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Click on words for more information A Simplified Model of Memory Retrieval Rehearsal recall (for declarative memory only) recognition Reference Memory (LTM) Working Memory * (STM) declarative (or explicit) * (Consolidation) Sensory Stimuli semantic ( what & where )

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a simplified model of memory

Click on words for more information

A Simplified Model of Memory



  • recall

(for declarative memory only)

  • recognition

Reference Memory (LTM)


Memory *


  • declarative (or explicit)*




  • semantic (what & where)
  • episodic (when)


  • procedural (or implicit)
  • motor learning (how)
  • perceptual learning (what)
  • nonassociative learning
  • simple (S-R) conditioning

(associative learning)

* accompanied by conscious awareness in humans as evidence by verbal behavior.

  • classical (Pavlovian)
  • instrumental (operant)
working memory stm
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
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

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)


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
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
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 termlearning. 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
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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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

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


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.


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
recognition continued

Retrieval cues may include any stimulus that was present when the to-be-remembered 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 re-emergence 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.)

Cognitivebehaviorists, 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 interval- that 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 conditioningor 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
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 itsy-bitsy spider” involves semantic memory, but remembering precisely when you first learned the children’s song involves episodic memory.

semantic memory what where
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 language- we 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 (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 (or implicit) memory

Procedural memory is a type of reference memory that involves well-learned 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
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
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
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
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
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 elicitresponses. 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
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
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 (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
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 retrieval through recognition. )

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instrumental operant conditioning continued33
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 goal-directed 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
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
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
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)