Sensation and Perception

  • sensation: stimulation of a sensory organ

    • eyes — seeing light

    • nose — smelling an odor

  • perception: identifying and/or interpreting sensation in the brain

    • mental representation

  • transduction: physical signals —neural signals


Detecting Sensations

  • absolute threshold:

    • minimal intensity of stimulus necessary to detect it 50% of the time

      • hearing tests - volume and pitch

      • amount of sugar

  • just noticeable difference:

    • minimal change in a stimulus necessary to detect a change has occured

Signal Detection Theory

  • not everyone detects a stimulus equally

  • signal detection theory:

    • a persons response to a stimulus depends on…

      • sensitivity to stimulus

      • decision criteria

        • do they choose to ignore it? why? - adaptive process

Seeing - Sensing Light

  • length of a wave — color/hue

  • amplitude of a wave — intensity

  • light — pupil

  • pupil — retina

    • cones: color, fine detail, best in daylight

    • rods: best in low light, periphery

  • fovea: no rods, only cones

    • clearest vision

  • retina — optic nerve

    • blind spot

  • optic nerve — area V1 (primary visual cortex)

    • brain then perceives visual info

    • flips image, combines info from both eyes

  • 12% of women are tetra-chromatic

Perceiving Light - Color

  • Color: perceiving lights wavelength

    • 3 types of cones: red, green, blue (combinations)

  • Color deficiency: one or more cones is missing (or fatigued)

    • Color blindness

  • Color-opponent system

    • Pairs of visual neurons work in opposition

    • Green — red

    • Yellow — blue

  • Fatigued cones can’t compete with their opponent

Perceiving Light - Recognizing Objects

  • perceptual constancy: recognizing objects across different contexts

    • small changes

  • Perceptual Organization: brain groups visual info in order to represent a unified object

Perceiving Light - Depth and Size

  • Depth cues: help determine shape and distance of objects

    • monocular or binocular

  • Linear perspective: lines coverage at the furthest point

  • texture gradient: textures further back are harder to see

  • interposition: objects further back are blocked

  • relative height: objects near the top = further

  • binocular disparity: our eyes see from slightly different positions

    • difference in what they see — position/depth of object

Percieving Light - Change

  • change in blindness: failure to detect a change in the visual

    • focused attention


Hearing - Sensing Sound

  • length of wave — pitch (high vs. low)

  • height of wave — loudness

  • ears work together to locate sound

  • cochlea — auditory nerve

  • auditory nerve — area A1 (primary auditory cortex)


  • sound — enter through inner ear

  • ear drum makes vibrations

  • cochlea picks up corresponding vibrations


Hearing Lost

  • conductive hearing loss:

    • due to damage, blockage, or impacted wax

    • sounds can’t make it through outer/middle ear

  • sensorineural hearing loss:

    • inner ear damage (cochlea) or auditory nerve damage

    • age, noise damage, or tumors

Percieving Sound

  • McGurk Effect:

    • visual information impacts how auditory imformation is percieved

    • lip shape

    • facial expressions

Sensing Touch

  • somatory sensory receptors within our:

    • skin

    • joints

    • muscles

  • somatory sensory cortex

  • more somatosensory cortex devoted = more fine detail

    • fingertips

    • lips/tongue

Perceiving Pain

  • referred pain: internal pain is felt at the surface of the skin

  • organ damage

  • gate control theory: signals from pain receptors can be stopped (gated) or increased

    • endorphins

    • drugs

    • infection

  • congenital insensensitivity to pain: one cannot perceive pain

    • gene mutation from birth

    • cannot turn pain signals into neutral signals (failure of transduction)

    • extremely dangerous

Sensing Smell

  • mucous membrane in nostrils — olfactory bulb

    • only sense to bypass the thalamus

  • preferences differ

  • smell can help us identify danger

  • strong link to memory

    • proximity to hippocampus

  • we can detect differences in peoples smell

    • children sexual orientation

Sensing Taste

  • taste buds — gustatory cortex (frontal lobe)

  • taste is dependent on smell

    • can detect toxins or expired food

  • cultural differences

  • wine test

    • people prefer wine they think is more expensive

    • cognitive influences

Consciousness

  • subjective expeirence of the world and our mind

    • it is personal to each person

  • problem of other minds: difficulty perceiving the consciousness of others

    • ex: human minds vs cat minds

Properties of Consciousness

  • INTENTIONALITY

    • directed at something

  • UNITY

    • combines info from all senses simultaneously

    • makes sense of multiple inputs

  • SELECTIVITY

    • can focus on a small part of the enviorment

    • filter out extraneous stimuli

    • cocktail party phenomonon

  • TRANSIENCE

    • tendency to shift, or change

    • “stream of consciousness”: cahnge in our attentional focus

Levels of Consciousness

  • Minimal Consciousness:

    • response to senses

    • lack of recollection

    • example: sleeping

  • Full Consciousness:

    • able to report mental state and expeirence

    • recall

  • Self-Consciousness;

    • attentional awareness on the self

    • inward focus

    • embarrassment, shame

    • self evaluation

  • Rouge Test:

    • self recognition in a mirror

    • children, elephants, apes, dolphins

    • to past the rouge test the animal or child needs to reach for their own forehead for self-recognition

Mind Wandering

  • mind wandering: off-task internal thoughts

    • day dreaming

    • planning for the future

  • mental control: controlling our thoughts can be difficult

  • rumination: obsessive thoughts that can impede normal daily function

    • mental control:

      • attempt the change content of thoughts

      • anxious worries — pleasant thoughts

    • thFought supression:

      • tempt to STOP a thought

White Bear Experiment

  • bound effect of thought supression (Wegner)

  • GROUP 1: no instructions (if you happen to think of a white bear ring the bell)

  • GROUP 2: DONT think of a white bear and if you happen to ring this bell

  • GROUP 2: thought of the white bear even more during later thinking period

The Unconscious Mind

  • something in our unconsious is outside of our awareness

  • Freud’s Take:

    • dynamic unconscious - active system below our awareness

    • Ex: maybe there is a reason I picked strawberries today (maybe I smelled strawberres earlier and it fueled me to pick strawberries later)

  • combination of…

    • hidden memories

    • acknowledged desires

  • repression: mental process that keeps undesirable thoughts/memories in the unconscious

    • peaceful, evolved society

  • Freudian slips: error in speech

    • suggests underlying unconscious thoughts/desires

    • mistakes that mean something

A Modern Take

  • cognitive unconscious:

    • underlying processes behind thoughts/feelings/behavior

    • below our awareness

    • save effort

  • duel process theory:

    • two cognitive systems in our brain

    • automatic: quick and effortless

      • 2 + 2

    • controlled: slow and effortful

      • intricate formulas and to solve problems in life

Subliminal Perception

  • influenced by stimulus we cant report perceiving