What is the difference between inborn and acquired reflexes

At four weeks the first muscular fetal activity can be observed in the beating heart; at seven weeks neck extension can be observed; at eight weeks a startle response, general movements, hiccups and isolated arm and leg movements are present; and, by twelve weeks head rotation, breathing movements, yawning, sucking and swallowing responses are present.

By the time an infant is born, a considerable movement repertoire has emerged, arming the newborn with the basic survival mechanisms, providing tools necessary to gain information about the outside world, and establishing the rudimentary basis for advanced motor development.

Once an innate reflex becomes active, it automatically generates a motor response whenever the triggering response is present and without conscious or directed control. Acquired reflexes are more complex learned motor responses that develop after birth. As a newborn learns to control and direct innate motor responses, he acquires his first learned reflexive motor responses.

As simple reflexive motor responses are mastered and become automatic , they are referred to as acquired motor reflex responses. An acquired motor reflex is sometimes difficult to distinguish from an innate reflex. Statistical interactions between genes and environment are well-documented in behavioural genetic studies on animals Fuller, Sarkar et al.

Whether this lesson can be extrapolated to human behaviour, and why or why not, is the subject of a set of interlocking controversies which are too intricate to pursue here. There is an extensive philosophical literature on these controversies and their history. Some recent contributions which include citations of the relevant scientific literatures include: Kaplan ; Sesardic ; Schaffner a; Schaffner b; Griffiths and Tabery While the difference between two individuals can be caused by a genetic or an environmental difference between them, the development of any trait in an individual depends on both genes and environment.

Every aspect of development, including learning, consists in the regulated expression of the genome. Conversely, innumerable aspects of the environment are required at each stage in the life of the organism to keep development on its normal course, or, in other words, to ensure that the right genes are expressed in the right cells at the right time.

Thus, all traits develop through the interaction of genome and environment. But if all traits depend on genes, it may still be that some traits depend on them in a special way. After all, everyone knows that there is a genetic code, so it must be coding for something. Considered as a language, the genetic code can only refer to the twenty-three standard amino acids and can only say which order to put them in. These proposals are discussed in more detail in the entry Biological information.

Here I will simply make two points about these proposals. Mammals have a chromosomal system of sex-determination. But many reptiles use temperature, an environmental signal, to switch genetically identical eggs between male or female developmental pathways.

Other reptiles have a genetic system which can be overridden by an environmental signal. Some fish even switch sex in adulthood in response to environmental cues. Moreover, the behaviours that parents use to give appropriate cues to their eggs, and some of the products of those behaviours, such as nests of rotting vegetation which maintain a suitable temperature range, are designed by natural selection to ensure the correct sex-ratio in offspring, so the teleosemantic program can be applied to them too.

These diagrams were introduced at around the same time as the idea of the gene and the distinction between genotype and phenotype Sarkar and have long been advocated as the clearest way to think about the role of genes in development Hogben ; Lewontin ; Gottlieb ; Kitcher Suppose, for example, that with respect to some environmental variable E an organism with a given genotype G1 will develop the same phenotype P way no matter what value the environmental variable takes Figure 1. Philip Kitcher suggests that some norms of reaction may have this form, but only in some limited, but perhaps contextually important, range of environments Kitcher For example, a disease caused by the loss of one or both normal copies of a gene might develop in every environment except those specifically structured as clinical interventions to cure the disease.

Genotype makes a constant difference across some range of environment. While the genetic variable does not determine the actual value of the trait in each individual, it does determine the differences between individuals.

Moreover, when the norms of reaction have this form, heritability scores become relevant to the question of whether and how much a phenotype can be altered by environmental intervention, as discussed in the previous section. If correct, this would mean that educational enrichment would cause everyone to get higher test scores, but would not change the ordering of their scores. In perhaps the most famous paper on this topic the geneticist Richard Lewontin argued that actual norms of reaction are likely to be non-additive Figure 3.

Genotype and environment jointly determine the outcome in the straightforward sense that the effect of each factor on the outcome is a function of the particular value taken by the other factor. In Section 4. The first identifies innate traits with those characteristic of an entire species and acquired traits with those that vary between populations and individuals.

The third, and currently most influential, distinguishes different patterns of interaction between genes and environment and identifies one pattern with the innate and another with the acquired.

One was that an innate trait might be defined as a trait an organism will manifest in the normal course of development. But Stich himself offered a counterexample to this analysis: universally held beliefs, such as the belief that water quenches thirst, will count as innate traits on this analysis, which seems counterintuitive Stich , p. Ariew suggests that Stich's analysis confuses evidence for innateness with innateness itself.

Universality is evidence for the existence of a particular kind of developmental mechanism Ariew , p. A similar analysis was independently suggested by Stich , 13— Stich's suggestion has been elaborated and defended by Muhammad Ali Khalidi who like Stich seems not to have encountered Lorenz's work Khalidi ; Khalidi Both Stich and Khalidi restrict the analysis to innate cognitive traits, although it seems clear from Lorenz's work that it can be made general.

Khalidi , Khalidi admits that severe difficulties stand in the way of actually measuring the information content of developmental environments and capacities. He suggests, however, that scientists have rough-and-ready ways to assess the informational gap, using various forms of deprivation experiment see Section 1 above. It is unclear whether Khalidi would endorse Lorenz's analysis of information and of the significance of the deprivation experiment.

The deprivation experiment is designed to eliminate just those factors that could explain the trait's functional adjustment to the environment.

Khalidi makes no reference to the adaptive value of innate traits, and like Stich he thinks that the idea of innateness should be applicable to disease phenotypes as well as to functional phenotypes Khalidi , But Khalidi's idea of an informational gap between the developmental environment and the innate trait seems rather problematic in the case of innate diseases.

What information is manifest in a child born anencephalic and thus, presumably, with no cognitive traits at all? This concept was introduced by the influential mid th century embryologist and theoretical biologist Conrad H. Waddington ; ; ; Developmental canalization was part of a broader vision of how an organism develops from the fertilized egg.

Many features of the phenotype are explained by the dynamical properties of that developmental system as a whole, rather than by the influence of one or a few specific alleles. Thus, for example, Waddington sought to explain one of the major biological discoveries of his day — the fact that extreme phenotypic uniformity can be observed in many wild populations despite extensive genetic variation in those same populations — by appealing to the global dynamics of developmental systems.

A genetically canalized developmental system takes development to the same endpoint from many different genetic starting points. The development of wild-type phenotypes can thus be buffered against genetic variation.

Figure 4. The state space is depicted as a surface, each point of which represents a phenotype. The genetic parameters are depicted as pegs that pull on the surface and thus determine its contours. Epistatic interactions between genetic loci are represented by links between the strings by which those loci pull on the surface.

Waddington intended this diagram to make vivid the idea that the effect of a change at one genetic locus depends upon the states of all the other genetic loci, since it is all the loci together which determine the shape of the landscape.

The phenotypic impact of a genetic change is not proportional to the magnitude of the genomic change, but depends on the structure of the developmental system. Furthermore, the phenotypic difference produced by a genetic difference is not explained by that genetic difference in itself, but by how that change interacts with the rest of the developmental system.

This picture retains considerably validity in the light of contemporary developmental genetics. A phenotypic outcome is environmentally canalised if those features of the surface which direct development to that endpoint are relatively insensitive to the manipulation of the environmental parameters.

A phenotypic outcome is genetically canalised if those features of the surface which direct development to that endpoint are relatively insensitive to the manipulation of the genetic parameters. Ariew proposes to identify innateness with environmental canalization. Innateness-as-canalization is a matter of degree.

A trait is more innate the more environmental parameters its development is buffered against and the wider the range of variation in those parameters against which it is buffered. Griffiths and Machery have offered a counterexample to Ariew's analysis Griffiths and Machery The developmental psychobiologist Celia Moore showed that the spinal cord nuclei of male rats differ from those of female rats in ways that allow the male to use his penis during copulation Moore ; Moore These neural differences result from differences in gene expression in the developing spinal cord of the rat pup, which in turn result from differences in the amount of licking of the genital area by the mother, which in turn results from greater expression in male pups of a chemical that elicits maternal licking.

According to Ariew's characterization of innateness as canalization, these experiments show that the rat's ability to copulate is not innate:. The rat's ability to copulate depends on an environmental condition that is found everywhere the system develops and so, according to Ariew, it is not innate. But intuitively the rat's ability to copulate is innate.

Griffiths and Machery argue that this intuition results from the fact that the ability to copulate is an evolutionary adaptation and universal in male rats. Additional counterexamples can be constructed using this formula. However, Ariew has argued, and his critics accept, that the existence of intuitive counterexamples is not really to the point. Instead, the analysis is meant to explicate a research strategy used by scientists like Chomsky. According to Ariew, canalised development is the hallmark of the development of these paradigmatically biological traits, and the research programs of scientists like Chomsky should be seen as attempts to demonstrate the canalised development of psychological traits.

Other recent contributors to the philosophical literature on innateness have adopted a similar methodological stance. The idea of a closed process remains in need of further elaboration. Mallon and Weinberg themselves are concerned about how to individuate developmental processes. They do not want early, general phases of development like the closure of the neural tube to count as part of the development of specific traits like language. Another significant hurdle for the account is to provide individuation criteria for developmental outcomes.

If we attend to the details of the nerve ganglia of the rat's spinal cord, different outcomes can be distinguished, resulting from different amounts of maternal licking and it becomes an open process.

Meaney and collaborators Meaney a; Meaney b and see below. Fiona Cowie and Richard Samuels have taken a rather different approach to the innateness concept. Samuels has suggested that this is the best explication of the concept of innateness in contemporary neo-nativist psychology. Primitivism becomes a more substantive thesis if it is linked to an account of the nature of psychological explanation, or perhaps of psychological explanation as conceived in the neo-nativist tradition.

Ariew suggests that innateness guides research by embodying a strategy of investigating psychological traits as if they were paradigmatically biological traits like hearts and hair. Cowie and Samuels suggest that innateness guides research by embodying a strategy of not investigating a trait as if it were a paradigmatically psychological trait like a belief or a phobia, but instead treating it as a boundary condition in psychological explanations of related traits.

The incorporation of Lehrman's critique of Lorenz into the ethological tradition had a lasting impact on animal behaviour research. After a half-century of research on the development of birdsong the doyen of researchers in that field, Peter Marler sums up his view of innateness like this:. Other leading animal behaviour researchers see even this casual use of the distinction as pernicious. They judge eight of these to be both genuinely independent definitions and potentially valuable scientific constructs Mameli and Bateson , p.

Several recent philosophical defenders of the innateness concept suggest in a spirit of common sense that whatever the limitations of the concept, traits can at least be placed along a rough continuum of dependence on the environment e.

Ariew ; Mallon and Weinberg ; Khalidi But this does not seem like common sense to many scientists who actually study behavioral development. Developmental psychobiology is a field that grew out of the research tradition of which Lehrman was part for a textbook treatment see Michel and Moore ; two excellent popular introductions are Bateson and Martin , and Moore The consensus in this field is that experimental research on the development of a trait typically reveals sensitive dependence on environmental parameters.

These parameters are highly varied, and they interact non-additively with genetic parameters. Developmental psychobiologists reject a basic idea at the heart of much discussion of innateness, which is that evolution makes development reliable by making it insensitive to environmental parameters.

Instead, they argue that evolution often makes development reliable by stabilizing environmental parameters at the right value or by exploiting pre-existing environmental regularities. West and King and their collaborators have conducted a long term study of the ontogenetic niche of the brown-headed cowbird Molothrus Ater West and King ; West and King ; West, King et al.

Cowbirds are obligate nest parasites like cuckoos and do not hear their parents sing as they grow up. West and King showed that, amongst other processes, male song is shaped by feedback from female cowbirds, whose wing stroking and gaping displays in response to the songs they prefer are strong reinforcers for males.

Female song preferences are themselves subject to social influences. As a result of these and other processes cowbirds reliably transmit not only species-typical song, but also the regional song dialects typical of birds that acquire their songs as a result of exposure to parental song. In stark contrast to the suggestions of the philosophers discussed in Section 4.

In many species, of course, the stabilization of the parameters of the ontogenetic niche is achieved through parental care, as we saw in the case of the development of penile reflexes in the rat in Section 4. But parental care can also be used as a mechanism of adaptive phenotypic plasticity. Michael Meaney and collaborators' account of the role of parental care in the development of temperament in rats is a good exemplar of this phenomenon.

Cross-fostering BALBc pups to mothers of the more laid-back C57 strain removes the differences between the two strains. Meaney and collaborators show how the amount of licking and arched-back nursing which pups receive from their mother regulates gene expression so as to direct the development of the pup's brain Meaney, Although the phenotypes of these inbred laboratory strains are constant, it is plausible that in wild rats maternal behavior reflects the mother's stress levels.

We might guess that the rat pup will respond to indicators of environmental quality, and we might guess that the mother's behavior is a useful source of information on this topic, but not that the information resides in whether the mother arches her back during suckling.

Non-obvious parameters are typically overlooked in deprivation experiments designed to establish that a trait is innate, but are often revealed by positive efforts to understand how behaviour develops Gottlieb Natural selection does not select for mechanisms which buffer traits against variation in the environment unless variation of that kind regularly occurs in the environments in which the species lives. In fact, any buffering mechanism which is not actively being used will tend to decay by mutation.

One famous example is the inability of humans and their relatives to synthesise ascorbic acid vitamin C. The ascorbic acid synthesis pathway was disabled by mutation during the long period in which our fruit-eating ancestors had no chance of developing vitamin C deficiences Jukes and King Short Answer Questions SA 3. Looking to do well in your science exam?

Learn from an expert tutor. Book a free class! Solution : Reflexes are of two types:- 1 Natural inborn reflex:-Is one in which no previous experience or learning is required. Example Blinking and watering of eyes coughing,sneezing,vomiting: these are protective reflexes.

Salviation when hungry ,swallowing,peristalsis:provide functional efficiency. Some examples of conditioned reflexes are : Watering of mouth salivation at the sight of a favourite or tasty food. Here,as an acquired reflex,salivation occurs because our brain remembers the taste of the food due to a previous experience Typing on the keyboard of a computer Playing a musical instrument.

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