Sensation/Perception

Sensation

• The process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment

  • Sensory receptors- sensory nerve endings that respond to stimuli

Perception 

• The process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events

  • Essentially, sensation is how we take in information and perception is what we do with it

• Bottom-up processing- analysis that begins with the sensory receptors and works up to the brain’s integration of sensory information

  • Big to little

• Top-down processing- information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations

  • Little to big

• Selective attention- focusing of conscious awareness of a particular stimulus

  • Our consciousness only has the ability to focus on 1 thing at a time 

    • We take in about 11 million bits of information per second, we process only 40. Still, the other 10,999,960 items remain in our unconscious mind at the ready

    • Ultimately, the things we consider important will be what grabs our attention

• Inattentional Blindness- failing to see visible objects when our attention is directed elsewhere

  • We are so good at focusing on one thing that we often miss or overlook another

  • Applies to our senses- our conscious mind can only be in one place at a time

  • Change blindness- failing to notice changes in the environment; a type of inattentional blindness and selective attention

    • This process truly brings out the concept out of sight out of mind 

    • When the change is so drastic and we experience a pop out we almost always notice the difference 

    • Frozen and tangled example

• Transduction- conversion of one form of energy to another

  • In sensation, transforming of stimulus energies, such as sights, sounds, and smells, into neural impulses our brain can interpret

    • Steps of transduction

      • Receive sensory stimulation, often using specialized receptive cells

      • Transform that stimulus into neural impulses

      • Deliver the neural information to our brains

• Psychophysics- the study of relationships between physical characteristics of stimuli such as their intensity and our psychological experience of them

• Thresholds- our ability to process some stimuli is extremely sensitive, no matter how faint the stimulus is

  • Absolute thresholds- the minimum stimulation needed to detect a particular stimulus 50% of the time

    • Sometimes you will hear/see/smell/taste/feel the stimulus

      • ex) see a flame 30 miles away, hear ticking of a clock across the room, can taste a teaspoon of sugar in a gallon of water

    • While the strength of the stimulus plays into our ability to process it, our psychological state- experience, expectations, alertness- plays into our ability as well 

  • Signal detection theory- predicts how and when we detect the presence of a faint stimulus amid background stimulation

    • Assumes there is no single absolute threshold and that detection depends on our life experiences

    • Why are our responses to the same stimuli not consistent?

    • Why do different people respond to the same stimulus differently?

  • Difference thresholds- the minimum difference between 2 stimuli required for detection 50% of the time

    • Experienced as a just noticeable difference

      • Ex) sound at a lower level increased slightly will be more noticeable than sound at a higher level increased at the same rate

  • Weber’s Law- to be perceived as different, 2 stimuli must differ by a constant minimum percentage (rather than a constant amount)

    • Based on stimulus

      • Light must differ by 8%

      • Weight must differ by 2%

      • Sound must differ by .3%

    • Developed by Ernst Weber (1795-1878)

  • Sensory adaptation theory- diminished sensitivity as a consequence of constant stimulation

    • Forgetting you are holding your phone

    • Eyes constantly move so we are never truly only focusing on one thing- so we never truly experience sensory adaptation- we focus on more and more elements

    • Can't ignore new stimulation- can be distracted by new stimuli

Perceptual set- mental tendencies and assumptions that affects, top down, what we hear, taste, feel, and see

• Background info influences what we perceive thru schemas - how we organize and interpret info 

• Context- the power of content is extremely significant. When were driving pedestrians are always in the way but when were walking drives are the worst

  • Culture has a huge impact on how we view things and do things

• Motivation- Motives often give us energy and drive which can give us biases in piercing certain situations 

  • Desirable objects and our performance can influence us 

• Emotion- Hearing happy/sad music can impact how we hear world like morning or die

  • Ultimately, we just don't see what's there - our experience, assumptions, and expecting shape our views of reality 

Vision

• How do we see?

  • What we perceive to be different colors are in fact slivers of light that travel toward our eye

    • Our eyes transduce the light into a neural impulse which is transported to our brain to create the image that we see

  • Since light travels in waves, the shape of the wave determines what we see

    • Wavelength- distance between one wave peak to the next

      • Long- red

      • Short- blue/purple

    • Hue- the color we experience based on the wavelength

    • Intensity- the amount of energy in a light wave, giving us bright or dull colors

      • Amplitude- the wave’s height, which determine the intensity

        • Tall- bright

        • Short- dull

  • The Eyes

    • Cornea- the clear, outermost layer of the eye that protects the pupil and iris

    • Iris- provide eye color; a muscle that controls the size of our pupil

    • Pupil- the opening in the center of eye that allows light to pass through; adjustable depending on the intensity of light

    • Lens- transparent structure behind the pupil that changes shape (focuses) so that the light rays can become an image

      • Accommodations- how our lens change shape for us to focus on near or far objects

    • Retina- the inner surface of the eye that begins the processing of visual information

      • We don't perceive an image as a whole, but rather the light particles we receive are converted into neural impulses which travel to out brain, where the complete image is created

      • Contains 130 million nerve receptors that convert the light into neural impulses

        • Rods- detect black, white, and gray and necessary for peripheral and twilight vision; sensitive to movement

        • Cones- detect fine detail and provide us with color sensations; near the center of the retina and function in daylight or well-lit conditions

          • Macula- the focus point of the retina; contains the fovea

            • High concentration of cones clustered together

    • Optic nerve- bundle of neurons that carries the neural impulses from the eye to the brain

      • Over 1 million messages or 1 million images can be sent at once

      • Blind spot- point where the optic nerve leaves the eye- no receptor cells as it leaves the brain

    • Color Processing

      • Ultimately, the word is only made up of color because of mind creates that color for us

      • We perceive a tree as being green because at that moment the tree is reflecting light waves of medium length to us

        • RECAP- our eye and brain perceives those light waves as the color and the object 

      • Hermann von Helmholtz and Thomas Young (19th Century) developed the idea that any color can be created by combining the light waves of three primary colors- GREEN, red, and blue- Young-Helmholtz Trichromatic Theory 

        • The retina contains 3 different types of color receptors (one for each red blue green) when stimulated together create nay color

          • While we cant perceive yellow naturally, a combination of primary “red cones” and “green cones” gives us yellow

        • Most people have the ability to perceive more than 1 million colors

        • 2% of people, 1/50 are considered colorblind- they posses color-deficient vision

          • For a person who is colorblind, there vision is normal to them

      • Opponent-Process Theory- opposing retinal processes (red-green, blue-yellow, white-black) enable our color vision

        • Impulses travel to our brain with some neurons in our retina and thalamus being turned on by red and turned off by green  and the opposite. Red and green messages cannot travel at once, so we don’t see a mix

          • Red and blue can so we see a mixed magenta   

            • Opposite american flag example

      • Today, we believe that color is processed in two stages that is essentially a combination of the 2 theories. 

  • Feature detection- states that our visual processing deconstructs an image and puts it back together in our occipital lobe 

    • Feature detectors- nerve cells that respond to a scene’s edges, lines, angles, and movements

      • Certain detectors will send certain parts of the image to our brain where it becomes whole

    • Our temporal lobe works with our occipital lobe in order for us to recognize faces, including from multiple angles

  • Parallel processing- concept of processing many aspects of a problem at once; the brain’s natural mode of information processing for many functions, including vision

    • As we’re analyzing a visual scene, our brain divides- motion, form, depth, color- and works on each area at the same time

    • Our ultimate perception is created through integrating (binding) the work of each together 

  • Perceptual organization

    • Gestalt- an organized whole; branch of psychology looking at our tendency to integrate pieces of information into a meaningful whole

      • We view our perception as being an example of an integrated whole - even if the whole isn’t actually there

        • Trying to make sense of what we’re seeing

    • Figure-ground perception- the organization of the visual field into objects (figures) that stand out from their surroundings (ground)

      • This is out first perceptual task - to establish what the image is and what the background is

      • Regardless of what we see, we follow this organizational technique on all that we perceive

        • White faces, black candlestick example

    • Grouping- the perceptual tendency to organize stimuli into coherent groups

      • Proximity- we will group nearby objects together (see the whole rather than the parts; can lead to false conclusions)

      • Continuity- we perceive smooth continuous patterns rather than discontinuous ones (we like these better than discontinuity)

      • Closure- we fill in gaps to create a complete, whole object (even if they really aren’t whole)

    • Depth perception- the ability to see objects in three dimensions although the images that strike the retina are two-dimensional; allows us to judge distance

      • The concept of depth perception is innate- we’re born with it- yet it takes time to develop

      • Sitting, cruising, crawling, walking

    • Binocular cues- depth cue, such as retinal disparity, that depends on the use of 2 eyes

      • Retinal disparity- by comparing retinal images from the 2 eyes, the brain computes distance- the greater the difference between the 2 images, the closer the object. 

    • Monocular cues- depth cue that can be perceived with one eye

      • Relative height- perceive objects higher in our field of view as being further away

      • Relative size- objects are similar in size, the one that creates a smaller image is further away

      • Relative motion- as we move, stationary objects also appear to move- fixation point (ahead moves with us, behind will move backwards- driving)

      • Interposition- one object blocks part of another object, we perceive the first object as closer, the one blocking

      • Linear perspective- parallel lines almost appear to meet in the distance 

      • Light and shadow- shading creates a sense of depth with the assumption that light comes from above

Hearing

• Audition- the sense of act of hearing

• Variations in sound are more easily distinguished 

  • We can pick out the voice of a friend from hundreds of others even when we can’t see them

• We have the ability to process sounds at least 10 times faster than we can process something we see

• Sound travels in a similar way to light- waves of energy that disrupt air pressure and travel towards our ear

  • Amplitude- height of the sound wave determines the perceived loudness

    • Tall waves- loud

    • Short waves- quiet

    • Heard in decibels- 0 decibels is the absolute threshold of hearing

    • Increase of 10 decibels= increase of tenfold the amplitude

      • 60 decibels= normal conversation

      • 20 decibels= whisper (10,000 louder)

  • Frequency- the length of a sound wave that determines the pitch that is perceived 

    • A tone’s experienced highness or lowness

      • Long waves- low pitch

      • Short waves- high pitch

• Parts of the ear

  • Outer ear- the part of the ear that we mostly see- STEP ONE

    • Sound waves travel into our outer ear and down our auditory canal as the first step of audition

    • The sound strikes our eardrum- tympanic membrane- which causes vibrations to travel further 

    •  

  • Middle ear- three small bones pick up the vibrations from the tympanic membrane and transmit to inner ear- STEP TWO

    • Malleus- hammer

    • Incus- anvil

    • Stapes- stirrup

  • Inner ear- vibrations travel through the oval window to the cochlea- STEP THREE

    • Cochlea- coiled, bony, fluid-filled tube in the inner ear; sound waves travel through the cochlear fluid to trigger neural impulses

      • The sound makes little hairs in the cochlea move, which triggers nerve cells that create our auditory nerve

      • Our auditory nerve carries the message to our brain (thalamus), which in turn transport the sound waves to the auditory cortex in the temporal lobe- makes sense of the sound waves

• Deafness

  • Sensorineural hearing loss- damage to the cochlea’s hair cell receptors or the adjacent auditory nerve; can happen naturally as a part of aging

  • Conduction hearing loss- less common; caused by damage to mechanical system that conducts the sound waves to the cochlea (outer and middle ear)

  • Cochlear implant- device for converting sounds into electrical signals that stimulate the auditory nerve

• Pitch Theories

  • Current studies on how we determine if something is a high or low frequency gives us a combination of two theories to explain the phenomena 

    • Place Theory- links the pitch we hear with the place where the cochlea’s membrane is stimulated

      • Different sound waves trigger activity at different places inside the cochlea, giving us pitch from the location of that trigger or simulation

    • Frequency Theory- the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling s o sense its pitch

      • The frequency and the neural impulses travel at the same rate (100 waves per second, 100 pulses per second)

Taste

• Gustation- our sense of taste

  • Each of our tastes is considered to be a chemical process

    • Each of the little bumps on our tongue contain approximately 200 taste buds (pores that catch food chemicals), with each containing 50-100 taste receptor cells

      • These receptor cells transport their message to our temporal lobe

      • Certain taste buds on certain parts of the tongue allow for certain tastes to be tasted or determined by the taste receptors and our temporal lobe

  • Taste goes beyond pleasure- they have a primal survival function for us

    • Sweet in the front

      • Energy source

    • Sour on the sides

      • Potentially toxic acid

    • Salty- lower front

      • Sodium essential to physiological processes

    • Bitter- back 

      • Potential poisons

    • Unami- middle

      • Proteins to grow and repair tissues

  • Taste receptors can pick up the faintest of tastes and changes in taste

  • Overtime,  the number of taste buds we have decreases and do not reproduce over time

    • Causes people to lose their taste for food and leads to difficulties eating

    • Our expectations influence the tastes we perceive

      • cost/expense of an item gives us the impression it tastes “better”

      • Vegetarian items vs. meat items

        • What is appealing depends on different people

Smell

• Olfaction- our sense of smell

  • With each breath we take, we breathe in scent-laden molecules into our nose

  • As a chemical sense, smell comes to use through tiny molecules that are collected by receptors cells at the top of our nasal cavities- 20 million olfactory receptors selectively alert our brain of the smells we’re bringing in 

  • Each smell that we take in does not have its own unique receptor type- they come to us through a combination of receptors working together

    • Gives us approximately 1 trillion different odors

  • Our brains tells our nose what we like and don’t like

    • Our own experiences also shape how we respond to smell

  • Our sense of smell is extremely important- but it is not as strong as our other senses

    • Vision and sound are both stronger and allow us to take in scenes more readily. BUT- the smell of something like a flower is extremely powerful for us when we do experience it

  • As we recall odors, we don't necessarily know how to name them or identify them, however, we can easily recall a smell from our past memories 

    • Smells have the ability to trigger emotions and memories for us

    • As smells trigger emotions, we will experience emotions previously associated with one experience during a totally unconnected experience

Touch

• Our body is covered with the touch receptors that allows us to feel pressure, temperature, and pain

  • The variety of sensational feeling across the body comes to us through these different receptor cells working together

    • ex) touching cold, dry metal can give us the feeling of touching something wet 

• Our sense of touch is a tactile sense that greatly aids our social development

• From a young age, we look at touch as reinforcement of attachment to people, particularly our parents

  • It is driven by our desire for love and belonging, and connectedness with other people

  • This idea does not change as we get older and becomes more tied to our own motivation and emotions

• Pain- our body’s alarm system that lets us know when something is right and increases out self-awareness in the world around us

  • Experienced through the perception of a stimulus-response connection in our skin, muscles, bones, and organs

    • Gate-Control Theory- our spinal cord contains a neurological “gate” that blocks pain signals or allows them to pass on to the brian 

  • Not just a physical sensation- there is a psychological element as well

    • People who are missing a limb/body part can experience what is known as phantom limb syndrome- the feeling of pain or movement in a nonexistent limb

  • Duration of pain is also a factor; we’ll ignore how long we are in pain for in favor of level of pain at its peak an at the end of a situation- and that's what we'll remember 

  • To combat pain, our body will release our own natural painkillers known as endorphins

    • Can be released after the pain-causing stimulus is experienced, as well as after physical activity

  • Distraction from the pain can also alter the sensation we experience

    • If we don’t focus on the pain, we are less likely to feel the pain