2.9 Animal Research in Behaviour: How animal research provides insights about human behaviour (and brain)

Define comparative psychology

The scientific study of animal behaviour and cognition, with the goal of understanding the evolutionary and ecological factors that shape behaviour and the cognitive mechanisms that underlie it

Number of animals used in psychological research annually in the USA

1.25 - 2.5 million; 7.5% of research = animal based

An animal model

Concept that refers to using animal research to test a certain cause-and-effect hypothesis about a certain human behaviour.

4 major types of experimental manipulation: (list)

Genetic manipulation

Invasive manipulation with the nervous system

Invasive manipulation with other body parts

Behavioural and environmental manipulation

Genetic Manipulation

Animals are bred in a certain way

Invasive manipulations with the nervous system

Part of the brain are stimulated with electrodes, lesioned, or removed

Invasive manipulations with other body parts

Parts may be stimulated by substances or damaged

Behavioural and environmental manipulations

electric shocks for rats depending on their performance in a maze-learning task

Based on which assumption

Animal and human brains are similar

However, recently in comparative neurobiology

microscopic differences between animals and humans in certain brain areas:

• some brain areas in common were different in terms of how neurons are structured

Advantages of working with animal models: 2 pros

Animal studies allow researcher to embrace full lifespan
- Human subjects outlive researchers - mice = 2-3 years

Can be highly controlled

Relatively inexpensive, easily accessible, easy to handle/manage

They do produce results: life-saving treatments

Disadvantages of working with animal models:

Animals and humans are never exactly the same

Similar biologically, still differ psychologically

When new biomedical treatments developed; first test with mouse models - however, mouse never directly applied to humans

Luby et al. Year

2013

Aim

To investigate how children’s brain development and therefore their cognitive development are affected by poverty.

Method

Natural Experiment

Design

Independent Measures

Sampling Strategy

Purposive; 145 right-handed children

IV

Whether they were raised in impoverished conditions

DV

Mass of White and Grey Matter in the Hippocampus and Amygdala

Procedure

Children were assessed annually for 3 to 6 years prior to the time of a magnetic resonance imaging scan, during which they were evaluated on psychosocial, behavioural, and other developmental dimensions

Pre-schoolers included in the study were 3 to 6 years of age and were recruited from primary care and day care sites

They were annually asses behaviourally for 5 to 10 years

Healthy pre-schoolers and those with clinical symptoms of depression participated in neuroimaging

Findings

Poverty = smaller white and cortical grey matter and hippocampal and amygdala volumes

The effect of poverty on hippocampal volume were mediated by caregiving support/hostility

Conclusion:

The findings that exposure to poverty in early childhood materially impacts brain development at school age further underscore the importance of attention to the well-established deleterious effects of poverty on child development.

Enhancing early caregiving should be a focused public health target.

.

.

Methodological Strengths

Longitudinal, measuring IV and DV over a long time

Triangulation

High internal validity

Findings were consistent with previous research

Methodological Limitations

Small sample, hard to generalize

Correlational, reduces internal validity

Hard to replicate

Parents no being able to afford school could also have an affect on brain development

Not a diverse sample

Which study can be used with Luby (2013)

Radley et al. (2006)

Aim

To investigate the relationship between repeated stress on dendritic spine number and grey matter in the PFC

Method

True lab experiment

Design

Independent Measures

Sampling Strategy

n/a; rats

IV

Whether they were restrained for 21 days

DV

Neural density and dendritic length in the PFC

Procedure

Male rats housed in cages; 2-3 rats per cage

8 control rats

8 stress rats

Procedure

Animals had unlimited food and water

Procedure

Controlled rats were in separate rooms to stressed rats

All rats were handled for 7 days prior

Procedure

Rats were restrained for 6 hours daily for 21 days with wire mesh restrains and were returned to their home cages through the restraining period

To ensure blind - each animal was encoded by independent observer

On day 22 - rats given euthanizing dose

Brains were dissected and examined with microscope to observe grey matter (post-mortem)

Findings

Stress = 16% decrease in grey matter in PFC

Dendritic density and length decreases - 20% length reduction

1/3 of synapses were lost during stress

Neurons were weaker and less able to produce and distribute neurotransmitters

No effect on basal dendrites

No correlation between spine density and ascending branch order

Weight gain was less in stressed rats

conclusion

Significant overall reduction of dendritic spine density in PFC after stress exposure

Chronic stress produces 20% decrease in number and length of dendrites

Also 33% decrease in total number of synapses

Methodological Strengths

Control conditions

IV manipulated - cause-and-effect

Quantitative analysis

Controlled environment - control extraneous variables

Methodological Weaknesses

Could not make humans stressed

Small sample

Only on cellular level