UNIT 4:

We do not actually experience the world directly, but instead we experience it through a series of “filters” we call senses The study of these senses and their effect on our behavior is called sensory psychology

13 How do we construct our representations of the external world? To represent the world, we must detect physical energy (a stimulus) from the environment and convert it into neural signals. This is a process called SENSATION. When we select, organize, and interpret our sensations, the process is called PERCEPTION.

Sensation- The process by which our sensory systems (eyes, ears, and other sensory organs) and nervous system receive stimuli from the environment a person’s awareness of the world Your nervous system sorts through all of this incoming information by means of BOTTOM-UP PROCESSING.

What is sensation? A person’s awareness of the world

Perception-The process of organizing and interpreting sensory information enabling us to recognize meaningful objects and events The analysis that takes place during TOP-DOWN PROCESSING is part of perception, which is our interpretation of the incoming sensory information

What is perception? The process of organizing and interpreting sensory information

18

Perceptual Expectancy - how we perceive the world is a function of our past experiences, culture, and biological makeup For example, as an American, when I look at a highway, I expect to see cars, trucks, etc, NOT airplanes. But someone from a different country with different experiences and history may not have any idea what to expect and thus be surprised when they see cars go driving by Another example - you may look at a painting and not really understand the message the artist is trying to convey. But, if someone tells you about it, you might begin to see things in the painting that you were unable to see before

You will notice that all of our sense organs are very much alike –They all transform physical stimulation (such as light waves or sound waves) into the neural impulses that give us sensations (such as light and dark)

Sensation allows you to know that an object is a red sphere, that it has a cool, hard surface, and that it fits comfortably in your hand The object has a pleasant aroma when you smell it, and a satisfying crunch when you bite into it. When chewed, it produces a taste both sweet and tart. Analysis of this bottom-up stream of data leads to the perception that you’re eating

Bottom-up process- analysis that begins with sensory receptors initiated by stimulus input and works up to the brain’s integration of sensory information Processing that focuses on the raw material entering through our eyes, ears, and other sensations Perception involves knowing what to make of the individual marks in the sentence, a top-down processing interpretation which relies on your experiences and expectations of language

23 Example: Bottom-up Processing Analysis of the stimulus begins with the sense receptors and works up to the level of the brain and mind Letter “A” is really a black blotch broken down into features by the brain that we perceive as an “A.”

Perception is also influenced by top-down processing, which draws on our experiences and expectations to interpret incoming sensations Top-Down Processing-Information processing that focuses on expectations and experiences in interpreting incoming sensory information

25 Example: Top-Down Processing Information processing guided by higher-level mental processes as we construct perceptions, drawing on our experience and expectations THE CHT

Both use previous expectations to make judgements about the world around us Although sterotyping can be negative, it can also be very efficient for people as they interact with certain stimuli Without top-down processing, we would have to interpret the world as if it were constantly new

What errors do you see in this writing?

28 Aoccdrnig to a rscheearch at Cmabrigde Uinervtisy, it deosn’t mttaer in waht oredr the ltteers in a wrod are, the olny iprmoetnt tihng is taht the frist and lsat ltteer be at the rghit pclae. The rset can be a total mses and you can sitll raed it wouthit a porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe. Amzanig huh?

What is top-down processing? Information processing that focuses on expectations and experiences in interpreting incoming sensory information What is bottom-up processing? Information processing that focuses on the raw material entering through the eyes, ears, and other organs of sensation

31 1.What stimuli cross our threshold for conscious awareness? 2.Could we be influenced by stimuli too weak (subliminal) to be perceived? 3.Why are we unaware of unchanging stimuli, like a band-aid on our skin?

Threshold- the point at which sensory information is strong enough to be noticed Absolute threshold- Minimum stimulation needed to detect a particular stimulus 50% of the time  Example: the dimmest visible star in the sky would be right at the absolute threshold for vision  Example: the least amount of basil you can taste in spaghetti sauce would be the absolute threshold for taste Difference threshold-Also called the just noticeable difference (JND): the size of a difference in a stimulus property needed to notice that a change has occurred 50% of the time  Example: how much does the volume have to increase before you can tell that your stereo has gotten louder?  Example: how much do the laces in your hiking boots need to be loosened so they feel slightly less tight?

34 No Intensity Absolute Threshold Detected Yes No Observer’s Response Tell when you (the observer) detect the light.

35 Difference Threshold: Minimum difference between two stimuli required for detection 50% of the time, also called just noticeable difference (JND). Difference Threshold Tell when you (observer) detect a difference in the light. No Observer’s Response NoYes

What are examples for absolute and difference thresholds? Absolute threshold: many classrooms have automatic light sensors. When people have not been in a room for a while, the lights go out. However, once someone walks into the room, the lights go back on. For this to happen, the sensor has a threshold for motion that must be crossed before it turns the lights back on. So, dust floating in the room should not make the lights go on, but a person walking in should. Difference threshold: when you pick up a 5 lb weight, and then a 10 pound weight, you can feel a big difference between the two. However, when you pick up 100 lbs, and then 105 lbs, it is much more difficult to feel the difference.

38 Two stimuli must differ by a constant minimum percentage (rather than a constant amount), to be perceived as different Works well for non-extreme sensory stimuli Example: If a $1 chocolate bar goes up 10 cents, shoppers might notice the change, and if a $40,000 Mercedes went up $4,000 it may be noticeable to potential buyers In both cases, the price went up by 10% StimulusConstant (k) Light8% Weight2% Tone3%

What would a day be like if you could feel the different items you wear on a daily basis as you were wearing them-watch, glasses, underwear, socks, and so forth Do you feel your socks gripping your ankles? Do you feel your watch squeezing your wrist?

Our adaptive nature means we are programmed to filter out the non-changing aspects of our environments, a process called sensory adaptation When stimulation is constant and unchanging, you eventually fail to respond because you usually don’t need to Example: when you get into a swimming pool filled with cold water, the water seems frigid at first, but once you are in it for awhile you’ll “get used to it” Sensory Adaptation- Diminished sensitivity as a result of constant stimulation If a stimulus is constant and unchanging, eventually a person may fail to respond to it Do you feel your underwear all day?

42 If we stare at an object without flinching, why doesn’t it vanish from our sight? Because our eyes are always moving and receptors continually change. A)A projector mounted on a contact lens makes the projected image move with the eye. B)Initially the person sees a stabilized image, but soon she sees fragments fading and reappearing

What is an example of sensory adaptation? Jumping into a cold swimming pool