IB Psych: Biological Approach

BIOLOGICAL APPROACH

Research Method (brain/pheromones): Quasi-experiments- IV/allocation into groups is done on the basis of pre-existing differences and DV measured; researchers cannot be sure that the groups are equivalent in all other characteristics, and a cause-effect relationship cannot be established.

Research Methid (genetics): Correlational study- two or more variables are measured and the relationship is mathematically quantified; since there is no variable being manipulated, cause-effect relationships cannot be established.

Ethical Considerations (brain): Informed consent- participation must be voluntary and fully informed.

Ethical Considerations (hormones): Deception- not revealing the true aim or other aspects to minimize demand characteristics should be discussed in debriefing. 

Ethical Considerations (genetics): Social implications- study conclusions may be distorted bu the media; if they become popular, they are resistant to change and may affect public policies (e.g education)

Technique to study the brain: For a long time, brain research was limited to conducting post-mortem autopsies on patients with unusual behavioural deviations. After the invention of brain imaging techniques, it because possible to study the human brain non-invasively, and by extension, study the brains of living humans. A commonly used brain imaging technique is magnetic resonance imaging (MRI), which generates a magnetic field and uses energy-emitted hydrogen nuclei to produce a 3D picture of brain structure.

Localization of function: The theory that certain areas of the brain are responsible for certain psychological functions. It has seen a shift from strict localization (clear correspondence between functions and areas) to weak localization (one area might be responsible for multiple functions and some functions occur in multiple areas) and widely distributed functions (functions that cannot be localized anywhere in the brain). 

Neuroplasticity: The brain’s ability to change through the making and breaking of synaptic connections between neurons. Occurs on different scales, from synaptic plasticity (level of the neuron) to cortical remapping (level of the cortex). Neuroplasticity can occur due to changes in environment.

Neurotransmission: Neurotransmitters are chemical messengers stored in the axon and released into the synaptic gap. Information transmission in the nervous system is partially chemical and partially electrical. Neurotransmitters are responsible for chemical transmission. Neurotransmitters can be reputaken (pulled back into the axon that released it) or reach the end of the synaptic gap and bind themselves to a receptor on the next neuron, changing that neuron’s membrane potential to build up the impulse. Dopamine is a neurotransmitter that controls the brain’s reward and pleasure centers and regulates movement and emotional responses (enables us to take action to obtain rewards).

Hormones: Chemical substances that are released into the bloodstream to regulate processes slower than those regulated by neurotransmitters. Oxytocin is released from the pituitary gland and plays a role in sexual reproduction, childbirth and social bonding. 

Pheromones: Chemical substances that are released into the environment to influence the behaviour of other members of their species. The human pheromone hasn’t been found, although there are hypothesized pheromones such as histocompatibility complex (MHC), a group of genes related to the immune system that may be encoded in body odour.

Genes: Genes are heritable factors that consist of a length of DNA and influence a characteristic. Several genes may be responsible for certain behaviours. However, research has shown that the presence/absence of certain genes has an effect on behaviours. 

Evolutionary behaviours: Evolution is a change in the allele frequency of a population’s gene pool over successive generations. Through natural selection, humans adapt characteristics that make us suited to our environment and way of life. Sexual selection states that humans finding mating partners look for characteristics that would make it beneficial for humans’ survival.

Maguire (2000): Investigated the difference between London taxi drivers’ brains to average brains. Experimental group: 16 taxi drivers with ~14 years of experience vs 50 non-taxi drivers. Quasi-experiment (IV not manipulated, comparison of pre-existing groups); correlational study (driving experience correlation w/ gray matter volume); MRI. Taxi drivers had increased gray matter volume in the posterior hippocampus, controls had increased gray matter in the anterior hippocampus. Redistribution of gray matter in the hippocampus occurs in taxi drivers in response to gaining navigational experience.

Fisher (2005): To investigate neural mechanisms of romantic love. 10 women/7 men in love. Experiment, repeated measures design. Participants underwent a semi-structured interview and completed the Passionate Love Scale (PLS) to establish the duration and intensity of their love. Under an fMRI, they viewed a photo of a loved one, filler activity, viewed a photo of an emotionally neutral acquaintance and did another filler activity. Increased activation in dopamine-related areas (ventral tegmental area and caudate nucleus) in response to photos of loved ones.

Kosfeld (2005): Investigated the role of oxytocin in trust. The experimental group received a nasal spray with oxytocin while the control group received a placebo. Lab experiment, independent measures. Two-player trust game where P1 could transfer some, all or no money to P2. If money was sent it was sent tripled. P2 could return any amount of money to P1. Trustworthiness was measured by the amount of money that was transferred. The experimental group transferred 17% more money than the placebo group. 2x as many people in the experimental group gave all their money to their partners. 

Wedekind (1995): Investigated the influence of MHC genes on females’ ratings of attractiveness of male sweat odour. 49 females and 45 males types for their MHC; quasi-experiment. Female participants were asked to report if they were taking oral contraceptives; men were asked to wear a cotton t-shirt for two nights in a row with no washing. Each worn shirt was placed in a box, 3 of them were MHC similar, 3 dissimilar and 1 odourless for controls and the women had to rate them from 1-10. Women who didn’t take contraceptives rated the odour of dissimilar men as more pleasant than the others, it was reversed in the women who were taking birth control. Dissimilar scents reminded women of their own partners or exes. MHC similarity may be a factor of sexual attraction. Contraceptives imitate steroids that are released during pregnancy, the reversal of odour preference may have been because it can help take care of the baby. Choosing a partner with different MHC could be an evolutionary advantage since it produces a stronger immune system for the baby.

Capsi (2003): Investigated the role of the 5-HTT gene in developing depression in response to stress. 1037 kiwi children were divided into 3 groups based on their 5-HTT allele (S/S, S/L or L/L). Longitudinal study, participants were assessed between ages 3-26 and a “life history calendar” was used to assess stressful life events as well as an interview to assess depression symptoms. S/L and S/S participants reacted to stressful life events with more depressive symptoms (e.g participants with stressful life events at age 21 tended to develop depression by age 26 ONLY if they carried a short allele). The 5-HTT gene is responsible for modulating an individual’s vulnerability to stress.

Bouchard (1981): Investigated heritability of IQ. 111 twin studies- included MZs, DZs and siblings that were either reared together or apart, their parents and offspring. Correlations were study and meta-analysis- researchers selected studies based on a number of criteria, cleaned the data and calculated median correlations between IQ and MZ/DZ twins. MZ together 0.85, MZ apart 0.67, DZ together 0.58, siblings together 0.45. Intelligence is inherited to an extent; even for MZ together the correlation is not perfect thus environment also plays a role in IQ development.

HM Milner (1968): A case study. Lobotomy of the temporal lobe led to HM’s partial retrograde amnesia (short-term memory) and anterograde amnesia (new memories) for episodic/semantic memories, but HM could not remember giving consent, may not have understood the procedures, consent was given by caretakers and mom thus HM may not have been able to withdraw.