autism is characterised by a triad of deficits: social interaction, social communication and repetition/restricted interests.
its prevalence is about 1-2 per 1000 people worldwide, occurring 4x more often in males than females. the number of people diagnosed with autism has been increasing since the 1980s, which is largely attributed to changes in diagnostic practise - it’s unclear whether there has been any real increase in the occurrence of autism.
the cause of autism is largely unclear, as it has been attributed to genetic, environmental and neural factors.
clear genetic cause:
- down syndrome
- williams syndrome
- fragile x syndrome
clear environmental cause:
- foetal alcohol syndrome
no real clear cause:
- specific language impairment
rosenzweig & diamond conducted numerous experiments in the 1960s and 70s to investigate the role of experience and environment on brain development.
they raised rats in three conditions:
- standard: small cage, other rats, no toys
- impoverished: small cage, alone, no toys
- enriched: large cage, other rats, toys
they found that in the enriched condition, the rats had a thicker cortex and more dendrites, while in the impoverished condition the cortex was thinner. however, this effect did not continue if longer was spent in the enriched condition: after 30 days there was no further increase, suggesting that the environment was no longer novel.
this research indicates that novel environments and experiences do stimulate brain development; it’s not just down to biology.
In its most basic form, the realistic conflict theory. This argues that conflict between groups comes from competition or mutually exclusive goals, and results in negative attitudes and behaviours toward outgroups.
some basic muscle facts:
- · movement results from stimulation of the skeletal muscle fibres of an effector (such as the arm). flexors act to bend or flex a joint, extensors act to extend it. for example, the biceps are flexors of the elbow joint and the triceps are extensors.
- · muscles that act in opposition are called antagonistic muscles and muscles that work together are called synergistic muscles.
- · muscles produce force by contracting in response to acetylcholine (a neurotransmitter) released by motor neurons at the neuromuscular junction.
neural control of muscle contraction:
- · the smallest functional unit of motor activity is called a motor unit, consisting of a single alpha motor neuron and the muscle fibres it innervates. each fibre is innervated by only one motor neuron.
- · the number of muscle fibres innervated by one motor neuron is called the innervation ratio (about 100 in hand muscles and 1000+ in leg muscles).
- · even without innervation muscles have spring-like properties
- · the frequency of the action potentials in a motor neuron & the number of muscle fibres recruited determine the force of muscle contraction.
even the simplest actions use many parts of the brain:
- preparing to act: a tennis player’s visual cortex computes size, direction & velocity of the approaching ball. their premotor cortex develops a motor program based on this information. the amygdala adjusts heart rate, respiration etc. and activates the hypothalamus, motivating the player to hit a good shot.
- action execution: the player’s motor cortex must send signals to the spinal cord. the basal ganglia recall and initiates learned motor patters, the cerebellum fine tunes movements based on proprioceptive information, the posterior parietal cortex computes frames of reference based on the players body relative to external space, and the hippocampus may allow recall of this event later.
the motor system is organised into a hierarchy; the spinal cord represents the lowest level within the central nervous system. it contains neuronal circuits capable of producing a rich variety of automatic & stereotyped motor patters which can be activated by sensory stimuli (reflex) or from the brain stem/cerebral cortex. the middle layer is formed by primary motor cortex & brainstem structures which (with the assistance of the cerebellum & the basal ganglia) translate action plans into movement. near the top of the hierarchy are the lateral premotor cortex (PMd & PMv) and the supplementary motor area (SMA) which are critical for action selection and planning.
receptor organs of muscles:
- muscle spindles: respond to the stretch of muscle fibres (muscle length). They are arranged in parallel with the main muscle fibres.the sensitivity of muscle spindles can be modulated by the contraction of intrafusal muscle fibres which are innervated by gamma motoneurons. alpha motoneurons are normally activated together for a delay-free adjustment of muscle spindle sensitivity.
- golgi tendon organs: are arranged in series with muscle fibres. they are sensitive to changes in tension and subserve a protective & complementary function to muscle spindles.
Carlos et al (2005) identified high extraversion and agreeableness as predictors of prosocial behaviour, while Weibe (2004) identified low conscientiousness and neuroticism as predictors of antisocial behaviour. The fact that there are different factors involved in each suggests that these behaviours are not opposites, as some might believe.
- Conscientiousness: is the biggest predictor (Chamorro-Premuzic & Furnham, 2003)
- Neuroticism: is detrimental due to anxiety (Spielberger, 1972); neurotics are prone to external stress (Lazarus & Folkman, 1984)
- Openness: is good because of its positive relation to crystallised intelligence (Ackerman & Heggestad, 1997)
- Extraversion: is a function of assessment type. Tasks that highlight social interaction are easier for extraverts. Introverts beneﬁt from long-term intellectual investment.
- Scmidt & Hunter (1998) found that conscientiousness only has a 0.31 correlation with job performance.
- Hurts & Donovan (2000) conducted a meta-analysis of trait predictors of job performance and found that neuroticism was the most unreliable predictor; results of studies varied most for this trait and were most consistent for conscientiousness.
- Meehl (1989) predicted the role of anxiousness etc in pre-morbidity.
- Caspi, Roberts & Skinner (2005) produced the following chart to illustrate
- Quirk et al (2003) found that certain traits correlate with mental health – most notably neuroticism.
Goldberg (1981) reviewed previous evidence and made a convincing case for a “universal” personality lexicon, suggesting that the “big 5” would emerge wherever a researcher looked into language.
- Saucier & Ostendord (1999) found the “big 5” in a German sample,
- Guthrie & Bennett (1971) found the “big 5” in people’s implicit theories
- Barrick & Mount (1991) found the “big 5” predicted job performance.
Costa and McCrae (1985, 1992) developed a questionnaire approach to measuring the Big-5. They began with measuring N & E, before adding O, then A & C. This was formulated into the NEO-PI. Costa and McCrae’s legacy is to demonstrate the mathematical importance of the Five Factors and they found evidence for it in large, diverse samples.
Despite wide evidence for the existence of the five factors, there have been issues of interpretation; there is some disagreement about what each factor really means.
Several have questioned why the five are so special, and others have suggested that evaluative traits like moral/immoral should also be included. The possibility of a sixth “honesty-humility” factor of “trustworthiness” was also suggested by Hahn, Lee & Ashton (1999).
One major criticism of the five factors is that they’re western centric and another comes from the fact that evidence doesn’t represent traditional psychological evidence.