Exam 2: Psychology 100

Sensations vs Perceptions, signal detection theory, psychophysics

Sensation

Physical process of detecting physical energy with our sense organs (eyes, ears, skin, nose, tongue)

Perceptions

Physiological process of the brains interpretations of the raw sensory information

Illusions

a distortion of the way we perceive a stimulus that is misinterpreted or misperceived by the brain

Transduction

active process of the conversion of an external stimulus like light or sound waves into an electrochemical neural signal

sensory receptors

Specialized cells designed to convert a certain kind of external stimulus into a neural signal

Sensory adaptations

 sensory neurons adjust their sensitivity based on recent stimulus history ex: perceiving smells, adjusting to light vs dark conditions, color after images, motion after effects 

Route of stimulus to sensing (5)

1. Physical stimulus (ex: sounds)

2. Transduction by receptors

3. Signal carried to the brain

4. Routed through the thalamus

5. Arrives at the appropriate location in the cortex 

After effect

opposing sensory or perceptual distortions that occur after sensory adaptation  

Crest vs trough

Crest: highest point or or peak of wave cycle 

Trough: lowest point of a wave cycle 

Amplitude

the height of the wave from its center (resting point) to peak 

Wavelength

the distance between two peaks of a wave

Perception of sound waves: What impacts wavelength and amplitude and how?

Amplitude is associated with the volume (loudness)

• The louder the noise the taller the amplitude  

Wavelength is associated with the pitch 

• The higher the pitch the larger the wavelength 

Perception of light waves: What impacts wavelength and amplitude and how?

Amplitude is associated with the brightness

• The brighter it is, the taller the amplitude 

Wavelength is associated with the color

• ROYGBIV: red has a higher wavelength lower frequency , Violet has a smaller wavelength larger frequency 

Psychophysics

The study of how our sensations (psychological events: what you experience) correspond to physical events (what an instrument measures)  in the world 

• Ex: how does weight in grams (physical event) correspond to how heavy it feels (psychological event)

Weber’s Law

The stronger the stimulus, the bigger the change needed to detect it The same added amount can be obvious or invisible. What matters is the fraction. Doubling the physical stimulus does not double what we experience, each step needs a bigger physical change then before

• Ex: dark room to 1 candle is noticed because 100% brighter vs 100 candles and add 1 more is not noticed because only 1% brighter

Two main avenues of psychophysics

1. Absolute threshold: something vs nothing 

• Ex: a faint sound in a silent room

2. Just noticeable difference (JND): something vs something 

• Two bags of oranges of slightly different weight

Absolute threshold

the faintest stimulus we can detect: the lowest level of a stimulus needed for the nervous system to detect a change 50% of the time 

*Ex: silence and then a faint beep you can hear 50% of the time*

Just noticeable difference (JND)

the smallest difference we can detect: the smallest change in the intensity of a stimulus that we can detect 50% of the time

• Ex: a beep and then a slightly louder beep you can detect 50% of the time 

Signal detection theory

How stimuli are detected under different conditions

Signal vs Noise

Signal: What you are trying to detect

Noise: similar stimuli that might compete with the signal and interfere with your ability to detect the signal 

Ex of signal and noise: 

Trying to watch a bird amongst the leaves (Bird-signal, leaves-noise)

Trying to listen to a friends story in a crowded and loud room( friends story-signal, crowded loud room-noise)

Signal to noise ratio

difficulty of detecting the signal depends on the strength of the signal in relation to the strength of the noise 

Ex: 

-Loud voice in a quiet room: high signal/low noise=easy

-Quiet voice in a loud room: low signal/high noise=hard

What are the four accuracies of detection of stimuli? What are the meanings?

Hit: True positive 

Miss: False negative

False alarm: False positive

Correct rejection: True negative

Key: 

Positive: stimuli is actually present either physically or psychologically 

Negative: stimuli is NOT actually present either physically or psychologically 

True: your assumption of the stimuli’s presence was accurate

False: your assumption of the stimulus presences was NOT accurate 

Attention

Acts as a filter that allows us to focus on some sensory information, and de emphasize other information, making it easier to detect what we’re interested in

What are two examples of attention and their results

 Dichotic listening: playing different information through each ear of headphones.Constructing the person to only listen to one ear of information. Result: Information reported only from the attended ear.

The cocktail party effect: happens when important information pops out in a conversation that you are not attending resulting in an involuntary shift of your attention

Intentional blindness

 Occurs when unattended stimuli are ignored as if they weren't there 

What is a type of intentional blindness?

Change blindness: is a version (type of) of inattention blindness that occurs when you fail to detect obvious changes in your environment.

Bottom up processing

constructing a representation from parts and basic features; a way our brains interpret sensory information directly from the environment. (beginning with raw data and construct meaning from that)

Top down processing

processing influenced by previous experience and knowledge  (start with meaning and use it to understand stimulus)

What are perceptual sets? what is an example?

Demonstration of top down processing: set of stimuli formed when our expectations influence our perceptions 

• Ex: 13 could be B or 13 but when you see A B C you are going to think it is B and when you see 12 13 14 you are going to think it is 13

Is sensations and perception top down processing or bottom up processing

Sensation: is a bottom up process

Perception: is a bottom up and top down processing

Sclera

The white of the eye

Pupil

circular dark hole where light enters

Iris

 colored portion of the eye that controls pupil size (letting in more or less light) 

Cornea

Curved, transparent layer covering the iris and pupil that lets light in and helps to focus light

Lens

Oval shaped disc that bends light and focuses the light on the retina 

What is accommodation: structure of the eye

Accomidation: changing of the lens shape to focus on near/far objects

Issues that result from the structure of the eye (2)

Myopia: nearsightedness-if your eye is too long 

Hyperopia: farsightedness-if your eye is too short 

Retina

Membrane at the back of the eye responsible for converting light into a neural signal 

Fovea

central portion of the retina that is responsible for visual activity

• has a high density of cones

• high acuity 

• 1% of retinal size

Acuity

sharpness of vision

Peripheral (Retina)

The rest of the retina has poor visual acuity and trades resolution for motion detection and low-light sensitivity

Saccades

goal is to put fovea on a new location; this is caused by small jerky movements of the eye allowing for rapid changes of focus

Optic nerve? What is the problem as a result?

Optic nerve:

bundle of axons that travels from the retina to the brain

Problem:

Blind spot: area of the retina where the optic nerve exits the eye 

What two kinds of photoreceptors does the retina contain?

rods and cones

Rods (3) (where located, color sensitivity, what does it respond under)

• Respond under low levels of light

• Not color sensitive

• More common outside of Fovea

Cones (4) (where located, color sensitivity, etc)

• Sensitive to fine detail

• Primarily located in the fovea

• Color sensitive

• Less plentiful than rods

Neural pathway of vision

The right visual field, which goes through both eyes, gets processed in the left side of the brain and the left visual field, which goes through both eyes, get processed in the right side of the brain 

Dorsal stream: Spatial processing what lobe does it go? What does it further process in terms of vision?(4)

Going to the parietal lobe

• Locations

• Movement

• Spatial transformations

• Spatial relations

Pathways of visual processing from occipital lobe

Dorsal stream and Ventral stream

Ventral stream: object processing what lobe does it go to? What does it further process in terms of vision? (4)

Going to the temporal lobes

• Color

• Texture

• Pictorial detail

• Shape size

Color perception

Color perception: When light hits an object, some is absorbed, and some is reflected

What we perceive: We receive the reflected light as color (white objects reflect all light, black objects reflect no light)

Trichromatic theory? What is its problem?

Trichromatic theory: Color vision is based on three primary colors: blue, green, and red

• We have three types of cones; one that like red, one green, and one blue 

Problem: it can not explain the existence of afterimages when you see the complementary color of the color you were staring at 

Hue? How does it respond to wavelength?

Hue: the color of light in which responds to wavelength 

• Higher wavelength: Red

• Lower wavelength: blue/violet

Opponent process theory

we perceive colors in terms of three pairs of opponent colors

• Red–green

• Blue—yellow

• Black—white

Color blindness

 Inability to see some or all colors due to the loss of one or more types of cones

Feature detector cells

specialized neurons in the brain (primarily located in the visual cortex) that respond selectively to specific, basic features of a stimulus, such as edges, lines, angles, and movement.

Depth perception problem? two main solutions?

Problem: multiple objects in the 3D world could cause the same 2D retinal image

Solutions:

1. Binocular depth cues: involves two eyes

2. Monocular Depth cues: Involves one eye

Types of Binocular depth cues (2)

1. Binocular disparity: our two eyes see slightly different images; brain can judge depth 

2. Convergence: eyes converge to see near objects: ex: moving finger to nose

Monocular depth cues (7) (Relative size, texture gradient, interposition, linear perspective, height in plane, light and shadow, motion parallax)

1. Relative size: distant objects look smaller than closer objects; closer objects look bigger than distant objects 

2. Texture Gradient: texture is more clear on closer objects

3. Interposition: closer objects appear in front of distant objects ex: things that are closer are not blocked, if you are blocked it is perceived further away 

4. Linear perspective: parallel lines converge with distance 

5. Height in plane: distant objects appear higher than closer objects ex: seeing a full body in picture would be in the back and higher up than the front people where you can only see half body 

6. Light and shadow: shadows can tell us about form; how light cast shadows on object gives us info about depth 

7. Motion parallax:  closer objects pass more quickly than distant objects (videos)

Mueller-lyer illusion

Depth illusion

is a famous optical trick that is a result of us living in rectangular world, where two identical straight lines look like they are different lengths because of the direction of the arrow ends attached to them

Ebbinghaus illusion:

Depth illusion

an optical illusion where two central circles of identical physical size appear to be different sizes because of the contrasting size of the surrounding shapes

• context clues help us obtain the relative size of objects

Perceptual consistency

We perceive objects as constant despite changes in sensations that arise from those objects

Size constancy

We perceive objects as constant despite changes in sensations that arise from those objects

Color constancy

perceive stimuli as consistent across varied conditions; lighting can make the same color look different 

Shape constancy

perceived shape is constant even though shape of the image (on retina) varies 

Gestalt principle

psychological principles explaining how the human brain creates a perception that  organizes individual visual or sensory elements into unified, meaningful wholes

Figure group separation

your visual system automatically tries to identify figures

• Figures are integrated units of perception

• Lots of cues converge to give us figure (motion, depth, patterns, even some 2D)

What are the gestalt principles (8) (Proximity, similarity, continuity, closure, symmetry, figure ground, common fate, synchrony)

1. Proximity: things that are close to another tend to be grouped together

2. Similarity: similar objects tend to be grouped together

3. Continuity: we are more likely to perceive continuous, smooth floing lines rather than jagged, broken lines 

4. Closure: things do not actually have to be enclosed; but the information present gives us enough to make an enclosed object ex: gaps on triangle still comes out as triangle) 

5. Symmetry: things that are relatively symmetric tend to be grouped together

6. Figure ground:  have clear objects and our ability to separate them from the background we tend to segment our visual world into figure and ground. Figure is the object or person that is the focus of the visual field, while the ground is the background.

7. Common fate: objects moving at the same direction and at the same speed are perceived as a group ex: geese flying in a V

8. Synchrony: stimuli that are perceived to occur at the same time are perceived as part of the same event ex: I drop my keys and a sound occurs at the instant you see them hit the floor

Auditory system

converts pressure waves into meaningful sound

Sound

vibration; mechanical energy that travels through some medium 

• Without medium there is no sound

Sound properties (4)

1. Vibrations: Sound is derived from tiny vibrations

2. Waves: Compressed & expanded air molecules create waves

3. Pitch: frequency of a sound wave 

4. Timbre: quality or complexity of sound (reason different musical instruments sound different when playing the same note)

Outer ear purpose and what it includes (3)

Purpose:  funnels sound to the ear drum

Includes: 

• Pinna: visible part of the ear 

• Ear canal: channel sound waves from the outside world into the middle ear

• Ear drum

Middle ear purpose and what it includes

Purpose: transmits sound from ear drum to inner ear

Includes:

•  Ossicles (three tiny bones): 

-malleus (hammer)

 -Incus (anvil)

-Stapes (stirrup)

Inner ear purpose and what it includes

Purpose: transduces sounds 

Includes

• Cochlea: fluid filled, snail shaped structure that contains the sensory receptor cells (hair cells)  is the basilar membrane, and the transduction is accomplished by movement of hair cells (cilia)

• vestibular sense: our body's primary sensory system for detecting movement, gravity, and spatial orientation to maintain balance.

Process of hearing (6)

1. Outer ear funnels sound toward ear drum

2. Ear drum vibrates, moving the ossicles in the middle ear

3.  Ossicles cause displacements of basilar membrane in the cochlea (inner ear)

4. Basilar membrane moves, hair cells bend

5.  Excited hair cells cause action potentials

6.  Information is sent to brain via auditory nerve

Pitch perception

Different frequencies of sound waves are associated with differences in our perception of the pitch of those sounds (ex: low frequency sounds are low pitch)

Place theory

*High frequencies* 

 specific locations on the basilar membrane match tones with specific pitches

• Base vibrates to high-frequency sounds

• End vibrates to low-frequency sounds

Frequency theory

low frequencies

neuron firing rate matches pitch

• Sound frequency corresponds to action potential frequency

Volley principle

*mid rangefrequency*

groups of neurons take turns firing in rotating shifts to match frequencies that are too fast for any single neuron

(modification of frequency theory)

Sound localization: binaural cues-what are the two types?

Binaural cues: depending on having 2 ears

Two types: 

1. Interaural level difference: sound coming from right side is more intense in right ear (because it doesn’t have to pass through your head)

2. Interaural timing difference: sound from the right side reaches the right ear first (just a little)

Conductive deafness

problem delivering sound energy to the cochlea because of the failure in vibration of eardrum or movement of ossicles

Sensorineural hearing loss

failure to transmit neural signals from the cochlea to the brain

Noise induced hearing loss

damage to hair cells due to Loud noises

Learning definition

change in an organism's behavior, thoughts, and response as a result of experience or changing conditions (relatively permanent) that can aid in survival. 

• adaptive and good (depending on context)

• Maladaptive and bad (depending on context)

What is Non associative learning? what are two examples?

Definition: A form of learning that involves responding to a single stimulus 
Two Types:

1. Habituation

2. Sensitization

Habituation

the process of responding less strongly over time to repeated stimuli; getting used ti a stimulus; usually a neutral stimulus (adaption of sensory receptors)

*Ex: background noise at a restaurant*

Sentitization

Definition: Process of responding more strongly over time to repeated stimuli; usually dangerous or irritating stimulus 

*Ex: sibling pokes you: responses start as dont—stop it right now—im gonna murder you*

Associative learning: what is it? what are the two types?

Definition: Occurs when an organism makes connections between 2 or more stimuli/events that occur together in the environment

Two types:

1. Opperant learning

2. classical condiq

Classical conditioning

Form of learning in which two stimuli are repeatedly paired neutral stimulus and stimulus that elicits an automatic response (reflex) eventually the neutral stimulus triggers the reflex on its own

Pre and Post conditioning

Pre conditioning: 

• Unconditioned stimulus (US): produces a reflexive/automatic response (Food)

• Unconditioned response (UR): that automatic response (already there not learned) (salivating) 

Post conditioning: 

• Conditioned stimulus (CS): initially neutral signal, becomes associated with UCS (bell)

• Conditioned response (CR): automatic response now triggered by CS (salivating at bell) 

Acquisition (classical conditioning component)

learning phase; when ucs is paired with CS after which CS produces or acquires CR

Extinction (classical conditioning component)

CS appears alone and the CR weakens CR is eventually eliminated (CR becomes extinct)

• Useful for getting rid of an undesired response 

• does not necessarily mean forgetting

Spontaneous recovery (classical conditioning component)

extinct CR suddenly emerges again after a delay

• Relearning happens more rapidly than initial learning

• Suggest that extinction inhibits rather than erases learned behavior

Renewal effect (classical conditioning component)

sometimes a response is  extinguished when the organism is in different contexts; however, the response may come back when the organism returns to the original setting

• Suggest that extinction inhibits rather than erases learned behavior 

Generalization (classical conditioning component)

Respond to stimuli that are similar to the conditioned stimulus so that learning is not tied to a specific stimulus (response will not be as strong) ex: dog salivating to other bell tones 

Discrimination (classical conditioning component)

Respond to a particular stimulus but not similar stimuli don't respond to stuff that is too different *prevents overgeneralization*

  *ex: dog does not salivate to the sound of a gong*

Blocking (classical conditioning component)

A prior association with a conditioned stimulus prevents learning of an association with another stimulus allowing  us to attend to the environmental stimuli in a predictive manner  (To learn through classical conditioning there must be some prediction error) 

• bell already leads to the expected outcome so there is no prediction error 

*Ex: light and bell are not going to be both the signal*

Preparedness(classical conditioning component)

Biological predisposition to learn some associations more quickly than other based on survival value associations

  *ex: phobias dark/heights/spiders*

Three examples of preparedness

1. Taste aversion conditioning

2. Fear conditioning

3. chronic drug use

Taste aversion conditioning

Rapid learning of taste aversion is important for survival and we do this by associating nausea with food to help us avoid food that has gone bad or in poisonous 

*Ex: Why do you associate the food you ate hours ago with getting ill? You are biologically redisposed to make this association*