Ch. 4 AP Sensation pt. 1 What is sensation? The process by which our sensory receptors and nervous system receive stimulus from the environment. The absorption of energy, such as light or sound waves, by our sensory organs Eyes Ears Tongue Nose Skin Stimulus- a detectable input from the environment Light- Vision Sound- Hearing Chemicals- taste and smell Pressure, temp, and pain- touch Orientation and balance- kinesthetic

Sensing the world: Basic Principles Perception: the process of selecting and identifying information from the environment

Bottom-up processing: we start with the sensory receptors sand work up to higher levels of processing. The human fovea can only focus on a very small area at one time We fixate on one location for a moment and then move on to the next fixation. We take in little at each fixation and it’s through a pattern of saccades, a rapid movement of the eye between fixation points, that we take in our visual environment.

Top-Down Processing Top-Down Processing The top-down process is driven by prior knowledge and expectations as well as our specific goals of the moment. Suppose though, I asked you to find all the occurrences of the letter “P” in the image? Now as you scan the image the letter “P” should start to stand out a bit more and it’s possible that even the highly visible red letters start to fade into the background. At the very least you likely aren’t noticing the words they spell out. You see more of what you’re looking for and less of what you aren’t.

Sensation Processing Bottom-up Top Down Recognize stimulus Combine specific features into more complex forms Detect specific features of a stimulus Formulate perceptual hypothesis about the nature of the stimulus as a whole Select and examine features to check hypothesis Recognize Stimulus

Perception is how your brain processes the information.

Senses are nature’s gift that suit an organism’s needs. Sensing the World Senses are nature’s gift that suit an organism’s needs. A frog feeds on flying insects; a male silkworm moth is sensitive to female sex-attractant odor; and we as human beings are sensitive to sound frequencies that represent the range of human voice.

Psychophysics A study of the relationship between physical characteristics of stimuli and our psychological experience with them. Physical World Psychological World Light Brightness Sound Volume Pressure Weight Sugar Sweet

22nd October 1850 A relative increase in mental intensity, [Fechner] realized, might be measured in terms of the relative increase in physical energy required to bring it about (Wozniak, 1999). Gustav Fechner (1801-1887) Say what now??

Fechner’s Law The magnitude of a sensory experience is proportional to the number of JNDs that the stimulus is above the stimulus To put simply- he is describing Threshold- at what point will you notice a sensation?

Sensation- Thresholds Absolute Threshold minimum stimulation needed to detect a particular stimulus 50% of the time Difference Threshold minimum difference between two stimuli required for detection 50% of the time Or also called the JND just noticeable difference (JND)

Absolute Thresholds for Humans SENSE STIMULUS RECEPTORS THRESHOLD Vision Electromagnetic Energy Rods & Cones in the retina A candle flame viewed from a distance of about 30 miles on a dark night Hearing Sound Waves Hair cells of the inner ear The ticking of a watch from about 20 feet away in a quiet room Smell Chemical substances in the air Receptor cells in the nose About one drop of perfume diffused throughout a small house Taste Chemical substances in saliva Taste buds on the tongue About 1 teaspoon of sugar dissolved in 2 gallons of water Touch Pressure on the skin Nerve endings in the skin The wing of a fly falling on a cheek from a distance of about 0.4 inches

Weber’s Law The idea that, to perceive a difference between two stimuli, they must differ by a constant percentage; not a constant amount. https://www.youtube.com/watch?v=wVhiezByMSU https://www.youtube.com/watch?v=-1e0uIS5j2Q (Webers Fraction)

Subliminal Threshold Subliminal Threshold: When stimuli are below one’s absolute threshold for conscious awareness. Kurt Scholz/ Superstock

Backmasking http://jeffmilner.com/backmasking/index.html Backmasking is the process of recording hidden messages in music which can only be revealed when a song is played backward. This technique was first used by the British Broadcasting Corporation in the 1920s, in an attempt to change people's negative attitude toward radio broadcasting http://jeffmilner.com/backmasking/index.html

Selective Attention The focusing of conscious awareness on a particular stimulus.

Signal Detection Theory (SDT) Predicts how and when we detect the presence of a faint stimulus (signal) amid background noise (other stimulation). SDT assumes that there is no single absolute threshold and detection depends on: Person’s experience Expectations Motivation Level of fatigue Carol Lee/ Tony Stone Images

Transduction is the process of changing one form of energy into another that your brain can use is called Transduction. 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. http://www.youtube.com/watch?v=el0BSM0WRlU

Sensory Adaptation Diminished sensitivity as a consequence of constant stimulation. OBJECTIVE 3| Describe sensory adaptation, and explain how we benefit from being unaware of changing stimuli. Put a band aid on your arm and after awhile you don’t sense it.

Activity- Sensation Movement Detectors

Sensory Restriction: Blakemore & Cooper, 1970 Kittens raised without exposure to horizontal lines later had difficulty perceiving horizontal bars.