Threshold is
An edge/boundary
AbsoluteThreshold is
the minimum amount of stimulation needed to detect a specific stimulus
Difference Threshold is
the minimum amount of difference needed to detect 2 stimuli that are not the same
- smallest detectable change
- also called noticeable difference
Signal Detection theory is
is a theory that predicts how and when we detect the presence of a faint stimulus (signal) amid
background stimulation (noise)
Three main types:
1. Stimulus variables (How bright is the stimuli?)
2. environmental variables (How much distracting noise is there?)
3. person variables (Is the operator properly trained, motivated, healthy?)
Selective attention is
focusing conscious awareness on a particular stimulus to the exclusion of others
• The ability to focus on one stimulus at a time
• Allows a person to function in a world filled with many stimuli
Sensation is
the process by which sensory systems (eyes, ears, and other sensory organs) & the nervous system receive stimuli from our enviromental
- A person’s awareness of the world
Bottom-up processing is
information processing that analyzes the raw stimuli entering through the many sensory systems
• Your nervous system sorts through all this incoming sensory information
perception is
the process of organizing and
interpreting incoming sensory information
Electromagnetic Energy is
• An energy spectrum that includes short Gamma rays, X-rays, UV rays,
Infrared rays, radar & long radio waves and visible light
• A small portion of the spectrum includes light visible to the human eye
• Light enters the eye as waves of electromagnetic energy
Hue is
• The low of light as determined by the wavelength of the light energy
• Includes: Red, Orange, Yellow, Green, Blue, Indigo, Violet
(ROY G BIV) ranging from
to longest to shortest wavelength
The eye can detect 7 million separate hues
Amplitude is
• The brightness of light as determined by the height of the wave
the taller the wave the brighter the colour
Iris is
a ring muscles tissues that forms the coloured portion of the eye and regulates the size of the pupil
- a change in size causes less or more light
Pupil is
the adjustable opening in the center of the iris, which controls the amount of light entering the eye
• in bright conditions the iris expands, making the pupil smaller
• In dark conditioning the iris contracts, making the pupil larger
Lens is
a transparent structure behind the pupil in the eye that changes shape to focus images on the retina
Muscles that change thickness of the lens change how the light is bent thereby focusing the image
• Glasses or contacts correct problems in the lens’ ability to focus
• Laser surgeries that can reshape the surface of the cornea.
Retina is
the light sensitive surface at the back of the eyeball
Contains cells that convert light energy to nerve impulses
Made up of three layers of cells:
• Receptor cells
Bipolar cells
Ganglion cells
Receptor cells are
the specialized cells in every sensory system of the body that can turn other kinds of energy into action potentials (neural impulses) that the brain can process
• Insight, they change light into neural impulses the brain can understand
Your visual system has two different types of receptor cells, rods and cones to change light energy into nerve impulses that the brain can interpret
Rods are
visual receptor cells located in the retina that can detect only white, black and gray
Respond to less light than cones do
So, under dim light conditions, only rods respond & you see the world in shades of gray.
Cones are
visual receptor cells located in the retina that can detect sharp detail & colour
Need more light than the rods
Many cones are clustered in the fovea, the area where your vision is best
Fovea is the
central Focal point of the retina
high concentration of cones
• The spot where the vision is best
(most detailed)
Bipolar Cells are
gather information from the rods and cones
and pass it on to the ganglion cells
• Cells that form the middle layer in the retina
Ganglion Cells are
• These pass information from bipolar cells through their axons
• Together these cells form the optic nerve
• The top layer of the cells in the retina
optic nerve is
the nerve that carries visual information from the eye to the occipital lobes
We tend to think that we see with our eyes, but it is our must process the information that the eyes deliver.
More specifically, remember that visual processing occurs in the occipital lobe of the brain.
Sensory adaptation is
diminished stimulation sensitivity to constant
and unchanging
If a stimulus is constant and unchanging, eventually a person may
dininishid sensitinty
is a consequence of constant afimulai
_to respond to it
Sensory adaptation is
diminished stimulation sensitivity to constant
and unchanging
If a stimulus is constant and unchanging, eventually a person may
dininishid sensitinty
is a consequence of constant afimulai
_to respond to it
