant school of
behaviorism essentially eliminated the study of consciousness and mental processes
from psychology- the emphasis was on the scientific study of observable behaviors.
Interest in consciousness and mental processes reemerged in the 1970s. Cognitive
psychologists developed methods to study mental processes such as attention,
memory, and thinking in people. Discussions of mental states and consciousness in
humans are again routinely observed in the pages of psychology journals. The
study of the animal mind, however, is a different story. Although some behaviorists
(radical behaviorists) continue to insist that cognition and consciousness is not an
appropriate subject of scientific study, cognitive behaviorists accept the importance
of cognitive processes in animal learning (animal cognition). The issue of
consciousness in animals, however, is still not approached by cognitive behaviorists
for two primary reasons. First, it is extremely difficult, if not impossible, to produce
evidence of consciousness in animals. Second, cognitive processes are assumed not
to require conscious awareness. Nevertheless in the early 1980s biologist Donald
Griffin advanced the field of cognitive ethology which aims to study the functional
value of consciousness in humans and animals.
(Also see the discussion on recognition)