Evolution, genes, environment & behaviour (chapter 3) Flashcards
1
Q
What do genes carry the blueprint for?
A
Making our whole body, including the brain
2
Q
What are half of our genes estimated to target?
A
Brain structure and function (Kolb & Whishaw, 2003)
3
Q
What is behavioural genetics?
A
A field of psychological science dedicated to investigating how genes and the environmental factors interact during the course of development so as to affect behaviour
4
Q
What is evolutionary psychology?
A
A field of psychological science that investigates the evolutionary origins of various psychological traits
5
Q
What do evolutionary psychologists argue?
A
That important aspects of human psychology and social behaviour, including aggression, altruism, nepotism, and mate choice , are influenced by evolved biological mechanisms
6
Q
What is evolution (biological)?
A
Gradual change over time in organic life from one form into another
7
Q
What does the theory of evolution suggest?
A
That life on Earth has been subject to a low, but inexorably powerful, process of change
8
Q
What is natural selection?
A
Characteristics that increase the likelihood of survival and reproduction within a particular environment will be preserved in the population and therefore become more frequent over time
9
Q
What is natural selection based on? (3)
A
It is an undirected/’blind’ process based on three factors:
1) biological variation
2) high reproduction rates and the fact that not all members of a population survive
3) competition over limited resources (Lewin, 2005)
10
Q
What might some of these biological differences convey?
A
An advantage in terms of survival and reproduction. E.g. some members of a particular prey species may possess more acute hearing than others and hence be better able to detect and avoid predators
11
Q
What can happen if adaptive traits are heritable?
A
They can be biologically passed on from parent to infant, and over time they will increase in frequency in the population
12
Q
What does natural selection affect?
A
Not just physiological features (such as degree of furriness) but also behavioural traits
13
Q
What can be seen, behaviourally, when the genomes of dogs and wolves are compared? (experimental evidence)
A
The largest areas of difference were related to brain function and nervous system development. Other findings concerning differences in interaction with humans.
These findings cannot be easily explained in terms of differences in learning or experience, since both species in the experiment were raised in a similar manner. Thus it would seem that certain behaviours, such as visually orienting to humans, are under the influence of inherited biological factors.
14
Q
How do new traits emerge in a population if organisms faithfully inherit parental characteristics?
A
Genetic mutation
15
Q
What are mutations?
A
Random events and accidents in gene reproduction during the division of cells
16
Q
What do mutations do?
A
Help create variation within a population’s physical and behavioural characteristics. It is this genetic variation that makes evolution possible.
17
Q
What is the blending theory?
A
Blending suggests that parental traits are blended together rather like mixing white and red paint to produce pink
18
Q
What is a problem with blending?
A
It is incompatible with natural selection (Jenkin, 1867)
Blending traits eliminates variability. Without variability, natural selection cannot operate because it has nothing to select among. Thus, one would end up with the mean or average pattern and any behavioural differences would be due to learning from the environment.
19
Q
Who solved the puzzle of inheritance?
A
an Austrian monk, Gregor Mendel in the 1860s
20
Q
How were the laws of inheritance worked out?
A
Through conducting elegant experiments on pea plants. Mendel used a pea plant which produces either all green, all yellow or a mixture of green and yellow peas
21
Q
How did Mendel carry the experiments out?
A
Used a baseline parent generation (P). He prevented them from self-fertilizing and manually cross-fertilized them. The resultant peas in the following generation (F1) were all yellow: the green characteristic had completely disappeared. He then planted the F1 generation and allowed the resultant plants to self-fertilize. The F2 peas showed that the green trait had re-emerged in an overall ratio of 3 yellow:1 green. He then left these to self fertilise and found that of this generation (F3), the green peas grew into plants which only produced green peas , one third of the yellow plants produced all yellow peas and the remaining plants produced the same 3:1 ratio again.
22
Q
What did Mendel propose following his findings?
A
That the yellow was the dominant trait, and the green was recessive. Furthermore, as the yellow peas from the cross-fertilized plants grew into plants that produced both green and yellow peas, they must still have been carrying the green trait, but unexpressed. Mendel proposed that heredity factors (genes) must come in double doses - each of which is called an allele. The particular combination of dominant and recessive alleles determines the outwardly expressed characteristic of an organism or its phenotype.
23
Q
What is a dominant characteristic?
A
The particular characteristic that it controls will be displayed (AA)
24
Q
What is a recessive characteristic?
A
The characteristic will not show up unless the partner gene inherited from the other parent is also recessive (aa)
25
What is an allele?
Alternative forms of a gene that produce different characteristics
26
How to gametes differ from other cells?
They only carry one allele.
27
How do the complementary pairs of alleles come together from sex cells?
They come together in different combinations during fertilization. Organisms that receive the same alleles, that is, two dominant or two recessive, for a trait are called homozygous and organisms with different forms of alleles, one dominant and once recessive, are called heterozygous
28
What does homozygous mean?
Organisms that possess the same type of allele for a trait, either two dominant or two recessive
29
What does heterozygous mean?
Organisms that possess different allele for a trait, one dominant and one recessive
30
What is the genotype?
The specific and complete genetic make-up of the individual
31
What is the phenotype
The individual's outward observable characteristics
32
When is genotype present from?
Conception
33
What is phenotype affected by?
By both other genes and the environment. The same phenotype can have different genotypes.
34
How can the same genotype have the same phenotypes?
Identical twins have the same genes, but if one eats more than the other they will differ in the phenotypic expression of body weight.
35
What are Phenylketonuria and Huntington's disease (relation to genes)?
They are directly relevant psychological conditions which manifest themselves primarily in terms of psychological malfunctioning. They are both based upon the inheritance of specific combinations of the alleles from single genes
36
What is Phenylketonuria (PKU)?
PKU is associated with developmental delay and severe learning difficulties (Williams et al., 2008). It occurs at a rate of approximately 1 in 10,000 births. Often parents of children with PKU do not exhibit the condition. It runs in families and it tends to occur at a higher incidence in small, inbred communities (sometimes referred to as the Kissing Cousins Disease)
37
What is PKU based on/how is it inherited?
It is based on the inheritance of a double dose of recessive alleles (pp).
If a parent is homozygous for the dominant allele (PP), they cannot pass on the disorder.
If one parent was a carrier (Pp) and the other parent is not (PP), none of their children will develop the disorder, but there is a 50% chance that they will be a carrier.
If both parents are carriers, they themselves will not have the disorder, but their offspring will have a 25% chance of inheriting two recessive alleles and being born with PKU
38
What is Huntington's disease?
A degenerative disorder in which the sufferer experiences personality changes along with decreasing mental, memory and movement functioning over time. It affects 1 in 20,000 people. The average age of onset is 40 years old and generally one parent has the condition and his/her children have a 50% chance of passing it onto their children (Plomin et al., 2013)
39
What is Huntington's based on/how is it inherited?
HD is based upon the inheritance of a dominant allele; so that the inheritance of the condition is somewhat similar to that found with yellow peas. Unaffected individuals have two recessive alleles, while affected individuals have usually inherited one of the dominant alleles from their affected parent.
Statistically, it would be very unlikely that two heterozygous (Hh) for HD would meet and have children, however if this did occur then their children would have a 75% chance of developing the condition, with a 50% chance of the child being heterozygous (Hh) for the condition, and a 25% chance of them inheriting a double dose of the dominant allele (HH)
40
Why does HD remain in the population?
Because of its late onset. Since the disorder does not being to manifest itself until the affected individual is around 40 years of age, and by that time they will often have had children. Those children will have a 50:50 chance of inheriting the dominant allele from their affected parent and so in turn eventually manifest the symptoms of HD
41
What are genes?
Genes are functional segments of a long molecule called deoxyribonucleic acid or DNA
42
What does each gene carry?
The chemical code for manufacturing specific proteins, as well as the codes for when and where in the body they will be made
43
What can proteins do?
Proteins can take many forms and functions, and they underlie every bodily structure and chemical process. For that reason, DNA has been described as the blueprint for the body.
44
Since the mapping of the entire human genome, how many genes are humans thought to have?
It is now thought that humans have around 20,000 genes. The average gene has about 3,000 chemical base pairs, but sizes vary greatly; the largest gene has 2.4 million bases. It is estimated that about half of all genes target brain structure and functions.
45
What is a chromosome?
A single or double stranded structure comprised of proteins and deoxyribonucleic acid (DNA)
46
Where are chromosomes found?
They are only found within a cell's nucleus. They come in pairs.
47
What form do chromosomes take?
They take the form of a single strong or rod (called a chromatid) until they copy themselves prior to cell division, which is when they assume their iconic X-like shape.
48
What are chromosomes comprised of?
Proteins and DNA. Histone proteins are tiny structures around which the string of DNA is wound rather like thread on a cotton reel. If unravelled, the DNA molecule, although invisible to the naked eye, would be approximately 6 feet or 2 meters long.
49
What is a somatic cell?
A somatic cell is any cell forming the body of an organism. They do not contain reproductive cells.
50
What do all non-sex or somatic cells contain?
The diploid number of chromosome, which constitutes the full complement with both members of each pair being present (except for red blood cells that have no nucleus)
51
What do sex cells or gametes contain?
The haploid number of chromosomes comprised of only one of each of the pairs from one or other of the parents, that is, 23 in humans.
52
What does diploid mean?
Diploid is a cell consisting of two sets of chromosomes
53
What does haploid mean?
Haploid is half the number of chromosomes found in a gamete
54
What is a gamete?
Sex cells (eggs and sperm)
55
What is a zygote?
A zygote is a fertilized egg containing 46 pairs of chromosomes
56
What happens when the human egg and sperm combine?
The fertilized egg or zygote contains all 46 chromosomes, with one of each pair coming from the father and its complementary pair from the mother. The fact that there are complementary pairs of chromosomes relates to alleles. Each gene is represented twice (i.e. as alleles) at the same locus (which is Latin for place; the plural is loci) on each of the chromosome pairs.
57
What are chromosomes made of?
Made of two substances: nucleic acids and proteins.
| Proteins are much more varied than nucleic acids. They are molecules made of chains of approximately 100 amino acids.
58
What does the precise order or amino acids along the chain determine?
The type of protein. There are 20 kinds of amino acids, thus there are 20 to the 100 possible combinations (20 to the 100 is more than the total number of atoms in the universe. Since there are so many potential proteins, initially scientists thought that proteins must contain the heredity code. instead, the code for life is found in the nucleic acid, DNA
59
Why does DNA have a distinctive structure?
Discovered by Watson and Crick (largely based on the experimental work of Wilkins and Franklin in the early 1950s), it has a geometric shape of a double helix, which looks a bit like a twisted ladder. The rails of the ladder are made up of alternating sugar and phosphate molecules. The rungs are made up of pairs of four chemical or nitrogenous bases - adenine (A), thymine (T), guanine (G) and cytosine (C). It is as if the ladder rungs are made of two halves locked together: the chemical base guanine is always opposite cytosine, and adenine is always opposite thymine.
60
How does DNA allow for very accurate copying?
During replication, the two halves of the ladder split lengthways down the centre and each half can be used as a template to reconstruct the whole again. When the ladder is split, free-floating nucleotides in the cell are attracted to their complementary open bases on the DNA strand. It is rather like a self-assembling, four-piece, 3D jigsaw
61
What are nucleotides?
Nitrogenous base, phosphate and sugar groups
62
What is a codon?
A non-overlapping triplet sequence of nucleotides
63
What creates the specific commands to make functions in your body?
The sequence of the four letters of the DNA alphabet (A,T,G and C) creates the specific, commands for every feature and function of your body. The basic unit of the genetic code is made up of non-overlapping triplet sequences of nucleotides each of which is called a codon. With four different 'letters' of the DNA alphabet being read in non-overlapping triplet sequences, there are 64 possible combinations or permutations, 4*4*4.
64
What are the two type of statements that the triplet sequences can make?
One type specifies an amino acid and the other signals 'stop' in the sense that it stops the process of 'translating' a gene. With 20 types of amino acid and a stop sign, the total number of statements needed is 21. With 64 possible permutations, there is a great deal of overlap in the triplet code so that nearly every type of amino acid is specified by more than one codon.
65
What other kind of nucleic acid helps with DNA transcription?
Ribonucleic acid or RNA. RNA has a simpler structure than DNA. It is comprised of a single strand of nucleotides. In addition, instead of the sugar being deoxyribose as it is with DNA, it is ribose in RNA. RNA has the same nitrogenous bases as DNA except that instead of thymine it has uracil
66
Where does transcription begin?
In the nucleus of he cell
67
What happens in transcription?
A section of DNA unzips itself exposing the nitrogenous bases of a gene. The nucleotides of messenger RNA (mRNA) are attracted to their complimentary bases and they form into a continuous strand along the length of the gene.
This strand of mRNA then travels out of the nucleus into the cytoplasm of the cell. A large molecule called ribose then travels along the length of the mRNA activating its codons as it goes. When a codon is activated, transfer RNA (tRNA), which is floating loose in the cytoplasm, fixes itself to its complementary codon, rather like a three-pronged key fitting into a lock. Specific amino acids are attached to the surface of particular types of tRNA. The particular amino acids from each tRNA bond together and forma chain.
This chain will fold into a particular shape depending on the order of the different types of amino acids along its length. The shape that the amino acids form determines the specific type of protein they become. Transcription is a very complex process.
68
What is the most important thing to understand about genetic transcription?
That the end product is a protein
69
Why are statements like "a gene for eye colour" and "a gene for autism" technically incorrect?
Since genes primarily code for proteins, it is not technically correct to state that there is a gene for any time of phenotypic feature. Genes influence phenotypic expression in a more indirect manner. Nonetheless, since proteins are involved in every structure of the body (including the brain) DNA has a profound effect on our cognitive processing, personality and behaviour
70
What does it mean when a condition or trait is monogenic?
They are based upon the influence of one gene
71
What is polygenic transmission?
When a number of gene pairs combine their influences to create a single phenotypic trait
72
What does polygenic transmission do (compared with monogenic transmission)?
It complicates the straightforward picture that would occur if all characteristics were determined by one pair of genes. It also magnifies the number of possible variations in a trait than can occur.
73
How many estimated genotypes can occur when a sperm and an egg joins together?
Despite the fact that about 99.9% of human genes are identical among people, it is estimated that the union of a sperm and egg cell can result in about 70 trillion potential genotypes, accounting for the great diversity of characteristics that occurs even among siblings
74
What does behaviourism assume?
That there are laws of learning that apply to virtually all organisms. Behaviourists treated the organism as a 'tabula rasa', or a blank slate, on which learning experiences were inscribed. Most of their research was conducted with non-human species in controlled laboratory settings. Behaviourists explained learning solely in terms of directly observable events and avoided speculating about an organism's mental state.
75
What do ethologists focus on?
Animal behaviour in the natural environment, viewing the organism as much more than a blank slate, and arguing that, because of evolution, every species comes into the world biologically prepared to act in certain ways. Thus, they possess inherited behavioural adaptations
76
What are inherited behavioural adaptations?
Traits that organisms are born with that help promote their chances of survival and reproductive success
77
What is a fixed action pattern (FAP)?
An unlearned response automatically triggered by a particular stimulus.
78
What is releasing stimuli?
External stimuli that trigger fixed action patterns
79
Give an example of FAP and realising stimuli ---
| see page 90 - Tinbergen
Niko Tinbergen suspected that the chicks enter the world with an innate fixed action pattern of pecking that could be triggered by pre-programmed releasing stimuli.
80
What is a superstimulus?
An exaggerated version of a releasing stimulus that triggers a stranger response than the naturalistic model
81
What became increasingly clear as ethology research proceeded?
That even quite apparently rigid behaviour such as fixed actions patterns is subject to refinement by learning. E.g. animal behaviour being a natural instinct but copied from adults and therefore refined
82
What does environment mean?
Environment is a very broad term, referring to everything from the prenatal world of the womb and the simplest physical environment to the complex social systems in which we interact with multiple people, places and things.
83
What is a shared environment?
The people who reside in these experience many of their features in common. E.g. environments such as family household or school classroom are shared with people such as siblings and classmates and as such they have many features in common.
Siblings living in the same home are exposed to a common physical environment, the availability and unavailability of books, a television or a computer. They share the quality of food in the home, exposure to the attitudes and other values transmitted by parents, and many other experiences.
84
What is an unshared environment?
Experiences that are unique to us. Even children in the same home have their own unique experience, including distinct relationships with their parents and siblings.
85
What type of study is particularly useful in studying group variance?
Twin studies (especially those that include twins raised together and apart) are particularly useful in estimating the extent to which genotype, shared environment and unshared environment contribute to group variance on a particular characteristic.
86
What is behavioural genetics?
How heredity and environmental factors influence psychological characteristics
87
What are behavioural geneticists trying to determine?
Try to determine the relative influence of genetic and environmental factors in accounting for individual differences in behaviour. E.g. a common question posed by behavioural geneticists is 'how important are genetic factors in aggression, intelligence, personality characteristics and various types of psychological disorders?'
88
In what two ways can genetic similarity be expressed?
First, we can take equivalent sections of DNA between different humans or different species and calculate the degree of similarity between base pairs. According to such comparisons, we share around 98-99% of our DNA code with chimpanzees and about 99.9% with other unrelated humans.
Second, we can express genetic differences in terms of the inheritance of specific alleles from our parents. We directly inherit half our alleles from our mother and the other half from our father. Thus we receive 50% of each of our parents' genes by direct common descent.
89
What does degree of relatedness mean?
The number of genes we share with others by direct common descent
90
Outline the probability of sharing genes with parents and siblings ---
The probability of sharing any particular gene with one of your parents is 50% or .50. If you have siblings, you also have .50 probability of sharing the same gene by common decent with each of them. Identical twins share the same genotype and thus have a 1.00 probability of sharing any particular twin. The probability of having a shared gene with a grandparent is .25 as half was passed onto your parent and then half to you. The probability of sharing a gene with a half-sibling is .25 also. First cousins share .125 of genes (mothers siblings share .50, you share .25 with your aunt and half of that with their children, .125)
91
What is concordance and what does having a high concordance rate mean?
concordance is co-occurrence. If a characteristic has higher concordance, or co-occurrence, in people who are more closely related to one another compared to unrelated individuals, this points to a possible genetic contribution, particularly if the people have lived in different environments.
92
What are adoption studies?
People who were adopted early in life are compared on some characteristic both with their biological parents, with whom they share genetic endowment, and with their adoptive parents, with whom they share no genes
93
What can adoption studies show?
If adopted people are more similar to a biological parent (with whom they share 50% of their genes) than to an adoptive parent (with whom they share a common environment but no genes), a genetic influence on a trait is indicated. If they are more similar to their adoptive parents, environmental factors are judged to be more important for that particular characteristic. (E.g. study showing a hereditary link with schizophrenia).
94
What are twin studies?
Twin studies compare trait similarities in identical and fraternal twins
95
How are twin studies important?
They are one of the more powerful techniques used in behavioural genetics. Because monozygotic, or identical twins develop from the same fertilized egg, they are genetically identical. Approximately 1 in 250 births produces identical twins. Dizygotic, or fraternal, twins develop from two fertilized eggs, so they share 50% off their genetic endowment, like any other set of siblings Approximately 1 in every 150 births produces fraternal twins
96
What are concordance rates?
Statistical expression of the probability that two individuals with shared genes will share a particular trait to the same degree
97
What can we assume in twin studies?
We assume that if the identical twins are far more similar to one another than the fraternal twins are on a specific characteristic, a genetic factor is likely to be involved.
98
What is a key drawback of twin studies?
Of course, the drawback is the possibility that because identical twins ae more similar to one another in appearance than fraternal twins are, they are treated more alike and therefore share a more similar environment. This could partially account for greater behavioural similarity in identical twins.
99
What have behavioural geneticists done to rule out the environmental explanation?
They have adopted an even more elegant research method. Sometimes researchers are able to find and compare sets of identical and fraternal twins who were separated very early in life and raised in different environments. By eliminating environmental similarity, this research design permits a better basis for evaluating the respective contributions of genes and environment
100
What tends to be found with twin & adoption studies?
Many (but not all) psychological characteristics, including intelligence, personality traits and certain psychological disorders, have a notable genetic contribution. Adopted children are typically found to be more similar to their biological parents than to their adoptive parents on these measures, and identical twins tend to be more similar to one another than fraternal twins, even if they were separated in early life and reared in different environments. On the other hand, identical twins reared together still tend to be somewhat more similar for some characteristics than those reared apart, indicating that the environment also makes a difference
101
What does a heritability coefficient do?
It estimates the extent to which the differences, or variation, in a specific phenotypic characteristic within a group of people can be attributed to their differing genes
102
What does heritability only apply to?
It only applies to differences within the particular group tested and estimates can and do vary, depending on the group
103
How are heritability coefficients estimated?
Subtracting each heritability coefficient from 1 provides an estimate of the proportion of variability in the particular group tested that is attributable to the environment in which they developed.
For example, for height, environment only accounts for only abut 1 minus .9, a proportion of .1 (or 10%), of the variation within the group, but for individual difference in preferred characteristics in a mate, environment accounts for virtually all differences among the people tested
104
What do behavioural geneticists realise in terms of genes and environment?
Even while they try to estimate the contributions of genetic factors, they realise that genes and environment are not really separate determinants of behaviour. Instead, they operate as a single, integrated system. Gene expression is influenced on a daily basis by the environment.
E.g. 2 children of equal intellectual potential may have differences in IQ as great as 15 to 20 points if one is raised in an impoverished environment and the other in an enriched environment.
105
What can environmental stress do?
High or low environmental stress can be responsible for turning on or off genes that regulate the production of stress hormones
106
How do we have predispositions to certain disorders?
The genetic influence on certain psychological disorders can be very significant, including a disposition for schizophrenia and autistic spectrum disorders. It is our genetics that provide some of us with a predisposition to suffer with a problem. This is certainly true of depression. Of course, a predisposition (or diathesis) to suffer with something does not mean that you certainly will, jut that it may happen given the correct experiences, and environment.
107
Examine the genetic argument of intelligence ---
Suppose that intelligence were totally heritable, that is, suppose that 100% of the intellectual variation in the population were determined by genes. In that case, any two individuals with the same genotype would have identical intelligence test scores, so the correlation in the IQ between identical (monozygotic) twins would be 1.00. Non-identical brothers and sisters (including fraternal/dizygotic) twins share only half their genes. Therefore, the correlation between the test scores of fraternal twins and other siblings should be substantially lower. Extending the argument, the correlation between a parent's test scores and his/her children's scores should be about the same as that between siblings, because a child inherits only half of his/her genes from each parent
108
Examine the correlation of intelligence regarding the genetic argument ---
The correlation between the test scores of identical twins is substantially higher than any other correlations, but they are not 1.00. Identical twins separated early in life and reared apart are of special interest because they have identical genes but experienced different environments. It is important to note that the correlation for identical twins raised apart is nearly as high as that for identical twins reared together. It is also higher than that for fraternal twins raised together. This pattern of findings is a powerful argument for the importance of genetic factors.
109
Looking at adoption studies, how large a factor is heritability in individual differences in intelligence?
IQs of adopted children correlate as highly with their biological parents' IQs as they do with the IQs of the adoptive parents who reared them. Overall, the pattern is quite clear: the more genes people have in common, the more similar their IQs tend to be. This is very strong evidence that genes play a significant role in intelligence, accounting for 50 to 70% of group variation in IQ. However, analysis of the human genome shows that there clearly is not a single 'intelligence' gene. The diverse abilities measured by intelligence tests are undoubtedly influenced by large numbers of interacting genes, and different combinations seem to underlie specific abilities.
110
Why isn't the genetic argument of intelligence accepted alone?
Because genotype accounts for only 50 to 70% of the IQ variation among the individuals in these studies, genetics research provides a strong argument for the contribution of environmental factors to intelligence. Good places to look for such factors are in the home and school environments.
111
How important to intelligence level is the shared environment of the home in which people are raised?
If home environment is an important determinant of intelligence, then children who grow up together should be more similar than children who are reared apart. Research shows that siblings who were raised together were indeed more similar to one another than those reared apart, whether they were identical twins or biological siblings.
Note also that there was a correlation of .32 between unrelated adopted children reared in the same home. Overall, it appears that between a quarter and a third of the individual differences in intelligence found in these particular groups could be attributed to shared environmental factors.
112
What other additional factor may be important in influencing intelligence alongside the home environment?
Recent research suggests that differences within home environments are much more important at lower socioeconomic levels than they are in upper class families. This may be because lower socioeconomic families differ more among themselves in the intellectual richness of the home environment than do upper class families. Indeed, a lower-income family that has books in the house, cannot afford video games and encourages academic effort may be a very good environment for a child with good intellectual potential.
113
How does environmental enrichment and deprivation influence environmental affected intelligence?
A line of evidence for environmental effects comes from studies of children who are removed from deprived environments and placed in middle or upper class adoptive homes. Typically such children show a gradual increase in IQ in the order of 10 to 12 points. Conversely, when deprived children remain in their impoverished environments, they either show no improvement in IQ or they actually deteriorate intellectually over time. Scores on general intelligence tests correlate around .40 with the socioeconomic status of the family in which a child is reared.
114
How do educational experiences impact intelligence?
Many studies have shown that school attendance can raise IQ and that lack of attendance can lower it. A small decrease in IQ occurs over summer holidays, especially among low-income children. Intelligence quotient scores also drop when children are unable to start school on time owing to teacher shortages or strikes, natural disasters, or other reasons. It appears that exposure to an environment in which children have the opportunity to practise mental skills is important in solidifying those skills.
115
Is personality heritable?
Behavioural genetics studies on personality have examined genetic and environmental influences on relatively broad personality traits.
116
What is the five factor model?
One prominent personality trait theory is called the five factor model. Five factor theorists believe that individual differences in personality can be accounted for by variation along five broad personality dimensions or traits known as the Big Five:
(1) extraversion-introversion (sociable, outgoing, adventuresome, spontaneous versus aloof, quiet, inhibited, solitary)
(2) agreeableness (cooperative, helpful, good natured versus antagonistic, uncooperative, suspicious)
(3) conscientiousness (responsible, goal-directed, dependable versus undependable, careless, irresponsible)
(4) neuroticism (worrying, anxious, emotionally unstable versus well adjusted, secure, calm)
(5) openness to experience (imaginative, artistically sensitive, refined versus unreflective, crude and boorish, lacking in intellectual curiosity)
117
What results are obtained if we compare the Big Five traits in identical and fraternal twins who were raised together and those who were raised apart?
Results show that heritability estimates of the Big Five personality factors are consistent with studies of other personality variables as well, indicating that between 40 and 50% of the personality variations among people included in these studies are attributable to genotype differences. Although personality characteristics do not show as high a level of heritability as the .70 figure found for intelligence, it is clear that genetic factors account for a significant amount of personality difference.
118
How does environment influence personality?
If genetic differences in previous twin studies account for only about 40 to 50% of variations in personality, then surely environment is important too. The assumption has been accepted that experiences within the family, such as the amount of love expressed by parents and other child-rearing practices, are critical determinants of personality development.
119
What has been found regarding major personality traits and the environment?
One study found that shared features of the family environment account for little or no variance in major personality traits. The key findings was that twins raised together ad apart, whether identical or fraternal, did not differ in their degree of personality similarity (although identical twins were always more similar to one another than were fraternal twins). In fact, researchers have found that pairs of children who are raised within the same family are as different from one another as are pairs of children who were randomly selected from the population
120
What do adoption studies show regarding personality and the environment?
In adoption studies, the average correlation for personality variables between adopted siblings who are genetically dissimilar but do share much of their environment, including the parents who raise them , the schools they attend, the religious training they receive, and so on, is close to .001. Except at child-rearing extremes, where children are abused or seriously neglected, parents probably get more credit when children turn out well personality-wise - and more blame when they do not - than they deserve
121
Despite findings suggesting that environment is not as important in impacting personality as was once thought, how can it still be important?
Rather than the general family environment, it seems to be the individual's unique or unshared environment, such as his/her unique school experiences and interaction with specific peers that account for considerable personality variance. Even within the same family, we should realise, siblings have different experiences when growing up, and each child's relationship with his/her parents and siblings will vary. It is these unique experiences that help shape personality development.
122
What have behavioural geneticists found shared environment to affect and not affect?
They have found important shared environment effects in intelligence, attitudes, religious beliefs, occupational preferences, notions of masculinity and femininity, political attitudes, and health behaviours such as smoking and drinking, these shared-environment effects do not extend to general personality traits such as the Big Five. At this point, we do not know whether there are some crucial unshared-environmental variables that researchers have missed because of their preoccupation with shared-environmental factors, or whether there are countless small variables that make the difference.
123
What is key to remember about genes and the environment and their influence?
They rarely operate independently. Even the prenatal environment can influence how genes express themselves, as when the mother's drug use or malnutrition retards gene-directed brain development. In the critical periods following birth, enriched environments, including the simple touching or massaging of newborns, can influence the unfolding development of premature infants and the future 'personality' of young monkeys. Although they cannot modify the genotype itself, environmental conditions can influence how genetically based characteristics express themselves phenotypically throughout the course of development
124
What does reaction range mean?
The range of possibilities - the upper and lower limits - that the genetic code allows
For example, to say that intelligence is genetically influenced does not mean that intelligence is fixed at birth. Instead, it means that an individual inherits a range for potential intelligence that has upper and lower limits. Environmental effects will then determine where the person falls within these genetically determined boundaries.
125
How has the concept of reaction ranges mostly been applied?
At present, genetic reaction ranges cannot be measured directly, and we do not know if their sizes differ from one person to another. The concept has been applied most often in the study of intelligence. There, studies of IQ gains associated with environmental enrichment and adoption programmes suggest that the ranges could be as large as 15 to 20 points on the IQ scale. If this is the case then the influence of environmental factors on intelligence would e highly significant. A shift this large can move an individual from a below-average to an average intellectual level, or from an average IQ that would not predict college success to an above-average one that would predict success
126
What does intellectual growth depend upon?
It depends on not only on genetic endowment and environmental advantage, but also on interests, motivation and other personal characteristics that affect how much we apply ourselves or take advantage of our gifts and opportunities
127
How do heritability estimates vary?
Heritability estimates are not universal by any means. They can vary, depending on the sample being studied, and they may be influenced by environmental factors.
128
What is thought to be likely about genetically based reaction ranges for personality factors?
That there are genetically based reaction ranges for personality factors too. This would mean that, personality-wise, there are biological limits to how malleable, or changeable, a person is in response to environmental factors. However, this hardly means that biology is destiny. Depending on the size of reaction ranges for particular personality characteristics - an even, perhaps, for different people - individuals could be quite susceptible to the impact of unshared environmental experiences.
129
How do genetically based characteristics influence aspects of the environment to which the child is exposed?
For example, we know that intelligence has strong heritability. Thus, a child born to highly intelligent parents is also likely to have good intellectual potential. If, because of their own interests in intellectual pursuits, these parents provide an intellectually stimulating environment with lots of books, educational toys, computers and so on, this environment may help foster the development of mental skills that fall at the top of the child's reaction range. The resulting bright child is thus a product both of the genes shared with the parents and of his or her ability to profit from the environment they provide.
130
What is evocative influence?
A child's genetically influenced behaviours may evoke certain responses from others
131
Give an example of evocative influence ---
For example, some children are very cuddly, sociable and outgoing almost from birth, whereas others are more aloof, shy and do not like to be touched or approached. These characteristics are, in part, genetically based. The outgoing children are likely to be cuddled by their parents and evoke lots of friendly responses from others as they mature, creating an environment that supports and strengthens their sociable and extraverted tendencies. In contrast, shy, aloof children typically evoke less positive reactions from others, and this self-created environment may strengthen their genotypically influenced tendency to withdraw from social contact
132
In what 3 ways can genetic and environmental factors interact with one another?
- Reaction range
- Genetically based characteristics influencing aspects of the environment
- evocative influence
133
What can behaviour patterns do to an environment?
Create an environment that counteracts the genetically favoured trait and discourages its expression. We know, for example, that activity level has moderate heritability of around .40. Thus, parents of highly active 'off the wall' children may try to get them to sit still and calm down, or those of inactive children may press the child into lots of physical activities designed to increase physical well-being, in both instances opposing the natural tendencies of the children. Thus, the environment may either support or discourage the expression of a person's genotype
134
How do people actively seek out environment and avoid others?
Genetically based traits may affect the environments that we select, and these environments are likely to be compatible with our traits. Thus, a large, aggressive boy may be attracted to competitive sports with lots physical contact, a highly intelligent child may shun social events and prefer solitary activities or a small number of friends. These varied self-selected environments may have very different effects on subsequent development. We therefore see that how people develop is influenced by both biology and experience, and that these factors combine in ways that are just beginning to be understood.
135
What is epigenetics?
Epigenetics is the study in gene expression due to environmental factors and independent of the DNA
OR
'alterations in the phenotype or gene expression due to mechanisms other than changes in the underlying DNA sequence'
136
What does the area of epigenetics research open up?
A new area where, not content with looking at naturally occurring genetic phenomena, scientists can now directly influence, manipulate and duplicate the structure of genes themselves. Of course, natural expressions and manipulations have been carried out for centuries, notably by Mendel and animal breeders, but epigenetics opens up a door to an as yet unthinkable level of flexibility regarding genetic expressions
137
What is important in gene expression?
It is not only the DNA itself that is vital in the expression of the gene. Researches say that the physical environment in which the genes resides, as well as the social environment of the host, can be influential in changing molecular structures that are themselves responsible for regulating gene expression
138
How can gene manipulation be achieved?
Therapies can be developed to modify the structure of brain tissue. To do this, you first need to find a virus that can travel into the brain. Next you need to modify the genetic code of the virus before it is released into the host. Enzymes are used that can split threads of the DNA to be inserted into pieces before, before combining it with the DNA of the virus, which then carries the inserted DNA to the brain. Similarly, the DNA of bacterium can be modified with pieces of DNA so that when inserted into a host, the new bacterium subdivides to produce multiple copies of itself, spreading the DNA throughout the host
139
What are the 2 types of genetic modification?
Knock-out procedures and knock-in procedures
140
What is a knock-out procedure?
Where a function of a gene is removed, or eliminated
141
What is a knock-in procedure?
Where a new gene is inserted into an animal at embryonic stage
142
What are the potential benefits of genetic screening?
There are at present more than 900 genetic tests available from testing laboratories. Proponents argue that screening can provide information that will benefit people. Early detection of a treatable condition can save lives. Screening could also affect reproductive decisions that reduce the probability of having children affected by a genetic disease.
143
How accurate is genetic screening?
Although screens for various diseases exceed 90% accuracy, it is still possible that there can be a false positive result (an indication that genetic predisposition to a disorder is present when it is not). Thus, a person may decide not to have children on the basis of an erroneous test that indicates a high risk of having a child with a particular problem. Alternatively a false negative test may indicate that a predisposition is not present when in fact it is. Moreover, some tests, called susceptibility tests, simply tell you that you are more likely than others to develop a particular disorder, with no assurance that that will indeed occur
144
How should people be educated and counselled about test results?
Because of the importance of decisions that might be made on the basis of genetic screening, there is strong agreement that clients should be educated and counselled by specially trained counsellors. In the sickle-cell anaemia screening of the 1970s, follow-up education was inadequate, the result being that some African-American men who were informed that they were carriers of the sickle-cell allele elected to remain childless because they were not told that the disorder would not occur in their offspring if their mated were noncarriers of the allele. The genetic counsellor's role is to help the person, couple or family to decide whether to be screened, to help them to fully understand the meaning of the test results, and to assist them during what might well be a difficult and traumatic time
145
How can evolution and human nature be connected?
The evidence from behavioural genetics has gone a long way to convincing people that human nature is indeed influenced by evolved predispositions. However, the application of principles of natural selection to psychology has not been without controversy. Indeed a healthy scepticism is to be recommended. There is a great danger in the misapplication of Darwin's thinking.
146
What danger can the application of evolutionary thinking pose?
Francis Galton argued that certain traits which might have been functional and useful in the past were not so in modern Victorian England. He coined the term 'eugenics' to describe a practice of improving the human race by encouraging the 'desirable' human traits through selective breeding. Those who had these 'desirable' traits should be encouraged to have children; those who did not (such as criminals) should be discouraged or prevented. Bitter experience has taught us that the principles of eugenics can be taken even further with horrifying consequences (e.g. Nazi Germany)
147
What are adaptations?
Physical or behavioural changes that allow organisms to meet recurring environmental challenges to their survival, thereby increasing their reproductive ability
148
What does eugenics do?
Eugenics placed an unmerited moral value on evolutionary adaptations. There is no 'should' or 'ought' in evolution - life just is the way it is.
149
What can the process of evolution be described as?
A mechanical, purposeless process. It is not directed toward any particular higher goal or value. It is based upon random genetic mutations. The name of the game is long-term genetic survival and there is no particular moral merit in that. Thus, one should not consider any particular extant species evolutionary more worthy or advanced than any other.
150
Why have eugenicists misunderstood the principles of evolution?
By placing value judgements onto natural selection, eugenicists fundamentally misunderstood the logic of the principles underlying Darwinian evolution as not in all circumstances is one gene preferable over another.
151
What did Darwin propose about natural selection?
The origin of the species argued that natural selection does not work for the 'good of the species' or 'the good of the group'. Instead, he proposed that natural selection would always favour biological traits that promoted the reproductive success of individuals over and above what is good for the group or species.
152
What does biological fitness refer to?
Biological 'fitness' does not necessarily refer to the strongest or fastest or even longest-lived members of a population. If an organism lived or a thousand years, but died without doing anything to ensure that some biological part of it survived after its death, it would be an evolutionary dead end.
Darwin measured fitness in terms of the number of offspring an individual produces. However, we now know that the unit of inheritance is the gene. Thus, modern evolutionary theorists measure reproductive success in terms of the estimated number of copies of individual genes that survive into future generations
153
What is kin selection?
An evolutionary strategy in which behaviours are selected which favour the reproductive success of an organism's relatives even if that is at a cost to that organism's our survival and reproduction
154
Give examples of kin selection ---
Lots of examples in nature of animals risking or even sacrificing their lives in order to protect their kin and the genes they carry. Thus, the world created by natural selection is not as entirely dog-eat-dog as one might suppose
155
What is reciprocal altruism?
a behaviour in an organism which reduces its fitness to survive and reproduce while increasing another organism's fitness, undertaken with the expectation that the favour will be returned later
156
What are culturally universal characteristics?
If nearly every human culture, even those that are relatively isolated from all other human groups, expresses a certain characteristic it suggests the expression of inborn biological tendencies that have evolved through natural selection. There exists a vast catalogue of human culturally universal characteristics and capabilities that unfold in all normally developing human beings.
157
Give some examples of culturally universal characteristics ---
1) Infants are born with an ability to acquire any language spoken in the world
2) Human newborns are pre-wired to perceive specific stimuli e.g. human faces and mothers milk
3) At one week of age (babies less than 1 month), human neonates show primitive mathematical skills, successfully discriminating between 2 and 3 objects
4) Humans seem to have a need to belong and strongly fear being ostracised from the group
5) Possession of a basic set of emotions
6) in virtually all cultures, males are more violent and more likely to kill others
158
How do men and women display different attitudes towards mating strategies and preferences?
Compared with women, men typically show more interest in short-term mating, prefer a greater number of short-term sexual partners, and have more permissive sexual attitudes and more sexual partners over their lifetime.
159
How do men and women display different behaviours in mating strategies and preferences?
Findings of a research study in mating behaviour suggest that, women tended to react negatively to seeing a member of the opposite sex and being asked to go to bed with them that night, and usually dismissed the research assistant as 'sleazy'. Not a single woman agreed to have sex. In contrast, 3 in every 4 men enthusiastically agreed, some asking why it was necessary to have to wait until that night.
Other findings show that men think about sex about 3x more than women do, desire more frequent sex and initiate more sexual encounters than women do.
Men are also much more likely to interpret a woman's friendliness as a sexual come-on, apparently projecting their own sexual desires onto the woman
160
What are the sex differences in mate selection?
Men typically prefer women somewhat younger than themselves, whereas women prefer somewhat older men. This tendency is exaggerated in the 'trophy wives' sometimes exhibited by wealthy and famous older men.
In mate preferences in terms of personal traits across 37 cultures, men and women show considerable overall agreement, but some differences emerge. Men place greater value on a potential mate's physical attractiveness, whereas women place greater value on a potential mate's earning potential, status and ambitiousness
161
What is the viewpoint of the sexual strategies theory (and a related model) and the parental investment theory?
Mating strategies and preferences reflect inherited tendencies, shaped over the ages in response to different types of adaptive problems that men and women faced.
In evolutionary terms, our most successful ancestors were those who survived and passed down the greatest number of their genes to future generations. Men who had sex with more partners increased the likelihood of fathering more children so they were interested in mating widely. Men may also have taken a woman's youth and attractive, healthy appearance as signs that she was fertile and had many years left to bear his children.
162
What evolutionary reasoning is there behind female mating behaviours?
Ancestral women had little to gain and much to lose by mating with numerous men. They were interested in mating wisely, not widely. In humans and other mammals, females typically make a greater investment than males: they carry the foetus, incur health risks and possible birth-related death, and nourish the newborn. Engaging in short-term sexual relationships with multiple males can in the end create uncertainty about who is the father, thereby decreasing a male's willingness to commit resources to helping a mother raise the child. For these reasons women maximized their reproductive success - and the survival chances of themselves and their offspring - by being selective and choosing mates who were willing and able to commit time, energy and other resources to the family. Women increased their likelihood of passing their genes into the future by mating wisely, and men by mating widely. Due to natural selection, it has been suggested that these preferences have become part of their biological nature
163
Why could these mate preferences be more pronounced in different parts of the world?
Some of these mate preference patterns are ore pronounced in parts of the world with historically high levels of pathogens that endangered survival than in areas that had historically low levels of pathogens. Where diseases like malaria, plague and yellow-fever are more prevalent, male factors such as physical attractiveness and robustness, intelligence and social dominance - all presumably signs of biological fitness - seem especially important to women even today. It has been suggested that in such environments, women seem willing to sacrifice some degree of male investment in their offspring in favour of a mate who has a higher probability of giving them healthy children. To men, a woman's attractiveness and healthiness (and that of her family) also is more important in high-pathogen environments, presumably because these historically were signs of a woman who would be more likely to give birth to healthy children and live long enough to rear them
164
What is the social structure theory?
Men and women display different mating preferences not because nature impels them to do so, but because society guides them into different social roles
165
How does the social structure theory suggest that adaptive behaviour patterns have been passed on?
Passed on from parents to children not through genes but through learning. Social structure theorists point out that despite the shift in the past several decades towards greater gender equality, today's women still have generally less power, lower wages and less access to resources than men do. In a two-income marriage, the woman Is more likely to be the partner who switches to part-time work or becomes a full-time homemaker after childbirth. Thus, society's division of labour still tends to socialize men into the breadwinner role and women into the homemaker role.
166
What is the division-of-labour hypothesis?
Given the power and resource disparities and the need to care for children, it makes sense for women to seek men who will be successful wage earners and for men to seek women who can have children and fulfil the domestic-worker role. An older male-younger female age gap is favourable because older men are likely to be further along in earning power and younger women are more economically dependent, and this state of affairs conforms to cultural expectations of marital roles. This hypothesis does not directly address why men emphasize a mate's physical attractiveness more than women do but it has been speculated by Alice Eagley and Wendy Wood (1999)that attractiveness is viewed as part of what women 'exchange' in return for a male's earning capacity
167
What are the two competing explanations for sex differences in mating behaviour?
The evolution-based sexual strategies approach and the social structure view
168
What is the evolutionary personality theory?
An approach which looks for the origin of presumably universal personality traits in the adaptive demands of our species' evolutionary theory
169
What does the evolutionary personality theory pose?
It asks the basic question, 'where did the personality traits exhibited by humans come from in the first place?' The focus here is on the traits that we (and other animals)have in common. But evolutionary personality theory also tries to account for the core question in the field of personality: why do we differ from one another in the personality traits?
170
How does the five factor model of personality link to evolution?
Because these 5 trait dimensions - extraversion, agreeableness, conscientiousness neuroticism and openness to experience - have been found in people's descriptions of themselves and others in virtually all cultures, some theorists regard them as universal among humans. And because evolutionary theory addresses human universals, the Big Five traits have been the major focus of evolutionary personality theory
171
Why are the Big Five traits found so consistently in the languages nd behaviours in cultures around the world?
According to Buss (1999), they exist in humans because they have helped us achieve two overriding goals: physical survival and reproductive success. Traits such as extraversion and emotional stability would have been helpful in attaining positions of dominance and mate selection. Conscientiousness and agreeableness are important in reproduction and the care of children, Finally, openness to experience may be the basis for problem-solving and creative activities that benefit not only the possessor but also are likely to be valued by other group members. Rewarding and encouraging these traits could be to the mutual benefit of everyone. Evolutionary theorists therefore regard the behaviours underlying the Big Five as sculpted by natural selection
172
How can the Big Five traits be linked with how we are biologically programmed to think about and discriminate among people? (5 Questions)
Goldberg (1981) suggests that over the course of evolution, people have had to ask some very basic questions when interacting with another person, questions that have survival and reproductive implications:
1) Is person X active and dominant or passive and submissive? Can I dominate X, or will I have to submit to X?
2) Is X agreeable and friendly or hostile and uncooperative?
3) Can I count on X? Is X consciousness and dependable?
4) Is X sane (stable, rational, predictable) or crazy (unstable, unpredictable, possibly dangerous)?
5) How smart is X, and how quickly can X learn and adapt?
Not surprisingly, Goldberg suggests that these questions relate directly to the Big Five factors. He believes that this is the reason analyses of trait ratings reveal Big Five consistency across very diverse cultures.
173
What is strategic pluralism?
The idea that multiple - even contradictory - behavioural strategies might be adaptive in certain environments and would therefore be maintained through natural selection
174
Why do we see variation in the Big Five traits?
Thus, Daniel Nettle (2006) theorizes that we see variation in the Big Five traits because all of them have adaptive trade-offs (a balance of potential benefits and costs) in the outcomes they may produce
Nettle believes that these trade-offs favour evolutionary variation in the Big Five traits and that the specific environment in which our ancestors evolved made it more or less adaptive to be an extravert or an introvert, agreeable or selfish, fearful or fearless, conscientious or immoral, and so on. This would help account for genes favouring individual differences on personality dimensions and for the great diversity we see in personality trait patterns
175
How do evolutionary psychologists account for individual differences in personality traits through gene-environment interactions?
Evolution may provide humans with species-typical behaviour patterns, but environmental inputs influence how they are manifested. For example, dominance may be the behaviour pattern encouraged by innate mechanisms in males, but an individual male who has many early experiences of being subdued or dominated may develop a submissive personality
