Transcript Vision
Sensation & Perception Unit 3 Chapter 4 Sensation Stimulation of sensory receptors and transmission of sensory info to the central nervous system (spinal cord/brain) – Sensory receptors – Stimulation automatic – Presence of chemicals Absolute Threshold Weakest amount of stimulus that can be sensed Vision, hearing, smell, taste, touch Differ from person to person – Psychological factors – Biological factors Examples of Absolute Thresholds Sense Absolute Threshold Vision A candle flame seen at 30 miles on a dark clear night Hearing The tick of a watch under quiet conditions at 20 feet Taste One teaspoon of sugar in two gallons of water Smell One drop of perfume diffused into entire volume of a six room apartment Touch The wing of a fly falling on your cheek from a distance of 1 centimeter Difference Threshold Minimum amount of difference detected between 2 stimuli Signal-Detection Theory Method for distinguishing sensory stimuli that accounts for stimuli strengths, and setting, your physical state, your mood, your attitude Also considers psychological factors – Motivation – Expectations – Learning Perception Psychological process through which we interpret sensory stimulation Reflects learning, expectations, attitudes Way in which we organize our sensory information Closure Tendency to perceive a complete or whole figure even when there are gaps in what your senses tell you Fill in the blanks Ground-Figure Perception Figures against a background What we perceive as figure and what we perceive as background influence our perception Proximity Group together events that are near each other Things which are close together are seen as belonging together Continuity Perceive things as belonging together if they form some type of continuous pattern Similarity Occurs when objects look similar to one another See groups which have the same characteristics Common Fate Tendency to perceive objects that are moving together as belonging together Depth Perception Monocular Cues Need only one eye to be perceived Cause certain objects to appear more distant from the viewer than others Binocular Cues Visual cues for depth that require the use for both eyes retinal disparity- images projected to different locations on right and left retinas pictorial depth cuesclues about distance given in a flat picture convergence- sensing the eyes converging toward each other as they focus on closer objects Stroboscopic Motion illusion of movement rapid progression of images or objects not moving at all our perceptions fill in the gaps Stroboscopic Photography Vision Unit 2.2 The Human Eye • cornea- transparent • • tissue where light enters the eye pupil- opening in center of iris that allows light to pass into the eye iris- controls pupil size • lens- focuses the light • • rays on the retina retina- contains sensory receptors that process visual information and send it to the brain optic nerve- carries visual info to brain Near + Far • Nearsightedness – Close objects are seen clearly but distant objects appear blurry – Eyeball is too long • Farsightedness – Distant objects seen clearly but close objects appear blurry – Eyeball is too short Rods and Cones • 2 kinds of photoreceptors – Neurons that are sensitive to light • Rods are sensitive to only brightness – Allow us to see black/white • Cones provide color vision Dark and Light Adaptation • Dark- adjustment to lower lighting – Continues to improve for up to 45 minutes • Light- adjustment to bright lighting – Occurs within minutes Visual Acuity • Sharpness of vision • Determined by ability to see visual details Color Vision • Cones enable us to perceive color – Sensitive to blue, green, red • Multi cone stimulation allows for other colors to be seen – Other colors are created through combinations of red, blue, green Color Compliment • Afterimage of a color is its complimentary color Color Blindness • People who don’t have normal color vision • Partially or totally unable to distinguish color – Malfunction of cones • Total color blindness is rare – Sensitive to only light and dark • Partial color blindness is more common – See red green but have hard time distinguishing between the two Depth Perception • • • Monocular Cues Need only one eye to be perceived Cause certain objects to appear more distant from the viewer than others Perspective, clearness, shadow • • • Binocular Cues Visual cues for depth that require the use for both eyes retinal disparitydepth of an object convergence- both eyes focus on the same object Hearing Unit 2.4 https://www.youtube.com/watch?v=flIAxGsV1q0 The Ear Outer ear- collects and sends sounds to the eardrum Cochlea- transforms sound vibrations to auditory signals Auditory nervetransmits neural impulses to brain Deafness Conductive damage to middle ear Affects sound amplification Can be corrected with hearing aids Sensorineural Damage to inner ear, auditory nerve Absence of sound perception for certain frequencies “artificial ear” Other Senses Unit 2.5 https://www.youtube.com/watch?v=EJud8MKrvBE Smell Essential to taste Odors are detected by receptor neurons in nostrils React when molecules come into contact with them Send information about odor to brain via olfactory nerve Adapts quickly Taste Sweet, sour, salty, bitter Flavor of food is more complex than taste Odor, texture, temperature, taste Receptors on taste buds of tongue Sensitivity to different tastes can be inherited Bitter = “taste blind” Taste cells reproduce rapidly https://www.youtube.com/watch?v=kyrIxAXZISc Skin Senses (Touch) Combination of pressure, temperature, pain Distinct sensory receptors Receive more than one type of sensory input Pressure Sensory receptors (pacinian corpuscle) located around the roots of hair cells Fire where skin is touched Different parts of body more sensitive more = fingertips, lips, nose, cheeks less = shoulders, thighs, calves Rapidly adapts Pain Receptors located all over body Not all equally sensitive to pain prostaglandins- help body transmit pain messages to brain Can experience pain in limbs no longer there = “phantom limb” Pain originates at the point of contact https://www.youtube.com/watch?v=1mHIv5ToMTM Message sent to spinal cord to thalamus in brain Projected to cerebral cortex where registration of severity/location of pain is determined The Gate Theory of Pain Only a certain amount of information can be processed by the nervous system at one time Different sensations compete with pain messages for attention Neurons cant get pain messages to brain “Flooding” prevents many or all messages from getting through Body Senses Vestibular- position of the body sensory organs located in the ears Enables balance Kinesthesis- position and movement of individual body parts Sensory organs in joints, tendons, muscles