Learn About Yawning

In this episode of the I Can't Sleep Podcast, fall asleep learning about yawning. We've arrived as a podcast by finally recording an episode on this subject. This is the ultimate snooze-fest of a topic and wish you all the luck in trying to learning anything in this one. Happy sleeping!

Transcript

Welcome to the I Can't Sleep podcast,

Where I read random articles from across the web to bore you to sleep with my soothing voice.

I'm your host Benjamin Boster.

Today's episode is from a Wikipedia article titled Yawn.

A yawn is a reflex in vertebrate animals characterized by a long inspiratory phase with gradual mouth gaping,

Followed by a brief climax or acme with muscle stretching,

And a rapid expiratory phase with muscle relaxation,

Which typically lasts a few seconds.

For fish and birds,

This is described as gradual mouth gaping,

Staying open for at least three seconds,

And subsequently a rapid closure of the mouth.

Almost all vertebrate animals,

Including mammals,

Birds,

Reptiles,

Amphibians,

And even fish,

Experience yawning.

A study of yawning is called chasmology.

Yawning,

Oscillation,

Most often occurs in adults immediately before and after sleep,

During tedious activities,

And as a result of its contagious quality.

It is commonly associated with tiredness,

Stress,

Sleepiness,

Boredom,

Or even hunger.

In humans,

Yawning is often triggered by the perception that others are yawning.

For example,

Seeing a person yawning or talking to someone on the phone who is yawning.

This is a typical example of positive feedback.

This contagious yawning has also been observed in chimpanzees,

Dogs,

Cats,

Birds,

And reptiles,

And can occur between members of different species.

Approximately 20 psychological reasons for yawning have been proposed by scholars,

But there is little agreement on the primacy of any one.

During a yawn,

Muscles around the airway are fully stretched,

Including chewing and swallowing muscles.

Due to these strong repositioning muscle movements,

The airway,

Lungs,

And throat dilates to three or four times its original size.

The tensor tympani muscle in the middle ear contracts,

Which creates a rumbling noise perceived as coming from within the head.

However,

The noise is due to mechanical disturbance of the hearing apparatus,

And is not generated by the motion of air.

Yawning is sometimes accompanied in humans and other animals by an instinctive act of stretching several parts of the body,

Including the arms,

Neck,

Shoulders,

And back.

The English yawn continues a number of Middle English forms.

Yawning from Old English,

Ghanian and Yenin,

Yonin from Old English frequentatives,

Yin-Yon from a Germanic root gin,

The Germanic root as Proto-Indo-European cognates from a root gay,

Found also from n-suffix in Greek to yawn,

And without the n in English,

Gap,

Gum,

Pallet,

And gasp via Old Norse,

Latin,

Hio,

Hiatus,

And Greek,

Chasm,

Chaos.

The Latin term used in medicine is oscitatio,

Anglicized as oscitazione,

From the verb oscito,

To open the mouth.

Pendiculation is the act of yawning and stretching simultaneously.

There are a number of theories that attempt to explain why humans and other animals yawn.

One study states that yawning occurs when one's blood contains increased amounts of carbon dioxide,

And therefore becomes in need of the influx of oxygen or expulsion of carbon dioxide that a yawn can provide.

Yawning may reduce oxygen intake compared to normal respiration.

However,

The frequency of yawning is not decreased by providing more oxygen or reducing carbon dioxide in the air.

Animals subject to predation or other dangers must be ready to physically exert themselves at any given moment.

At least one study suggests that yawning,

Especially psychological contagious yawning,

May have developed as a way of keeping a group of animals alert.

If an animal is drowsy or bored,

It will be less alert than when fully awake and less prepared to spring into action.

Contagious yawning could be an instinctual signal between group members to stay alert.

Nervousness,

Which often indicates the perception of an impending need for action,

Has also been suggested as a cause.

Anecdotal evidence suggests that yawning helps increase a person's alertness.

Paratroopers have been noted to yawn during the moments before they exit their aircraft,

And athletes often yawn just before intense exertions.

Another notion states that yawning is the body's way of controlling brain temperature.

In 2007,

Researchers,

Including a professor of psychology from the sunny Albany,

US,

Proposed yawning may be a means to keep the brain cool.

Mammalian brains operate best within a narrow temperature range.

In two experiments,

Subjects with cold packs attached to their foreheads and subject asked to breathe strictly nasally exhibited reduced contagious yawning when watching videos of people yawning.

A similar hypothesis suggests yawning is used for regulation of body temperature.

Similarly,

Gutman and Dopart,

2011,

Found that when a subject wearing ear plugs yawns,

The air moving between the subject's ears and the environment causes a breeze to be heard.

Gutman and Dopart determined that a yawn causes one of three possible situations to occur.

The brain cools down due to an influx or outflux of oxygen.

Pressure in the brain is reduced by an outflux of oxygen and the pressure of the brain is increased by an influx of air caused by increased cranial space.

One review hypothesized that yawning's goal is to periodically stretch the muscles of the throat,

Which may be important for efficient vocalization,

Swallowing,

Chewing,

And also keeping the airway wide.

Yawning behavior may be altered as a result of medical issues such as diabetes,

Stroke,

Or adrenal conditions.

Excessive yawning is seen in immunosuppressed patients such as those with multiple sclerosis.

A professor of clinical and forensic neuropsychology at Bournemouth University has demonstrated that cortisol levels rise during yawning.

With respect to a possible evolutionary advantage,

Yawning might be a herd instinct.

Theories suggest that the yawn serves to synchronize mood in gregarious animals,

Similar to howling in a wolf pack.

It signals fatigue among members of a group in order to synchronize sleeping patterns and periods.

Research by Garrett Norris,

2013,

Involving monitoring the behavior of students kept waiting in a reception area,

Indicates a connection supported by neuroimaging research between empathic ability and yawning.

We believe that contagious yawning indicates empathy.

It indicates an appreciation of other people's behavioral and physiological state,

Says Norris.

The yawn reflex has long been observed to be contagious.

In 1508,

Erasmus wrote,

One man's yawning makes another yawn,

And the French proverbialized the idea to,

Un bon bailleur en fin bailleux sept.

One good gaper makes seven others gape.

Often,

If one person yawns,

This may cause another person to empathetically yawn.

Observing another person's yawning face,

Especially their eyes,

Reading or thinking about yawning,

Or looking at a yawning picture,

Can cause a person to yawn.

The proximate cause for contagious yawning may lie with mirror neurons in the frontal cortex of certain vertebrates,

Which,

Upon being exposed to a stimulus from conspecific and occasionally interspecific organisms,

Activates the same regions in the brain.

Mirror neurons have been proposed as a driving force for imitation,

Which lies at the root of much human learning,

Such as language acquisition.

Yawning may be an offshoot of the same imitative impulse.

In 2007,

A study found that young children with autism spectrum disorders do not increase their yawning frequency after seeing videos of other people yawning,

In contrast to neurotypical children.

In fact,

The autistic children actually yawned less during the videos of yawning than during the control videos.

The relationship between yawn contagion and empathy is strongly supported by a 2011 behavioral study conducted by Ivan Norshia and Elisabetta Pallaggi,

University of Pisa,

Italy.

The study revealed that among other variables,

Such as nationality,

Gender,

And sensory modality,

Only social bonding predicted the occurrence,

Frequency,

And latency of yawn contagion.

As with other measures of empathy,

The rate of contagion was found to be greatest in response to kin,

Then friends,

Then acquaintances,

And lastly strangers.

Related individuals showed the greatest contagion in terms of both occurrence of yawning and frequency of yawns.

Strangers and acquaintances showed a longer delay in the yawn response latency compared to friends and kin.

Hence,

Yawn contagion appears to be primarily driven by the emotional closeness between individuals.

The social asymmetry in contagious yawning,

With contagious yawning being more frequent between familiar subjects than between strangers,

Remains when only yawns that are heard but not seen are considered.

This finding makes it unlikely that visual attentional biases are at the basis of the social asymmetry observed in a contagious yawning.

Two classes of yawning have been observed among primates.

In some cases,

The yawn is used as a threat gesture as a way of maintaining order in the primate social structure.

Specific studies were conducted on chimpanzees and stumptail macaques.

A group of these animals was shown a video of other members of their own species yawning.

Both species yawned as well.

This helps to partly confirm a yawn's contagiousness.

The Discovery Channel's show Mythbusters also tested this concept.

In their small-scale informal study,

They concluded that yawning is contagious,

Although elsewhere the statistical significance of this finding has been disputed.

Gordon Gallup,

Who hypothesizes that yawning may be a means of keeping the brain cool,

Also hypothesizes that contagious yawning may be a survival instinct inherited from our evolutionary past.

During human evolutionary history,

When we were subject to predation and attacks by other groups,

If everybody yawns in response to seeing someone yawn,

The whole group becomes much more vigilant and much better at being able to detect danger.

A study by the University of London has suggested that the contagiousness of yawns by a human will pass to dogs.

A study observed that 21 of 29 dogs yawned when a stranger yawned in front of them,

But did not yawn when the stranger only opened his mouth.

Heldt and Eichste,

2010,

Showed that dogs,

Like humans,

Develop a susceptibility to contagious yawning gradually,

And that while dogs have seven months catch yawns from humans,

Younger dogs are immune to contagion.

The study also indicated that nearly half of the dogs responded to the humans' yawn by becoming relaxed and sleepy,

Suggesting that the dogs copied not just the yawn,

But also the physical state that yawns typically reflect.

In a study involving gelida baboons,

Yawning was contagious between individuals,

Especially those that were socially close.

This suggests that emotional proximity rather than spatial proximity is an indicator of yawn contagion.

Evidence from the occurrence of contagious yawning linked to empathy is rare outside of primates.

It has been studied in candidate species,

Such as the domestic dog and wolf.

Domestic dogs have shown the ability to yawn contagiously in response to human yawns.

Domestic dogs have demonstrated they are skilled at reading human communication behaviors.

This ability makes it difficult to ascertain whether yawn contagion among domestic dogs is deeply rooted in their evolutionary history,

Or is a result of domestication.

In a 2014 study,

Wolves were observed in an effort to answer this question.

The results of the study showed that wolves are capable of yawn contagion.

The study also found that the social bond strength between individuals affected the frequency of contagious yawning in wolves,

Supporting previous research which ties contagious yawning to emotional proximity.

Some evidence for contagious yawning has also been found in budgerigars,

A species of social parrots.

This indicates that contagious yawning may have evolved several times in different lineages.

In budgerigars,

Contagious yawning does not seem to be related to social closeness.

In certain neurological and psychiatric disorders,

Such as schizophrenia and autism,

The patient has an impaired ability to infer the mental states of others.

In such cases,

Yawn contagion can be used to evaluate their ability to infer or empathize with others.

Autism Spectrum Disorder,

ASD,

Is a developmental disorder which severely affects social and communicative development,

Including empathy.

The results of various studies have shown a diminished susceptibility to contagious yawn compared to the control group of typically developed children.

Since atypical development of empathy is reported in Autism Spectrum Disorder,

Results support the claim that contagious yawning and the capacity of empathy share common neural and cognitive mechanisms.

Similarly,

Patients with neurological and psychiatric conditions,

Such as schizophrenia,

Have shown an impaired ability to empathize with others.

Contagious yawning is one means of evaluating such disorders.

The Canadian psychiatrist Heinz Lehman claimed that increases in yawning could predict recovery in schizophrenia.

The impairment of contagious yawning can provide greater insight into its connection to the underlying causes of empathy.

There is still substantial disagreement in the existing literature about whether or not yawn contagion is related to empathy at all.

Empathy is a notoriously difficult trait to measure,

And the literature on the subject is confused,

With the same species sometimes displaying a connection between contagious yawning and social closeness,

And sometimes apparently not.

Different experimenters typically use slightly different measures of empathy,

Making comparisons between studies difficult.

And there may be a publication bias,

Where studies which find a significant correlation between the two tested variables are more likely to be published than studies which do not.

By revising in a critical way the literature for and against yawn contagion as an empathy-related phenomenon,

A 2020 review has shown that the social and emotional relevance of the stimulus,

Based on who the yawner is,

Can be related to the levels of yawn contagion,

As suggested by neurobiological,

Ethological,

And psychological findings.

Therefore,

The discussion over the issue remains open.

Mammals,

Birds,

And other vertebrates yawn.

In animals,

Yawning can serve as a warning signal.

Charles Darwin's book,

The Expression of the Emotions in Man and Animals,

Mentions that baboons yawn to threaten their enemies,

Possibly by displaying large canine teeth.

Similarly,

Siamese fighting fish yawn only when they see a conspecific same species or their own mirror image,

And their yawn often accompanies aggressive attack.

Guinea pigs also yawn in a display of dominance or anger,

Displaying their impressive incisor teeth.

This is often accompanied by teeth chattering,

Purring,

And scent marking.

Adelie penguins employ yawning as part of their courtship ritual.

Penguin couples face off,

And the males engage in what is described as an ecstatic display,

Opening their beaks and pointing their faces skyward.

This trait has also been seen among emperor penguins.

Researchers have been attempting to discover why these two different species share this trait,

Despite not sharing a habitat.

Snakes yawn,

Both to realign their jaws after a meal,

And for respiratory reasons,

As their trachea can be seen to expand when they do this.

Dogs,

And occasionally cats,

Often yawn after seeing people yawn,

And when they feel uncertain.

Dogs demonstrate contagious yawning when exposed to human yawning.

Dogs are very adept at reading human communication actions,

So it is unclear if this phenomenon is rooted in evolutionary history,

Or a result of domestication.

Fish can also yawn,

And they will increase this behavior when experiencing a lack of oxygen.

Socially contagious yawning has been observed in budgerigars,

And anecdotally when tired in other parrot species.

Yawning is often perceived as implying boredom,

And yawning conspicuously in another's presence has historically been a faux pas.

In 1663,

Francis Hawkins advised,

In yawning,

Howl not,

And thou should sustain as much as thou can to yawn,

Especially when thou speakest.

George Washington said,

If you cough,

Sneeze,

Sigh,

Or yawn,

Do it not loud,

But privately,

And speak not in your yawning,

But put your handkerchief or your hand before your face,

And turn aside.

These customary beliefs persist in modern age.

One of Mason Cooley's aphorisms is,

A yawn is more disconcerting than a contradiction.

A loud yawn may even lead to penalties for contempt of court.

In biology,

A reflex or reflex action is an involuntary,

Unplanned sequence or action,

And nearly instantaneous response to a stimulus.

Reflexes are found with varying levels of complexity in organisms with a nervous system.

A reflex occurs via neural pathways in the nervous system called reflex arcs.

A stimulus initiates a neural signal,

Which is carried to a synapse.

The signal is then transferred across the synapse to a motor neuron,

Which evokes a target response.

These neural signals do not always travel to the brain,

So many reflexes are an automatic response to a stimulus that does not receive or need conscious thought.

Many reflexes are fine-tuned to increase organism survival and self-defense.

This is observed in reflexes such as the startle reflex,

Which provides an automatic response to an unexpected stimulus,

And the feline riding reflex,

Which reorients a cat's body when falling to ensure safe landing.

The simplest type of reflex,

A short latency reflex,

Has a single synapse or junction in the signaling pathway.

Long latency reflexes produce nerve signals that are transduced across multiple synapses before generating the reflex response.

The myotatic or muscle stretch reflexes,

Sometimes known as deep tendon reflexes,

Provide information on the integrity of the central nervous system and peripheral nervous system.

This information can be detected using electromyography,

EMG.

Generally,

Decreased reflexes indicate a peripheral problem,

And lively or exaggerated reflexes a central one.

A stretch reflex is the contraction of a muscle in response to its lengthwise stretch.

While reflexes are stimulated mechanically,

The term H-reflex refers to the analogous reflex stimulated electrically,

And tonic vibration reflex for those stimulated to vibration.

A tendon reflex is the contraction of a muscle in response to striking its tendon.

The Golgi tendon reflex is the inverse of a stretch reflex.

Newborn babies have a number of other reflexes which are not seen in adults,

Referred to as primitive reflexes.

These automatic reactions to stimuli enable infants to respond to the environment before any learning has taken place.

They include asymmetrical tonic neck reflex,

Palmomental reflex,

Moro reflex,

Also known as the startle reflex,

Palmar grasp reflex,

Rooting reflex,

Sucking reflex,

Symmetrical tonic neck reflex,

Tonic labyrinthine reflex.

Other reflexes found in the central nervous system include abdominal reflexes,

Gastrocolic reflex,

Enocutaneous reflex,

Barrel reflex,

Cough reflex,

Chromosteric reflex,

Diving reflex,

Lazarus sign,

Muscular defense,

Photic sneeze reflex,

Scratch reflex,

Sneeze,

Startle reflex,

Withdrawal reflex,

Crossed extensor reflex.

Many of these reflexes are quite complex,

Requiring a number of synapses in a number of different nuclei in the central nervous system,

E.

G.

The escape reflex.

Others of these involve just a couple of synapses to function,

E.

G.

The withdrawal reflex.

Processes such as breathing,

Digestion,

And the maintenance of the heartbeat can also be regarded as reflex actions,

According to some definitions of the term.

In medicine,

Reflexes are often used to assess the health of the nervous system.

Doctors will typically grade the activity of a reflex on a scale from 0 to 4.

While 2 plus is considered normal,

Some healthy individuals are hyporeflexive and register all reflexes at 1 plus,

While others are hyporeflexive and register all reflexes at 3 plus.

Some might imagine that reflexes are immutable.

In reality,

However,

Most reflexes are flexible and can be substantially modified to match the requirements of the behavior in both vertebrates and invertebrates.

A good example of reflex modulation is the stretch reflex.

When a muscle is stretched at rest,

The stretch reflex leads to contraction of the muscle,

Thereby opposing stretch,

Resisting reflex.

This helps to stabilize posture.

During voluntary movements,

However,

The intensity gain of the reflex is reduced or its sign is even reversed.

This prevents resistance reflexes from impeding movements.

The underlying sites and mechanisms of reflex modulation are not fully understood.

There is evidence that the output of sensory neurons is directly modulated during behavior,

For example,

Through presynaptic inhibition.

The effect of sensory input upon motor neurons is also influenced by interneurons in the spinal cord or ventral nerve cord,

And by descending signals from the brain.

Breathing can also be considered both involuntary and voluntary,

Since breath can be held through internal intercostal muscles.

In physiology,

The all-or-none law,

Sometimes the all-or-none principle or all-or-nothing law,

Is the principle that if a single nerve fiber is stimulated,

It will always give a maximal response and produce an electrical impulse of a single amplitude.

If the intensity or duration of the stimulus is increased,

The height of the impulse will remain The nerve fiber either gives a maximal response or none at all.

It was first established by the American physiologist Henry Pickering Bowditch in 1871 for the contraction of heart muscle.

An induction shock produces a contraction,

Or fails to do so according to its strength.

If it does so at all,

It produces the greatest contraction that can be produced by any strength of stimulus in the condition of the muscle at the time.

This principle was later found to be present in the skeletal muscle by Keith Lucas in 1909.

The individual fibers of nerves also respond to stimulation according to the all-or-none principle.

The first recorded time of isolating a single action potential was carried out by Edgar Adrian in 1925 from a set of cross-cut muscle fibers.

Using a thermionic triode valve amplifier with 1850 amplification,

Adrian noticed that when the muscle preparation was left to hang,

It produced oscillations.

Yet,

When supported,

No such activity occurred.

Later,

With the help of Ingo Zauterman,

Adrian isolated and stimulated one sensory fiber.

The impulses externally on the fiber were uniform,

As simple as the dots in Morse code.

The magnitude of the action potential set up in any single nerve fiber is independent of the strength of the exciting stimulus,

Provided the latter is adequate.

An electrical stimulus below threshold strength fails to elicit a propagated spike potential.

If it is of the threshold strength or over,

A spike,

A nervous impulse of maximum magnitude,

Is set up.

Either the single fiber does not respond with spike production,

Or it responds to the utmost of its ability under the conditions at the moment.

This property of the single nerve fiber is termed the all-or-none relationship.

This relationship holds only for the unit of tissue.

For nervous tissue,

The unit is the nerve cell.

For skeletal muscle,

The unit is the individual muscle fiber.

And for the heart,

The unit is the entire auricles of the entire ventricles.

Stimuli too weak to produce a spike do,

However,

Set up a local electronus,

The magnitude of the electronic potential progressively increasing with the strength of the stimulus until a spike is generated.

This demonstrates the all-or-none relationship in spike production.

The above account deals with the response of a single nerve fiber.

If a nerve trunk is stimulated,

Then as the exciting stimulus is progressively increased above a threshold,

A large number of fibers respond.

The minimal effective,

I.

E.

Threshold,

Stimulus is adequate only for fibers of high excitability.

But a stronger stimulus excites all the nerve fibers.

Increasing the stimulus further does increase the response of whole nerve.

Heart muscle is excitable,

I.

E.

It responds to external stimuli by contracting.

If the external stimulus is too weak,

No response is obtained.

If the stimulus is adequate,

The heart responds to the best of its ability.

Accordingly,

The auricles or ventricles behave as a single unit,

So that an adequate stimulus normally produces a full contraction of either the auricles or ventricles.

The force of the contraction obtained depends on the state in which the muscle fibers find themselves.

In the case of muscle fibers,

The individual muscle fiber does not respond at all if the stimulus is too weak.

However,

It responds maximally when the stimulus rises to threshold.

The contraction is not increased if the stimulus strength is further raised.

Stronger stimuli bring more muscle fibers into action,

And thus the tension of a muscle increases as the strength of the stimulus applied to it rises.

Classical conditioning,

Also respondent conditioning and Pavlovian conditioning,

Is a behavioral procedure in which a biologically potent physiological stimulus,

E.

G.

Food,

Is paired with a neutral stimulus,

E.

G.

The sound of a musical triangle.

The term classical conditioning refers to the process of an automatic condition response that is paired with a specific stimulus.

The Russian physiologist Ivan Pavlov studied classical conditioning with detailed experiments with dogs and published the experimental results in 1897.

In the study of digestion,

Pavlov observed that the experimental dogs salivated when fed red meat.

Pavlovian conditioning is distinct from operant conditioning,

Instrumental conditioning,

Through which the strength of a voluntary behavior is modified,

Either by reinforcement or by punishment.

However,

Classical conditioning can affect operant conditioning.

Classically conditioned stimuli can reinforce operant responses.

Classical conditioning is a basic behavioral mechanism,

And its neural substrates are now beginning to be understood.

Though it is sometimes hard to distinguish classical conditioning from other forms of associative learning,

E.

G.

Instrumental learning and human associative memory,

A number of observations differentiate them,

Especially the contingencies whereby learning occurs.

Together with operant conditioning,

Classical conditioning became the foundation of behaviorism,

A school of psychology which was dominant in the mid-20th century and is still an important influence on the practice of psychological therapy and the study of animal behavior.

Classical conditioning has been applied in other areas as well.

For example,

It may affect the body's response to psychoactive drugs,

The regulation of hunger,

Research on the neural basis of learning and memory,

And in certain social phenomena such as the false consensus effect.

Classical conditioning occurs when a conditioned stimulus,

CS,

Is paired with an unconditioned stimulus,

US.

Usually,

The conditioned stimulus is a neutral stimulus,

E.

G.

The sound of a tuning fork.

The unconditional stimulus is biologically potent,

E.

G.

The taste of food,

And the unconditioned response,

UR,

To the unconditioned stimulus is an unlearned reflex response,

E.

G.

Salivation.

After pairing is repeated,

The organism exhibits a conditioned response,

CR,

To the conditioned stimulus when the conditioned stimulus is presented alone.

A conditioned response may occur after only one pairing.

Thus,

Unlike the UR,

The CR is acquired through experience,

And it is also less permanent than the UR.

Usually,

The conditioned response is similar to the unconditioned response,

But sometimes it is quite different.

For this and other reasons,

Most learning theorists suggest that the conditioned stimulus comes to signal or predict the unconditioned stimulus,

And go on to analyze the consequences of the signal.

Robert A.

Rescorla provided a clear summary of this change in thinking and its implications in his 1988 article Pavlovian Conditioning.

It's not what you think it is.

Despite its widespread acceptance,

Rescorla's thesis may not be defensible.

Classical conditioning offers from operant or instrumental conditioning.

In classical conditioning,

Behaviors are modified through the association of stimuli,

Whereas in operant conditioning,

Behaviors are modified by the effect they produce,

I.

E.

Reward or punishment.

The best-known and most thorough early work on classical conditioning was done by Ivan Pavlov,

Although Edwin Twitmire published some related findings a year earlier.

During his research on the physiology of digestion in dogs,

Pavlov developed a procedure that enabled him to study the digestive processes of animals over long periods of time.

He redirected the animals' digestive fluids outside the body where they could be measured.

Pavlov noticed that his dogs began to salivate in the presence of the technician who normally fed them,

Rather than simply salivating in the presence of food.

Pavlov called the dogs anticipatory salivation psychic secretion.

Putting these informal observations to an experimental test,

Pavlov presented a stimulus,

E.

G.

The sound of a metronome,

And then gave the dog food.

After a few repetitions,

The dog started to salivate in response to the stimulus.

Pavlov concluded that if a particular stimulus in the dog's surroundings was present when the dog was given food,

Then that stimulus could become associated with food and cause salivation on its own.

In Pavlov's experiment,

The unconditioned stimulus US was the food,

Because its effects did not depend on previous experience.

The metronome sound is originally a neutral stimulus NS,

Because it does not elicit salivation in the dogs.

After conditioning,

The metronome sound becomes the conditioned stimulus CS,

Or conditional stimulus,

Because its effects depend on its association with food.

Likewise,

The responses of the dog follow the same conditioned versus unconditioned arrangement.

The conditioned response CR is a response to the conditioned stimulus,

Whereas the unconditioned response UR corresponds to the unconditioned stimulus.

Pavlov reported many basic facts about conditioning.

For example,

He found that learning occurred most rapidly when the interval between the CS and the appearance of the US was relatively short.

It is often thought that the conditioned response is a replica of the unconditioned response,

But Pavlov noted that saliva produced by the CS differs in composition from that produced by the US.

In fact,

The CR may be any new response to the previously neutral CS that can be clearly linked to experience with a conditional relationship of CS and US.

It was also thought that repeated pairings are necessary for conditioning to merge,

But many CRs can be learned with a single trial,

Especially in fear conditioning and taste aversion learning.

Learning is fastest in forward conditioning.

During forward conditioning,

The onset of the CS precedes the onset of the US in order to signal that the US will follow.

Two common forms of forward conditioning are delay and trace conditioning.

Delay conditioning.

In delay conditioning,

The CS is presented and is overlapped by the presentation of the US.

For example,

If a person hears a buzzer for five seconds,

During which time air is puffed into their eye,

The person will blink.

After several pairings of the buzzer and the puff,

The person will blink at the sound of the buzzer alone.

This is delay conditioning.

Trace conditioning.

During trace conditioning,

The CS and US do not overlap.

Instead,

The CS begins and ends before the US is presented.

The stimulus-free period is called the trace interval or the conditioning interval.

If in the above buzzer example,

The puff came a second after the sound of the buzzer stopped,

That would be trace conditioning with a trace or conditioning interval of one second.

During simultaneous conditioning,

The CS and US are presented and terminated at the same time.

For example,

If a person hears a bell and has air puffed into their eye at the same time and repeated pairings like this led to the person blinking when they hear the bell,

Despite the puff of air being absent,

This demonstrates that simultaneous conditioning has occurred.

Second-order or higher-order conditioning follow a two-step procedure.

First,

A neutral stimulus,

CS1,

Comes to signal a US through forward conditioning.

Then a second neutral stimulus,

CS2,

Is paired with a first,

CS1,

And comes to yield its own conditioned response.

For example,

A bell might be paired with food until the bell elicits salivation.

If a light is then paired with the bell,

Then a light may come to elicit salivation as well.

The bell is the CS1 and the food is the US.

The light becomes the CS2 once it is paired with the CS1.

Backward conditioning occurs when a CS immediately follows a US.

Unlike the usual conditioning procedure in which the CS precedes the US,

The conditioned response given to the CS tends to be inhibitory.

This presumably happens because the CS serves as a signal that the US has ended,

Rather than as a signal that the US is about to appear.

For example,

A puff of air directed at a person's eye could be followed by the sound of a buzzer.

Reviews

I yawned for about two minutes then fell right asleep 😴