Unit 3

Chapter 1-Threshold

• Sensation, the process by which we take in information from our environment, is studied by viewing the relationship between physical stimulation and its psychological effects

  • Psychophysics, or the branch of psychology that studies the effects of physical stimuli on our sensory responses, was founded by Gustav Fechner, a physicist 

    • Fechner discovered and then coined the term absolute threshold: the smallest amount of stimulation a person can still detect

    • Anything lower than the absolute threshold is undetectable, while everything higher is still detectable

    • Subliminal Perception: anything below the absolute threshold; if presented with a picture quickly this is subliminal if we are then shown that very same picture but can view it for a more extended period of time then we will recognize it pretty well

    • We can only detect absolute threshold 50% of the time!!!

  • Signal Detection Theory (SDT): a stimulus is either present or not and a patient responds if they can detect it; it looks at our moods and possible biases that can affect the likelihood of giving a wrong response…

1. Hit: a stimulus was present and the patient detected it

2. Miss: a stimulus was present and the patient did not detect it

3. False Alarm: a stimulus was not present and the patient detected it somehow

4. Correct Rejection: a stimulus was not present and the patient did not detect anything

• Discrimination Threshold: the point at which someone can tell the difference between two stimuli

  • Ernst Weber founded Weber’s Law, “the greater the magnitude of the stimulus, the larger the difference must be to be noticed,” which led to the creation of the difference threshold

  • The Difference Threshold, or the Just Noticeable Difference (JND), is the minimum difference between two stimuli required for detection 50% of the time

  • ex:/ when lifting weights, you cannot tell the difference between 65 and 70 pounds, but you can tell the difference between a 5-pound and 10-pound - the difference is equal but the magnitude is unequal

  • ex:/ the eye doctor asks you which lens is better, 1 or 2, and he keeps narrowing the difference between the two lenses until its difficult for you to notice the difference - this is JND

Chapter 2-Reception

• All sensory organs have receptor cells, cells that are specialized to detect certain types of energy, and the area they receive the information/energy is called the receptive field

  • There are many types of energy…

1. Mechanical (for touch)

2. Electromagnetic (for vision)

3. Chemical (for taste and smell

4. Vibration Waves (for hearing)

5. Body positioning (for vestibular and kinesthetic)

• The receptor cells in their respective receptive fields convert the detection of their respective energy sources into electrochemical signals to send to the rest of the neurons

  • This process is called transduction, and these processes are sent to the brain

  • ex:/ when our receptor cells in our ear detect a change in vibration waves in their receptive field, they convert said detection into an electrochemical signal and send that signal to the brain

• To be more specific, all sensory information is sent straight to the thalamus (except for smell which is sent to the olfactory bulb)

  • The thalamus redirects the sensory input to other parts of the brain to be processed

  • The thalamus is like a filterer, it receives information and then converts it into brain-favorable signals, and an adaptive mechanism we humans have is to filter out certain signals so that we are not overwhelmed with too much information

  • Additionally, the phenomenon called contralateral shift, a process in which the sensory input from one side of the body travels to the opposite side of the brain, occurs at the thalamus level

Chapter 3-Visionary System

• Visual Sensation: the ability to see due to photoreceptors on the eye receiving light input from the environment

  • When someone sees, for example, a plant the plant represents the distal stimulus, while the photons (light particles) that stimulate the photoreceptors are the proximal stimulus

    • Retina: the receptive field of the visual system

    • Photoreceptors: receptor cells of the retina

  • The retina is covered with rods and cones - these are the two photoreceptors found in animals

    • Rods: detects black, white, and gray; located in the periphery of the retina; they are light sensitive which is why they allow us to see in the dark

    • Cones: detects color; located in the center of the retina (fovea); they work best in the daylight

  • David Hubel and Torsten Wiesel discovered that as long as impairments are corrected in the critical period, the first months after birth, then vision will develop normally

Lesson 1-Process

• The visual process is complex…

1. First light passes through the cornea, a protective layer for the visual system

2. The light then passes through the lens, whose curvature allows the individual to perceptualize the distance between them and the object- in a process called accommodation

3. The light is then transmitted to the photoreceptors of the retina, which then transduce the energy into a neural-electrochemical signal

4. After the photoreceptors in the retina receive the stimuli and convert them into a neural message, the signal travels to horizontal cells called the bipolar and amacrine cells, each of which is where low-level information processing occurs

5. The signal eventually reaches the optic nerve which sends the information to the optic chiasm

   1. Information from the left eye travels through the left optic nerve to the optic chiasm

   2. Information from the right eye goes through its respective optic nerve to the optic chiasm

   3. After reaching the optic chiasm the signals are sent in the opposite directions, left to the right hemisphere and right to the left hemisphere

6. The information then finds its way to the primary visual cortex, in the back of the occipital lobe, for processing the color, movement, depth, and form of the object visualized

Lesson 2-Processing

• Serial Processing, a process in which the brain step-by-step computes information, differs from parallel processing, a process in which the brain computes many pieces of information simultaneously

  • All things start as serial processing, however, eventually, parallel processing takes over

  • ex:/ at first we need to be methodical when riding a bike, but eventually, it becomes a “second nature”

• Feature Detectors are neurons in the brain that respond to specific features of the stimulus such as shape, angle, or movement - in all, it helps find patterns

  • This pattern starts at the back of the occipital lobe and moves forward, as it moves forward it becomes more complex and integrated, this process is called convergence

  • Convergence occurs in all senses

Lesson 3-Dorsal and Ventral Stream

• Once the information has been sensed, the information travels through one of two pathways…dorsal and ventral streams

  • Ventral Stream: processes visual information for the purpose of perception (“vision for perception”)

    • Sends information to the temporal lobe

    • Allows us to understand what something is

  • Dorsal Stream: processes visual information for the purpose of execution (“vision for action”)

    • Sends information to the parietal lobe

    • Allows us to understand where something is and then perform an action

Lesson 5-Color Blindness

• Two different theories proposed why we can see (both are believed to be true…)

  • According to the Young-Helmholtz Theory or Trichromatic Theory, the cones in the retina are activated by light waves that are associated with red, green, and blue - we see color by mixing these three colors together (like tv do)

  • Adding to the previous theory, the Opponent Process Theory believes that cells within the thalamus use three sets of opposing retinal processes — red-green, blue-yellow, and white-black — so as the impulse travels to our visual cortex, some of the neurons are turned on by red and then off by green, or on by blue and off by yellow…US-PIC

    • This is because your green receptors, in the flag example, got tired and the red ones took over because they were more active - this is called afterimage

• Most Color Blindness occurs in males meaning this is a sex-linked genetic condition and is likely found in the x-chromosomes (remember males only have one x-chromosome)

  • Dichromats: people who cannot distinguish between red/green and blue/yellow

  • Monochromats: people who only see black/white (rarer than dichromats)

Chapter 5-Auditory System

• Auditory Input: a process by which sound waves travel through the outer ear and into the ear canal where the energy is transduced into an electrochemical signal for neural understanding

  • The cochlea, literally meaning “snail shell” which is what it looks like, is the main organ involved in hearing and is the receptive field of the auditory system

    • Within the cochlea are small hair-like structures known as cilia and these cilia are the receptive cells of the auditory system

    • These cilia are aligned in a structure known as the basilar membrane

Lesson 1-Process

• The process is not as complex as the visionary process…

1. The outer ear, the part of the ear that is on the outside of our head, collects and magnifies sound waves

2. The vibrations then enter the middle ear, or the space between the outer ear and the ear drum, and then to the oval window (the membrane “wall” that encloses the cochlea)

   1. When entering the middle ear, the vibrations vibrate the tympanic membrane (more popularly known as the eardrum)

   2. The vibrating membrane leads to the “rattling” of the three ossicle bones (malleus, incus, and stapes)

   3. The last of these ossicle bones, stapes, vibrates the oval window

3. The oval window is the beginning of the inner ear - which is only made up of the cochlea - and when the oval window vibrates, it jiggles the cochlea which in turn jiggles the cilia within the cochlea on a structure called the basilar membrane

4. The sound wave energy is transduced by the cochlea into an electrochemical signal which is then sent to the auditory nerve

5. The auditory nerve sends the signal to the temporal lobe for processing

Lesson 2-Theories

• Many theories have been proposed as to how hearing occurs…

  • According to Georg von Bekesy, a traveling sound wave “energizes” the basilar membrane, as the frequency increases so do the peaks of the sound wave which increases the stimulation for hearing

  • The place theory asserts that sound waves generate activity in different “places” on the basilar membrane

  • Frequency Theory states that we sense pitch because the rate of neural impulses is equal to the frequency of a particular sound

Lesson 3-Deafness

• Deafness: any damage to the ear structure or neural pathway

1. Conducive Deafness: injury to outer or middle ear structures (ex:/ ruptured ear drum) which can be healed through the use of hearing aids

2. Sensorineural Deafness: injury to the inner ear or neural pathway; may require intense surgery to replace the entire cochlea

Chapter 6-Other Senses

Lesson 1-Olfaction

• Olfaction, or the smelling system, transduces chemical/scent molecules into an electrochemical signal for the brain

1. A scent molecule enters the nose and eventually reaches the olfactory epithelium where they react with receptor cells

2. The signal is transduced and then sent directly to the olfactory bulb

3. The signal then is sent to the olfactory cortex and the limbic system

   1. Since the amygdala and hippocampus are connected to olfactory nerves, past memories can be obtained by smelling something

Lesson 2-Gustation

• Gustation, or the tasting system, transduces chemical/taste particles into an electrochemical signal for the brain

  • Your tongue is fully encompassed by bumps which are called papillae - on each papilla is a taste bud (the receptor cells of the gustatory system)

  • There are five tastes — sweet, salty, better, sour, and umami — each of which has an evolutionary background (ex:/ sweet usually means calories so our ancestors developed a sweet taste to know if it was high in calories and bitter for seeing if something is poisonous - we naturally do not like bitter for this reason)

  • Taste buds transduce the signal and send it to the medulla, which then sends it to the pons, then the thalamus until it finally reaches the cerebral cortex as well as the limbic system (again tastes = memories)

Lesson 3-Vestibular

• The Vestibular Sense, or our sensation of balance, is also due to the cochlea

  • The sense is found in the semicircular canals of the cochlea and as you walk the fluids in these canals shake

  • This is why you get headaches when you spin your chair, the liquid in these canals shakes making your body think you moving when in reality you are not so your brain gets confused and then pissed off and decides to one-up you

Lesson 4-Somatosenation

• The skin has cutaneous and tactile receptors which provide information about pressure, pain, and temperature

  • These receptor cells transduce mechanical energy (ex:/ someone poking you) into an electrochemical signal which is sent to the thalamus and eventually the parietal lobe

  • Temperature is due to cold fibers, receptor cells that are sensitive to cold stimuli, and warm fibers, receptor cells sensitive to warm stimuli

Chapter 7-Sensory Adaptation

• Two processes are used to respond to changing stimuli…

1. Adaptation: an unconscious change in response to environmental stimuli - your sensitivity to a stimulation diminishes

   1. ex:/ you enter a dark room and your pupils dilate (expand) and if you enter a bright room your eyes constrict (narrow)

2. Habituation: the process by which we become accustomed to a stimulus and we end up noticing it less and less

   1. Dishabituation: when a small change in the stimulus, the one that the individual became accustomed to, then causes us to notice the stimulus again

      1. ex:/ a friend of yours likes to walk around the class for no reason, it's strange so your attention is captivated by it, but then it becomes old and you stop caring for it (we habituated to the occurrence) - but then that person stops walking around class one day and you notice it and then the very next day when that friend walks around class your attention is once again directed at him

      2. ex:/ air conditioner constantly makes noise in your room and you notice it for a while until you get used to it, or habituate to it - but then the sound gets louder one day and then goes back down the next day, despite the sound going back to normal you will once again notice the air conditioner every time it makes the noise until you habituate once again

   2. Habituation and dishabituation are usually not conscious processes, however, certain circumstances can make them a conscious power

      1. ex:/ One day someone makes fun of the person who was walking around the class and now you will once again notice that friend walking around the class

      2. ex:/ Mom walks into your room and asks you a question about the air conditioner noise, you will once again notice the sound

Chapter 8-Attention

• Attention: the ability to “pay attention” to a select portion of the millions of stimuli we are constantly receiving, simply put, our ability to focus

  • ex:/ when we are having a conversation with a friend in a busy park, we can close out other sound stimuli (ex:/ dog barking, people throwing frisbee…) so that we can concentrate on the sound stimuli related to the conversation

Lesson 1-Selective Attention

• Selective Attention: we choose to pay attention to one thing and ignore the other… (ex:/ ignoring people in a movie theater)

  • “Cocktail Party Phenomenon”: our ability to carry on and follow a single conversation in a room of many conversations (ex:/ having a conversation with someone in a concert)

    • Many things can unconsciously divert our attention… Someone calls our name - you were taught all your life to respond when you hear your name so your brain automatically assumes conversations involving your name as important

  • Divided Attention: our ability to “multi-task” - everyone can multi-task, however, you will learn during either of these tasks because your attention is not there 100% - additionally, as we age our ability to multitask decreases

  • Change Blindness: the gorilla in the “count the basketball throws video”

Lesson 2-Theories

• There are two main categories of theories regarding selective attention…

1. Filter Theories: a group of theories that believe all sensory stimuli must go through a filter to distinguish between important and unimportant stimuli (but where is this filter?)

   1. Donald Broadbent proposed the filter was at the receptor level, however, we believe his theory is wrong

   2. Today we believe it's a higher processing level

2. Attentional Resource Theories: believes we have a fixed amount of attention, and this resource can be divided up as is required in a given situation (we now believe that this theory is wrong)

Chapter 9-Perception

• Perception: how the mind interprets the stimuli collected by the receptor cells

  • The bottom-up processing, the process by which our receptor cells receive and then relay information to the brain, is another name for sensation — while top-down processing, the process by which our brain organizes and then interprets information, is another name for the perception

    • ex:/ you taste a steak for the first time, your taste buds (receptor cells) relay tastes stimuli to the brain for processing (bottom-up processing) — the brain then processes the information and releases dopamine to like the steak

    • Sometimes top-down processing can occur without the use of bottom-up, for example, the second time you eat a steak you will, without tasting it (or in other words, not using bottom-up) will salivate and dopamine would be released even before you taste the steak

Chapter 10-Visual Perception

• Visual Perception can be divided into monocular and binocular depth cues… (mono and bino)

  • Eleanor Gibson and Richard Walk wanted to see if depth perception was innate or learned (nature v nurture)

    • They used the visual cliff, a lab-produced technology used to test depth perception in infants (since that cannot report what they see)

    • In the end, they found that depth perception is innate (nature won)

Lesson 1-Monocular Depth Cue

• Monocular Depth Cue: anything that requires only a single eye to see, or in other words, only requires a 2D image of it

  • Relative Size: things that are farther away appear smaller to us because we cannot see a full 3D look at the object

  • Texture Gradient: if you were to photograph two people, one farther and one closer, you will see more defining features of the closest person and only a basic understanding of what the farther person looks like

  • Interposition: when a near object partially blocks the view of another object then you will think the object obstructing your view would be closer

  • Linear Perspective: you are standing on two perfectly parallel railroad tracks and you look straight to see how far these tracks go and notice that the further away from you the tracks are, the closer they get to each other - Vanishing Point is where these two tracks appear to intersect

  • Ariel Perspective: gaseous molecules distort our view and make things look farther (ex:/ fog)

  • Relative Clarity: light distorts our view and makes things look farther (ex:/ cowboy running into the sun)

  • Motion Parallax: objects closer to us appear to move faster than objects far away (ex:/ riding in a train and looking out the window - things far away move slowly)

Lesson 2-Binocular Depth Cues

• Binocular Depth Cues: anything that requires two eyes to see, or in other words, only require a 3D image of it (because each eye sees the image from a different angle)

  • Stereopsis: the ability to see the world in 3D

  • Retinal Convergence: the ability to focus both eyes inward toward each other to look at a close object

  • Binocular Disparity: the slight difference between the left and right eye

Chapter 11-Gestalt

• Gestalt Approach, meaning “pattern” or “configuration,” is an approach in psychology in that organisms perceive patterns and configurations alongside the usual individual components - As the quote goes, “the whole is more than the sum of its parts” - together, all Gestalt principles represent the Law of Pragnanz, the minimum tendency (or the tendency to see objects in their simplest form)

  • There are many types of gestalt…

1. Figure Ground: the ability to differentiate between the figure (the obvious version of a picture) and the ground (the not-so-obvious version of a photo)

   1. Children who lack this will grow up having trouble learning to read

2. Proximity: the tendency to see objects near each other as forming a group

   1. ex:/ If we saw three tracks of railroads in front of us, we will not see six different lines, rather we would see three grouped together lines

3. Similarity: the tendency to prefer grouping “like” objects together

   1. ex:/ if there were five dogs of all different breeds and five cats of different breeds, then we would group them as cats and dogs

4. Symmetry: the tendency to perceive mirror images of an object

   1. ex:/ when we look at a pizza, we will perceive it being cut in half into equal pieces

5. Continuity: the tendency to perceive things as continuous and smooth rather than discontinuous or disjointed

   1. ex:/ A movie is simply a bunch of pictures put together and flipped through at an extremely fast pace, rather than make us perceive these individual photos, our brain makes us see a continuous, cohesive unit

   2. ex:/ music notes are just single symbols strung together on a page, musicians can see this as one continuous, cohesive unit

6. Closure: the tendency to see complete photos rather than incomplete, additionally we tend to “fill in the blanks”

   1. ex:/ if you were shown an alphabet with certain letters in random places, rather than singing the alphabet in the wrong order you will end up singing it in the correct order

7. Constancy: the ability to know that a stimulus will remain the same shape, size, brightness, weight, volume…

   1. ex:/ that video Neri showed of a kid not understanding that just because a liquid is poured into a different cup, does not mean that the volume changed

   2. ex:/ someone who has never seen an airplane on the ground will have trouble perceiving the actual size of an airplane

8. Motion Detection: our ability to sense that an object is moving (either through the use of our retinas or simply moving our heads)

   1. Phi Phenomenon: an illusion in which two light bulbs are placed near each other and flash on and off seconds after each other to make the viewer believe light is moving

Chapter 12-Summary