Psychology

• Sensation

  • Detecting a stimulus from the environment, data  the body notices

    • Receive 

      • Specialized receptor cells receive information from stimuli in our environment 

    • Transform

      • Information is transformed into neural impulses through the process of transduction 

    • Deliver

      • Sensory neurons deliver the transformed information to the brain

• Perceptions

  • Selecting, organizing, and interpreting sensations, what the brain does with data 

• Transduction

  • Process of transforming one form of energy into another, transformation of stimulus energies into neurochemical messages 

• Thresholds

  • For transduction to occur, the sensory information must meet a certain threshold 

  • Absolute threshold

    • Minimum stimulation needed to detect a stimulus 

      • Must be detected 50% of the time 

• Difference threshold/just noticeable difference

  • The smallest difference between two stimuli in order to notice there is a difference between them 

    • Also must be detected 50% of the time 

  • Always a constant percentage, not amount 

    • It’s proportional

• Weber’s law

  • It is easier to detect a change between stimuli when they are less intense 

    • Due to proportional nature of the JND 

• Sensory adaptation

  • Diminishing sensations as a result of constant stimulation

    • Sensory receptors respond less to unchanging stimuli 

• Our senses interact with each other to accurately perceive our surroundings

  • Holistic system

• Synesthesia

  • When one system of sensation is experienced through another

• Synesthetic abilities vary by person

  • Some people have strong sensory overlap and might see colors when listening to music or other sounds or feel tastes when looking at words

Vision and Hearing

• With vision, transduction changes electromagnetic light waves into neural signals that our brain can understand 

• Cornea

  • Protects the eye ans directs light to the center of the eyeball

• Iris

  • Colored part. Is a muscle that controls the amount of light entering the eye

  • Relaxes in bright light

  • Contracts in dim light

• Lens

  • Behind the pupil. Directs light

  • Focuses visual stimuli onto the retina

• Retina

  • A photosensitive surface at the back of the eye

  • Contains photoreceptor cells that perform transduction

• Optic Nerve

  • Sends nerve impulses that eventually get to the brain

• Accommodation

  • When the eye changes its output to focus on objects at different distances

    • Alterations can result in nearsightedness(myopia) or farsightedness(hyperopia)

• Retina → Ganglion Cells → Bipolar cells → Rods and Cones 

• Rods

  • Detect shapes and movement but not color

    • Work in dim environments

    • Play a role in light/dark adaptation

• Cones

  • Process color and detail

    • Red, Green, and Blue

    • Only work in bright light 

• Fovea

  • Center of the retina

  • Cones cluster and vision is best here

• Optic nerve sends neural impulses from the eye to the brain(occipital lobe)

  • Blind spot

    • Area where the optic nerve leaves the eye. We can’t see here

• Trichromatic Theory

  • The three cone types (RGB) are sensitive to long, medium, and short wavelengths respectively

    • See specific colors by comparing responses of types of cones

    • Eye based theory

• Opponent-process theory

  • Optic nerve cells process complementary colors from the cones(brain based theory)

    • 4 Primary colors split into pairs. One color in pair is excited while the other is inhibited

    • A black-white pair detects luminance(light-dark changes)

• Afterimages

  • Visual sensations that remain after a sensation is removed

    • Staring at one color long enough will fatigue the sensors for that color

    • Result when certain ganglion cells in the retina are activated while others are not

• Color vision deficiencies usually involve problems with cones

  • Monochromatism(seeing no color) is very rare. Most color blind people have dichromatism(lack functioning in one type of cone)

• Most common form of color blindness is an inability to distinguish red and green

  • Genetic(recessive on the X chromosome)

  • Effects 8% of men and 1% of women 

• Damage to the occipital lobe can result in vision disorders such as prosopagnosia( face blindness) or varying degrees of blindness.

• Sound occurs through the movement of air molecules at different wavelengths and amplitudes

  • Audition-biological process where ears process sound waves

• Number of complete wavelengths that pass a point in a given time determine pitch

  • There are multiple theories on perceiving pitch

• The amplitude(aka height) of the wavelength determines loudness

• Place Theory

  • Higher and lower pitches excite different areas of the cochlea

  • “Hair cells” then bend differently

  • Location respond differently to different pitches 

• Volley Theory

  • Groups of neurons work together to create a more accurate perception of pitch

  • The neurons fire slightly out of phase with one another, creating a more accurate combination

• Frequency Theory

  • The brain reads pitches by monitoring the frequency of neural impulses traveling up the auditory nerve

  • As pitch rises, the entire membrane in cochlea vibrates at that frequency

• Sound Localization

  • How we identify where sounds in our environment are coming from 

    • The ear does this based on the intensity and timing of the sound

    • May involve turning head or moving

• Conductive Hearing Loss

  • Condition where there is poor transfer of sounds from the tympanic membrane to the inner ear

  • Common as people age or due to damage to bones in the ear

• Sensorineural Hearing loss

  • Caused by damage to the inner ear or auditory processing areas of the brain

  • “Hair” cells can be abnormal at birth or damaged by infection or trauma

  • “Hair” cells are also lost as people age 

Smell, Taste, Touch, and More!

• Smell

  • Olfaction

  • Begins with receptors in the mucus membrane in the upper nasal cavity

  • Only sense not routes through the thalamus

    • Nasal fibers send signals through the temporal lobe, amygdala, and hippocampus

• Taste

  • Gustation

  • Transduced by taste bud receptors called papillae

    • Signals from papilla -> thalamus -> Cerebral Cortex

  • The amount of receptors on the tongue is relates to taste sensitivity

    • Supertasters

    • Medium Tasters

    • Non-tasters

  • Sweet

    • Good source of glucose(energy)

  • Sour

    • Possibly toxic or acidic in nature 

  • Salty

    • High in sodium(needed for mental abilities)

  • Bitter

    • Potential poison(often in plants) 

  • Umami

    • High in proteins(tissue growth & repair)

  • Oleogustus 

    • “A taste for fat”; very present in rotten/ranic foods(avoid)

  • Smell + Taste= Chemical senses

    • They interact to form the perception of taste

    • Without sense of smell, taste sensations are either muted or not experienced

• Touch

  • Our sense of touch is actually a mix of four distinct skin senses(somesthetic senses)

    • Pressure

    • Warmth

    • Cold

    • Pain

  • Warm and cold receptors on the skin are responsible for understanding temperature 

• Pain

  • Processed both in the body and brain

  • Gate-Control theory

    • Pain messages from different nerve fibers pass through the same gate in the spinal cord

      • If gate is closed by one pain message, others cant pass through 

  • Cognitive factors influence perception of pain

    • Distraction is another way to regulate pain

  • Phantom Limb Sensation

    • Occurs when people who have lost limbs report sensation or pain where the limb used to be

• Body position and movement

  • Vestibular sense

    • Helps with sense of balance

    • Primarily detected by the semicircular canals(above the cochlea)

  • Kinesthesis

    • Sense of body position and movement

    • Receptors in muscles, tendons, and ligaments sense muscle force & joint position 

• While senses often work together, at other points they are in conflict

  • Mismatches between sight and vestibular and/or kinesthetic senses can lead to motion sickness