PSYC 3220 Exam 1 Lecture Notes

Sensation and Perception

The means by which we gain knowledge about what is in the world around us

Fundamental Purpose of Perception

Transforms raw data from sensory receptors into meaningful experiences and information; gives us prospective control

Prospective control

The steering of physical actions using perceptual information to anticipate and manage future events (ex. moving to the middle pf a doorway as to not hit the wall)

Aristotle

• Perception involves 3 things: the animal perceiving and doing, the object being perceived, and the medium between that coneys information

• Principle of representation: copies mediate our contact with the world (this is how info crosses the gap between the obejct and animal without touching the object)

Intromission

The whole outside world has spiritual energy, the energy emanates from an object to out heads

Emanation

Spiritual energy originates within you, rather than the outside world

Ankindi

Pointillistic theory of emanation

Pointillistic theory of emanation

The emanation is built up of spearate elements (aka pencils or rays)

• modern technology still uses individual points

Alhazan

First to treat the eye as an optical instrument

• copies are carried by structured light (bends to convey dimensions)

• an intromission theory that follows Alkindi’s pointilism

  • rays of light make points in the eye (copies are precise - spacial order is preserved)

Mental Entity

required to reconstruct and enrich the representations

Does intromission or emanation happen?

Both intromission and emanation happens

Kepler

• discovered the retina as a sensitive part of the eye upon which images are formed

• noted destructive mapping

Destructive mapping

the proximal stimulus is an impoverished version of the distal stimulus

Proximal Stimulus

the image in the back of the eye (upside down, backwards, 2D)

Distal stimulus

The real object being perceived

• The farther the stimulus is from the eye, the smaller the image is made in the eye

  • the same distal stimulus can get an infinite number of different proximal stimuli; different distal stimuli can get the same proximal stimulus

Leonardo DaVinci (and other artists)

used the camera obscura (pinhole camera)

• first ones abel to paint 3D images

• realized the eyeball makes images in the back of the eye (just like the camera does)

Molyneux’s Premise

Distance is a line presented to the eye with its end toward us, which therefore must be a point, thus distance is invisible

• the 3rd dimension is “lost” on the 2D retina (the near and far point are the same on the screen in the back of the eye)

The problem of perception:

The proximal stimulus is an inverted, distorted, 2D ambiguous, changing, copy of the distal stimulus

Sensation vs. Perception

Sensation: Info coming in

Perception: Mental interpretations of what we decide to perceive (a mental entity is needed to perceive)

• sensation is a support for perception

Mental enrichment

something added to sensation in order to form perception

• we are doing unconscious calculations to make sense of the world

Bottom-up / sensation-based procesing

When your brain builds an understanding from the world from only sensory details

• ex. when you touch a hot stove, your sensory receptors fire so you know you have touched something hot

Top-down / knowledge-based processing

When your brain uses what you already know to make sense of your surroundings

• ex. knowing how something will feel because you’ve felt that texture before

Ontology

Theories about what exists (physical/ spiritual)

Materialism

A form of monism; People who don’t believe in God, ghosts, spirits, or anything out of the laws of physics/ dynamics

Plato’s Mind-Matter Dualism

There are both then physical and spiritual world

Epistemology

Theories about how things can be known (nativism, empiricism, rationalism)

• All 3 are enrichment theories of perception (how the mind makes sense of what comes through our eyes)

Nativism

Knowledge in inherited

• ex. birds born knowing how to build a nest without seeing it done

Empiricism

Knowledge is learned through observation

• ex. bird watching its mother build a nest then knowing how to do it

Rationalism

Knowledge comes through reason (creating you own knowledge)

• ex. your eyeballs pointing inward and you can rationalize how far your car is

Rene Descartes

Changed mind-matter dualism into mind-body dualism

• his radical idea: much of out bodies (and most human function) are just machinery

  • this idea came from early robots. Before this, it was believe that every cell in your body needs to b spiritual to stay alive and work

• This theory helped launch the discipline of medicine, as it was now believed that someone won’t lose a part of their soul during an operation on their body

Mind-Body Dualism

Not only is the world populated by both matter and spiritual things (dualism), but each human person as an individual possesses dualism

Perception

An active mental process.

Why is perception indirect?

The mind directly knows only what the nervous system senses, not the outside world itself.

Dualism in perception

The view that there is an external world and an internal world of bodily or mental states.

How does dualism explain knowledge of the world?

Because we are directly aware only of bodily states, we infer the external world through reasoning, like a sailor reading sonar.

Johannes Müller’s contribution

Perception is of states of nerves, not objects directly in the world.

Theory of specific nerve energies

The quality of a sensation depends on which particular nerves are stimulated.

What does specific nerve energies imply?

A perception can occur without the usual external stimulus if the relevant nerve is activated.

Awake-patient surgery evidence

Stimulating sensory nerves can produce experiences such as hearing a noise when no sound exists.

Monistic ontology with dualistic epistemology

A perceiver can be treated as one physical system, such as a computer, while still distinguishing the outside world from internal experience.

Empiricism

The view that mental contributions to perception are learned through experience.

John Locke’s view of the mind at birth

People are born without ideas and gain knowledge through experience.

Primary qualities

Qualities believed to exist in the world independently of a perceiver.

Secondary qualities

Qualities imposed by the perceiver and existing only in experience, such as color, taste, and some temperature sensations.

George Berkeley’s challenge

The perceiver cannot reliably tell which qualities are primary and which are secondary.

Why might ideas in the head fail to match the world?

The nervous system responds to receptor activity, which may be produced by unusual stimulation.

Can distance be sensed directly?

No. Distance is inferred from cues such as size, angle, eye position, and occlusion.

How do distance cues gain meaning?

Through learned associations and reasoning.

Cue theory of perception

The mind uses sensory cues to construct an internal representation of the world.

Sensory transduction

The transformation of physical energy into neural energy.

Photoreceptors

Light-sensitive retinal cells that convert light into neural signals.

Photopigments

Chemicals in photoreceptors that absorb light and initiate neural activity.

Blind spot

The retinal area where the optic nerve exits; it has no photoreceptors.

Fovea

The retinal center with the highest cone concentration and most detailed vision.

Retinal processing pathway

Photoreceptors send signals to bipolar cells, then ganglion cells; ganglion axons go to the brain.

Neural convergence

Signals from many receptors funnel into fewer ganglion cells.

Rod convergence

About 120 rods may converge on one ganglion cell.

Cone convergence

About 6 cones may converge on one ganglion cell.

Rods versus cones

Rods provide sensitivity in dim light; cones provide sharp spatial resolution and color vision.

Why are cones ineffective at night?

Available light often is not sufficient to activate cone pathways.

Why can rods support night vision?

Many rods converge and combine their signals, increasing sensitivity.

Adaptation

A change in sensory sensitivity over time.

Sensory adaptation example

A person stops noticing clothing on the skin or a fan’s hum.

Dark adaptation

Increased visual sensitivity after spending time in darkness.

What happens to threshold during dark adaptation?

The threshold decreases, meaning less energy is needed for detection.

Threshold

The amount of energy needed to produce a detectable response.

Calibration

Keeping the perception system and action-control system coordinated.

Prism adaptation

After vision is shifted by prism glasses, a person learns compensatory eye and arm movements.

Prism aftereffect

After removing prism glasses, a person initially points in the opposite direction and must recalibrate.

Sensory coding

Information is represented in patterns of neural firing.

How is intensity coded?

Primarily by the frequency or rate of neural firing.

How is quality coded?

By which specific nerves or receptor types are active.

Purpose of taste

To motivate organisms to consume useful substances and avoid harmful ones.

Five primary tastes

Sweet, salty, sour, bitter, and umami.

Sweet taste

Often signals energy and is generally pleasant.

Salty taste

Can signal a necessary mineral and is generally pleasant in appropriate amounts.

Sour taste

Can signal acidic or decaying food and is often unpleasant.

Bitter taste

Can signal toxins and is often unpleasant.

Umami taste

Often signals nutritional proteins or amino acids and is generally pleasant.

MSG and umami

Monosodium glutamate can activate umami receptors.

How do taste chemicals reach receptors?

They dissolve in saliva and interact with taste-bud receptors.

Flavor

The combined experience of taste and smell.

Single-cell recording

Using a fine electrode to measure one neuron’s activity while presenting stimuli.

Qualitative coding for smell

The brain identifies odors from patterns or ratios of activity across odor receptors.

Newton’s color experiments

White light can be separated into spectral colors, and a second prism does not split them further.

Additive color mixing

Combining wavelengths of light, such as red, green, and blue, to produce other colors.

Subtractive color mixing

Combining pigments or filters that absorb selected wavelengths and reflect the remainder.

How does the brain construct color?

It uses the relative ratio of activity across short-, medium-, and long-wavelength cones.

Why is purple nonspectral?

It is produced by combining red and blue signals, not by one wavelength.

Principle of univariance

A single receptor signals how much light it absorbed but cannot separately specify wavelength and intensity.

Dichromacy

Color vision based on two functioning receptor pigments instead of three.

Trichromacy

Normal color vision based on three cone pigments.

Anomalous trichromacy

All three cone types are present, but one has altered sensitivity.

Why are humans good at distinguishing red from green?

This likely helped identify food and poisonous plants.

Purkinje shift

Daylight vision is more sensitive to yellow; dark-adapted vision shifts toward blue and away from red.

Light

Electromagnetic energy that varies in amplitude and wavelength.

Amplitude of light

The amount of energy in a light wave; greater amplitude is perceived as greater brightness.

Wavelength of light

The distance between wave peaks; it contributes to perceived color.

Selective absorption and reflection

Surfaces absorb some wavelengths and reflect others toward the eye.

Radiant light

Light traveling directly from a source; it provides energy but little information about surfaces.