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Classic study: Olds and Milner (1954) (Evaluation (Strengths (Conducted in…
Classic study: Olds and Milner (1954)
Aim
To explore whether electrical brain stimulation acts as a positive reinforcement in rats
Stimulate different parts of the brain to see what behaviour rats showed in response
Examine brain regions that produced reinforcement responses, see if they could find areas linked to producing rewards
Background
Original experiment: investigating systems regulating sleep through stimulation in a cage
They observed a rat returning to the location where the stimulation was given --> pleasurable
Sample
15 male hooded rats
Procedure
Implanted electrodes into 15 male rats
Each rat was tested in a Skinner box which delivered a current to the brain when they pressed the lever
Acquisition --> 6-12 hours, stimulator turned on so electric current passes to the rat when the lever is pressed
Extinction --> 1-2 hours, no stimulator when lever is pressed
'Response' if there was clear behaviour show once in 30 seconds, and brain structures were examined after
Results
Highest scores found together in the central area of the brain (septal)
More than 75% responding in acquisition testing (pressing the lever)
22% of extinction testing spent responding
The stimulation of the septal area acts as a primary reward
Conclusion
Existence of the pleasure centre in the septal areas of the brain, leads to rewarding effect on behaviour
Evaluation
Strengths
Conducted in controlled environment, all rats implanted with electrodes and tested in the same way
No reinforcement used except the electrical stimulus = cause and effect relationship
All external variables minimised, increases validity of the findings
Ethical guidelines related to storage and use of animals intact
Rats weren't deprived of food or water
Researchers monitored if rats showed signs of pain after implantation and during testing
Numbers of rats used was small, shows consideration for species
Weaknesses
Variations in voltage of the stimulation
Future experiments may have rats that require different voltage amounts before they respond
Inconsistency --> reduces replicability
Setting and conditions for experiment are not natural for rats
Wires attached to skulls and electric shocks given
Observation actually a reaction to the conditions rather than behaviour being due to reinforcement
Rats unnecessarily harmed after the experiment to examine the brain
Sample size not large enough to draw meaningful conclusions