Pearson Edexcel · GCSE · Psychology
Course version: 1PS0 · Version from Sept 2017
Understand Activation Synthesis Theory (Hobson and McCarley, 1977),…
Full specification wording
Sleep and dreaming: 9.1.5 Understand Activation Synthesis Theory (Hobson and McCarley, 1977), including strengths and weaknesses of the theory: a. random activation b. sensory blockade c. movement inhibition
Hobson and McCarley (1977) proposed the Activation Synthesis Theory, arguing dreams are biological by-products of REM sleep.
Checked against the Pearson Edexcel 1PS0 specification (opens in a new tab) on .
- Point 5 of 5
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Hobson and McCarley (1977) proposed the Activation Synthesis Theory, arguing dreams are biological by-products of REM sleep. 'Random activation' occurs when brainstem neurons fire spontaneously, sending signals to the neocortex. The brain attempts to synthesise these signals, creating a dream narrative. 'Sensory blockade' prevents incoming sensory information from reaching the brain, and 'movement inhibition' stops motor commands, preventing us acting out dreams. A strength is its strong scientific basis, supported by EEG evidence of brain activity during REM sleep. However, weaknesses include its inability to explain highly structured dreams or dreams occurring outside of REM sleep, suggesting it may oversimplify the dreaming process.
What earns the marks
- Random activation refers to spontaneous neural firing in the brainstem during REM sleep.
- The neocortex attempts to synthesise these random signals into a coherent dream narrative.
- Sensory blockade prevents external stimuli from interfering with the sleep state.
- Movement inhibition prevents the dreamer from physically acting out their dreams.
- A strength is the objective, scientific evidence from EEG recordings during REM sleep.
- A weakness is that it struggles to explain dreams that occur in non-REM sleep.
Common mistakes and how to put them right
Confusing sensory blockade with movement inhibition.
Put it right: Sensory blockade stops information coming in, whereas movement inhibition stops motor signals going out.
Stating that the theory claims dreams have deep psychological meaning.
Put it right: The theory explicitly argues that dreams are meaningless biological by-products.
Assuming random activation happens in the neocortex.
Put it right: The random activation originates in the brainstem and is sent to the neocortex for synthesis.
Exam tips
- Clearly distinguish between the biological cause (random activation) and the cognitive result (synthesis).
- Use the terms 'sensory blockade' and 'movement inhibition' accurately when describing the physical state of REM sleep.
- Contrast this biological approach with Freud's psychoanalytic approach when evaluating theories of dreaming.
Try the lesson
The start of the Sleep and dreaming: 9.1.5 Understand Activation Synthesis Theory (Hobson and McCarley, 1977), including strengths and weaknesses of the theory: a. random activation b. sensory blockade c. movement inhibition lesson, made from checked teaching notes for this specification point.
Have a go first
According to the activation synthesis theory, what is meant by the term 'sensory blockade' during REM sleep?
Listen
Hobson and McCarley (1977) proposed the Activation Synthesis Theory, arguing dreams are biological by-products of REM sleep. Random activation' occurs when brainstem neurons fire spontaneously, sending signals to the neocortex. The brain attempts to synthesise these signals, creating a dream narrative. Sensory blockade' prevents incoming sensory information from reaching the brain, and 'movement inhibition' stops motor commands, preventing us acting out dreams. A strength is its strong scientific basis, supported by EEG evidence of brain activity during REM sleep. However, weaknesses include its inability to explain highly structured dreams or dreams occurring outside of REM sleep, suggesting it may oversimplify the dreaming process. A strong answer earns marks for these points. Random activation refers to spontaneous neural firing in the brainstem during REM sleep. The neocortex attempts to synthesise these random signals into a coherent dream narrative. Sensory blockade prevents external stimuli from interfering with the sleep state. Movement inhibition prevents the dreamer from physically acting out their dreams. A common slip: Confusing sensory blockade with movement inhibition. Instead, Sensory blockade stops information coming in, whereas movement inhibition stops motor signals going out. Exam tip: Clearly distinguish between the biological cause (random activation) and the cognitive result (synthesis).
Key words
Say what each word means before you turn the card.
Random activation
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Sensory blockade
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Movement inhibition
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Scientific evidence
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See every definition
- Random activation
- Spontaneous firing of brainstem neurons during REM sleep, sending signals to the neocortex.
- Sensory blockade
- Prevents incoming sensory information from reaching the brain during REM sleep.
- Movement inhibition
- Stops motor commands, preventing the dreamer from physically acting out their dreams.
- Scientific evidence
- Objective evidence from EEG recordings during REM sleep, which is a strength of the theory.
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