PSY 217 Lecture 3: PSY217_Week3
5 May 2018
School
Department
Course
Professor
Environmental Perception
●Sensation: stimulation of the sense organs (i.e. eyes, ears, skin, nose,
tongue, etc)
●distal stimulus: things out there in the world e.g., a drawing of a Necker
cube, a sweater, fire alarm
●proximal stimulus: physical energy that stimulates specialized "receptor"
cells in eyes, ears, skin, nose, tongue, etc.
●e.g., light bouncing off the cube drawing or sweater and stimulating the
retina, sound waves from the alarm stimulating auditory receptors
●"raw data" sent to the brain
●Perception: the organization and interpretation of sensations -> brain
makes sense of "raw data", influenced by knowledge of the world,
expectations, & context, attention, etc
●Necker Cube shows that sensation and perception are different -> what is
sensed by our eyes is just an arrangement of two-dimensional lines, but
we perceive it as a three-dimensional shape
●What we sense does not change over time, but we perceive the shape as
reversing in depth (front becomes back and vice versa) over time
●Selective attention test: Simons & Chabris (1999) found that 73% of
participants failed to spot the gorilla -> Inattentional blindness, shows
that attention plays an important role in perception
●“poverty of the stimulus” assumption: Our senses are not very sensitive
●Information that we receive with our senses is impoverished
●Need our big brains to “fill in the gaps” (perception)
●Vision: a light source emits electromagnetic radiation that travels as a
wave
●Waves can differ in amplitude (height of the peaks) and wavelength
(distance between peaks)
●Tiny range of possible wavelengths visible as light, within that range;
1. Brightness= subjective perception of amplitude (low amplitude = dull,
high amplitude = bright)
2. Colour or hue= subjective perception of wavelength (low frequency =
violet, high frequency = red)
●Pupil: regulates amount of light passing into the eye
●Lens: focuses light rays to fall on the retina -> curvature of the lens adjusts
(accommodates)
●closer object = fattens
●further object = flattens
●Retina: tissue lining the inside back of the eye that contains the receptors
for seeing
●Cones: receptors for daylight, fine detail, and color vision
●Rods: receptors for night and peripheral vision
●Stimulation of rods and cones converted to neural impulses that are sent
to the brain via the optic nerve
●Trichromatic theory of colour vision: three types of receptors with
differing sensitivities to different wavelengths
●Short = blue; medium = green; long = red
●Perception of colours in the brain depends on activation levels of each
receptor
●Evidence: (dichromaticism) color-blindness to green or red (rarely blue)
●Opponent process theory of colour vision: cells in the visual pathway
increase their activation levels to one colour and decrease their activation
to another colour
●Red versus green; yellow versus blue; black versus white
