What Is A Critical Period In Psychology?
- Sabrina Sarro
- Critical period is an ethological term that refers to a fixed and crucial time during the early development of an organism when it can learn things that are essential to survival. These influences impact the development of processes such as hearing and vision, social bonding, and language learning.
- The term is most often experienced in the study of imprinting, where it is thought that young birds could only develop an attachment to the mother during a fixed time soon after hatching.
- Neurologically, critical periods are marked by high levels of plasticity in the brain before neural connections become more solidified and stable. In particular, critical periods tend to end when synapses that inhibit the neurotransmitter GABA mature.
- In contrast to critical periods, sensitive periods, otherwise known as “weak critical periods” happen when an organism is more sensitive than usual to outside factors in influencing behavior, but this influence is not necessarily restricted to the sensitive period.
- Scholars have debated the extent to which older organisms can develop certain skills, such as natively-accented foreign languages, after the critical period.
- 0.1 What is the critical period for psychological development?
- 1 What is a real life example of critical period?
- 1.1 What is the critical period psychology Chomsky?
- 1.2 What happened in the critical period?
- 1.3 Why was this called the critical period?
- 1.4 What are the characteristics of a critical period?
- 1.5 Is critical period a theory?
- 1.6 Do only humans have critical periods?
- 2 What was the critical period and why was it critical?
- 3 Who created the critical period theory?
- 4 What is Chomsky’s main theory?
- 5 What is an example of a critical period and sensitive period?
- 6 What is an example of critical period in pregnancy?
- 7 What is an example of a sensitive period?
What is critical period in psychology examples?
For example, the first 3 days of life are thought to constitute a critical period for imprinting in ducks, and there may be a critical period for language acquisition in human infants. See also sensitive period.
What is the critical period for psychological development?
Critical periods of development – A critical period is a time during early postnatal life when the development and maturation of functional properties of the brain, its “plasticity,” is strongly dependent on experience or environmental influences. This concept plays an important role in the nature versus nurture debate ( Sengpiel, 2007 ).
However, not all neuroscientists agree on what defines a critical period for neural circuit development. One strict interpretation defines the critical period as a subset of sensitive periods. Sensitive periods are special time-windows in early development where experience has a profound effect on the brain, while critical periods are a special case wherein experience is absolutely required at fixed developmental periods for subsequent normal function.
The critical period should include the onset of robust plasticity response to sensory experience, a defined period of time when induction of plasticity is possible. One of the major concepts currently being investigated in neuroscience is that such critical periods represent heightened epochs of brain plasticity, and that sensory experience during these periods produces permanent, large-scale changes in neuronal circuits.
- The various critical periods start very shortly after the relevant sensory information first becomes available and a certain level of intracortical inhibition marks the onset of the critical period.
- The development of cortical inhibitory circuitry initially lags behind that of the excitatory circuitry.
The critical period is characterized by changes not only at the level of synaptic transmission, but increasingly by structural changes, which result in closure of the critical period. The most significant changes in the cortex towards the end of the critical period are those seen in the extracellular matrix, a network of macromolecules, which becomes more and more rigid during postnatal development.
Thus, three phases of plasticity define the critical period: (1) pre-critical period: the initial formation of neuronal circuits that is not dependent on experience; (2) critical period: a distinct onset of robust plasticity in response to experience when the initially formed circuit can be modified by experience; and (3) closure of the critical period: after the end of the critical period, the same experience no longer elicits the same degree of plasticity ( Hooks and Chen, 2007 ).
In humans, critical periods are extended over years and there are different critical periods for different brain functions (for example binocular vision or language acquisition) and unless a certain function is learned during this period, the function will remain poor.
- The well-known classic experiments by Hubel and Wiesel showed how early sensory deprivation dramatically affects anatomy and functional organization of the visual cortex.
- These authors reported that occluding one eye (monocular deprivation) early in development led to a severe reduction in the number of visual cortical cells responding to that eye, with a very strong increment in the number of neurons activated by the open eye.
They termed this the critical period during which synaptic connections in the primary visual cortex are modified by visual experience. The critical period shown by Wiesel and Hubel (1963) has remarkably influenced not only biologists but also psychologists, philosophers, physicians, politicy makers, parents, and educators.
- In fact, this sensitive period is also considered present in humans, involving language, music, sport, and even sociability.
- The brain continues to develop throughout infancy, childhood, and adolescence and psychologists assert that, through the same periods, one acquires increasingly higher mental functions.
During growth, the brain accumulates information about the external world in order to build an internal world in the temporo-parietal association cortex. In thinking, the frontal association cortex exerts its executive function on the internal world to manipulate thought models such as images, ideas, and concepts to simulate what could happen in the external world.
- In fact we acquire knowledge and new skills over our entire lives; it is likely that there are differently timed sensitive periods for acquiring different types of knowledge and skills such as literacy, numeracy, music, art, and physical education.
- A new field of research, called “nurturing the brain,” is expected to provide accurate knowledge about sensitive periods, which will help formulate an efficient learning timetable for curricula in nurseries and schools ( Hensch, 2004; Ito, 2004; Konishi, 2004 ).
Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9780444528919000014
What period is known as the critical period?
The ‘Critical Period’ of American history— the years between the end of the American Revolution in 1783 and the ratification of the U.S. Constitution in 1789 —was either the best of times or the worst of times.
What is a real life example of critical period?
Critical Periods vs Sensitive Periods – Critical periods are similar to sensitive periods, and scholars have, at times, used them interchangeably. However, they describe distinct but overlapping developmental processes. A sensitive period is a developmental stage where sensory experiences have a greater impact on behavioral and brain development than usual; however, this influence is not exclusive to this time period (Knudsen, 2004; Gallagher, 2020).
These sensitive periods are important for skills such as learning a language or instrument. In contrast, A critical period is a special type of sensitive period – a window where sensory experience is necessary to shape the neural circuits involved in basic sensory processing, and when this window opens and closes is well-defined (Gallagher, 2020).
Researchers also refer to sensitive periods as weak critical periods. Some examples of strong critical periods include the development of vision and hearing, while weak critical periods include phenome tuning – how children learn how to organize sounds in a language, grammar processing, vocabulary acquisition, musical training, and sport training (Gallagher et al., 2020).
What is an example of a critical period in humans?
Vision System – There are different critical periods for different visual functions. They usually fall between birth and puberty 7, Early research shows that visual acuity develops from birth to around age 5 and the period between ages 3 and 5 shows the most growth.
What is the critical period psychology Chomsky?
UG and the critical period hypothesis – A key question about the relationship of UG and SLA is: is the language acquisition device posited by Chomsky and his followers still accessible to learners of a second language? The critical period hypothesis suggests that it becomes inaccessible at a certain age, and learners increasingly depended on explicit teaching.
What is the difference between critical and sensitive periods in psychology?
3.3. Maternal Caregiving Disruptions in Nonhuman Primates – Animal research on the importance of maternal caregiving has not been limited to rodents. For example, the work on the effects of maternal separation was extended to nonhuman primates by Harlow and Zimmermann more than half a century ago,
- In a series of studies, infants were separated from their mothers at an early age, and either reared in isolation or with peers.
- These separated (and in some instances, isolated) animals exhibited symptoms of depression and motor stereotypies.
- More importantly, when these animals were exposed to younger peers, this experience appeared to reverse many of the negative effects of the early separation,
The work of Harlow and Suomi delineated how maternal deprivation and being raised with peers led to animals who were anxious and impulsive as adults and displayed an abnormal stress response, Rosenblum and Paully examined the effects of inadequate care in Bonnet macaques.
They observed infants where the mother had either consistently available resources, lack of resources, or inconsistent/unpredictable conditions. They reported that in the inconsistent conditions infants displayed significantly greater emotionality and alternations in their stress physiology. Sanchez and colleagues also demonstrated that inconsistent and abusive caregiving in the Rhesus macaques compromised infant behavior and stress physiology.
Across these studies, there is strong evidence that inadequate care is associated not only with heightened stress physiology in the infant but also maladaptive behaviors as they mature. O’Connor and Cameron as well as Sabatini et al. assessed the effects of maternal deprivation in Rhesus macaque infants by removing the mother from the infant’s social group at different infant ages.
- This led to dramatic social abnormalities and aberrant behaviors in the infant monkeys depending upon whether the mother was removed at 3 months, one month, or one week after birth.
- The earlier the removal, the more disturbed the behaviors in the monkey.
- Many abnormalities in these maternally deprived monkeys persisted into adulthood, and they were associated with reductions in dendritic branching in the prefrontal cortex and in gene expression in the amygdala.
The notion of critical periods may be traced to the work of ethologists such as Konrad Lorenz who described imprinting in birds. Lorenz noted that baby ducklings would follow the individual who moved within their line of sight right after they were hatched.
If there was no one there, they would not imprint. If a bird was only present after a certain period of time, then the ducklings would not imprint. A moving stimulus was most effective in initiating imprinting during the “critical period”, Hubel and Wiesel’s studies on the visual system reinforced the idea that experiences during a critical period impacts typical development.
Hubel and Wiesel were interested in the effects of early experience on the typical development of visual function. They completed experiments first on cats, and then on monkeys, in which they either deprived a single eye or both eyes of visual experience and examined the changes that occurred in the occipital cortex, the area of the brain involved in early visual processing.
- They found that depriving one eye of typical visual experience led to aberrant vision, and in fact the second eye actually “took over” regions of the occipital cortex normally activated by the other eye.
- In addition, there appeared to be a sensitive period during which experience had a significant role in the development of typical visual processing.
After that sensitive period, it was more difficult for brain organization supporting typical visual processing to occur, Hubel and Wiesel’s work stands as the preeminent work on the effects of early experience and sensitive periods. There have been a number of other researchers who have examined the idea of sensitive periods in the visual and other domains in human infants.
- Before describing that work, it is important to have a clear definition of just what a sensitive period means.
- Eric Knudsen, a neurobiologist at Stanford who studies the effects of early experience, writes: ” Experience exerts a profound influence on the brain and, therefore, on behavior.
- When the effect of experience on the brain is particularly strong during a limited period in development, this period is referred to as a sensitive period.
Such periods allow experience to instruct neural circuits to process or represent information in a way that is adaptive for the individual. When experience provides information that is essential for normal development and alters performance permanently, such sensitive periods are referred to as critical periods.
- Nudsen differentiates between a sensitive and critical period.
- A sensitive period is one during which experience exerts its effect during a limited time.
- However, when experience is essential and alters performance permanently, then such a period is called a critical one.
- He provides a possible mechanism by which this may occur in the brain, in which experience “instructs” neural circuits to process information.
That is, somehow, experience wires brain circuitry in a way that is adaptive for the individual.
What happened in the critical period?
Numerous disputes arose between the states. An economic depression threatened many citizens with the loss of their farms, homes, and jobs. These years of troubles from 1783 to 1789 came to be known as the ‘Critical Period.’ In 1789 the United States Constitution went into effect.
Why was this called the critical period?
The Constitutional Convention During what historians often call the “critical period” after the American Revolution, many were concerned that the Articles of Confederation were inadequate for the states to grow commercially and economically. Not only that, but George Washington was especially worried that a disparate group of states would not nurture the uniquely American character he had fought for in the Revolution.
In response to the recommendation of the Annapolis Convention, the Confederation Congress announced a meeting to revise the Articles of Confederation. This meeting would take place in Philadelphia during the summer of 1787. But not everyone was convinced that the Articles needed revision—or that complete revision of the Articles was necessary or desirable.
Patrick Henry from Virginia, for example, said that he “smelt a rat” and declined to attend. Later, Henry would become a leading opponent of the Constitution. The Anti-Federalists like him were suspicious of the strong, centralized power of a nation. They feared the cost to liberty of a national government with vast new powers over all the states and the people as individuals. Patrick Henry refused to attend the Constitutional Convention. These concerns notwithstanding, every state except Rhode Island sent delegates. Fifty-five men in all would participate in the Convention, including George Washington of Virginia, Alexander Hamilton of New York, and Benjamin Franklin of Pennsylvania.
Although they were leading statesmen and are regarded as Founders today, Thomas Jefferson and John Adams were not at the Convention. They were serving in diplomatic posts in Europe at the time. They did, however, share their thoughts and opinions on the Convention’s activities in correspondence. James Madison of Virginia was the first to arrive at Independence Hall in Philadelphia in May, 1787.
The 36-year old had already done a great deal of thinking about the form and principles of a new government, and he had a plan ready to present. He and some others were convinced that one needed change was the creation of an energetic and independent executive. James Madison, “Father of the Constitution” Many feared the tyranny of a King. It took them almost the entire summer to agree on Article II and the office of President as it exists now—an individual (rather than an executive council), elected through the Electoral College (rather than appointed by the legislature) for a four-year term.
(Many years later, the Twenty-Second Amendment ratified in 1951 would limit the President to two four-year terms.) In the end, the security that George Washington would be the nation’s first president eased the concerns of most delegates. Washington had proven his republican virtue many times over, including when he resigned after being General.
They knew he would shape the role for future generations with prudence. Divisions emerged among the delegates regarding other issues as well. There was a rift between those from large states and small states. Should all states have equal representation in the national legislature, or should states be represented based on their population? The idea of representation by equal states was favored, not surprisingly, by small states. Roger Sherman helped create the Great Compromise. The “Great Compromise,” suggested by Roger Sherman of Connecticut, created a bi-cameral (two-chamber) legislature where the states would be represented equally in one chamber, and by population in the other.
The states would have two Senators each, selected by state legislatures; the states would also send a number of Representatives to the House of Representatives based on their state’s population. This compromise preserved the federal character of Congress and added a national one: The states would be represented in the Senate, and the people of the United States of America would be represented in the House of Representatives.
The bicameral legislature was also chosen as a way of checking the power of the legislature. Dividing it into two houses would lessen the chances of usurpation. The different modes of election to each branch also kept the houses distinct. More than a century later, one key aspect of this compromise would be modified with the Seventeenth Amendment.
- That amendment changed the way Senators were selected, making them elected by the people in each state.
- Another issue on which the Convention compromised was slavery.
- The Northwest Ordinance, passed by the Confederation Congress, had banned slavery in New Territories.
- Southern delegates from slave states feared the new government would try to regulate slavery or ban it outright.
The delegates eventually agreed that Congress would not be able to interfere with “the importation ofpersons” until 1808. (Congress indeed banned the international slave trade in 1808, while never using the word “slaves.”) They also compromised on how slave-holding states would count enslaved persons for the purposes of taxation and representation. Former slave and abolitionist, Frederick Douglass, later stated the Three-Fifths clause, “leans to freedom, not to slavery.” Desiring to have union in one nation the anti-slavery delegates had to accept compromise with the slave-holding states that would allow slavery to continue.
- The Three-Fifths Compromise gave the South increased political power in Congress, by allowing it to count three-fifths of their slaves’ population towards representation.
- Proponents of slavery would have had even more political power, if those states had been able to count every slave person as one.
- Many fault the Convention for failing to abolish slavery right then and there.
As a group, the Founders were conflicted about slavery. All of them knew it was evil. But to have a union, it was necessary to live with it. The delegates put the creation of one nation ahead of the desire many had to do away with what they knew was a terrible and unjust violation of the very natural or inalienable rights the revolution was fought to secure.
To state the principle of human equality in the Declaration was as much as they could do at that time. Slavery had already been done away with in some places, and they hoped that it would die out in future generations. They did not see a way to take further action against slavery in their lifetimes, though many freed their slaves after their deaths.
They put their hopes in later generations to eradicate this terrible evil. The Constitutional Convention and the Constitution it produced were truly unique and monumental in history. Its system of separated powers, federalism, and numerous checks and balances were a remarkable experiment.
- Federalist author James Madison wrote in Federalist No.37 about the uniqueness of the Constitution’s history (James Madison, Federalist No.37, 1788).
- Alexis de Tocqueville called the Constitution a triumph of human deliberation under the pressure of a critical moment (Alexis de Tocqueville, Democracy In America, 1835).
In effect, one form of government had been abolished and replaced with another, and the rule of law prevailed. Not a single shot had been fired; not a single “enemy of the revolution” had been put to death, not a single life had been lost. The Founding of the United States of America was and remains to this day truly exceptional in human history.
What are the characteristics of a critical period?
A critical period is a time during an organism’s life span when it is more sensitive to environmental influences or stimulation than at other times during its life.
Is critical period a theory?
The critical period hypothesis is a linguistic theory that directly links age and language acquisition. Originally developed by Wilder Penfield, the hypothesis suggests that it is only possible for people to learn a language fluently (either a first or second language) if they start learning it before the age of nine.
What is important about critical periods?
Auditory processing – Many studies have supported a correlation between the type of auditory stimuli present in the early postnatal environment and the development on the topographical and structural development of the auditory system. First reports on critical periods came from deaf children and animals that received a cochlear implant to restore hearing.
Approximately at the same time, both an electroencephalographic study by Sharma, Dorman and Spahr and an in-vivo investigation of the cortical plasticity in deaf cats by Kral and colleagues demonstrated that the adaptation to the cochlear implant is subject to an early, developmental sensitive period.
The closure of sensitive periods likely involves a multitude of processes that in their combination make it difficult to reopen these behaviorally. The understanding of the mechanisms behind critical periods has consequences for medical therapy of hearing loss.M.
Merzenich and colleagues showed that during an early critical period, noise exposure can affect the frequency organization of the auditory cortex. Recent studies have examined the possibility of a critical period for thalamocortical connectivity in the auditory system. For example, Zhou and Merzenich (2008) studied the effects of noise on development in the primary auditory cortex in rats.
In their study, rats were exposed to pulsed noise during the critical period and the effect on cortical processing was measured. Rats that were exposed to pulsed noise during the critical period had cortical neurons that were less able to respond to repeated stimuli; the early auditory environment interrupted normal structural organization during development.
In a related study, Barkat, Polley and Hensch (2011) looked at how exposure to different sound frequencies influences the development of the tonotopic map in the primary auditory cortex and the ventral medical geniculate body. In this experiment, mice were reared either in normal environments or in the presence of 7 kHz tones during early postnatal days.
They found that mice that were exposed to an abnormal auditory environment during a critical period P11- P15 had an atypical tonotopic map in the primary auditory cortex. These studies support the notion that exposure to certain sounds within the critical period can influence the development of tonotopic maps and the response properties of neurons.
What is the most critical stage of human life?
Video transcript of “Mini Parenting Master Class: What’s the most important phase of life?” – Pia: “Hello there, I am Dr Pia Rebello Britto, a scientist at UNICEF where we work to help babies’ brains develop.” Grover: “And it is I, your cute and adorable pal, Grover!” Pia: “And Grover is going to help me explain how we make sure babies grow up to be smarter, stronger and kinderbecause that’s what they do on Sesame Street every day.” Grover: “I thought we were going to talk about this little baby seedling! Aww! See how cute it is! Yes, you are! Yes, you are!” Pia: “It looks very healthy, Grover.
You must be taking good care of it.” Grover: “Oh, I am.” Pia: “But before we start, I have an important question for you.” Grover: “What is that?” Pia: “Do you know, over the whole life of a human being – from when we are babies to grown up adults – what is the most important phase of life?” Grover: “Dr Pia! Of course I know what the most important phase” Pia: “Mmm hmm?” Grover: “of life” Pia: “Mmm hmm?” Grover: “is.” Pia: “I’ll help you out.
The most important phase of life is the first few years when you are a child. That’s when the brain grows really fast – faster than any other time in our life. The brain makes new connections every second! In fact, some believe that more than 80% of the brain is formed by the time a child turns three.” Grover: “Wait.
You are saying that my little furry monster brain did all of that? Before I was even three? I’m even smarter than I knew haha!” Pia: “You absolutely are! But the brain can only do this when it gets nutritious food, play time, lots of love and security That’s ‘eat, play, love’!” Grover: “Yes, well that is easy, Dr Pia! I eat, play and love every day with my friends on Sesame Street.” Pia: “And that’s why you’re helping me out! A brain of a child is not that different from a seedling.” Grover: “Wait, what do you mean?” Pia: “They both need to be fed! Did you know that more than half of each meal goes to build a baby’s brain? All that energy sparks the brain connections.” Grover: “Just like the little seedling here needs lots of water Oh, you have some water.
Yeah, and soil and sunlight so it can grow big and strong!” Pia: “Exactly. So if the seedling doesn’t get water and sunlight, it won’t blossom. The next is play. Talking, singing, cuddling, playing with a young child is not just fun, it’s also important to fire up those brain connections.” Grover: “Oh, I know how to play! Tag! You’re it!” Pia: “Lastly, babies need love – lots of love and a safe, happy environment to thrive.” Grover: “Oh yeah, love.
I will put you by my window where you will sit in the warm sun and be happy and safe – and have a great view of Sesame Street too!” Pia: “So, in other words, babies grow and learn through everyday moments. We shouldn’t underestimate the power of nutritious food, playtime and lots of love – loving babies, that’s what they need to be healthy and strong.” Grover: “Yes, just like how this cute baby seedling will someday grow into a big, beautiful flower!” Pia: “And when each flower is cared for, Grover, we have a beautiful garden.
So, please join Sesame Street and UNICEF in making early moments matter to give the little ones in your life the best start!” Grover: “The best. You deserve it, after all.” Dr. Pia Britto is UNICEF’s Chief of Early Childhood Development. Filmed with Grover from Sesame Street,
Do only humans have critical periods?
Only humans have critical periods. What happens if a pregnant woman smokes, drinks, or does drugs during her pregnancy?
What was the critical period and why was it critical?
The term Critical Period, coined by John Fiske (philosopher) in 1888 with his book ‘ The Critical Period of American History’, refers to the 1780s, a time right after the American Revolution where the future of the newly formed nation was in the balance.
- More specifically, the “Critical Period” refers to the period of time following the end of the American Revolutionary War in 1783 to the inauguration of George Washington as President in 1789.
- During this time, the newly independent former colonies were beset with a wide array of foreign and domestic problems.
Some historians believe it was a bleak, terrible time for Americans, while others believe the term “Critical Period” is exaggerated, and that, while the 1780s were a time of dispute and change, they were also a time of economic growth and political maturation.
Who created the critical period theory?
Tom Scovel writes, “The CPH is conceivably the most contentious issue in SLA because there is disagreement over its exact age span; people disagree strenuously over which facets of language are affected; there are competing explanations for its existence; and, to top it off, many people don’t believe it exists at all” (113).
Proposed by Wilder Penfield and Lamar Roberts in 1959, the Critical Period Hypothesis (CPH) argues that there is a specific period of time in which people can learn a language without traces of the L1 (a so-called “foreign” accent or even L1 syntactical features) manifesting in L2 production (Scovel 48).
If a learner’s goal is to sound “native,” there may be age-related limitations or “maturational constraints” as Kenneth Hyltenstam and Niclas Abrahamsson call them, on how “native” they can sound. Reducing the impression left by the L1 is certainly possible after puberty, but eliminating that impression entirely may not be possible.
Enji Hakuta et al. explains that the relationship between age and L1 interference in L2 production is really not up for debate: “The diminished average achievement of older learners is supported by personal anecdote and documented by empirical evidence.What is controversial, though, is whether this pattern meets the conditions for concluding that a critical period constrains learning in a way predicted by the theory” (31).
Some learners manage to overcome the “constraints” that Scovel believes are “probably accounted for by neurological factors that are genetically specified in our species” (114), but these learners are exceptional rather than the rule. It may be biology; it may be due to something else.
- The debate will continue, but evidence seems to indicate that the older learners become, the more difficult complete acquisition can be.
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What is Chomsky’s main theory?
Chomsky’s theory is based on the idea that all languages hold similar structures and rules, also known as a universal grammar. This theory states that all languages have formal universals and principles in common, with specific options and limits for variation in grammar and features between languages.
What is an example of a critical period and sensitive period?
Examples of putative critical/sensitive periods in biobehavioral development include the establishment of social and food preferences (imprinting), shaping the structure and function of sensory systems, and possibly in the area of language and language acquisition.
What is an example of critical period in pregnancy?
This fact sheet is about the critical periods of development and types of birth defects that can result from exposures at different stages of pregnancy. This information should not take the place of medical care and advice from your healthcare provider.
What are critical periods of development? In pregnancy, each part of the baby’s body forms at a specific time. During these times, the body can be very sensitive to damage caused by some medications, alcohol, or other harmful exposures. This specific time is called the “critical period of development” for that body part.
Does the chance for different types of birth defects change throughout pregnancy? Every pregnancy starts out with a 3-5% chance of having a birth defect. This is called the background risk. If an exposure can increase the chance for birth defects, the chance depends on what body part is developing at the time of exposure.
Once a body part has formed, it is no longer at risk to develop major birth defects. Some exposures could still affect a body part’s growth and/or function. The chart in this fact sheet shows the critical periods of development for different parts of the body. The chart starts from the time of conception when the egg and sperm join.
The weeks listed on the chart are the “embryonic age” or “fetal age” of a pregnancy. Note that this is different from a common way of dating a pregnancy called “gestational age.” Gestational age begins with the first day of a person’s last menstrual period.
This day is usually about two weeks before a baby is conceived. This means that you can change gestational age to embryonic/fetal age by subtracting two weeks. For example, 12 gestational weeks (since the first day of your last period) is the same as 10 fetal weeks (since the first day of conception).
The solid bars on the chart show when each part is most sensitive to harmful exposures and at risk for major birth defects. Birth defects are typically classified as “major” if they cause significant medical problems and need surgery or other treatment.
Heart defects, spina bifida, and clubfeet are examples of major birth defects. The striped bars show periods when the body parts are still at risk to develop minor birth defects and functional defects. “Minor” birth defects by themselves do not cause significant medical problems and usually do not require treatment or surgery.
Minor birth defects can also be variations of typical development. Wide-set eyes and large ears are examples of minor birth defects. Both major and minor birth defects are physical or structural changes. However, “functional defects” change how a part of the body works without changing its physical structure.
Intellectual disability and hearing loss are both examples of functional defects. The chart also shows the location of the most common birth defects that can occur during each week. In general, major defects of the body and internal organs are more likely to occur between 3 to 12 embryo / fetal weeks.
This is the same as 5 to 14 gestational weeks (weeks since the first day of your last period). This is also referred to as the first trimester. Minor defects and functional defects including those affecting the brain are also able to occur later in pregnancy. *Adapted from Moore 1993, and the National Organization of Fetal Alcohol Syndrome (NOFAS) 2009. What is the greatest risk from a harmful exposure during very early pregnancy? Harmful exposures during very early pregnancy have the greatest risk of causing miscarriage.
- A fertilized egg divides and attaches to the inside of the uterus during the first two weeks of embryo development.
- Very harmful exposures during this period (first four weeks after the first day of your last period) may interfere with the attachment of the embryo to the uterus.
- Harmful exposures during this time can also damage most or all of the cells of the growing embryo.
Problems with uterine attachment and severe cell damage can both result in a miscarriage. Sometimes this miscarriage is before a person even realizes that they are pregnant. Less severe exposures during this time may only damage a few of the embryo’s cells.
The cells of the embryo have a greater ability to recover at this early stage than they do later on in pregnancy. If an individual does not have a miscarriage, it is expected that the exposures during this time are not likely to cause a birth defect. The first four weeks of gestation are called the “all or none period.” “All” refers to high exposures damaging all of the embryo’s cells.
This damage can cause early miscarriage. “None” refers to exposures that are not high enough to have a significant effect on the pregnancy. The rule of the “all or none period” can be used to determine the chance of many different types of exposures. However, there are some important exceptions to this rule.
Please contact MotherToBaby to discuss your specific exposure with our experts. What are the greatest risks from harmful exposures during the first trimester of pregnancy? The first trimester of pregnancy is defined as up to the 14th week of pregnancy (13 weeks and 6 days) counting since the first day of your last menstrual period.
Harmful exposures during the first trimester have the greatest chance of causing major birth defects. This is because many important developmental changes take place during this time. The major structures of the body form in the first trimester. These include the spine, head, arms and legs.
The baby’s organs also begin to develop. Some examples of these organs are the heart, stomach and lungs. While the heart and stomach completely form during the first trimester, the lungs continue to develop past the first trimester. What are the greatest risks from harmful exposures during the second and third trimesters of pregnancy? Harmful exposures during the second and third trimesters can cause growth problems and minor birth defects.
Growth is an important part of the second and third trimester. The structures and organs that developed during the first trimester grow larger. Babies with growth problems may be much smaller or much larger than average. This size difference can put babies at risk for certain health problems.
- Harmful exposures during the second and third trimesters can also cause functional defects like learning problems.
- The brain is part of the central nervous system and it develops during the entire pregnancy.
- Major, structural brain development lasts until about 16 fetal weeks (18 gestational weeks).
- However, the brain continues to develop for the rest of the pregnancy, after birth and through young adulthood.
While usually less well studied, some exposures in the second or third trimester might cause other pregnancy complications, such as preterm delivery (delivery before 37 weeks gestation) or low levels of amniotic fluid (the fluid that surrounds the developing baby in the uterus).
- The use of certain medications and substances at the end of pregnancy can cause withdrawal in some newborns.
- You should always tell your healthcare provider about all of the medications, supplements and/or other substances that you take.
- Does this mean that an exposure might be harmful at certain times during pregnancy but not at other times? Yes.
Imagine your healthcare provider gives you a new medication to take during your third trimester. We will call this “Medication A.” You read that Medication A increases the chance for heart defects. This means that babies may have a higher chance for major heart defects if they are exposed to this medication during the heart’s critical period of development.
What is an example of a critical period quizlet?
What is the best known example of a critical period in development? Imprinting.e.g., a newly hatched mallard duckling will attach to and follow the first noisy moving object encountered after birth. However, psychologists have yet to identify any specific critical period for any human mental process or behavior.
What is an example of a sensitive period?
Order is one of the most important sensitive periods. When a child is between the ages of two and three, he needs order in his environment, otherwise, he will throw tantrums. The following sensitive period is language, in which the child is fascinated by the human voice.