The chapter on Sensitive Periods by Gariépy et al. (2020) introduces a number of theories, concepts, and research themes we will explore further during the semester. You come to this class with diverse interests in the subject matter and a wide-ranging knowledge base. So, as a basis for writing this first Reflection paper, select from this chapter a theme that resonates well with your interests and current knowledge.
Your goal is to inform a naïve (but educated) reader on the theory, concepts, and/or research theme that got your attention. The key to taking your reader by the hand through your line of argumentation is to introduce the topic in a way that outlines its central themes (unpacks, not opaque), and opens the road to elaborate, step-by-step, the logic of the ideas you want to share with a community of readers. Finally, keep in mind that good writing wraps up emphasizing the richness of what was presented with a view to its broad implications.
This is doable in the space provided with good organization, astute selection of material to include, economy of words (by using the right concepts) careful sentence construction, and thoughtful organization of paragraphs (i.e., providing a logical structure for your line of argumentation).
In the end, you want your reader to exclaim: “Thank you so much for communicating your knowledge in such as clear, convincing, and engaging way!”
PS: You have hereby explained the basis of my evaluation of your work (see also the Rubric).
Limit your entries to the equivalent of 1and 1/2pages, Times 12, double spaced
In the attached document is where you will get your source and information from.
In the paper talk about critical periods and newborn screening this info is in the attached document as well.
if you have a hard time finding it here is a copy and paste of most of it
We can conclude with confidence that critical or sensitive periods in their original biological sense do exist, but this conclusion is
largely based on research showing that animals that have been deprived of naturally occurring experiences or exposed to a toxic
stimulus show varying degrees of severity and permanence of impairment depending on the timing of those experiences in development. Researchers cannot manipulate human experiences the same way they do in experiments with animals, so circumscribing
critical periods in human development remains a difficult task. It is possible, however, to approach this question by using natural
occurrences of neglect, maltreatment, or exposure to noxious stimuli. In this section, we examine what can be learned from studies
of such occurrences. As a note of caution, let us mention at the outset that these are quasi-experimental studies. The participants in
this kind of research are taken as they come and without the possibility of controlling (as we do under laboratory conditions) for
extraneous variables that cannot rule out alternative explanations. To make the matter more complex, we would like, ideally, to
determine whether critical periods exist not just in the formation of biological structures, but also in the developmental organization of adaptively significant behaviors, including as examples the formation of an affective bond with the caregiver, the acquisition
of language, or the capacity to think abstractly. The added difficulty in these cases is that multiple neurobiological systems develop
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and build on each other over time to support these complex behaviors. In turn, this organization generates buffering or compensatory mechanisms not present in simpler systems or, for that matter, in species where development does not advance at that level of
sophistication.
Critical periods in the development of biological structures are perhaps the best-known and least controversial example of a critical period in human development. For example, around the ninth week of gestation, the Y chromosome becomes involved in the
synthesis of testosterone. This release of testosterone is accompanied by the masculinization of the genital ridge and release of
testosterone in a brain that is still undergoing differentiation and functional organization at a rapid pace. This transformation takes
place within a well-specified time window, and the effects of testosterone release in the brain during this period are irreversible. We
have here a very good example of a critical period at the level of biological structures, whose mechanism of action has been documented in other species and which we know takes place via the same mechanism of induction in our own species as errors of nature
have confirmed it.
Other critical periods are more difficult to document. For example, understanding whether there is a critical period for lead exposure on development requires identifying a large group of children who are diverse with respect to whether they were exposed to
lead, when that exposure occurred, how much lead was ingested, and for how long. Precise estimates of the timing and amount of
exposure are difficult to determine because these data are retrospective. Nevertheless, studies suggest that late in the prenatal period
may be the most dangerous time for lead exposure, with effects that are more severe and more permanent than exposure at other
times. Thus, although not definitive and not a real test of a true critical period, findings such as these can help policy makers decide
when and where to invest limited resources to maximize the potential benefit or minimize potential harm. Of course, there is no
period in development when lead exposure is good, but evidence showing that exposure during a specific time in development has
much more severe or less reversible consequences than other times would be quite useful.
Another approach is to study the effects of naturally occurring instances of early deprivation. One of the most informative studies
in this regard is the Bucharest Early Intervention Project conducted by Nathan Fox, Charles Nelson, Charles Zeanah, and Dana Johnson at Harvard, the University of Minnesota, and Tulane. In this project, children previously institutionalized in Romanian orphanages were placed (at 9, 18, 30, or 42 months of age) into high-quality foster care in the United States and Canada and observed over
several years for placement effects on their intellectual, social–emotional, and brain development (Fox et al., 2017). Prior to institutional placement, these children had been exposed to a variety of risk factors including alcohol and prenatal drug exposure, as well
as abandonment and social and material deprivation. At the time of their placement in foster care, these children were behind on
virtually every measure of typical development. The Bucharest Early Intervention group hypothesized that foster care placement
would have little effect on experience-expectant processes, which depend on stimulation during a critical or sensitive period, but
that foster care placement would have more influence on experience-dependent processes in other domains that are less restricted
to a narrowly defined critical period.
Children showed improvements in virtually every developmental domain measured, including IQ, emotional expression, attention, and social development; the only domain in which they did not show improvement was physical growth. Moreover, infants
who were institutionalized for the shortest periods of time and who were placed early in foster care showed the most rapid and
complete recovery from exposure to early adverse conditions. The effects of early deprivation on emotional attachment were
striking. Zeanah and his colleagues noted among these children the prevalence of a syndrome called ‘reactive attachment disorder,’
which consists of two opposing but equally maladaptive responses to social contact: emotional withdrawal and inhibition and
indiscriminate, disinhibited approach of strangers. Remarkably, over the course of 2 or 3 years of foster care placement and the experience of sensitive, child-centered interactions, these atypical behaviors were progressively replaced by more organized attachment
patterns (e.g., using the caregiver as a secure base for exploration). Equally striking was improvement in physiological measures
indexing cognitive and behavioral competence (e.g., magnitude and amplitude of brain activity) over time. In every case, the effects
of intervention were a joint function of the age at which placement in foster care took place and how much time had elapsed since
placement. Clearly, these effects show that the cognitive, behavioral, and social–emotional domains (including their neuronal
support), quite unlike basic cellular processes of differentiation, all develop following an experience-dependent process. In other
words, they are not fixed by stimulation encountered within a narrow window of time. In fact, as noted above, the only developmental domain that appeared so constrained by early experience in this research was physical growth, a biological process more
intimately tied to the perinatal effects of exposure to adversity.
Other examples of neglect have been taken as evidence of critical periods in language development. For ethical reasons it would
be impossible to systematically vary the time at which a child first hears language. However, it is possible to study the rare cases of
children who were deprived of language under conditions of abuse or neglect. A well-known case study is that of Genie, a child who
was discovered after 13 years of being placed by her father in complete isolation in the backroom of a house where she had been
strapped to a potty chair, beaten, abandoned, and prevented from any contact with other humans. By the time she was discovered,
Genie could not speak, presumably because she had never been spoken to. The fact that sustained attempts to teach her language
failed (she had considerable language but could not master the most elementary rules of grammar) was taken by the linguist Eric
Lennenberg as evidence that there is a critical period for the acquisition of language, somewhere between ages 2 and 13, after which
the biological window closes, making it impossible to acquire language later. As popular as this case has been, it remains what it is:
a single case. Moreover, as pointed out by Kevin McDonald at California State University, Genie is also an account of trauma,
extreme abuse, and attachment failuredall factors that may, just the same, explain her failure to learn language. Under any circumstance, it would be extremely difficult to determine whether there is a critical period for acquiring language. Exposure to language in
our species is virtually inevitable. Consider, for example, what a mother who just gave birth naturally does when the nurse places the
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newborn in her arms for her to hold: She places her child in a face-to-face position and talks to her. Isolating exposure to language
while keeping other factors approximately constant would be very difficult.
Finally, we can gain some insight into critical periods by examining the effects of corrective intervention on sensory development. For example, it has been possible to study children born deaf who have received a cochlear implant, an electronic device surgically implanted under the skin of individuals with congenital deafness to stimulate the auditory nerve and provide some sounds
that otherwise would be impossible to detect. Studies of children who have received cochlear implants at varying ages suggest
that those who receive implants before 4 to 6 years of age have superior speech and language development than those who receive
implants after 8 years of age. These data do not provide positive proof of the existence of a critical period, but they do provide useful
information for clinicians and parents about the optimal timing of exposure to sound and the best time to have this surgery
performed.
Time and Timing in Development
Although full proof of critical periods in humans remains difficult to obtain, timing is an important consideration in infant and
early childhood development. And just as important is that complex behaviors, as mentioned earlier, are likely to have less welldefined, and probably less constrained, windows of time. However, while a window for learning may be open for a long time,
competent development of a skill builds on earlier experiences, and learning may be more difficult as one gets older.
The development of literacy is a clear example of these points. Many nonreading adults can be taught to read; thus, there is not
likely to be a critical period for learning to read. However, it is much more difficult for an adult to learn to read, and the reading
fluency of adult learners usually lags compared with those who learned to read earlier. Likewise, most first graders learn to read.
However, the ease of learning to read is enhanced by exposure to critical experiences during the early childhood years, such as
rhyming games to build awareness of similarities and differences in sounds and early exposure to books and print materials.
Thus, although the infant and preschool years may not be considered a critical period for literacy development, per se, a window
of opportunity during this developmental period seems to exist in which exposure to certain types of experiences provides an important foundation that enables more complex learning to occur earlier and with greater ease.
Although critical periods may not strictly apply to early human development, timing is clearly important, and concepts such as
foundational skills, windows of opportunity, and optimal times for learning are quite relevant. Two examples are presented to here
to show the importance of timing of treatments or experiences in early development.
Newborn Screening
Newborn screening is a public health program that rests heavily on the urgency of early treatments to prevent morbidity or mortality
caused by a range of endocrine, metabolic, or genetic disorders. Newborn screening can be traced back to the 1960s when Robert
Guthrie developed a screening test for phenylketonuria (PKU) using blood spots. PKU is an inborn error of metabolism in which
the body is unable to process phenylalanine, a critical amino acid. If untreated, PKU results in severe intellectual disability, small
head circumference, and behavioral problems, signs of which begin to emerge by 6 months of age. However, PKU is easily treatable
by a diet that dramatically lowers phenylalanine in food. To be maximally effective, the diet must be started early. Changing the diet
at a later point in development does not undo the damage done if PKU is not treated early.
Today every state operates a screening program for all newborns. Newborn screening is based on a fundamental assumption that
early identification of children with selected conditions allows for treatments that must be provided early if they are to be effective.
Although research on critical periods has not typically been used to justify newborn screening, a condition-by-condition review is
conducted to determine the consequences of the disorder and the benefits of timely treatment (Kemper et al., 2014). For example,
children with severe combined immunodeficiency (SCID) (sometimes referred to as the ‘bubble boy’ disease) have an inherited
disorder that compromises the immune system. If children with SCID are not diagnosed and treated early, most die from ordinary
infections by 2 years of age. Currently, the only way to ‘cure’ SCID is through hematopoietic stem cell transplantation, a bone
marrow transplant procedure that can restore normal immune function. But the transplant must be done before the onset of infections. Timing of the identification and treatment of this condition is essential, a critical period of identification that must occur
within the first few days of life for children to survive (Puck, 2019).
Disorders such as SCID clearly exemplify the practical application of the concept of critical periods. But newborn screening is
about to enter a period of radical transformation, as rapid changes in technology such as genomic sequencing are making it possible
to identify literally hundreds of disorders for which there is no current treatment or for which treatment during the earliest weeks or
months of life may not be critical (Bailey and Gehtland, 2015; Grosse et al., 2010). Some have argued that no condition should be
identified unless it meets a standard closely associated with critical periods, with proof that early identification and early treatment
are necessary and would be less effective or even ineffective if provided later; others argue that a critical-period type standard is too
restrictive and that information about a condition has other potential benefits to families and society, even if no treatment currently
exists. Important discussions are needed about the ethical, legal, and social issues that accompany rapid expansion of genetic knowledge and the benefits of newborn screening for conditions in which the urgency of timing early treatments does not yet exist (Valdez
et al., 2016).
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