Chapter 4: Sensation and Perception

Chapter 4: Sensation and Perception

Introductory Psychology (PSY100H5)

Prof. Dax Urbszat

10/16/2023

I love Jesus.

LECTURE NOTES

  • Sensation is how you take information and turn it into everything we see, taste, touch, smell, and hear.
  • This is a headset that you can take off. There is so much more to reality. Our science is still limited to a tiny frame.

Psychophysics

  • Sensation is pretty much the same for all of us.
  • There are exceptions to sensation (sinestesia - a crossing of two senses; see colour; hair shapes; taste words).
  • We used to say that there is no taste and smell in your dreams. But this is not true, as there are exceptions (but not a rule).
  • In general, we are all taking the same stimulation of sense orbits.
  • Perception is uniquely subjective; qualia.
  • We all agree with words because we're all looking at the same frequency, although, we have no way of seeing a person's subjective perspective; we just assume that we all see the world the same but truly we all see it differently.
  • Our perceptions are created and shaped by our experiences and the memories of our experiences (and even what we tell ourselves).
  • You could be hit with someone with a stick across your back and hurt so badly that you would want to kill that person, but another person might be compassionate enough to not mind, but others might even be sexually aroused by that.
  • We all have a different 10% of what we pay attention to.
  • Your ability to control your consciousness is limited by nature (you can be tired, drunk, hungry, etc.)
  • Some people have an iron attention and some people have a 2-second attention.
  • The ability to have some control over how you interpret anything, is one good thing.

Thresholds

  • Sensory receptors are tuned to a particular form of energy
    • Auditory receptors in the ear code for sounds pressure changes, not for light
    • The eardrums tap on the tiniest bone of your body (ossicles)
    • Sensory systems require a minimum amount of energy for activation (absolute threshold)
      • Just noticeable difference (JND): The minimum difference in stimulation that is just noticeable
      • How much light you have to add to know that it got brighter
      • How much sound do you have to add to know that it got louder
      • Weber noted that the JND is a fraction of the original stimulus intensity
      • There is a different vapour fraction for everything.
      • If the vapour fraction of lifting a 90 pound weight is ⅓ to notice the change in weight, you would have to add 30 pounds.
      • If there is so much light in one room, a tiny bit of light added will not make you notice that the room got brighter; but if the room has no light, that tiny bit of light becomes a lot of light.
    • Interface between energy outside of us and the neurotransmitters in our brain
    • You cannot improve your vision by working on it; it can only get worse
    • You should be able to see a candle from 50 kilometres away on a dark night; then you meet threshold, if you do it again and don’t see it then that’s fine because you saw it ½ times, but if you do it one more time and don’t see it again, then you are under the threshold
      • The point is can you get 50% of the trials

The Visual System

  • There may be things that travels faster than the speed of light (ie. information)
  • Light travels in straight lines (no distortion)
  • Light travels rapidly (no delay, unlike hearing)

Electromagnetic Spectrum

  • We have technology to see the different spectrum of light, but our vision is not able to see all of that light in the spectrum
  • Roy G. Biv, some light guy
  • We have different cones that are able to detect colours in relation to their actual visible weight
  • When we measure light, we measure it in a wave length
  • Wavelength is measured from the peak of one wave to the other peak of another wave
  • The brightness or intensity is derivative from the amplitude (height of the weight from baseline); this would be the intensity of light
  • Saturation, the purity of the colour; its fading colour; anyone can look at a colour and determine if it is bright or not; difficult to explain, easy to look at

Details of My Eye

  • If they ain’t working, you’re not seeing.
  • Cornea is the thin film that keeps the eye from dust; not very strong; keeps the water in your eyes
  • If your eyes dry up too much then you cannot open them
  • Aqueous humour (eye water) - liquids in the body; watery liquid
  • Iris - eye colour; one of the most genetically verified things; When it's dark your iris contacts, which dilates the pupil.
  • Rods are super sensitive to light (what helps us see in the dark); if you sit in a dark room, you won’t be able to see, if you wait 2-3 minutes you will start to see better, and after thirty minutes you would have fully adapted to the light
  • Fovea
  • Lens
  • Optic nerve
  • Blind spot
  • Vitreous humour
  • Retina
  • Matter is not what we see, we create matter when we perceive it.
  • You have two giant hoes in your vision (put your hands in an o shape) we can’t see them because your brain fills in the blank
  • Visual sensation is everything is upside down.
  • We are able to perceive only in the ways that WE are able to perceive them.
  • Things can change, just not easily.

Transduction of Light

  • Light travels through the retina
  • Don’t look at an eclipse without the proper glasses (rods are being exposed to a bunch of radiation and UV light that may destroy it)
  • DO NOT STARE AT THE SUN

Visual Pathways in Brain: “Where” versus “What”

  • From the occipital lobe there are interneurons that will send the information to the temporal lobe

Perception of Colour

  • Colour is a psychological perception
  • Know which berries to eat, know NOT to eat the green bananas
    • Three dimensions of colour:
      • Hue is the apparent colour of an object (blue)
      • Brightness is the intensity of the colour

Colour Vision Theories

  • Young-Helmholtz:
    • Colour is explained by differential activation of 3 colour elements in the eye
      • Could not account for negative colour afterimages
  • Hering: Opponent-Process Theory
    • Colours are derived from activity of 3 antagonistic
      • Full colour blindness; black-white (really rare)
      • Blue-yellow (pretty rare)
      • Red-green (can’t be a pilot)

Negative Colour Afterimages

  • Why does this occur?
  • Antagonistic pairs (one cell excites green and inhibits red, is touching another cell that excites red and inhibits green)

Sound

  • Sound waves are vibrations of molecules that travel through air
  • Amplitude - decibels
  • Wavelength - frequency (cps or hertz)
  • Purity - timbre
  • We hear from within 20 hertz and 20,000 hertz
  • When your ears are ringing that is the final death cry of the “hair” cells
  • When you get older you don’t lose hearing, you lose frequencies.
  • It’s not that they cannot hear you, it's just that they cannot hear your voice; your voice becomes very quiet.
  • Sound waves move quicker in water
  • These tiny bones take these big vibrations and turn them into tiny vibrations; so then they tap on the window which turns into little waves around the cochlea.

Taste: The Gustatory System

  • Taste buds
  • Primary tastes: sweet, sour, bitter, salty
  • Perception of flavour
  • Spice is just killing your tastebuds; spice comes from the hottest environments
  • Papillae: circumvallate, foliate, & fungiform
  • There is one thing that humans don’t eat: faeces. Some people do tho, so there’s that.

Smell: The Olfactory System

  • Most of flavour/taste perception is smell
  • Smell: chemical substances dissolved in mucus
  • Olfactory cilia
  • Olfactory
  • When you’re smelling something you’re capturing small parts of it. Just like hearing.
  • Knowing this changes our perception, but that shouldn’t affect us that much. Teach said to get a grip. Ok 😮‍💨
  • Smell is much more important in all other species except humans.
  • Dogs release pheromones for doggy intercourse.
  • Smell will habituate just like vision. If you’re driving down the country road it may stink , but 10 minutes later the smell will go away; you adapt to it.

Skin Senses

  • Receptors are localised within the skin to detect physical stimuli in the outside world
  • Three classes of skin receptors:
    • Touch: physical contact of objects with the skin
    • Temperature of objects
    • Pain: destruction of skin tissue
    • The experience of pain is entirely subjective.

wenis.

KEY TERMS

Absolute threshold: The minimum amount of stimulus energy that a person can detect.

Apparent movement: The perception that a stationary object is moving.

Attention: The process of focusing awareness on a narrow aspect of the environment.

Auditory nerve: The nerve structure that receives information about sound from the hair cells of the inner ear and carries these neural impulses to the brain’s auditory areas.

Binding: In the sense of vision, the bringing together and integration of what is processed by different neural pathways or cells.

Binocular cues: Depth cues that depend on the combination of the images in the left and right eye and on the way the two eyes work together.

Bottom-up processing: The operation in sensation and perception in which sensory receptors register information about the external environment and send it up to the brain for interpretation.

Cones: The receptor cells in the retina that allow for colour perception.

Convergence: A binocular cue to depth and distance in which the muscle movements in an individual’s two eyes provide information about how deep and/or far away something is.

Depth perception: The ability to perceive objects three-dimensionally and perceive their distance from you.

Difference threshold: The degree of difference that must exist between two stimuli before the difference is detected.

Feature detectors: Neurons in the brain’s visual system that respond to particular features of a stimulus.

Figure-ground relationship: The principle by which we organize the perceptual field into stimuli that stand out (figure) and those that are left over (ground).

Frequency theory: Theory on how the inner ear registers the frequency of sound, stating that the perception of a sound’s frequency depends on how often the auditory nerve fires.

Gestalt psychology: A school of thought interested in how people naturally organize their perceptions according to certain patterns.

inner ear: The part of the ear that includes the oval window, cochlea, and basilar membrane and whose function is to convert sound waves into neural impulses and send them to the brain.

kinesthetic senses: Senses that provide information about movement, posture, and orientation.

middle ear: The part of the ear that channels sound through the eardrum, hammer, anvil, and stirrup to the inner ear.

monocular depth cues: Powerful depth cues available from the image in one eye, either the right or the left.

Noise: Irrelevant and competing stimuli—not only sounds but also any distracting stimuli for the senses.

Olfactory epithelium: The lining of the roof of the nasal cavity, containing a sheet of receptor cells for smell.

Opponent-process theory: Theory stating that cells in the visual system respond to complementary pairs of red-green and blue-yellow colours; a given cell might be excited by red and inhibited by green, whereas another cell might be excited by yellow and inhibited by blue.

Optic nerve: The structure at the back of the eye, made up of axons of the ganglion cells, that carries visual information to the brain for further processing.

Outer ear: The outermost part of the ear, consisting of the pinna and the external auditory canal.

Pain: The sensation that warns an individual of damage to the body.

Papillae: Rounded bumps above the tongue’s surface that contain the taste buds, the receptors for taste.

Parallel processing: The simultaneous distribution of information across different neural pathways.

Perception: The process of organizing and interpreting sensory information so that it makes sense.

Perceptual constancy: The recognition that objects are constant and unchanging even though sensory input about them is changing.

Perceptual set: A predisposition or readiness to perceive something in a particular way.

Place theory: Theory on how the inner ear registers the frequency of sound, stating that each frequency produces vibrations at a particular spot on the basilar membrane.

Retina: The multilayered, light-sensitive surface in the eye that records electromagnetic energy and converts it to neural impulses for processing in the brain.

Rods: The receptor cells in the retina that are sensitive to light but not very useful for colour vision.

Selective attention: The act of focusing on a specific aspect of experience while ignoring others.

Semicircular canals: Three fluid-filled circular tubes in the inner ear containing the sensory receptors that detect head motion caused when an individual tilts or moves the head and/or the body.

Sensation: The process of receiving energy from stimuli in our internal or external environment, and transforming this energy into action potentials.

Sensory adaptation: A change in the responsiveness of the sensory system to the average level of stimulation.

Sensory receptors: Specialized cells that detect stimulus information and transmit it to sensory (afferent) nerves and the brain.

Signal detection theory: An approach to perception that focuses on decision making about stimuli under conditions of uncertainty.

Subliminal perception: The detection of information below the level of conscious awareness.

Thermoreceptors: Sensory nerve endings under the skin that respond to changes in temperature at or near the skin and provide input to keep the body’s temperature at 37 degrees Celsius.

Top-down processing: The operation in sensation and perception, launched by cognitive processing at the brain’s higher levels, that allows the organism to sense what is happening and to apply that framework to information from the world.

Transduction: The process by which a specialized receptor cell converts energy from an external stimulus (e.g., light, sound, heat) to an internal electrical signal (action potentials).

Trichromatic theory: Theory stating that colour perception is produced by three types of cone receptors in the retina that are particularly sensitive to different, but overlapping, ranges of wavelengths.

Vestibular sense: Sense that provides information about balance and movement.

Volley principle: Modification of frequency theory stating that a cluster of nerve cells can fire neural impulses in rapid succession, producing a volley of impulses.

Weber’s law: The principle that two stimuli must differ by a constant minimum percentage (rather than a constant amount) to be perceived as different.