Chapter3 Gen
- 1. Sensation & Perception Chapter 3
- 2. Sensation & Perception Sensation Stimulation of the senses How input is registered by our senses Perception How we organize & interpret sensations An active, not passive process Enables us to understand & make sense of the sensations we continually experience Perception & sensation are dual processes; you need both!
- 3. Sequence of events that produce a sensation: 6. You respond! 5. Signal reaches the brain. 4. As a signal passes along sensory nerves to CNS, it is further coded. 3. Receptor sends out a coded electrochemical signal. 2. Stimulates a receptor cell in a sense organ (energy must be sufficient enough for receptor to respond). 1. Need a form of energy, either external or internal.
- 4. Sensation Sensory receptors: Highly specialized cells Located in eyes, ears, nose, tongue, skin, & elsewhere Accomplishes coded task The Brain “Creates” Sensory Experiences: The brain is isolated within the skull, listening to the “clicking” of coded neural signals coming over millions of nerve fibers. The “clicks” of an optical nerve are not any more visual than the “clicks” of an auditory nerve, but the brain interprets the “clicks” on an optic nerve as visual nerve energy & they give rise to visual experience instead of sounds, tastes, or smells.
- 5. Sensation: The Process Transduction Process by which physical properties of stimuli are converted into neural signals & then transmitted to brain Sensory deprivation When deprived of sensations, we create it by means of hallucinations What is the least amount of sensation we can detect? TASTE SMELL TOUCH AUDITORY VISUAL What stimuli we can detect seems to be designed to maximize our survival.
- 6. Thresholds Difference Threshold `You have heard a sound. How much stronger does the sound have to be before you notice that it has become louder?` Aka: “just noticeable difference” Will vary from person to person The stronger the stimulation, the bigger the difference must be in order for you to detect it Some sense are more sensitive than others to change Stimuli below threshold Subliminal perception Q: Can we sense or be affected by subthreshold stimuli that remain outside our conscious awareness? Sensory Adaptation Our sensitivity to an unchanging stimulus tends to decrease over time Practical advantages Disadvantages
- 7. Vision The Eye: Light enters the eye through the cornea Light passes through the pupil Light passes through the lens Light leaving the lens is projected on the retina , in the back of the eyeball 2 Types of light-sensitive receptors: 1. Cones (named for their shape) Located in the center of the retina Responds to light & dark & colors Operates chiefly in daylight Connected to bipolar neurons 2. Rods (named for their shape) Responds to only varying degrees of light & dark, not colors Chiefly responsible for “night vision” Connected to bipolar neurons
- 8. Vision Bipolar neurons Neurons with only one axon & one dendrite Carry info to ganglion cells optic nerve brain Light Electromagnetic spectrum Wavelength determines what we experience as color As wavelength increases from small to large our sensations shift from violet-blue (short) to orange (med.) to red (long) Brightness Functions of the Visual System: Acuity 2 Types: Static visual acuity Dynamic visual acuity Abnormalities Nearsightedness farsightedness
- 9. Vision Dark adaptation Rods & cones become more sensitive to light in response to lowered levels of illumination Light adaptation Reverse process Eye Movements Version Movements Involuntary Saccadic pursuit Eye Movements Vergence Movements Color Vision 2 Theories: Trichromatic Theory Helmholtz suggested certain cones were sensitive to green, while others were sensitive to red, or blue & by mixing the three you could experience all hues Opponent Processing Theory Hering proposed the existence of 3 pairs of color recptors
- 10. Processing Visual Information Research: feature detectors 3 Types: Simple cells Complex cells Hypercomplex Cells Do we process visual information hierarchically?
- 11. Hearing Q: If a tree falls in the woods and there is no one there to hear it, does it make a sound? (How would psychologists answer this question) A: The Ear Pinna Middle Ear Malleus Incus stapes Oval Window Cochlea Basilar Membrane Receptor Cells Thousands of tiny hair cells Fibers are pushed & pulled by vibrations of basilar membrane
- 12. Sound Properties of Sound: Sound waves Amplitude Frequency Timbre Pitch Perception (2 Views) Place Theory -sound is detected by different places that are vibrating on the basilar membrane Frequency Theory - sounds of different pitch cause different rates of neural firing
- 13. Touch Skin – largest sensory organ Skin Senses Different receptors for different sense? Pain Some have a high tolerance for pain Beliefs about pain can affect our perception of it Research has found that pain is not related to level of tissue damage 2 Types of pain Quick & sharp Dull & throbbing Pain Perception Gate-Control Theory: a “neurological gate” in the spinal cord controls transmission of pain impulses to the brain Current emotional state affects pain perception
- 14. Smell Sense of smell is @ 10,000 x’s more sensitive than taste Appears to decrease with age How we smell: Substance enters nasal passage Dissolves in moist nasal tissue Receptor cells in olfactory epithelium Why can we smell alcohol in drinks and not sugar in drinks? Odor Sensitivity: Related to gender & age Can people distinguish many different odors?
- 15. Taste 4 Basic Tastes: Sweet Salty Sour Bitter Why do we perceive more flavors?
- 16. Kinesthesia & Vestibular Sense Kinesthesia Gives information about the location of our body parts Allows us to perform movements Where does information come from? Vestibular Sense Monitors equilibrium and gives information regarding body position, movement, and acceleration 2 Kinds of Vestibular Sensation: Body Rotation – arises from 3 semicircular canals in inner ear. Gravitation & Movement – forward, backward, up, and down. Sense arises from vestibular sacs
- 17. Perception The “way” in which we select & organize sensory input How we experience meaningful patterns in the jumble of sensory information Selective Attention Can we attend to all stimuli? Advantages = we don’t get overwhelmed Disadvantages = we “miss” stimuli that may be meaningful Laws of Perceptual Grouping:(108) Laws of Similarity Law of Good Continuation Law of Proximity Law of Closure Laws of Common Region Laws of Simplicity
- 18. Perceptual Constancies Tendency to perceive aspects of the world as unchanging despite varied sensory input Size Constancy – tendency to perceive a physical object as having a constant size. Shape Constancy – to perceive a physical object as having a constant shape. Brightness Constancy – to perceive objects as having a constant brightness even when they are viewed under different illumination. Figure & Ground Relationship: Figure – has a definite shape & location in space. Ground – has no shape, seems to continue behind the figure & has no definite location.