Sensation & Perception Day 1

Scientific Names for the Seven Senses (You Should Know These) Seeing: Hearing: Tasting: Smelling: Sense of Touch: Balance: Body Sense

Transduction Transforming signals into neural impulses. Information goes from the senses to the thalamus, then to the various areas in the brain. Remember Ethan in Sky High. He changes his body to slime. Solid form to liquid form. Change from one form of energy to another. Click the picture to watch power placement.

Sensation Information coming into our brain from our sensory receivers Perception The way the brain organizes and interprets the data received by our senses Prosopagnosia Complete sensation in the absence of perception Can you have sensation without perception?

Selective Attention: the idea that we are only aware of a small percentage of what we experience Ex. “Cocktail party effect” x

Selective Attention Inattentional Blindness Failing to see something because our attention is elsewhere Change Blindness Failing to notice changes in the environment

Bottom-up Processing We use the features of an object to build a perception. i.e. first impressions Letter “A” is really a black blotch broken down into features by the brain that we perceive as an “A.”

Top-Down Processing Our experiences and expectations guide our perceptions THE CHT

Psychophysics Psychophysics: study of the relationship between physical characteristics of stimuli and our psychological experience of them –Light - brightness –Sound - volume –Pressure - weight –Taste - sweetness

Thresholds Absolute Threshold Minimum stimulation needed to detect a particular stimulus 50% of the time. Subliminal Messages Messages presented below absolute thresholds – not consciously perceived

“Subliminal Messages” Some have argued that humans still “pick up” these messages that influence our “unconscious.” Do these messages have suggestive powers? Skeptics argue “Subliminal Messages” are heavily influenced by top down processes. Example: Feeling “hungry” during subliminal advertisements.

“Subliminal Messages” What does the research say?

Difference Threshold Smallest amount of change needed to a stimulus for us to notice the change Weber’s Law : Measurement for difference threshold; the greater/stronger the original stimulus, the greater it will need to change for us to notice the difference (always differs by a constant percentage) JND = just noticeable difference

Weber’s Law of Sensation You see two stars in the sky. Which one is brighter? How much brightness does one star have to be compared to the other so that you will notice a difference in brightness? It turns out that you will notice a difference in brightness if the star is about 2.5 times brighter than the other star. Another example. You hear two noises. Which one is louder? If one is just a little bit louder can you tell the difference? Most people cannot. When there is a very small difference in sound, one cannot tell which sound is louder. Our decibel scale is constructed so that we can use a decibel to indicate the amount of noise we can differentiate in loudness. Let us take holding an object. How heavy is that object? Let's say you are holding a 15 lb bowling ball. If I placed a piece of paper on that bowling ball, would you be able to tell the difference in weight? Most likely if you were not looking at the situation, you would not be able to tell the difference. I would need to add something heavier relative to the bowling ball so that you can feel the difference. How much difference in something that you are observing will allow you to be able to tell that something is different. Related to term JND (Just Noticeable Difference)

Sensation: Thresholds Signal Detection Theory: What we notice is dependent upon what we expect, what we are doing, how tired we are, etc. Assumes that there is no single absolute threshold because the idea of a threshold ignores the decision- making ability of the test subject. i.e. A new mother may be able to sleep through loud traffic, but will wake up to the slightest whimper by the baby

Signal Detection Theory There are four possible stimulus/response 1.Hit: Stimulus is presented and observer responds “Yes” 2.Miss: Stimulus is presented and observer responds “No” 3.False alarm: Stimulus is not presented and observer responds “Yes” 4.Correct rejection: Stimulus is not presented and observer responds “No”

Sensory Adaptation Diminished sensitivity as a consequence of constant stimulation. Put a band aid on your arm and after awhile you don’t sense it.

Now you see, now you don’t

Energy v. Chemical senses Energy SensesChemical Senses

The EYE vision

David HUBEL & Torsten WIESEL Discovered that most cells in the visual cortex only respond to particular features. For example, maybe a cell responds only to lines at this \ angle. key name Wiesel was awarded the 1981 Nobel prize in Medicine and Physiology. His Nobel Lecture was entitled 'The postnatal development of the visual cortex and influence of environment.’ Wiesel recognized that covering one eye of a young animal could cause that eye to lose its connection to the visual cortex.

Feature Detection Nerve cells in the visual cortex respond to specific features, such as edges, angles, and movement. Ross Kinnaird/ Allsport/ Getty Images

Visual Processing

Photoreceptors E.R. Lewis, Y.Y. Zeevi, F.S Werblin, 1969 Let’s do a little experiment to “map” our rods & cones Blind spot – There are no photoreceptors at the spot where the optic nerve leaves the retina

Most Common Errors In Vision Acuity: the sharpness of vision NearsightednessFarsightedness Astigmatism

COLOR vision

Phase One: Gathering Light The height of a wave gives us it’s intensity (brightness). The length of the wave gives us it’s hue (color). ROY G BIV The longer the wave the more red. The shorter the wavelength the more violet.

Young & Helmholtz Trichromatic Theory Three types of cones: Red Blue Green These three types of cones can make millions of combinations of colors. Does not explain afterimages

Typical cases of Color Blindness support the Trichromatic theory.

Opponent-Process theory The sensory receptors come in pairs. Red/Green Yellow/Blue Black/White If one color is stimulated, the other is inhibited.

Trichromatic and Opponent Process Theories Both are considered accurate Explains vision at a different level of processing. Tri in the cones in the retina Opponent-Process in the ganglion cells, thalamus, and visual cortex