Sensations & Perception

Sensation

The process of sensing our environment through touch, taste, sight, sound, and smell.

The process by which our sensory systems (eyes, ears, and other sensory organs) and nervous system receive stimuli from the environment

• A person’s awareness of the world

The brain processes taste sensations in the primary taste cortex is located at the side

of the head.

Perception

The process of organizing and interpreting sensory information.

Stimulus

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

A stimulus is anything that causes a reaction or response.

Illusions

A misperception or misinterpretation of a real sensory stimulus.

Real Stimulus: Always involves an actual external object or event.

Brain is "Tricked": Your brain processes the sensory info in a way that doesn't match objective reality.

Systematic Errors: Often experienced by most people, revealing normal perceptual processes.

Reveals Perception: Studied to understand how our brains interpret sensory data.

All Senses: Can occur in vision, hearing, touch, etc.

Perceptual set

A mental predisposition to perceive one thing and not another.

It influences how we interpret ambiguous stimuli, shaping our perceptions based on expectations, experiences, and context.

Perceptual set is your brain getting ready to perceive something based on what it already knows, expects, or feels. It's about how your mind influences what you actually "see" or "hear."

Transduction

The conversion of physical energy into electrical signals in the brain.

Info from sense organ (eyes, nose, ears, tongue, & skin)

changes physical energy into electrical signals that becomes neural impulses sent to the brain for interpretation

Top-down processing

Your brain uses what it already knows (experiences, expectations, context) to interpret new info.

It's like your brain is making an "educated guess" about what you're seeing or hearing.

"Top" (your thoughts/knowledge) → "Down" (influences how you see/hear sensory details).

Helps you quickly understand ambiguous or incomplete things.

Reading jumbled words: You can understand "Tihs is an exmaple" because your brain expects real words.

Seeing faces in clouds: Your brain applies its knowledge of "faces" to random shapes.

Perceptual Set: This is a perfect example of top-down processing in action!

Basically: Your mind shapes your perception, not just what your senses tell you.

This cognitive process allows prior knowledge to shape perception, enabling efficient interpretation of incoming sensory information.

Top-Down: Using the big picture/what you know to understand the details. (Like having the box cover of the puzzle to guide you)

Bottom-up processing

Analysis that begins with the sensory receptors and works up to the brain's integration of sensory information.

• "Bottom" (raw sensory details) → "Up" (brain gradually builds a complete picture).

• No guesses or expectations involved at first.

• Purely based on what your eyes, ears, nose, etc., are telling you right now.

example:

• Seeing a new drawing: You first notice the individual lines, colors, and shapes, then your brain puts them together to understand the whole picture.

• Touching something for the first time: You feel the texture, temperature, and pressure first, then realize what it is.

• A baby learning: They're mostly using bottom-up processing to understand the world, taking in all the basic sensory details.

Basically: Your senses inform your mind, starting with the little details.

This cognitive process involves piecing together sensory details to form a complete perception, without relying on prior knowledge or expectations. It begins with the raw input from our senses and leads to the brain's interpretation.

Bottom-Up: Building from the details up to the big picture. (Like a puzzle where you start with individual pieces)

Loudness

A perceptual quality of sound that corresponds to the intensity of the sound wave.

– subjective experience of a sound’s intensity

– brain calculates loudness from specific physical energy (amplitude of sound waves)

How the ear functions

The ear converts sound waves into neural signals for the brain to process.

Ear Function:

1. Outer Ear (Collector):

• Pinna: Gathers sound waves.

• Ear Canal: Directs waves to eardrum.

2. Middle Ear (Amplifier):

• Eardrum: Vibrates when hit by sound waves.

• Ossicles (Hammer, Anvil, Stirrup): Tiny bones that amplify vibrations (20x) and pass them to the inner ear.

3. Inner Ear (Translator - Transduction!):

• Cochlea: Snail-shaped, fluid-filled. Vibrations create fluid waves.

• Hair Cells: Inside cochlea, these tiny cells bend from fluid waves.

• Transduction: This bending converts mechanical vibrations into electrical signals (neural impulses).

• Auditory Nerve: Carries these electrical signals to the brain.

4. Brain (Interpreter):

• Receives electrical signals and interprets them as sound.

Outer Ear collects sound waves, Middle Ear amplifies vibrations, Inner Ear translates them into neural signals.

Parts of the Ear

Includes the outer ear, middle ear, and inner ear which help in hearing.

Parts of the Ear

1. Outer Ear (Sound Collector)

• Pinna: The visible part; funnels sound.

• Ear Canal: Tube to eardrum.

• Eardrum (Tympanic Membrane): Vibrates from sound.

2. Middle Ear (Amplifier)

• Ossicles (3 tiny bones):

  • Hammer (Malleus): Attached to eardrum.

  • Anvil (Incus): Connects hammer to stirrup.

  • Stirrup (Stapes): Pushes on oval window.

• Function: Amplify vibrations.

• Eustachian Tube: Equalizes pressure in middle ear.

3. Inner Ear (Translator & Balancer)

• Cochlea: Snail-shaped, fluid-filled; contains Hair Cells.

  • Hair Cells: Sensory receptors that convert vibrations into electrical signals (Transduction).

• Auditory Nerve: Sends electrical signals to the brain.

• Vestibular System (for Balance):

  • Semicircular Canals: Detect head rotation.

  • Utricle & Saccule: Detect linear head movement & gravity.

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Sound waves

Vibrations that travel through the air or another medium and can be heard when they reach a person's or animal's ear.

• stimuli for hearing (audition)

• ripples of different sizes

• sound waves travel through space with varying heights

and frequency

Direction of Sound

The ability to locate the direction from which a sound is coming.

Semicircular Canal

The part of the inner ear that helps maintain balance.

Threshold

The level of stimulation required to trigger a neural impulse.

The minimum point at which a stimulus (like light, sound, touch) can be detected.

It's the boundary between what we can sense and what we can't.

Helps us understand the limits of our senses.

Absolute Threshold

The minimum level of stimulus that can be detected 50% of the time.

It represents the lowest intensity at which a stimulus is perceived and is crucial for understanding sensory perception.

• The faintest sound you can hear.

• The dimmest light you can see.

• The slightest touch you can feel.

Basically: The minimum energy needed for a sense to barely register something.

The lowest level of stimulus detected reliably.

Weber’s Law

The principle that noticeable differences in stimuli are proportional to the original stimulus.

To notice a change in something (like brightness, weight, loudness), the change has to be a constant PERCENTAGE of the original amount, not a constant AMOUNT.

This law describes how much more of a stimulus is needed for it to be perceivable as different.

If you're holding a light 1 kg bag, adding 0.1 kg (10%) is noticeable.

If you're holding a heavy 10 kg bag, you'd need to add 1 kg (10%) to notice the same amount of change. Adding only 0.1 kg wouldn't be noticeable!

In a dim room, a tiny bit more light is obvious.

Out in bright sunlight, that same tiny bit more light is unnoticed. You need a much bigger percentage increase to notice a change.

Basically:

Our senses are better at detecting relative changes (percentages) than absolute changes.

The stronger the original stimulus, the larger the change needs to be for us to notice it

Just noticeable difference

The minimum difference in stimulation that a person can detect 50% of the time.

The smallest possible change between two stimuli that a person can detect.

It's the minimum amount a stimulus needs to change for you to notice that it's different.

Detected 50% of the time (because our sensitivity varies).

The smallest detectable change in stimulus intensity.

Subliminal stimulus/messaging

Stimuli that are below the threshold of conscious perception.

A stimulus below conscious awareness.

Subliminal Stimulus:

• A sensory input (light, sound, image) presented below your conscious awareness.

• You don't "see" or "hear" it, but your brain can still detect it.

• Example: A word flashed too quickly to read consciously.

Subliminal Messaging:

• Using subliminal stimuli to try and influence thoughts, feelings, or behaviors.

• Goal: To bypass conscious critical thinking.

Effectiveness (Science Says):

• Can the brain process it? YES. (Your brain registers it).

• Can it control you? NO. (Doesn't force you to buy/do things you don't want).

• Can it have any effect? Sometimes, very subtle & temporary, usually only if you have an existing need/motivation (e.g., if you're already thirsty, a subliminal drink ad might nudge you).

Basically: Your brain sees/hears more than you know, but it's not easily tricked into doing things.

Perceptual constancy

The tendency to perceive objects as unchanging despite changes in sensory input.

What it is:

• Your brain's clever trick to make the world seem stable.

• It's how things look the same to you, even when your eyes (or ears) get different information.

Think of it like this:

• Size: A friend walking away looks tiny to your eye, but your brain knows they're still normal size.

• Shape: A door opening looks like a weird shape, but your brain knows it's still a rectangle.

• Color: A red apple in a dark room still looks red, even if it sends less "red light" to your eye.

Basically: Your brain "corrects" what your senses tell it, so you see things as they really are, not just how they appear at that moment.

Perceptual adaptation

The ability to adjust to changed sensory input.

What it is:

• Your brain's ability to adjust and adapt to new or changed sensory information.

• It makes unusual sensations eventually feel "normal."

How it works:

• When your senses get unusual input (e.g., blurry vision, weird sounds), your brain re-calibrates its interpretation.

Classic Example:

• Wearing special glasses that flip your vision upside down or shift it sideways.

• At first, everything is confusing. But after a few days, your brain adapts, and you start to see things correctly again, even with the glasses on!

Why it matters:

• Helps us function normally even if our sensory input changes.

• Allows us to tune out constant, unchanging stimuli (like the feeling of your clothes on your skin).

Basically: Your brain is super flexible and can "get used to" new ways of seeing, hearing, or feeling so you can keep acting effectively.

Synesthesia

A condition in which stimulation of one sensory pathway leads to automatic, involuntary experiences in a second sensory pathway.

What it is:

• A unique way some people experience senses.

• When one sense is triggered, another unrelated sense automatically responds.

How it feels (Examples):

• Hearing music and seeing colors (e.g., a specific note is always blue).

• Seeing numbers or letters and seeing specific colors (e.g., the letter 'A' is always red).

• Tasting words or feeling shapes when touching objects.

Key points:

• It's automatic and involuntary (you can't control it).

• It's consistent (the same trigger always causes the same cross-sensory experience).

• It's not a disease; it's a different way the brain is wired.

• Often linked to enhanced memory or creativity.

Basically: Your brain blends senses, so you might "see" sounds or "taste" words, experiencing the world with extra layers of perception.

Sensory Adaptation

Reduced sensitivity to constant stimulus over time.

Light waves

Electromagnetic waves that are visible to the human eye.

Rods vs. cones

Two types of photoreceptor cells in the retina; rods are sensitive to low light, cones are sensitive to color.

Trichromatic Theory

The theory that the retina contains three different color receptors for red, green, and blue.

What it is:

• A theory explaining how we see color.

• It states that your eye has three types of color receptors (cones).

The Three Cones:

• Each type of cone is most sensitive to a different wavelength of light (color):

  1. Red (long wavelengths)

  2. Green (medium wavelengths)

  3. Blue (short wavelengths)

How we see all colors:

• Our brain mixes the signals from these three types of cones to create the perception of millions of different colors.

• Example: When red and green cones are stimulated together, we see yellow.

Basically: All the colors you see are made by combining signals from just three basic color detectors in your eyes.

Visible spectrum

The portion of the electromagnetic spectrum that is visible to the human eye.

Function of the eye

The eye collects light and focuses it onto the retina, where it is converted to neural signals.

Parts of the eye

Includes the cornea, lens, retina, and optic nerve.

Chemical senses

Senses that involve the detection of chemical stimuli; includes taste and smell.

Flavour vs Taste

Taste refers to basic sensations (sweet, sour, salty, bitter), while flavour encompasses taste along with aroma and other factors.

How the tongue functions

The tongue has taste buds that detect different flavors in food

• Taste buds on your tongue detect chemical molecules from food.

• They send signals to your brain for the five basic tastes (sweet, sour, salty, bitter, umami/savory).

• Smell also helps create the full flavor.

• Moves food for chewing and swallowing.

• Helps form speech sounds (talking).

• Detects texture (rough, smooth) and temperature.

Basically: Your tongue is a powerful muscle that lets you taste, helps you eat and speak, and even feel things in your mouth.

Supertasters & nontasters

Supertasters have a heightened sense of taste, while nontasters have a diminished ability to taste.

Olfaction

The sense of smell.

Olfaction is your sense of smell, allowing you to detect and identify various airborne chemical molecules. This sense plays a powerful role in memory, emotion, and our perception of flavor.

How the olfactory functions

Olfactory receptors in the nasal cavity detect airborne chemicals.

1. Odor Molecules In:

   • Tiny smell chemicals float into your nose.

2. Sensors Find Them:

   • They stick to special receptors (nerve cells) high up in your nose.

3. Signal Sent:

   • Receptors turn the chemical signal into an electrical message.

4. Direct to Brain:

   • This message goes straight to your olfactory bulb, then to brain areas for smell, memory, and emotion.

5. You Smell It!

   • Your brain then recognizes the unique smell. This link makes smells strong with memories and feelings.

Basically: Chemicals in the air trigger sensors in your nose, sending direct signals to your brain to create the sense of smell.

How the sense of touch works

Involves pain sensors, pressure sensors, and temperature sensors.

1. Skin Sensors (Receptors):

   • Your skin has tiny nerve endings (receptors) that detect pressure, temperature, and pain.

2. Signal Sent:

   • When touched, these receptors turn the feeling into an electrical signal.

3. Brain's Path:

   • This signal travels up nerves to your spinal cord, then to the thalamus (relay station).

4. Feeling Center:

   • The thalamus sends the signal to your Somatosensory Cortex in the brain.

5. You Feel It!

   • Your Somatosensory Cortex figures out what you touched, where it is, and how intense it feels.

Basically: Your body's sensors pick up a feeling, turn it into a message, and send it to your brain's special "feeling center" to understand it.

Pain sensors

Nerve endings that react to potentially damaging stimuli, signaling the brain to interpret as pain.

Pressure Sensors

Nerve endings sensitive to mechanical pressure or distortion.

What they are: Special nerve endings that detect mechanical force (like pressure, touch, vibration, stretch)

Temperature sensors

Nerve receptors that detect changes in temperature.

Found mostly in your skin, but also inside your body.

They tell your brain if something is hot, cold, or just right.

Crucial for avoiding harm (like burns) and keeping your body temperature stable.

Somatosensory cortex

A region of the brain that processes sensory information from the skin.

• Located in the Parietal Lobe of your brain (just behind the Motor Cortex).

• Each side of your brain processes sensations from the opposite side of your body.

What does it do?

• It receives and interprets all your bodily sensations:

  • Touch (light touch, pressure, texture)

  • Temperature (hot/cold)

  • Pain

  • Proprioception (your body's position and movement in space)

  • Vibration

The "Homunculus":

• This area has a "body map" (called the sensory homunculus, or "little man").

• Different body parts send signals to specific areas of the somatosensory cortex.

• Sensitive areas (like lips, hands, face) have much larger areas dedicated to them in the cortex, reflecting their higher number of nerve endings and sensitivity.

Basically: It's the part of your brain that makes sense of everything you feel on or in your body, allowing you to know what's touching you, if it's hot or cold, or where your arm is in space.

Function of pain

Pain serves as a protective mechanism to alert an organism to potential harm. For survival and to make sure you heal.

Structuralists

Psychologists who aimed to understand the structure of the mind by breaking down mental processes into their most basic components.

Who:

• Early psychologists (Wundt & Titchener).

What they wanted:

• To find the basic building blocks of your conscious experience.

How they tried:

• By asking people to look inward and describe their simplest sensations.

Big Idea:

• First group to try to study the mind scientifically.

Depth perception

The ability to perceive the world in three dimensions and judge distance.

Gestalt organization rules

Gestalt organization rules describe how our brains automatically group individual sensory pieces into meaningful patterns or complete wholes, rather than just seeing a jumble of separate parts.

figure-ground

The organization of visual field into objects that stand out from their surroundings.

Your brain's automatic way of seeing a main object (the "figure") that stands out against a less important background (the "ground").

Reading this card right now! The words are the figure, and the white space of the card is the ground. Your brain just picks them out.

This rule helps your brain quickly decide what to focus on in a busy scene. It organizes whaat you see so you don't get overwhelmed.

closure

The tendency to perceive incomplete objects as whole.

Your brain's tendency to fill in missing gaps to complete a shape or object. It prefers complete patterns.

Think:

A circle with a small chunk missing. Your brain still sees a whole circle, not just a broken curve. It "closes" the gap.

This rule helps you recognize objects quickly, even if parts are hidden or incomplete. Your brain is smart enough to finish the picture!

proximity

The grouping of objects that are physically close to each other.

Your brain's tendency to group things that are close together as belonging to the same group or unit.

Think:

If you see these dots: . . . . . . You see two groups of three dots, because they're spaced closely.

It helps your brain quickly organize cluttered information. Things that are near each other are likely related, so your brain just assumes they are.

continuity

The tendency to perceive continuous patterns rather than separate items.

Your brain's tendency to see smooth, continuous lines or patterns, rather than broken or jagged ones. It prefers natural flow.

Ex. An "X" made by two lines crossing. Your brain sees two smooth lines passing through each other, not four separate lines meeting in the middle.

This rule helps your brain understand complex shapes and movements by following the most predictable path. It helps you see objects as continuous, even if parts are hidden.