Biological Structures, Neurochemistry & Evolution (AQA AS Psychology)

Biological structures & neurochemistry

• The biological approach assumes that structures such as the nervous system, the endocrine system and the brain play a key role in human behaviour

The nervous system

• The human nervous system  comprises

  • Central Nervous System (CNS):

    • This consists of the brain and the spinal cord

    • The CNS receives, sends and responds to sensory information

  • Peripheral Nervous System (PNS):

    • This relays information between the body and the brain

    • This information includes involuntary responses such as breathing and heartbeat as well as sensory information and control of voluntary movement

The endocrine system

• The endocrine system is a chemical messaging system that operates throughout the body 

• The endocrine system secretes hormones into the bloodstream from different glands e.g.

  • The pituitary gland is the major endocrine gland (known as the master gland )

    • it makes, stores and releases hormones

    • it instructs other glands to release hormones as well

  • Examples of hormones include adrenaline (flight or fight), testosterone (male sex hormone), oxytocin (attachment and bonding)

The brain

• The brain is made up of different regions which are localised to specific tasks e.g.

  • Temporal Lobe

    • This lobe controls hearing/auditory perception 

    • It also controls speech comprehension

  • Frontal Lobe  

    • This lobe is linked to voluntary movement and expressive language

    • The prefrontal cortex in particular is linked to executive functioning e.g. impulse control

  • Cerebellum 

    • This lobe receives information from the spinal cord, sensory systems and other parts of the brain 

    • It regulates balance and motor movements 

Evolution & behaviour

• Evolutionary psychology is part of the biological approach to explaining behaviour (based on Darwin’s theory)

• The evolutionary approach to explaining behaviour looks at how and why specific human traits have evolved via the process of natural selection e.g.

  • aggression

    • evolutionary usefulness to fight off predators and enemies

  • memory

    • evolutionary usefulness to recall the location of food sources

  • language

    • evolutionary usefulness to communicate with tribe members

  • mate selection 

    • evolutionary usefulness to select a mate who will bear healthy offspring

• Due to natural selection, behaviours and traits which are useful for survival and reproduction are retained – and those which are not eventually die out

Adaptive behaviours

• Adaptive behaviours are those which increase the chances of survival and reproductive success

  • This is why these behaviours are inherited through the generations i.e. how we behave now is the product of causes rooted in the distant past

    • This is known as the ultimate causes theory of behaviour

• Genes are the mechanisms which drive evolution

  • Any genetically determined behaviour which increases the chances of survival per species will be inherited to future generations

• Biological psychologists believe the characteristic of intelligence is adaptive as it enhances human survival

  • For our ancestors, intelligence manifested as knowing where to find the best food source, understanding weather patterns, fashioning tools, creating transport, negotiating with other tribes etc.

  • Intelligence today equates to further education, training, an entrepreneurial drive, a good job

    • These accomplishments ensure security and abundance of resources i.e. survival and reproductive success

Evaluation of biological structures & neurochemistry

Strengths

• Research into biological structures uses objective, clinical methods and measures e.g.

  • Zak et al. (2009) measured testosterone levels in blood samples and linked these to a lack of prosocial behaviour

  • Maguire et al. (2000) used MRI scans to investigate the role of the hippocampus in spatial navigation

    • The results derived from using these measures can be checked for consistency across time and samples which means they have good reliability

• There is some compelling evidence in support of evolution and behaviour

  • Curtis et al. (2004) found that people showed higher levels of disgust for disease-salient images than for neutral images

  • Disgust is an evolutionary mechanism as it prevents people from ingesting toxic materials

  • Thus, if people have an innate disgust response to rotten, mouldy food this lends validity to the idea that humans are biologically programmed for survival

Limitations

• The results of research into biological structures are overly reductionist e.g.

  • levels of testosterone cannot alone account for a lack of prosocial behaviour, other factors such as personality and upbringing could explain this

  • spatial navigation is also a product of cognition and social factors e.g. having a good memory and being familiar with specific London streets since childhood

• Some behaviours which are not advantageous to a 21st-century person remain e.g.

  • aggression is, on a practical level, unnecessary for most people

    • We don't need to fight competitors for food or grapple with dangerous predators daily

    • Being overly aggressive is likely to lead to police involvement and/or alienation from friends and family

    • Thus, an evolutionary explanation of behaviour has limited usefulness