Sensation & Perception

2.1 Sensation

Sensation: the information we get from the real world

Perception: understanding what we sense mean things

Ex. sensation: we see a dog, perception: we understand that it is a dog

Proximal Stimulus: information given off by the distal stimuli that we make us of

Distal Stimulus: the thing itself

We always sense an impression of things:

  • you will never actually hear voices

  • you will never actually see a dog

Transduction: mechanism that turns proximal stimuli into neural impulses

Accessory systems: things that modify the proximal stimuli

  • ex. outer ear, lenses of eyes

Sensory Quality: the nature of the stimulus

  • ex. color, pitch

Sensory Intensity: how strong the stimulus is

  • ex. brightness, volume

Absolute Threshold: least amount of proximal stimulus we can detect

We can detect the proximal stimulus 50% of the time

  • touch: fly wing dropped on cheek from 1 cm away

  • light: candle from 30 miles away

Just-noticeable differences: the smallest proportional change necessary to detect a change in proximal stimulus intensity

  • much easier to detect a change from 1 db to 2db than 60 db to 61 db

  • vision is the most sensitive to changes

2.2 Vision

Subtractive color: making wavelengths shorter, art class

  • red + blue = purple

Additive color: how light produces color with red, green, blue

  • red + green = yellow

  • how computer screens work

Frequency of light waves: color

  • shorter = ultraviolet, longer = infrared

Amplitude of light waves: brightness of light

  • bigger wavelength = brighter light

Sensory Adaptation: reduction in sensitivity after constant exposure

Accessory systems of the eye

cornea:

  • clear outermost layer of eye to focus light

  • “permanent glasses”

pupil/iris:

  • pupil: hole in eye

  • iris: tiny muscle that contracts around pupil

lens:

  • focuses light

  • adaptable glasses"

2.3 Vision

Retina: area made of photoreceptors

Fovea: part of retina where visual acuity is highest

Blind spot: part of retina with no light sensitive cells so you cannot see

Photoreceptors

Rods: photoreceptors that can see white/black

  • two kinds of rods

Cones: photoreceptors that see colors

  • three kinds of cones - red, green, blue

Opsin: “magic molecule” that does the transduction

  • in rods and cones

  • “snaps” and neurons fire messages to the brain

  • photoreceptors → bipolar cells → ganglion cells → thalamus

2.4 Audition

Sound waves: vibration of air molecules

Sound amplitude: volume (intensity)

Sound wavelength: pitch (quality)

Accessory Systems of Sound

  1. outer ear: gathers sound waves

  2. tympanic membrane (eardrum): transfers vibrations from sound

  3. ossicles: small bones in the ear that amplify vibrations and transfers them to the cochlea via the oval window

    • incus, malleus, stapes

Oval window moves water

Place Theory: theory that says sound depends where in the cochlea it vibrates

Volley Theory: theory that says multiple neurons work together to make each sound

2.5 Smell and Taste

Accessory Systems of Smell

  1. nose: “gathers” molecules

  2. mucus: “catches” molecules

Accessory Systems of Taste

  1. teeth

  2. tongue

  3. saliva

Transduction of Taste

tiny cilia (hair cells) are triggered when a taste enters the proper gate

Taste receptors: salty, sweet, sour, bitter, savory/umami

Primary visual association area: in the occipital lobe

Primary auditory association area: in the temporal lobe

Sensory (touch) association area: in visual, auditory and somatosensory cortexes

Pheromones: chemicals signal that an animal sends to others

  • ex. female lets out pheromones to show males she is ready for mating

  • usually between same species

  • humans (probably) don’t do it

2.6 Touch and Other Sensations

Proximal stimulus of touch: molecular electrical fields of the object

Touch Quality: pain, pressure, cold, heat

Touch Intensity: how strong the touch is

  • ex. little pressure vs great pressure

  • intensity can affect quality

    • ex. too much pressure leads to pain

Accessory Systems of Touch

  1. skin: transfers kinetic energy into the various touch receptors

  2. hair: connected to certain nerves in the skin

Afferent Nerves: feeling nerves that record sensation of touch and sends them to the brain

Efferent Nerves: nerves that move muscles

ATEM - afferent touch efferent move

free nerve endings: nerve endings in skin, muscle, etc.

We can CONFUSE these nerve endings

phantom limb: pain you feel in a limb that is no longer there

  • because you don’t have inhibitory signals to stop the pain signals

vestibular sense: sense of balance

  • semicircular canals: fluid filled tubes in the inner ear that help you keep your balance

kinesthetic sense: body’s internal sense of touch

  • ex. you know where your finger is without looking at it

Gate Control Theory: non-painful sensations can override painful ones

  • pain signals transmitted from free nerve endings to spinal cord BUT

  • inhibitory signals try to shut down pain signals

2.7 Perception

Top-down: concepts and expectations lead you to interpret data in a certain way

  • perception constructs cognition

  • inputs fit the map

Bottom-up: take individual bits of data and build a meaningful picture

  • sensation → perception → cognition

  • inputs make the map

Schema: concepts and knowledge we already have that we can use to interpret new information

  • ex. knowing how to order at a restaurant even if you’ve never been to that particular restaurant before

  • “framework” that you already have in your mind

Gestalt Psychology: fundamental principles of psychology

  • people perceive things as a whole rather than as separate parts

  • whole thing is more important than individual parts

Form cues: what is it?

  1. Figure-ground: brain automatically focuses one thing into the figure and everything else into the background

  2. Closure: mind’s tendency to close the gaps

    • Panda of WWF logo

  3. Similarity: mind’s tendency to see objects that share visual characteristics together

  4. Proximity: mind’s tendency to group geographically close things together

2.8 Perception

Depth cues: where is it?

Monocular depth cues: cues that allow us to tell how far away something is with just 1 eye

  1. Relative size: things farther away appear smaller than things that are closer

  2. Relative clarity: things that are closer appear clearer

    • atmosphere can make things fuzzy

  3. Linear perspective: parallel lines appear to converge/diverge

  4. Interposition: nearer objects block further objects

Binocular vision: we have two eyes so we “see” two of everything

  • but our brain combines it into 1

Detecting motion:

  1. relative displacement: an object moves on retina

  2. apparent movement: being fooled into thinking an object is moving when it isn’t

    • ex. train next to you looks like it’s moving but it’s actually you!

Visual tracking: watching an object as it moves around

Perceptual problems:

Blindsight: eyes work but brain doesn’t

  • ex. you can tell when someone is there but no picture of them

Prosopagnosia: face blindness

  • can’t recognize faces

Attention: boundary between perception and cognition

  • you can sense something but if you aren’t paying attention to it, you might not perceive it

Multitasking vs Task-Switching: you can multitask ONLY if they use two different senses

  • you can talk and drive but can’t text and drive at the same time

Dichotic listening: CAN’T listen to two conversations at once

Cocktail party effect: ability to focus on one stimuli while blocking out all the others

  • ex. white shirt and gorilla

Change blindness: phenomenon when visual stimulus is changed but observer doesn’t notice