Perception Unit 1 Exam

Conscious perception

Knowing that something is there (sound, sight, etc.)

Recognition

Being able to assign meaning to it

Perception

The state of being or process of becoming aware of something through the senses

Our experience of perception is just

neural activity

What can create percepts?

Mind-altering substances, dreams, hallucinations

Percept

The mental result or product of perceiving

Chemotaxis

Perhaps the oldest form of perception: single celled organisms move based on chemicals in the environment

Senses that animals have that we dont

magnetoreception

electroreception

infrared vision

Why study perception?

To understand how and why we can perceive

Computer vision

Medical applications

Perceptual process

1. Stimulus in the environment

2. Light is reflected and focused

3. Receptor processess

4. Neural processing

5. Perception

6. Recognition

7. Action

Stimulus

Any object or event that elicits a sensory or behavioral response in an organism

Distal stimulus

Environmental stimulus (something out there in the world)

Distal stimulus → Proximal Stimulus

Distal stimulus makes contact with our sensory organs and becomes a proximal stimulus

Proximal stimuli

Light (vision)

Chemicals (smell and taste)

Air pressure (hearing)

Force, heat, cold (touch)

Receptors

Specialized cells that occur in our sensory organs

What do receptors respond to?

Specific proximal stimuli

-eyes to light

-ears to air pressure

Transduction

The proximal stimulus signal is converted to electrical signals by the receptors

(visual receptors in the eye turn light into electrical energy)

What is the brain’s currency?

Electrical energy- neural action potentials

What is transduction like?

Translation

Neural processing

Activity in sensory receptors generates neural signals that are transmitted to the brain

different sensory organs send the electrical signals to different parts of the brain

Percepts from dreams and hallucinations start at this stage

Neural processing

Conscious perception

By it’s most specific definition, perception is the conscious experience itself

But the entire process is also referred to as perception

Recognition

The categorization of a stimulus into a semantic class

the stimulus is given meaning

Action

Occurs when the perceiver initiates activity in response to perception and/or recognition

medical breakthroughs that have restored perception to people

Artificial retina

Cochlear implants

Prosthetic limbs that can feel

Brain implants for vision

Describe 1 Receptor process (Transduction)

Receptors convert the proximal stimulus into electrical signals via transduction

Describe 1 receptor process (light)

Visual receptors turn light into electrical energy

Full perceptual process in the correct order

Distal Stimulus

Proximal Stimulus

Receptor processes

Neural processing

Perception

Recognition

Action

Transduction again

Receptors convert various types of energy into electrical energy that is transmitted to our brains where it undergoes neural processing

Based on the electrical energy being processed in our brains, we have:

-Conscious perception

-The abilitiy to recognize stimuli

-The ability to take action on it

Knowledge

influences how and what we perceive

What is knowledge?

Any information that the perceiver brings to the situation

Knowledge is often used for

Conscious perception

Knowledge is always used for

Recognition

One particularly common effect of knowledge on perception/recognition is

contextual knowledge

Your brain makes inferences about what a stimulus is likely to be based on

contextual knowledge

Why do we use knowledge to perceive?

Perception often requires inference

There isn’t always enough information in the stimulus to unambiguously identify it

Why do we use knowledge to perceive? (Formal answer)

The proximal stimulus is usually ambiguous about the nature of the distal stimulus

Do knowledge and inference have to be conscious?

No

What is top-down processing?

Using knowledge to interpret sensory information

Also called knowledge based procesing

Examples of top down influences on perceptual processes

Knowledge

Memory

Goals

Expectations

Reward and motivation

What is bottom-up processing?

Perceiving based only on incoming sensory information

Also called stimulus-based or data-driven processing

Does bottom-up processing involve knowledge?

NO

Examples of particularly powerful bottom-up influences on perceptual processes

Salient information

Motion

Changes and abrupt onsets

Powerful stimuli

What does perception involve?

The interaction of bottom-up signals with top-down processing

How do we measure perception?

Manipulate stimulus

Measure physiology

Measure behavior

Stimulus: manipulate the distal stimulus

Examples: images, video, people, text

Auditory: speech, tones, music

Tactile: pressure, electrical shocks

Taste: foods, flavors

Smell: scents

Physiology: Typically measured as brain activity

Examples:

Recording single neurons

Scanning techniques

Electrical Potentials

Behavior: Typically measured as responses

Examples:

Reporting what you see

Pressing a button when you hear a sound

Making a decision based on stimulus

Blinking;startling

Thresholds

One of the earliest ways of measuring behavior

Used to measure the limits of perceptual systems

Example of behavior threshold

The dimmest light we can see, the quietest sound we can hear

Absolute Threshold

the lowest level of a stimulus that can be detected half the time

Difference threshold

the smallest difference between two stimuli that we can detect

Reaction time (behavior measure)

The time between stimulus presentation and a person’s reaction

3 main types of relationships studied

Stimulus-Behavior

Stimulus-Physiology

Physiology- Behavior

Stimulus-behavior relationship

How the presence of squirrel changes driving

Stimulus-physiology relationship

How the presence of squirrel changes neural activity

Physiology-behavior relationship

How perception-related neural activity predicts driving

Example of stimulus-behavior measured

Showing people gratings with smaller and smaller lines until they can no longer tell that there are lines

Example of Stimulus-physiology measured

Horizontal and vertical orientations caused larger brain responses in visual brain areas than slanted lines

Physiology-behavior experiment

Measure how brain activity changes when experiencing different words

What is the first step of seeing something?

Light bounces off stimulus and into the eye

What is light?

Electromagnetic radiation that can be perceived by the human eye

has properties of waves and particles, but we focus on wave properties

Wavelengths

The distance between peaks

Why are wavelengths important?

Wavelength of light is the key determinant of what we can and can’t see, as well as colors

What is part of the electromagnetic spectrum?

Light

Visible light is a tiny sliver of the spectrum

Which wavelengths are longer than what we can see?

Radio waves

Infrared

Which wavelengths are shorter than what we can see?

UV, X-Rays, and Gamma Rays

Why does our eye only detect that tiny sliver of the electromagnetic spectrum?

That specific range of wavelengths is very useful

Why is light particularly useful 1

Sun produces it, and it passes through the atmosphere

The sky looks red at sunrise/sunset because more blue light gets scattered

Why is light particularly useful 2

Light tends to reflect off surfaces instead of going through them

Light needs to reflect back to use for us to see things

Why is light particularly useful 3

It isn’t too big- with huge waves, we wouldn’t be able to see small objects

In lecture, showed an experiment that had a blob with various backgrounds (e.g., on a road vs on someone’s foot). What did that experiment illustrate

Contextual knowledge is used to recognize objects

The eye

Different parts of the eye work together to focus reflected light

Step 1: Light passes through cornea

outer layer of eye - Protects the eye

transparent

does most of the job in focusing light to get it into the eye

Astigmatism

Cornea is oval-shaped rather than round
1/3 people have it

Compared to humans, what can bees see?

Bees see less visible light than humans (can’t see red) but more UV

Types of eye conditions and the parts of their eye

Glaucoma- aqueous humor

Astigmatism- cornea

Cataracts- Lens

Myopia/Hyperopia- lens

Acanthamoeba- cornea

Compared to humans, what can birds see?

They can see a broader range of visible light than we can, and UV light

What waves are blocked by the atmosphere?

Gamma

X-Rays

Most UV

Most Infrared

What waves can pass through the atmosphere?

visible light

most radio waves

some infrared

Aqueous Humor

A fluid derived from blood that supplied oxygen and nutrients to the cornea and lens

Glaucoma

Results when there is a build up of aqueous humor, causing high pressure in the eye

second leading cause of blindness in the world

Light enters the eye through the

Pupil

Pupil

A hole in the iris

What does the iris do in bright light?

Iris relaxes

What does the iris do in dim light?

Iris contracts

Which muscles control the size of the pupil to change how much light can get in?

The iris muscles

Cameras do the same thing with the aperture

What focuses the light further after passing through the pupil?

The lens

Ciliary muscles

Around the lens make it change shape, which changes it’s thickness

Far accommodation

Relaxed ciliary muscles

Near accommodation

Contracted ciliary muscles

Accommodation

Ciliary muscles change lens thickness depending on the distance of what we’re looking at

Close up objects

Thicker lens (near accommodation)

Far away objects

Thinner lens (far accommodation)

Myopia (Nearsightedness)

Difficulty seeing distant objects clearly

Hyperopia (Farsightedness)

Difficulty seeing close objects clearly

Cataracts

A clouding of the lens that often happens with age:

alot of sun exposure

steroid use

drinking/smoking

Vitreous humor

Gel-like tissue

Light passes through it

Where are floaters located?

Bits of debris floating inside the vitreous humor