Textbook Notes (290,000)
CA (170,000)
UofM (1,000)
PSYC (200)
Chapter 4

PSYC 1200 Chapter Notes - Chapter 4: Occipital Lobe, Opponent Process, Ames Room

Course Code
PSYC 1200
Jason Leboe- Mcgowan

This preview shows page 1. to view the full 5 pages of the document.
Ian Howard is known internationally as a pioneer in sensation/perception research
People can rely on 3 types of cues to determine which way is up - visual, gravity, and body
Sensation: the stimulation of sense organs
Perception: the selection, organization, and interpretation of sensory input
Psychophysics: the study of how physical stimuli and translated into psychological
Thresholds: Looking for Limits
Stimulus: any detectable input from the environment
o Sensation begins with a stimulus
Threshold: a dividing point between energy levels that do and do not have a detectable
Absolute threshold: for a specific type of sensory input is the minimum amount of
stimulation that an organism can detect
Weighing the Differences
Just noticeable difference (JND): the smallest difference in the amount of stimulation that a
specific sense can detect
Weber's law: states that the size of a JND is a constant proportion of the size of the initial
o As the stimulus increases in magnitude, the JND becomes larger
Psychophysical Scaling
Fechner's law: states that the magnitude of a sensory experience is proportional to the
number of JNDs that the stimulus causing the experience is above the threshold
Signal Detection Theory
Signal detection theory: proposes that the detection of stimuli involves decision processes
as well as sensory processes which are both influenced by a variety of factors other than
stimulus intensity
o The more 'noise' in a system, the harder it will be for you to pick up a weak signal
Subliminal Perception
Subliminal perception: the registration of sensory input without conscious awareness
('limen' is another term for threshold, so 'subliminal' means below threshold)
o Subliminal messaging controversy began in 1957 - with James Vicary hiding 'eat
popcorn' on the screen at a film showing
o Cooper and Cooper demonstrated subliminal presentations of Coca-Cola cans and the
word 'thirsty', in 2002
Sensory Adaptation
Sensory adaptation: a gradual decline in sensitivity due to prolonged stimulation
The Stimulus: Light
Light is a form of electromagnetic radiation that travels as a wave, moving, naturally
enough, at the speed of light
Light waves vary in amplitude (height) and in wavelengths (the distance between peaks)
o Amplitude affects the perception of brightness
o Wavelength affects the perception of color
Light can also vary in its purity (how varied the mix is)
Purity influences perception of the saturation, or richness, of colors
The Eye: A Living Optical Instrument
You're Reading a Preview

Unlock to view full version

Only page 1 are available for preview. Some parts have been intentionally blurred.

The eye serves two main purposes
o Channels light into neural tissue that receives it - retina
o Houses that tissue
Light enters the eye through the cornea
o The cornea and the crystalline lens located behind it form an upside down image of
objects on the retina
Lens: the transparent eye structure that focuses the light rays falling on the retina
Nearsightedness: close objects are seen clearly but distant objects appear blurry
o Occurs when cornea bends light too much - light falls short of retina - or eyeball is
too long
Farsightedness: distant objects are clear, but close objects are blurry
o Focus of light from close objects falls behind the retina
o Typically occurs when eyeball is too short
Pupil: the opening in the center of the iris that helps regulate the amount of light passing
into the rear chamber of the eye
Saccades: when looking at something, eyes make brief fixations at various parts of the
The Retina: the Brain's Envoy in the Eye
Retina: neural tissue lining the inside back surface of the eye
o Absorbs light, processes images, and sends visual information to the brain
o Contains two types of receptors - rods and cones
Cones: specialized visual receptors that play a key role in daylight vision and color vision
o Provide better visual acuity - sharpness and precise detail - then rods
Fovea: a tiny spot in the center of the retina that contains only cones
o Visual acuity is greatest at this spot
Rods: specialized visual receptors that play a key role in night vision and peripheral vision
Optic disk: a hole in the retina where the optic nerve fibers exit the eye
Dark adaptation: the process in which eyes become more sensitive to light in high
The receptive field of a visual cell: the retinal area that, when stimulated, affects the firing
of that cell
Lateral antagonism: occurs when neural activity in a cell opposes activity in surrounding
Vision and the Brain
Optic chiasm: the point at which the optic nerves from the inside half of each eye cross
over and then project to the opposite half of the brain
Optic nerve divides into 2 paths
o The main path projects into the thalamus, the brains major rely station
Here, about 90% of the axons from the retinas synapse in the lateral geniculate
nucleus (LGN)
Subdivided into 2 more pathways - magnocellular and parvocellular
These channels engage in parallel processing: involves simultaneously
extracting different kinds of info from the same input
o The second path braches off into an area in the midbrain called the superior colliculus
Principle function appears to be the coordination of visual input with other
sensory input
You're Reading a Preview

Unlock to view full version