What are the specific sensory thresholds our bodies contain? Logan D

Normal Human Absolute Thresholds The smallest amount of stimulation necessary for a stimulus to be detected Normal Human Absolute Thresholds Vision: a candle flame on a clear, dark night = 30 miles Hearing: A ticking watch in a quiet room = 20 feet Taste: Tablespoon of sugar dissolved in two gallons of water = One Smell: Perfume diffused in a small house = one drop (1 part in 500 mil) Touch: Pressure of the wing of a fly falling on a cheek from .4 inch

What is going on in your head if you are super sensitive to sound What is going on in your head if you are super sensitive to sound? Madison R

Figure 6.2 Absolute threshold Myers: Psychology, Ninth Edition Copyright © 2010 by Worth Publishers

Signal Detection Theory Sensation is a judgment the sensory system makes about incoming stimulation A combination of sensation and decision-making processes When something goes ‘bump in the night’ you must decide what it is. What you decide depends on the keenness of your hearing, what you expect to hear as well as other background noises Individual characteristics affect detection Stimulus event Neural activity This is why parents can hear a baby crying in the middle of the night but their siblings don’t hear the baby Comparison with personal standard Action (or no action)

Just Noticeable Difference The minimal amount of change in a signal that is still recognizable Example How many lights must be turned off before you notice a difference Difference threshold and JND are used interchangeably

Unnumbered Figure 6.1 The difference threshold Myers: Psychology, Ninth Edition Copyright © 2010 by Worth Publishers

Weber’s Law The JND is always large when the stimulus intensity is high, and small when the stimulus intensity is low For Example: If the TV volume is high, you have to turn it down a lot to make the difference noticeable

If a weightlifter adds 2 pounds to 10 pounds of weight, he’ll notice a difference. If he adds 2 pounds to 100 pounds, he won’t notice a difference…it would take 20 pounds to do that

Marsha was listening to her Ipod and when she turned it down turned ¼, she noticed a big difference. Later, when she was listening to it at a much louder level, she turned it down the same amount as before, but did not notice as much of a difference

For example, if you are buying a new computer that costs $1,000 and you want to add more memory that increases the price $200 (a 20% increase), you might consider this too much additional money to spend. However, if you were buying a $300,000 house, a $200 feature may seem like nothing. It might take an additional $10,000 to make you stop and think if it's too much to spend. In this example, the amount stays the same ($200), but the proportion changes and that's what makes the perceptual difference.

How do subliminal messages work? -Sarah Glenn

Subliminal Persuasion Use of weak stimulations to influence behavior Subliminal means below the level of the conscious mind. The brain perceives the information in theory, but the mind does not interpret the information for meaning. No controlled research has ever shown that subliminal messages delivered to a mass audience can influence people’s buying habits But different people have different threshold levels, it may work for some, not others

Subliminal priming can alter behavior Winkielman, Berridge, & Wilbarger (2005): Subliminal priming can alter behavior Exposed participants to subliminal images of happy or angry faces Participants then tasted a new, lemon-lime flavored drink. After reporting how thirsty they were, they were told to drink as much as they wanted. Participants exposed to happy faces consumed more than twice as much—but only if they were already thirsty Priming may act as a “trigger,” but only if there is a prior need, goal or drive.

Cautions regarding subliminal priming effects Effects of priming are short-lived The subliminal prime must still be perceived, even if perception is without awareness No proof of commercial viability

This ad ran in Time Magazine (July, 2007) Note the drink to the left. Two olives and a straw create male genital. Note the drink in the man's hand. We have a very similar use of olives and a straw. This time the straw points right to the woman's genital.

How Are the Senses Alike? How Are They Different? The senses all operate in much the same way, but each extracts different information and sends it to its own specialized processing region in the brain Each sense organ has as different design, and each sends neural messages to its own specialized region of the brain

Can the sensory threshold of an individual vary based on their environment (ie. an individual no longer noticing a sound because they are used to it)? Devan C.

The diminished responsiveness of senses to prolonged stimulation Sensory Adaptation The diminished responsiveness of senses to prolonged stimulation For Example: Getting used to cold water Skin touching the chair your are sitting in The heater blower in the room Any change in the stimulation, such as a noise getting louder, draws one’s attention Our nervous system "pays more attention" to changing stimuli than to constant stimuli.

Sensory adaptation occurs due to…. The loss of responsiveness in receptor cells after stimulation has remained unchanged for a while You feel the socks on your feet when you put them on…but not for long…

Chromatic adaptation in action Look first at the image of the airplane, and fix your gaze right on the dot. You'll notice immediately that the lighter portions on the left half of the plane have a definite bluish cast, while those on the right half of the plane have a definite yellowish cast Fix your gaze on the dot between the blue and yellow rectangles for 20 seconds. It's OK to blink normally, but keep your gaze fixed on the dot while your eyes are open. After 20 seconds, shift your gaze to the dot in the airplane image If you keep your eyes trained on the dot while examining the picture, you will notice that now the lighter portions of the plane now look the same in both halves of the picture.