Sensation and Perception

Sensation/bottom-up processing

The stimulation of sensory receptors (cilia in ears, rods/cones in vision, taste buds) by the properties of the stimulus (sound waves, light energy, chemicals) and the transmission of sensory information into the central nervous system

Perception/top-down processing

The process by which the brain organizes and interprets the data received from the senses, enabling us to recognize meaningful objects and events.

Transduction

sensory receptors (eyes, ears, nose, skin, tongue) convert the stimulus into neural impulses which are sent to the brain

Absolute threshold

the lowest amount of stimulus needed to notice it 50% of the time.

Difference threshold

the lowest difference between two stimuli that person can detect 50% of the time.

Weber’s Law

regardless of magnitude, two stimuli must differ by a constant proportion for the difference to be noticeable. 

Fechner’s Law

larger and larger increases in stimulus intensity are required to produce perceptible increments in the magnitude of sensation. Constant increments in stimulus intensity produce smaller and smaller increases in perceived magnitude of sensation.

Sensory adaptation

lowered sensitivity due to constant exposure from a stimulus. After constant exposure to a stimulus, our nerve cells fire less frequently

Signal detection theory

predicting when we will notice a weak stimulus (signal).

Subliminal stimulus

below our threshold for being able to consciously detect a stimulus

Nearsightedness

nearby objects seen more clearly; lens focuses image of distant objects in front of retina

Farsightedness

faraway objects seen more clearly; lens focuses near objects behind retina

Receptive field

Retinal area that, when stimulated, affects the firing of that cell

Lateral inhibition

Neural activity in a cell that opposes activity in surrounding cells. One part of the receptive field wants to become active while the other part does not.

Hermann grid

Ganglion cells get confused and show dots in periphery when there are none

Parallel processing

simultaneous processing of several aspects of a problem simultaneously

Feature detectors

nerve cells in the visual cortex respond to specific features

Abstraction

High-level cells respond to combined info from feature-detector cells

Recognition

Brain matches the constructed image with stored images

Color constancy

Perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object

Pinna

collect and direct “sound” into auditory canal

Auditory canal

amplify and funnel “sound to tympanic membrane

Tympanic membrane

collect “sound” and vibrate ossicle

Malleus (hammer)

vibrate & move the Incus

Incus (anvil)

vibrate & move the Stapes

Stapes (stirrup)

vibrate against Oval Window of Cochlea

Cochlea

filled with fluid & contains receptors for hearing (Hair Cells)

Basilar membrane

divides length of cochlea and holds the hair cells

Place theory

At high sound frequencies, signals are generated at different locations in the cochlea, depending on pitch. The brain reads pitch by reading the location where the signals are coming from.

Frequency theory

At low sound frequencies, hair cells send signals at whatever rate the sound is received.

Volley principle

At ultra high frequencies, receptor cells fire in succession, combining signals to reach higher firing rates.

Conduction deafness

Caused by the failure of the three tiny bones inside the middle ear to pass along sound waves to the inner ear or the failure of the eardrum to vibrate in response to sound waves

Sensory-neural deafness

Damage to the inner ear or auditory nerve. Most often caused by loss of hair cells that will not regenerate

Stimulation deafness

Exposure to very loud sounds, tinnitus

Presbycusis

Older people tend to hear low frequencies well but suffer hearing loss for high frequencies

Kinesthesis

The sense that informs us about the positions and motion of parts of our bodies

Vestibular sense

The sense of equilibrium that informs us about the positions of our bodies and our heads relative to gravity; sense of balance

Cocktail party effect

We can focus our mental spotlight on a conversation even when other conversations are going on around us.

Size and shape constancy

Objects remain unchanged in regard to size or shape as their image on the retina changes. Just because an image might get bigger on our retina, we know it is not actually expanding in real life.

Retinal disparity

The closer an object is, the more disparity there is between the images each retina receives.

Relative size

Monocular cue in which we perceive the object that casts smaller image on our retina to be farther away than the similar sized object that casts a larger image

Interposition

Monocular cue in which we perceive the object that partially blocks our view of another object as closer.

Texture gradient

Monocular cue in which indistinct (fine) texture signals an increasing distance, while coarse (distinct) texture signals a close distance

Relative motion (motion parallax)

Monocular cue in which objects closer to (in front of) a fixation point moves faster and in opposing direction to those objects that are farther away from (behind) a fixation point, moving slower and in the same direction. 3 parts to definition - stationary fixation point, speed and direction of stationary objects in front and behind fixation point.

Linear perspective

Monocular cue in which parallel lines appear to converge in the distance. The more the lines converge, the greater their perceived distance.

Relative clarity

Monocular cue in which we perceive hazy objects to be farther away than those objects that appear sharp and clear.

Relative height

Monocular cue in which we perceive objects higher in our field of vision to be farther away than those that are lower.

Figure-ground principle

Gestalt principle in which we organize the visual field into objects (figures) that stand out from their surroundings (ground)

Proximity principle

Gestalt principle in which we group nearby figures together

Closure principle

Gestalt principle in which we see complete figures even when part of the information is missing

Continuation principle

Gestalt principle in which we perceive smoothly flowing or continuous forms rather than disrupted or discontinuous ones.

Similarity principle

Gestalt principle in which we perceive things that share visual characteristics, such as shape, size, color, texture, value or orientation will be seen as belonging together.

Connectedness principle

Gestalt principle in which spots, lines, and areas are seen as a unit when connected

Stroboscopic motion

Illusion of motion when visual images are presented in rapid sequence

Phi phenomenon

Illusion of motion when lights flash in rapid sequence

Expectations (i.e. perceptual set, familiarity, schemas, context effects)

A readiness to perceive a stimulus in a particular way based on preconceptions. Preconceptions will prime us to modify what we see, such as causing us to delete, insert, or transpose stimuli, etc.

Context effects

Immediate surroundings of a figure influences one’s perception of it.

Cognitive style

Way of processing the stimuli within the environment, which affects how we see the world.

Field-dependent approach

perceive the environment as a whole and do not clearly distinguish in their minds the shape, color, size, or other qualities of individual items. No details. “Levelers”

Field-independent approach

perceive the elements of the environment as separate and distinct from one another and to draw each element as standing out from the background. A lot of details. “Sharpeners”

Color constancy

Perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object.

Selective attention

Our failure to notice part of our environment when our attention is directed elsewhere.

Inattentional blindness

Inability to perceive something that is within one’s direct perceptual field because one is attending to something else.

Change blindness

failing to detect non-trivial changes in the visual field