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Lecture 5

Lecture 5 Perceptual Development PSY312

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Stuart Kamenetsky

February 3, 2014 Lecture 5: Perceptual Development -5 senses: smell(olfactory), sight(visual), touch, taste(gustatory), hear(auditory) -incoming sensory information, you adult developed person, able to detect 5 incoming sensations -what are those sensations? -perception -how they develop? -we rely the most on visual sensation -other vertebrates don't rely on visual sensation as much -second most important sensory input is auditory -third most important, involved in evolution, other vertebrates rely on olfactory (smell) -touch is a complex sense, because they are many touch receptors: pain, temperature, pressure, vibration -vestibular system is right behind the ear, balance Principles of Sensation -Transduction; physical energy to neural signal -taking complex information and transducing it into meaningful information that is useful to you (thought- sophisticated and complex) -Absolute threshold-- smallest strength of a stimulus that can be detected -important because the sensory detectors that we have are really sensitive -detect differences in colour, detect things that are really far away using visual system -detecting difference sounds (long and short 'a') -Difference threshold; (jnd) smallest difference that can be detected -somatosensory cortex (touch) -lips and hands -Sensory adaptation -use sensation to adapt to an environment -infants are born legally blind, we rely on it so much as adults but it's the least developed at birth -hearing well developed at birth Vision Purpose of the visual system -transform light energy (protons) into an electrochemical neural response -represent characteristics of objects in our environment such as size, colour, shape and location -electromagnetic radiation (incoming input of vision) - energy -energy occurs in a spectrum, of waves, can be converted into mass, mass can be converted to energy (interchangeable) -energy is frequency(length) waves -visual part of the spectrum is very concise, particular part of that energy spectrum (400-700 February 3, 2014 nHz) -visual system is detecting nanometres - radio waves are really long (driving in a car) -a wave has a hill and a trough -light waves cannot get through the molecules in skin -gamma rays can get through molecules in skin (really short waves of electromagnetic radiation) -they can disrupt the molecules and organs in your skin (radiation poisoning) -visual spectrum don't hurt you -even larger than radio waves are electricity (AC circuits) -people don't want to live beside power source because it causes the waves are too long, it cannot get inside of you -frequency, wave length determines colour -amplitude, how high the waves are (tall or short), determines brightness -different receptors that detect colour and contrast -magnocellular system and parvocellular system -system that detect movement, shape, location -separate that detects object, colour -put together at the back of the brain ADD IN LIGHT: THE VISUAL STIMULUS PICTURE - Light: The Visual Stimulus -light can be described as both a particle and a wave -wavelength of a light is the distance of one complete cycle of the wave -visible light has wavelengths from about 400nm to 700nm -wavelength of light is related to its perceived colour -number of waves that occur per second (hertz) -eyeball unable to detect other frequencies, only the narrow band -other species that can detect other frequencies -in through the eye -artificial eye, camera, incoming radiation -front of the eye, protective layer called the cornea, transparent -right behind the cornea, lens, to focus, the lens bends the light to accommodate (the lens changes shape) - muscles attached to lens that accommodate to distance -lens accommodate in infancy not so good -iris: different colours (brown is the most common colour) , also accommodates -iris causes muscles in pupil to dilate -too much incoming electromagnetic radiation can hurt you, so eye accommodates (amplitude -black dot in the middle of the eye is called a pupil (too bright, pupil shrink, too dark, pupil opens, more light- reflexive) February 3, 2014 -accommodate for distance, brightness -pupil is a hole, covered by the cornea, radiation comes through pupil and hits the back of the eye -back of the eyeball, transduction takes place, well developed in infancy but not working very well (back of the eyeball is called retina, which has receptors called rods and cones) -blind spot filled in cognitively by the cortex (behind the retina) -optic disk, optic nerve leaves the eye, (no receptors there) -receptors come in different layers and detect and transduce -3 layers of transducing cells at the back of the eyeball -sensory receptor cells -magnocellular and parvocellular -lights turned off, now detecting contrast -lights on, now see colour, detected by cones, very sensitive to wavelength -part of visual system that develops the soonest is the rods (sensation contrast) -sensation colour not so early -less colour looking out the sides of your eyes -cones focus on central part of visual -more rods on the periphery (sides) of the eyes (high for contrast) -rods develop first (movement, contrast) -connected to the bipolar cells, coordinating sensation from the rods and cones -multiple rods connect to bipolar cells -only one connect to cones -bipolar then connected to ganglion cells, form the optic nerve Difference Between Rods and Cones Cones: -allow us to see in bright light -allow us to see fine spatial detail -different colours Rods: -see in dim light -cannot see fine spatial detail -cannot see different colours Which is more sensitive to electromagnetic radiation, in the 400-700, cones or rods? Rods are very sensitive. Develop earlier than cones -rods more numerous in the periphery, cones more in the central Processing Visual Information -Ganglion cells: neurons that connect to the bipolar cells; their axons form the optic nerve February 3, 2014 -Bipolar cells: neurons that connect rods and cones to the ganglion cells -Optic chiasm: point in the brain where the optic nerves from each eye meet and partially crossover to opposite sides of the brain (inner crosses, the outer doesn't) -chemical in the eye that transducin electromagnetic radiation and changes it into a chemical signal: Rhodopsin -after the optic chiasm it becomes the optic tract Hearing: Sound Waves -Auditory perception occurs when sound waves interact with the structures of the ear -Sound Wave: changes over time in the pressure of an elastic medium (for example, air or water) -without air (or another elastic medium) there can be no sound waves, and thus no sound Are you transducing electromagnetic radiation when you hear? No, not detecting energy, d
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