Chapter 4 Notes

Sensation- physical stimulation

Perception- interpretation of sensory stimulus

• Bottom up processing- info from sensation, and then we think and act on it.

  1. Sensory receptors send signals via distinct neural pathways.

  2. Transduction- converts energy into electrochemical energy

     • Photoreception- vision. Detection of light

     • Mechanoreception- touch and hearing: detection of pressure, vibration, and movement

     • Chemoreception- smell and taste: detection of chemical stimuli.

  3. Deliver to brain: PNS→CNS

• Number of receptors can affect differences in sensation.

• Top-down- observers knowledge, expectations, and goals affect perception. What you expect or what you are used to seeing.

• Selective Attention: focusing awareness on a narrowed aspect of environment.

  • Change blindness- miss changes that occurs in a scene. Gorilla Video

Sensory Thresholds

Absolute threshold- minimum amount of energy that is detectable in an environment.

• light- a candle flame at 30 miles on a dark clear night

• Sound- hear the tick of watch at 20 feet

• Taste- one teaspoon of sugar in 2 gallons of water

• Smell- one drop of perfume in 3 bedroom apartment

• Touch- the wing of a bee falling on your check from a distance of 1 cm.

Difference threshold- minimum amount of change in stimulus that is detectable

• Just noticeable difference (JND)- difference between 2 stimuli that can be detected 50% of the time.

• JND increases with stimulus magnitude.

  • Increasing volume of music in loud room wouldn’t make a difference, but in a quiet room, it would be noticeable.

Noise- irrelevant and competing stimuli.

Signal Detection Theory (SDT)- separates perceptual ability from decision bias.

• framework for measuring how people make decisions based on noisy perceptual evidence; provides way to measure perceptual sensitivity apart from decision-making style.

Sensory Adaptation- gradual decline in sensitivity to prolonged sensitivity.

• helps focus on informative changes in the environment without being distracted by background chatter.

• Influences perceptions of emotions.

Visual System

• light has properties of waves and particles

Color- wavelengths of light that are reflected to the organism.

The Eye

• retina- photoreceptors transducer light into neural signals to be sent to brain

  • Fovea- region in center of retina where the light from objects at the center of our gaze strikes the retina. All cones, no rods.

  • Rods- more sensitive to lower light levels

    • Poor acuity

  • Cones- provide information about light

    • Differences in color

    • Greater acuity

    • Trichromatic Theory- 3 types of cones

      • Red light- long wavelength

      • Green light- medium wavelength

      • Blue light- short wavelength

• Left visual field goes to the right hemisphere, right to left hemisphere.

• After image- sees color after info goes away. Neuron kept firing.

Visual Perception

• Interpreting visual signals

• Gestalt Psychology- “form” “whole” in German

  • People organize sensations into a meaningful whole

  • Perceptions are naturally organized to certain patterns.

  • Shape: figure vs. (back)ground- what stands out from background

  • Grouping- tendency to organize stimuli into meaningful groups.

    • Proximity

    • Similarity

    • Connectedness

    • Continuity

    • Closure

  • Depth- ability to see in 3 dimensions despite the images that strike the retina are 2D

  • Motion

    • Apparent motion happens when stimuli are presented at different locations in sequential manner

    • Figure-ground organization- movement allows us to see boundaries separating objects otherwise camouflaged

  • Constancy- recognition that objects do not physically change despite changes in vantage point and viewing conditions.

    • Sensory information changes, but perceptual interpretation does not.

    • Size Constancy:  Perception that objects have a constant size, even when one’s distance from them varies

    • Shape Constancy: Perception that the form of a familiar object is constant, even when retinas receive changing images of them

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

Audition

• place theory- refers to where displacement on the basilar membrane is most pronounced

  • location of stimulation along basilar membrane

    • Only explains perception of high frequencies 5000 Hz and higher

• Frequency theory- frequency of nerve firing

  • Works for lower frequency- 20-5000 Hz

• Pathway

  1. Cochlea

  2. Auditory nerve

  3. Brainstem

  4. Midbrain

  5. Thalamus

  6. Temporal lobe

• Localizing sounds

  • Sound waves strike one ear sooner and more intensely than the other

  • Our heads block sound- acoustic shadow; area on the other side of head from sound source- loudness is reduced.

    • Greater affect on high frequencies

Body Senses

• Tactile senses

  • Touch- tactile perception

  • Temperature- thermoregulation

  • Pain- nociception

  • Shape perception- haptic perception

  • Limb movement/ position- propioception

  • Balance/ speed- vestibular system

• Pain- body’s way of telling you something’s wrong

• Pain is not triggered by one type of stimulus

• Nociceptors- detect hurtful temp, pressure, or chemicals

• Pain experience may not be remembered

  • Pain is a product of individuals attention, expectations, and culture

• Olfaction- perceiving odors

  • Bypasses thalamus and directly alerts brain

  • Changes in odor identification with age and smoking

  • Smell is an early warning system

• Gustation- perceiving taste

• Taste- Gives pleasure and helps us survive

  number of taste buds and taste sensitivity decrease with age.

  • the stimuli for taste (tastants) are molecules the can be dissolved in saliva.

    • Sweet- indicates energy source

    • Salty- sodium essential to physiological processes

    • Sour- potentially toxic acid

    • Bitter- potential poisons

    • Umami- proteins to grow and repair tissue

  • Flavor- not same as taste.

    • Smell is the main contribution to flavor

    • Other contributions are texture, temperature, vision, audition

  • Information from taste buds travels not far from where the brain receives info from our sense of smell. Both are near memory area