Evolutionary Perspectives On Dreaming Flashcards
Functional explanations of dreaming
Need to dream, has a function
Consciousness is the dream
Threat simulation theory
Dreams are rehearsals for dealing with threats
Survival advantage
Functional explanation- Environment of evolutionary adaptedness (EEA)
Started dreaming long time ago
Must be evolutionary reason why
Assumes animals don’t dream, only humans
Revonsuo’s evolutionary hypothesis
To understand dreaming you have to look back to this ancient time & consider the evolutionary pressures that existed
Full of theses & multiple sources of danger
Full of enemies
An anxious, frightening, sad place
Survival needed rapid detection of foes & prey
Survival needed physical skill- to escape, to fight
Dreaming (practising survival) helped to survive & pass on offspring
What advantage could dreaming give?
If dreaming was selected this must be the case
Current dreaming reflects the activation of the brain system that evolved for dreaming long ago
Dreaming doesn’t have the input to do what it’s designed to do anymore
A virtual reality
Dream experience is not random & disorganised, instead it constitutes an organised & selective simulation of the perceptual world
Everything in a dream feels real
Dreams simulate threatening events
Consistent with work on content analysis of dreams
Emotions (80% negative) misfortune (36%) & aggression (40%) in dreams (big categories)
Similar to what you’d expect in threat-simulating world
The original evolutionary element
Enemies in dreams
Recurring dreams & nightmares
Absence of reading, writing, typical & calculation (not dangerous)
Brain activation during REM sleep reflects the neural correlates of threat simulation
Real threats affect dream content
Effect of traumatic experience on dream content
Real threats once activated the threat simulation system
Now, typically there are only weak stimuli for threat simulation system
Tests of TST: Valli et al. (2008) method
evidence from frequency & intensity of threatening dreams of Finish & Swedish uni students
Traumatised Kurdish, Palestinian & compared them to Finish children
Recurrent dreams & nightmares collected from Canadian pp
Valli et al (2008) results
Compared dream reports & waking event logs for 2 weeks
Interviewed pp about real threat they had experienced
39 uni students over 2 weeks produced 419 dreams & 490 event logs
714 real life remembered threat experiences were reported
Threatening experiences were much more frequent & severe in dreams than real life
Valli et al (2008) results on traumatised children
Trauma groups consisted of children who had faced military violence and/or lost a caretaker or several relatives in war or military attacks
Control group 1- children with ordinary lives, saved from military persecution or who had lost a caretaker due to illness or accident
Control group 2- Finnish children
Results
Dreams reports collected over 6 consecutive nights
More dreams recalled by the trauma group
Number of dreams with at least 1 threat-
Kurdish trauma (80%, all respondents)
Kurdish non-trauma (56%, 6% no threat)
Finnish non-trauma (31%, 43% no threat)
Severity of the events Life threatening & other wise severe Kurdish trauma (34% & 24%) Kurdish non-trauma (28% & 19%) Finnish (22% & 9%)
Results continued- reactions to threat
No difference between groups
Self reacts 35%
Someone else reacts 10%
No one reacts 30%
Implications for predicted improvement of threat avoidance skills?
Palestian children study (2006)
Trauma group- from Gaza, extremely violent & dangerous conditions
Control group- peaceful area of Galilee, Israel
Results
More dreams recalled by trauma group
Number of dreams with at least 1 threat-
Trauma (58%)
Non- trauma (48%)
Dreamer was more often the object of threat
Results continued- reaction to threat
No difference between groups
Self reacts (29%)
Someone else reacts (10%)
No one reacts (36%)
Implications for predicted improvement of threat avoidance skills?
Recurrent dreams- Zadra te so (2006)
212 recurrent dreams- collected over 10 years
Defined as over a period of at least 6 months with the content of the recurrent dream as being always or almost always identical
Results- Zadra at al (2006)
66% of reccurent dreams reports contained 1 or more threats
65% are likely to result in death or serious injury
22% additional serious threats
94% threats aimed at the dreamer
54% dreamer tended to take defenders or evasive actions that were possible & reasonable
17% happy outcomes, 40% threat fulfilled, 37% dreamer awakens, dreamer rarely succeeded in fleeing
20% were probably threats
Evidence from video game play- Gackenbach & Kuruvilla (2008)
41 high end gamers recruited
Expectation-
Would experience fewer threat simulation dreams because of frequent threat resolution rehearsal during game play
When they do experience threat they will show more pro-active & effective solutions
Results
High end gamers do experience fewer threat severity variables in their dreams
Revonsuo’s threat simulation theory
Malcolm-Smith & Solms (2004)
410 dreams collected
21% physical threat to the dreamer
9% report realistic life-threatening events in dreams
A realistic escape occurred on 1/3 of reports
3% of dreams (11/401) contained realistic escapes from realistic, life threatening events
Revonsuo’s threat simulation theory
Assuming that these are simulated in this virtual world so that they can enhance survival in the real world
They are where practice occurs
To make sense 2 conditions need to be fulfilled-
1) realistic rehearsal
2) transfer of learning to waking life
Realistic rehearsal
Perceptual realism
Lack of insights
Motor realism
Transfer of learning to waking life
Mental training
Implicit learning & implicit memory
Stumbry et al (2016)
People remember when they dream (lucid dreaming)
Finger tapping sequence task- 20% increase 17% in physical practice 12% in mental practice 5% control
Other studies
Coin tossing
Dart throwing
Balancing on one leg
Bias towards evolutionally olds threats
Original environment humans lived in included frequent dangerous events
Ecologically valid threat cues in the human ancestral environment fully activated the threat simulations system
Recurring realistic threat simulations led to improved threat perception & avoidance skills & therefore increased the probability of succesfull reproduction of any given individual
Consequently the TSS was selected for during our evolutionary system
Virtual reality dream theory- predictive codes
Dreaming has been selected by evolution because it enhances survival for a more abstract reason
Dreaming reflects a basic more general process- inference generation
- not replay of remembered experience. No identifiable mnemonic
- dream synthesis suggests a predictive creative role for dreaming
Features noted-
- dreaming is vivid with detailed perceptions
- narrower range & a greater depth of emotion
- movement is imagined but not actually acted out
VRDT
The brain is an organ of interference
The perceptual world is both too detailed & too under specified
Brain generates models of the world
Both dreams & the everyday phenomenal world may be thought of as constructed virtual realities
It is the same inferential system that generates our perception of the real world & generates the dream world
What has the brain evolved to do?
Perhaps not threat rehearsal but evolution has shaped the brain to produce models of the world
Construct models of the perceptual world
The claim
Dreaming allows the optimising of generative models during sleep
A basic, fundamental process essential to survival
Needed to see, to understand, to anticipate, to make sense of sensory stimuli
In sleep, the brain is free from having to process sensory input
This is necessary for model optimisation, during which the brain can rehearse fictitious scenarios that may or may not be encountered in waking
The Bayesian brain
Prior beliefs are combined with sensory evidence to produce a posterior belief
Effective prediction requires the updating of expectations about hidden states of the world generating sensory data
This updating is driven by sensory info that can not be explained by current expectations/beliefs
Striving for accurate models of how the world works
Complexity minimisation
Need a model that makes few errors in prediction but also that is very simple ‘there is an imperative to minimise the complexity of VR models to maximise their evidence”
‘The function of complexity minimisation is to ensure that the model can generalise’ detailed models predict very well but are limited to specific cases
Dreaming may prepare the brain for the unpredictable diversity of scenarios it encounters during waking
It refines & develops a model that can generalise to the diversity of sensory scenarios are encountered during waking
We need to be asleep for this to work
Sleep is an optimisation process that becomes visible when we fall asleep & sensory processing element is less dominant
They suggest that sleep is necessary to minimise complexity in order to ensure that our models are optimal during waking
The brain needs to be off-line, so that synaptic plasticity & homeostasis can reduce the complexity it has accrued during wakefulness
Summary of virtual model
Model requires maintenance
Has to account for vast amount of sensory input during waking & can only do this if it generalises to every context encountered
This generalisation rests upon minimising model complexity
This happens during dreams, which we witness
Simplifying models of the world that can be used to make inferences in the future
Evolutionary perspectives on dreaming
Necessary function for why we dream
Contrasts with brain stem theories which see dreaming as a random by-product of brain activation
Whether there is any function to awareness of dream content is disputed
Evolutionary perspectives on dreaming continued
Even if evolution has led to dreaming, might natural selection have chosen some other mental ability where dreaming is just an incidental side-show
Much like side effect/by-product explanations
Not all firms & functions are a direct product of natural selection
Dolmhoff’s option
Dreaming may be a by-product of imaginative waking cognitive capacities that turned out to have great adaptive value
The default network
Seen when fMRI brain scans are done
A set of brain areas that activate at the same time whenever ‘not otherwise employed’
I.e. when not being asked to do a task in a fMRI scanner
Brain activation when dreaming
There is a considerable overlap with the default network & the brain areas active during REM sleep (dreaming)
They are the areas whose damage affect dreaming
The areas that they do not include are also areas where damage does not affect dreaming
Perhaps dreaming is simply activity of the default network
The default network when thinking about nothing, daydreaming, worrying
Considerable overlap with areas activated by-
- vivid recall of recent real autobiographical memories
- vivid recall of previously created imaginary experiences
Imagined experiences were associated with increased activity in many of the same brain areas- the imagination network
Considerable overlap in the brain areas activated when with mind wandering & with experimental self (stories of what happen to us to who we are), self reflection, self criticism, rumination, thinking about what others think- perspective taking
Dreaming is the imagination wandering freely, powered by embodies simulation
Continued
Enables the internal rehearsal of events or scenes- creating a setting in which a simulated event can unfold whether past, present, future or hypothetical
The ability to pre-experience hypothetical events confers an evolutionary advantage in planning for the future
So dreaming is a by-product of evolutionary selection for the default network, which makes it possible to think about the past & prepare for the future
The ability does not depend on or need dreaming, it is the default network active during sleep
Continuity hypothesis
Consistent with continuity hypothesis that dreaming reflects waking life experiences (continuum between waking experiences & experiences within dreams)
Dreams are mostly about everyday waking themes & by ages 11-13 they very often dramatise personal concerns relating to important people & avocations in the dreamers life
There is consistency in dream content over months, years, decades in terms of major characters, interests/hobbies & types of frustrating situations
There is a continuity between elements of dream content & waking conceptions
Embodied simulation
The key cognitive process in dreaming is simulation, a particular kind of subset of thinking that involves imaginatively placing oneself in a hypothetical scenario & exploring possible outcomes
Embodies simulation is supported by the activated secondary sensory & sensorimotor areas in the default network, which support all forms of mental imagery
Dreaming may be the accidental intersection of the default network
With the occlusion of external stimuli during long periods of drifting waking thought
That enable the full sensory motor realism to exist as it is implemented in secondary sensory cortices
Evolutionary perspectives on dreaming
Not all forms & functions are a direct product of natural selection
Even if evolution has led to dreaming, natural selection may have chosen some other mental ability such as the imagination network where dreaming is just one manifestation? It is not key or unique
Much like side-effect/by-product explanations
