The Genetics of Behavior Are we nature or nurture? Two basic views Nativists Emphasize genes and inborn characteristics Empiricists Emphasize learning and experience Evolutionary Psychology Emphasizes evolutionary mechanisms that may help explain human commonalities in; Cognition, development, emotion, social practices and other behavior. Behavioral Genetics An interdisciplinary field of study concerned with the genetic basis of behavior and personality. An Understanding All scientists understand there is an interaction between heredity and environment. Set point - a genetically influenced weight control mechanism vs. obesity in the US. The Secrets of Genes Genes - are the basic units of heredity located on chromosomes which contain threadlike strands of DNA. Egg and Sperm contain 23 chromosomes each. Creating the genome Genome and what it means After conception each cell has 23 pairs of chromosomes. (46) Most traits depend on more than one gene pair. How are traits studied? Linkage studies - look for patterns of inheritance of genetic markers in large families. A genetic marker is a segment of DNA that varies among individuals. The Genetics of Similarity Evolution is a change in gene frequencies within a population over many generations. (mutation) Natural Selection is a process in which individuals adapt to a particular environment and survive. Evolutionary Psychologists They look to the prehistoric record to draw inferences about behavior that solved survival problems Because of evolutionary history some qualities are universal… Evolutionary Psychologists Universal qualities are. 1. 2. 3. 4. 5. Reflexes Attraction to novelty A desire to explore and manipulate objects An impulse to play and fool around Basic mental skills Our Human Heritage The origins of perception 1. 2. Sensation - the detection of physical energy emitted or reflected by physical objects. Perception - the process by which the brain organizes and interprets sensory information Our Human Heritage 3. 4. 5. Some abilities develop from certain experiences at certain times. Complex features are processed by specialized detectors Inborn perceptual abilities include… 1. 2. Startle reflex Audio location 3. Voice recognition 4. Discrimination of smells The Face of Emotion Some expressions are universal and present from birth Universal facial expressions function in communication. Sociability and Attachment Synchrony and sociability Newborns are sociable from birth They pay attention to human faces show synchrony Attachment and - the emotional tie that children and their caregivers feel toward each other… Sociability and Attachment Attachments Contact cont’d comfort which is the innate pleasure derived from close physical contact. Infants who do not develop secure attachments may develop emotional and physical problems. The Capacity for Language Language is a system for combining meaningless elements into utterances that convey meaning. A child’s vocabulary increases at a rapid rate. Language Development Requires the mastering of a complex set of rules including: Surface structure - the way a sentence is actually spoken Deep structure - the meaning inferred by a sentence Syntax - the rules of grammar Language Development Children They do not simply imitate adults are able to perceive deep structure Noam Chomsky theorized that we have a biologically based “language acquisition device” that aids in language development. Chomsky’s Examples Children of different cultures go through similar stages of linguistic development Children combine words in ways that adults never would Adults do not consistently correct their children’s syntax yet they learn to speak or sign correctly. Chomsky’s Examples Even children who are profoundly retarded acquire language. Infants as young as 7 months can derive simple linguistic rules from a string of sounds. Does Nurture Play a Role? Imitation does play a role because parents correct the child’s ungrammatical sentence. There appears to be a window of opportunity to learn language. Evolution, Courtship and Mating Sociobiology - an interdisciplinary field that emphasizes evolutionary explanations of social behavior in animals. The view is that nature has selected psychological traits and social customs that promote propagation. Evolution, Courtship, and Mating Sociobiologists argue that males and females have evolved different mating strategies. Males to inseminate as many females as possible and females be more selective. As a result, males are thought to be more promiscuous and drawn to sexual novelty, females are more interested in stability. Sociobiology vs. Evolutionary Sociobiologists tend to argue by analogy to nonhuman animals. Evolutionary biologists recognize these are simplistic and misleading. Critics argue that evolutionary explanations are based on stereotype of gender. Theories are also nonfalsifiable. The Genetics of Difference Heritability - is the statistical estimate of the proportion of the total variance in some trait that is attributable to genetic differences among individuals within the group… The Genetics of Difference 1. 2. 3. An estimate of heritability applies only to a particular group living in an particular environment. Heritability estimates do not apply to individuals, only to variations within a group. Even highly heritable traits can be modified by the environment. Computing Heritability Research methods are used in an attempt to infer heritability by studying people whose degree of genetic similarity is know. Adopted children share half their genes but not environments with birth parents. Computing Heritability Identical (monozygotic) twins develop when a fertilized egg divides into two parts. Fraternal (dizygotic) twins develop from two separate eggs fertilized by different sperm. Identical twins raised apart from each other are of special interest because they have identical genes but a different environment. Heritability and Intelligence Intelligence quotient (IQ) - is a measure of intelligence originally computed by dividing a person’s mental age by his or her chronological age multiplied by 100 Currently it is norms based. Genes and Individual Differences IQ scores are highly heritable with estimates averaging around .50 in children and .60 to .80 in adults. Scores of identical twins are always more highly correlated than those of fraternal twins. Scores with adopted children correlate higher with birth parents vs. adoptive parents. The Question of Group Difference Race differences are controversial Asians as a group score higher than whites who score higher than African Americans. Some theorists have confused intragroup findings with inter-group. The Question of Group Difference Minority children tend to have access to fewer educational and material resources. Well designed studies have failed to reveal genetic differences. Genes and Personality Temperaments - physiological dispositions to respond to the environment in certain ways; present in infancy and are assumed to be innate. Heredity and Temperament Differences in children’s temperaments appear early in childhood. Temperaments tend to remain stable throughout childhood. Heredity and Traits A trait analysis isof a characteristic measures or scores of an that Clusters Factor - a statistical method are individual, highly correlated describing aare habitual assumed wayto for analyzing the inter-correlations of measure behaving, the thinking samemeasures underlying and feeling. trait or among different now ability. applied to traits. Big Five Factors Introversion vs. extroversion Neuroticism or negative emotionality Agreeableness Conscientiousness openness Why are genes not everything? Not all traits are equally heritable or unaffected by shared environments Some studies may underestimate the impact of the environment Even traits that are highly heritable are not rigidly fixed and can be modified by experience.