Plaud psyc chapter 3 (20 Jan)

## Keywords

`Sensory Perception` `Synesthesia` `Sense Receptors`

## Key Learnings

1. Sensation: Sensation is the activation of various sense receptors in the sense organs, which are specialized neurons that make up our senses.

2. Sense Receptors: Different sense receptors are responsible for detecting specific stimuli, such as light, sound, pressure, and chemicals.

3. Synesthesia: Synesthesia is a phenomenon where senses are interpreted as more than one sense, often resulting in associations between letters, numbers, and colors.

4. Just Noticeable Difference and Absolute Thresholds: These concepts define the limits of sensory perception, including the smallest detectable difference between stimuli and the minimum energy needed to detect a stimulus.

5. Subliminal Messaging: Subliminal messaging involves stimuli presented below the level of conscious awareness, potentially influencing behavior.

6. Habituation and Sensory Adaptation: Habituation is the brain's reduced response to constant stimuli, while sensory adaptation is the sense receptors' reduced response.

7. Sensory Adaptation in Sight: The sense of sight does not experience sensory adaptation due to micro-saccades, which are tiny vibrations of the eyes that prevent visual information from disappearing when staring at an object for too long.

8. Change Blindness: Change blindness is a phenomenon where people fail to notice changes in a visual scene because they focus on certain elements while ignoring others.

9. Structure of the Eye: The eye consists of several parts, each with a specific function in processing visual information.

10. Rods and Cones: Rods and cones are specialized sense receptors in the retina responsible for different aspects of vision.

11. Opponent Process Theory of Color Vision: This theory suggests that color vision is based on opposing pairs of colors: red-green and blue-yellow.

12. Color Blindness: Color blindness is a condition where individuals have difficulty distinguishing certain colors due to defective cones.

13. Color Vision in Animals: Discussion on how animals perceive colors differently than humans, with a focus on dogs and color blindness.

14. Sense of Hearing: Explanation of how hearing works, including the anatomy of the ear and the process of sound wave transmission.

15. Hearing Impairment and Cochlear Implants: Types of hearing impairments and the role of cochlear implants in restoring hearing.

16. Sense of Hearing: The sense of hearing involves the ability to perceive sound through the ear.

17. Sense of Taste: Taste is primarily linked to smell and involves five primary taste buds.

18. Sense of Smell: Smell involves the olfactory system and is processed differently from other senses.

19. Sense of Touch: Touch involves detecting pressure, temperature, and pain through various receptors.

20. Gate Control Theory of Pain: Pain signals pass through a 'gate' in the spinal cord that can open or close.

21. Sense of Balance: Balance is maintained by the semi-circular canals in the ear.

## Explanations

### 1. Sensation

- **Key Points**

- Sensation involves the activation of sense receptors in the brain.

- Different sense organs include eyes, ears, nose, and body.

- Sense receptors are specialized neurons in sense organs.

- **Explanation**

Sensation occurs when sense receptors in various sense organs are activated. These receptors are specialized neurons that detect specific types of energy or stimuli, such as light for vision or vibrations for hearing.

### 2. Sense Receptors

- **Key Points**

- Rods and cones in the eyes detect light.

- Hair follicles in the ears detect sound vibrations.

- Touch receptors detect pain, temperature, and pressure.

- Smell and taste receptors detect chemicals.

- **Explanation**

Each sense organ has specialized receptors that respond to specific stimuli. For example, rods and cones in the eyes detect light, while hair follicles in the ears detect sound vibrations. Touch receptors on the skin detect pain, temperature, and pressure, and smell and taste receptors detect chemicals.

### 3. Synesthesia

- **Key Points**

- Synesthesia involves interpreting senses in more than one way.

- Common forms include associating letters and numbers with colors.

- It is considered a brain disorder but not debilitating.

- **Explanation**

Synesthesia occurs when a person's senses are interpreted in more than one way, such as associating letters and numbers with specific colors. This phenomenon is considered a brain disorder but is not debilitating and can be seen as a unique ability.

- **Artist with Sound and Color Synesthesia**

> An artist with sound and color synesthesia listens to music and paints the colors she sees in her mind.

1. The artist perceives musical notes as colors.

2. She translates these perceptions into paintings, reflecting the mood of the music.

- **Friend with Number and Color Synesthesia**

> A friend associates numbers with colors and realized this when he identified a historical date by its color.

1. He associates the combination of numbers 1 and 7 with the color orange.

2. He realized his perception was different when he mentioned a date as being 'orange'.

### 4. Just Noticeable Difference and Absolute Thresholds

- **Key Points**

- Just noticeable difference is the smallest difference between two stimuli detectable 50% of the time.

- Absolute threshold is the minimum energy needed to detect a stimulus 50% of the time.

- **Explanation**

Just noticeable difference measures the smallest detectable difference between two stimuli, while absolute threshold measures the minimum energy required to detect a stimulus. These concepts help define the limits of sensory perception.

### 5. Subliminal Messaging

- **Key Points**

- Subliminal perception involves stimuli below conscious awareness.

- It is controversial whether subliminal messaging can influence behavior.

- **Explanation**

Subliminal messaging involves presenting stimuli below the level of conscious awareness, with the idea that it can influence behavior. The effectiveness of subliminal messaging is debated, with some studies suggesting it can influence behavior and others suggesting it cannot.

- **Vickery's Subliminal Advertising Claim**

> Vickery claimed that flashing 'eat popcorn' and 'drink coke' during movies increased sales, but it was later revealed to be false.

1. Vickery's claim started the idea of subliminal advertising.

2. His claim was later debunked as false.

- **Strahan's Thirst Study**

> Participants exposed to subliminal thirst-related words drank more water than those exposed to random words.

1. Participants were divided into two groups, one exposed to thirst-related words and the other to random words.

2. The group exposed to thirst-related words drank more water, suggesting subliminal influence.

### 6. Habituation and Sensory Adaptation

- **Key Points**

- Habituation is the brain's reduced attention to constant stimuli.

- Sensory adaptation is the sense receptors' reduced response to constant stimuli.

- **Explanation**

Habituation occurs when the brain stops attending to constant, unchanging stimuli, while sensory adaptation occurs when the sense receptors themselves stop responding. These processes help individuals adapt to their environment by reducing the perception of constant stimuli.

### 7. Sensory Adaptation in Sight

- **Key Points**

- Micro-saccades prevent sensory adaptation in sight.

- Eyes are constantly vibrating to keep visual information active.

- Without these vibrations, staring at an object would cause it to disappear.

- **Explanation**

Micro-saccades are tiny, involuntary eye movements that prevent the visual system from becoming desensitized to constant stimuli. This ensures that visual information remains active and prevents objects from disappearing from view when stared at for extended periods.

### 8. Change Blindness

- **Key Points**

- Change blindness occurs when changes in a visual scene are not noticed.

- Focus is typically on the main elements, ignoring background changes.

- Visual scenes with more elements are harder to detect changes in.

- **Explanation**

Change blindness demonstrates how the brain processes visual information by focusing on key elements and ignoring less important details. This is often tested by showing two images with slight differences and observing if the viewer can detect the changes.

- **Change Blindness Example with Pictures**

> Two pictures are shown with one difference between them. The task is to identify the difference without yelling it out.

1. The first picture is simple, with a change in the bottom left corner.

2. The second picture is more complex, with a change above the continue button.

3. The third picture is the hardest, with two changes involving large windows.

### 9. Structure of the Eye

- **Key Points**

- Cornea: A clear membrane covering the eye's surface, protecting it from dust and dirt.

- Iris: The colored part of the eye, a muscle that changes the pupil's size.

- Pupil: A hole through which light enters the eye.

- Lens: Focuses images onto the retina, changing shape based on distance.

- **Explanation**

The cornea protects the eye, the iris controls the amount of light entering by adjusting the pupil size, the pupil allows light to enter, and the lens focuses the image onto the retina. Vision problems often arise from issues with the lens's shape or focusing ability.

### 10. Rods and Cones

- **Key Points**

- Rods: Responsible for non-color sensitivity in low light, used for black and white vision.

- Cones: Responsible for color vision and sharpness, concentrated in the retina's center.

- **Explanation**

Rods are spread out in the retina's periphery and are not meant for visual acuity, which is why human night vision is poor. Cones are tightly packed and responsible for color and detail, allowing for sharp vision and color differentiation.

### 11. Opponent Process Theory of Color Vision

- **Key Points**

- Four primary colors are arranged in pairs: red-green and blue-yellow.

- The firing of these cones determines the perceived color.

- **Explanation**

According to the opponent process theory, the perception of color is determined by the balance of activity between opposing pairs of cones. This explains phenomena like afterimages, where prolonged exposure to one color can lead to the perception of its opposite.

- **Afterimages and Opponent Process Theory**

> Staring at a dot in the center of a colored image can lead to seeing an afterimage in complementary colors when looking at a blank screen.

1. The activity of red-green and blue-yellow cones creates the perception of complementary colors.

2. Afterimages occur when the cones become fatigued and the opposing color is perceived.

### 12. Color Blindness

- **Key Points**

- Monochromatic colorblindness: Lack of functioning cones, resulting in black and white vision.

- Dichromatic colorblindness: Two cones are defective, commonly red-green colorblindness.

- **Explanation**

Color blindness occurs when cones in the retina are defective or absent, affecting color perception. Monochromatic colorblindness is rare and results in seeing only shades of gray, while dichromatic colorblindness affects the ability to distinguish between certain colors, such as red and green.

- **Color Blindness Test**

> A test involving identifying numbers within colored circles to determine color blindness.

1. Individuals with normal vision can see the numbers clearly.

2. Those with color blindness may see different numbers or none at all.

### 13. Color Vision in Animals

- **Key Points**

- Dogs were once thought to see only in black and white, but they can see some colors.

- Dogs may not see certain shades of green but can see bright objects like tennis balls against grass.

- Color blindness is more common in men than women due to its link to the X chromosome.

- **Explanation**

The perception of color in animals varies, and while dogs can see some colors, their vision is limited compared to humans. Color blindness is linked to the X chromosome, making it more prevalent in men.

### 14. Sense of Hearing

- **Key Points**

- Sound waves travel through the air, hitting the eardrum and causing vibrations.

- The ear is divided into three sections: outer ear, middle ear, and inner ear.

- The outer ear includes the auditory canal and eardrum.

- The middle ear contains three tiny bones: hammer, anvil, and stirrup.

- The inner ear includes the cochlea and auditory nerve.

- **Explanation**

Hearing involves sound waves causing vibrations in the eardrum, which are transmitted through the middle ear bones to the inner ear. The cochlea and auditory nerve play key roles in sending sound information to the brain.

### 15. Hearing Impairment and Cochlear Implants

- **Key Points**

- Conduction hearing impairment involves structural damage to the ear.

- Nerve damage can prevent sound signals from reaching the brain.

- Cochlear implants can help restore hearing by bypassing damaged parts of the ear.

- **Explanation**

Hearing impairments can result from damage to the ear's structure or nerves. Cochlear implants provide a solution by directly stimulating the auditory nerve, allowing some hearing restoration.

- **Cochlear Implant Activation**

> A video showing an eight-month-old baby hearing his mother's voice for the first time after cochlear implant activation.

1. The cochlear implant is turned on, allowing the baby to hear.

2. The baby reacts to hearing his mother's voice, showcasing the implant's effectiveness.

### 16. Sense of Hearing

- **Key Points**

- Hearing is the perception of sound.

- Sound travels through the ear to be processed.

- **Explanation**

The example of a deaf woman receiving cochlear implants illustrates the process of hearing sound for the first time.

- **Deaf woman hearing her husband's voice for the first time**

> A woman who is deaf receives cochlear implants and hears her husband's voice for the first time in the doctor's office.

1. The doctor turns on the cochlear implants.

2. The husband speaks in a high-pitched voice, surprising the wife.

### 17. Sense of Taste

- **Key Points**

- Taste and smell are closely linked.

- Five primary taste buds: sweet, sour, salty, bitter, umami.

- Taste buds are replaced every few weeks.

- **Explanation**

Taste is perceived through specialized receptors on the tongue, and foods that stimulate multiple taste buds are generally more liked.

- **Ketchup as a universally liked food**

> Ketchup hits all five taste buds and is generally liked by most people.

1. Ketchup contains sweetness, sourness, saltiness, bitterness, and umami.

2. It has remained largely unchanged since its invention in the 1870s.

### 18. Sense of Smell

- **Key Points**

- Smell is processed by the olfactory bulbs.

- Smell involves airborne particles entering the nose.

- **Explanation**

The sense of smell bypasses the thalamus and is directly processed by the olfactory bulbs, making it unique among the senses.

### 19. Sense of Touch

- **Key Points**

- Pressure, temperature, and pain are detected by different receptors.

- Thermoreceptors detect warm and cold sensations.

- Pain can be fast or slow, with different pathways.

- **Explanation**

Touch involves multiple types of receptors that detect different stimuli, and the gate control theory explains how pain signals are managed.

### 20. Gate Control Theory of Pain

- **Key Points**

- The gate can block or allow pain signals.

- Adrenaline and other factors influence the gate's state.

- **Explanation**

The theory suggests that pain perception can be modulated by the state of the gate, which is influenced by various factors such as adrenaline.

### 21. Sense of Balance

- **Key Points**

- Semi-circular canals contain crystals and fluid.

- They help determine the position of the ground.

- **Explanation**

The semi-circular canals in the ear play a crucial role in maintaining balance by detecting changes in head position.