Unit 2-A ID's: Sensation and Perception

Prosopagnosia

“Face blindness”, lack of facial recognition

• damage to the FFA (fusiform face area) in the fusiform gyrus or connectivity errors in the occipital-temporal lobe regions

Sensation

sensory receptors and nervous system receive sensory info from environment

• ex. vision vs. blindness

Perception

organizing and interpreting sensory info; allows us to prescribe meaning

• ex. facial recognition vs. prosopagnosia

Absolute threshold

Min. stimulation needed to detect a particular stimulus 50% of the time

Difference thresholds

different threshold is the min. difference between two stimuli required for detection 50% of the time

Weber’s Law

to be able to tell the difference between degrees of stimulation, two stimuli must differ by a constant min. percentage, not a constant number

Bottom-up processing

starting with the sensory input, the brain attempts to understand/make sense of new stimuli

Top-down processing

interpreting new stimuli is guided by previous experience and higher-level processes (what we expect to see)

Perceptual sets

a mental predisposition to perceive one thing and not another  

• we see what we expect to see

Context effects & cultural influence

influence of our environment, culture, preconceived notions, etc on our perception of a stimulus

Priming

activation, often unconsciously of certain associations, thus predisposing one’s perception, memory, or response 

• ex. hair vs. hare

Selective attention

attention that is focused on certain stimuli, while filtering out and excluding other stimuli deemed “unimportant” 

Cocktail party phenomenon

focuses auditory attention on one person in the midst of background noise 

Inattentional blindness

failing to see visible objects when our attention or focus is directed elsewhere

Change blindness

failing to notice a stimulus change in the visual environment

Sensory adaptation

diminished sensitivity to stimuli as a consequence of constant stimulation

Transduction

converting external stimuli (light waves, etc) into neural impulses 

Visual Sensation

how shape of a light wave impacts our visual perception 

Electromagnetic spectrum

full range of electromagnetic radiation, only a limited portion is visible to the human eye

Wavelength

distance from peak to peak

Frequency

number of waves per a given unit of time

Amplitude

relative “height” of the wave

Cornea

outer protective layer, first surface where light hits

Pupil

light enters eye, size controlled by iris

Lens

focuses light rays on retina

Accommodation

ciliary muscles adjust the curvature of the lens to make images of objects clear and detectable of the retina 

Nearsightedness

sees close but not far, blurry vision for distant objects

• Myopia

Farsightedness

sees far but can’t see close, blurry vision for up close objects

• Hyperopia

Retina

photoreceptors

Rods

low amplitude light, black/white, flicker/movement

Cones

color vision and details

Fovea

region of highest visual acuity on the retina

• highest cone density: detail, bright light, color

Bipolar cells

“bipolar” = 2 extensions from soma

• propagate neural info from photo

• retina

Ganglion cells

send neural signal from bipolar cells to optic nerve

• retina

Blind spot

here the optic nerve leaves the eye; no photoreceptors (rods or cones) in this region of the retina

Optic nerve

Signals from ganglion cells pass along optic tract

Thalamus

Sensory relay center in limbic system

Young-Helmholtz trichromatic theory

cones in the retina contain diff. photopigments and are activated by one of three ranges of light waves 

• red, green, blue

Opponent-process theory of color vision

opposing networks of ganglion cells in the retina enable color vision, activation of one color suppresses the opponent color

Afterimages

staring at a color(s) long enough

Visual Information Processing

Parallel Processing – the processing of several aspects of the stimulus simultaneously

Feature Detection

nerve cells in the visual cortex respond to specific features, such as edges, angles, and movement

Shape Detection

Specific combinations of temporal/occipital lobe activity occur as people look at different objects

Figure-ground

objects are perceived as foreground or background 

Proximity

things are close together, are grouped together

Continuity

objects are perceived as continuous, smooth, continuous vs. broken, jagged

Closure

shapes with missing parts are perceived as closed

Connectedness

Connected elements are perceived as single units

Changes in wavelength →

correspond to changes in perceived color

Changes in Amplitude →

correspond to changes in perceived intensity or brightness