Flashcards in P&A Deck (136)
Evolutionary needs of P&A
1. Find food
2. Avoid danger
What is a modality?
A class of stimulus (energy transmitted) and the specialised receptors that 'sense' that energy, all perception occurs within certain modalities.
Why can the perceptual system be tricked?
Because the system often 'estimates', we have evolved to rapidly extract useful info from the environment.
What's the more modern overall model corning the way we perceive and act?
Sample info - process info -interact with the world (in a loop)
What is the classic view of perception? Why is this no longer so relevant?
There is a distinction between perception and action in the classic model sensation leads to perception and separately cognition leads to action.
However the lines between perception and action are arbitrary - where does action begin and perception end.
Examples of a perceptual Energy?
Chemical energy i.e. taste, smell
Heat and tactile energy
Energy from waves of air pressure (audition)
What are the differences between light and sound energy that mean bats and dolphins are more adapted to using it?
Sound is present at all times (bats hunt in the dark)
Sound travels faster underwater (dolphins inhabit water)
What is filtering?
Active process of selectively keeping some information , and discarding others
Example of filtering in the eye?
The fact it uses only the visible light part of the spectrum.
What is sampling?
The active seeking of useful information
Are eye movements an example of filtering or sampling?
Sampling (looking for info)
Why is perception and action important to study?
Help humans with impairments in visuomotor activities i.e stroke survivors
What did Smith et al (2015) show (stroke patients)?
They developed novel computerised tools to assess whether stroke survival patients had adequately compensated for their impairments, this has implications on whether they could be allowed to drive in the future, driving offering a larger QoL.
What did Yarbus (1967) say about eye movements?
Human eyes fixate on those elements of a visual scene that carry essential and useful information.
Fixate for longer on more useful info, people who think differently see differently
- Related to the task
Model of P&A using eye-movements as an example?
Motor commands sent to eye to move - visual info sampled from new point of fixation - info informs future eye-movements - Loop back to start.
What are the different types of eye movements?
Conjugate movements (both eyes in same direction):
- Smooth pursuit
- Vestibulo-Ocular reflex
Disconjugate (different directions)
Most recent way to measure eye movements?
What are saccades?
Rapid ballistic eye-movements, very short duration (15-100ms)
The most frequent movement we make
What is saccadic suppression?
The mechanism by which we do not see motion blur during saccades - as we are effectively blind during saccades.
What is fixation?
Time where the eyes focus on one area in order to allow us to absorb the information from that area:
Not completely still as photoreceptors and neuronal connections would adapt/fatigue if completely still. (red dot test - Troxler effect)
Micro-saccades/ocular drifts and ocular tremors keep this from happening.
What is smooth pursuit movements? How are they accomplished?
Smoothly follow a moving target
Requires the system to make predictions about where the target will be moving
What is the vestibular ocular reflex?
The interaction of the vestibular system and eye movements when the head is moving - counter rotates the eye when the head moves, in order to maintain fixation when moving, does not need visual input.
What is Optokinetic (OKN) Nystagmus?
Optokinetic nystagmus - non-pathological behaviour, it is when making very large head turns or for example looking out a train, relies on both smooth pursuit movement and saccades. The smooth part is characterised by slow-phase velocity.
Findings of Costa (2011) on Down syndrome patients and OKN Nystagmus?
The DS patients had increased number and amplitude of intruding saccades during smooth pursuit movement.
May help understand why DS people struggle with everyday tasks - e.g. reading may affect intellectual capacity.
What interaction may eye-movements have on visual field loss i.e. after neurovascular incident. Study?
May help compensate.
What real-world functions do eye-movements have?
Direct actions towards those objects
Guide actions upon those objects
Check the status of actions
What type of scales does the human perceptual system use?
An example of the human perceptual system using logarithmic scales?
Small weight changes are easier to detect in lighter weights than heavier weights - Fechners law
6 extraoccular muscles?
Superior Rectus, Lateral Rectus, Inferior rectus, medial rectus
Superior oblique, inferior oblique