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

4 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

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

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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

12 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.”

Backmasking Is Backmasking top-down or bottom-up? Judas Priest (heavy metal rock band) Accused of encouraging suicidal behavior or subvert morality of teens Queen; Another One Bites the Dust 8:57- 11:15http://

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

15 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

18 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

21 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?

23 A study of the relationship between physical characteristics of stimuli and our psychological experience with them Physical World Psychological World LightBrightness SoundVolume PressureWeight SugarSweet

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?

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

26 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

Subliminal Thresholds  Subliminal Threshold: When stimuli are below one’s absolute threshold for conscious awareness Based on studies, some people do respond to stimuli below the absolute threshold, under some circumstances –The problem is people have different thresholds at different levels, so what could be subliminal (or below the threshold) for one person, may be supraliminal (above the threshold) for another person LowAbsolute threshold Medium Intensity of stimulus Percentage of correct detections Subliminal stimuli

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What is a subliminal message? Below “absolute threshold” Smallest amount of a stimulus that a person can detect Sight: A candle flame at 30 miles away Sound: A watch ticking 20 feet away

Subliminal messages Sights & sounds presented so briefly or faintly that we fail to perceive them. But can these feeble stimuli influence our behavior?

Some hope you’ll think so! Self-help: “Relax to the Max” Advertising: Corporate logos Widespread belief that these messages work!

View popularized in 1950’s James Vicary Subliminal advertising “Drink Coca-Cola,” “Hungry? Eat Popcorn” flashed 1/3,000 of a second Reported that sales increased 1962, Vicary admitted he lied

Canadian Broadcasting System Nationwide test Viewers informed Subliminally flashed “phone now” (352 times during program) Phone usage did NOT increase A few called in to say they felt hungrier and thirstier!! A few called in to say they felt hungrier and thirstier!! Still NO evidence!

Signal Detection Theory- describes and predicts how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise) SDT assumes that there is no single absolute threshold and detection depends on: Person’s experience Expectations Motivation Level of fatigue exhausted parents of a newborn will notice the faintest whimper from the cradle while failing to notice louder, unimportant sounds people’s ability to catch a faint signal diminishes after about 30 minutes

Signal- target stimulation Noise- meaningless sensations Sensitivity-ability to detect a stimulus Response criterion: a person’s willingness or reluctance (bias) to respond to a signal (reflects both motivations and expectations)

At a party, you order a pizza...you need to pay attention so that you will be able to detect the appropriate signal (doorbell), especially since there is a lot of noise at the party. But when you first order the pizza, you know it won't be there in 2 minutes, so you don't really pay attention for the doorbell. As the time for the pizza to arrive approaches, however, your criterion changes...you become more focused on the doorbell and less on extraneous noise.

42 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?

46 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