9.2 Human Performance and Limitations Flashcards
What is the cornea?
The clear window at the front of the eyeball. Responsible for 70-80% of the focusing.
What is the iris?
It controls the amount of light that enters by varying the pupil.
What is the lens?
Achieves final focusing by movement of the ciliary muscles.
What is the change of the shape of the lens called?
Accomodation
What can affect accomodation?
Fatigue and ageing.
What is visual acuity?
The sharpness of vision.
What is found in the retina?
Cones and rods.
Where do cones function well and what ability do they give?
Well lit conditions, and the ability to identify over 1000 colours.
Rods can’t detect colour but what do they give?
Peripheral vision, due to being able to detect movement on the edges of vision.
What is the central area of the retina known as?
The fovea, made up of cones.
How does a visual image reach the brain?
Light stimulates the cells and passes the electrical impulses by way of the optic nerve to the cortex in the brain.
What happens where the optic nerve joins the back of the eye?
There is a blind spot.
How many nerve cells are there in the eye?
1.2 million.
How many times more sensitive is the eye compared to the ear?
24 times.
How is visual acuity tested?
Snellen chart.
What happens to the visual acuity as the angular distance from the fovea increases?
As little as 5 degrees drops acuity by 50%.
What can affect visual acuity?
Myopia/Hypermetropia (Short/Long)
Age
Foreign substances
Environmental (light, clarity).
What is hypermetropia?
Shorter than normal eyeball causing the image to be formed behind the retina (long sighted).
What is presbyopia?
As a person ages the lens becomes less flexible. It’s a form of long sightedness.
Hypoxia reduces the sensitivity of the rods, what is it?
The effect of foreign substances on the eye, it causes less oxygen to be carried in the blood.
How long does it take the cones and rods to adjust to low light?
Cones- 7 minutes
Rods- 50 minutes
How long should contact lenses be worn for?
8-12 hours max.
Why is good colour vision important for engineers?
Recognising and Distinguishing.
Colour blindness effects 8% of men, what percentage of woman?
0.5%
With ageing what happens to the lens colour?
It yellows, affecting the blue yellow colour range.
What CAA leaflet gives guidance on eyesight requirements?
CAP 562 Leaflet H60
What is astigmatism?
Clouding of the lens
What are the two functions of the ear?
Hearing and balance/sensing acceleration.
What are the three divisions of the ear?
Outer, middle and inner.
What is the outer ear responsible for?
Directing sound down the auditory canal and onto the eardrum.
What does the middle ear do?
Transmits vibrations through three small bones called the ossicles to the fluid of the inner ear.
What are the names of the three ossicles?
Hammer, anvil and stirrup.
The middle ear has two muscles that protect from noises above 80db. How does it do it and by how much does it reduce the noise level?
Acoustic and aural reflex, reduces the noise by up to 20db.
How is the air in the middle ear refreshed?
The eustachian tube.
What is the inner ear filled with?
Fluid.
The last of the ossicles in the middle ear is connected to what in the inner ear?
The cochlea.
What is the cochlea?
An area containing a fine membrane covered in hair like cells, they detect movement in the fluid.
What is the cochlea membrane called?
Basilar membrane.
What is the typical range a young person can hear?
20 to 20,000 Hz
Where is the greatest sensitivity in the hearing range?
3000 Hz
What impacts can noise have in the workplace?
Annoying
Interfere with comms
Be fatiguing
Damage hearing
What did the Control of Noise at Work Regulations 2005 replace?
Noise at Work Regs 1989
What are some of the key points in the Control of Noise at Work Regulations 2005?
Employer to provide protection at 85db
Risk assessments at 80db
Exposure limit 87db when protection is on
What is a noise dose?
The combination of duration and intensity.
How much do ear plugs and ear defenders reduce db respectfully?
Plugs 20db
Defenders 40db
Degree of hearing impairment is influenced by the intensity of noise, what is this known as?
Noise Induced Hearing Loss
What is presbycusis?
Age related hearing loss.
What is the test for an engineers hearing?
The ability to hear an average conversational voice in a room at 2 metres.
What is information processing?
Process of receiving information through the senses, analysing it and making it meaningful.
What forms can attention take?
Selective
Divided
Focused
Sustained
What is selective attention?
Monitoring several sources of information and choosing which is more important.
What is divided attention?
One task suffers at the expense of the other, known as time sharing.
What is focused attention?
Focusing on one source of information.
What is sustained attention?
Long term attention.
What is perception?
The process of assembling sensations into a usable mental representation of the world.
How can decision making be defined?
Thinking, problem solving and judgement.
What are good decisions based on?
Knowledge supplemented by written information, procedures and observations.
What is short term memory also known as?
Working memory.
What two types of ultra short memory are there?
Iconic memory- visual
Echoic memory- auditory
Is long term memory unlimited?
Yes.
What are the two classes of long term memory?
Semantic- factual
Episodic- past experiences
What is it believed a persons episodic memory is influenced by?
Their expectations of what should have happened.
What is a motor programme?
An organised series of movements made up of sub routines.
What is an example of a motor programme?
Driving a car.
What is neuroplasticity?
Changes that take place in your brain as you continuously experience and adapt to the world.
What is situational awareness?
Synthesis of an accurate and up to date ‘mental model’ of the environment.
What helps situational awareness?
Feedback, tells us how accurate the mental model and their predictive power.
What does the ability to project a system status backwards allow?
Effective fault finding and diagnostic behavior.
What three things can situational awareness for an aircraft engineer be divided into?
Status of the system
Relationship between defect/rectification
Possible effect on other systems
What is context?
The circumstances that form the setting for an event, statement or idea.
What is the influence of expectation?
Where you only see what you expect to see, this can lead to things being missed or seen when not there.
Which type of memory is susceptible to interference?
Short term
What is sensory storage also known as?
Ultra-Short term memory.
In the event of claustrophobia, heights, poor lighting etc, what must a manager and employee do?
Employee must avoid these situations that cause issues where possible for safety, and the manager is responsible for making the job as comfortable as possible.
How can short term memory be enhanced?
Splitting memory into chunks, i.e. a phone number.
How much information can short term memory store?
5-9 items for 10 to 20 seconds.
What three processes does memory depend on?
Registration
Storage
Retrieval
What is Visual Acuity?
The eyes ability to perceive sharp detail at varying distances.
How long is visual information stored in the iconic memory?
Half a second.
How long are sounds stored in the echoic memory?
Two seconds.
