23. Seeing.docx - 23 Seeing Original chapter by Charles...

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23 SeeingOriginal chapter by Charles Stangor with adaptations byJennifer Walinga, adapted by the Queen’s UniversityPsychology DepartmentYou’ll notice that this chapter looks a bit different from our earlier chapters. Abenefit of an Open Access textbook is that we have the ability to source andadapt content written by experts globally that address issues that areimportant for our course. This chapter is from the text “Introduction toPsychology–1st Canadian Edition.” You can find the bookhere.Learning ObjectivesIdentify the key structures of the eye and the role they play in vision.Summarize how the eye and the visual cortex work together to senseand perceive the visual stimuli in the environment, including processingcolours, shape, depth, and motionWhereas other animals rely primarily on hearing, smell, or touch tounderstand the world around them, human beings rely in large part on vision.A large part of our cerebral cortex is devoted to seeing, and we havesubstantial visual skills. Seeing begins when light falls on the eyes, initiatingthe process of transduction. Once this visual information reaches the visualcortex, it is processed by a variety of neurons that detect colours, shapes, andmotion, and that create meaningful perceptions out of the incoming stimuli.The air around us is filled with a sea ofelectromagnetic energy:pulses ofenergy waves that can carry information from place to place. As you can seein Figure 5.6, “The Electromagnetic Spectrum,” electromagnetic waves vary intheirwavelengththe distance between one wave peak and the next wavepeak —with the shortest gamma waves being only a fraction of a millimeter inlength and the longest radio waves being hundreds of kilometers long.Humans are blind to almost all of this energy —our eyes detect only therange from about 400 to 700 billionths of a meter, the part of theelectromagnetic spectrum knownas thevisible spectrum.
The Sensing Eye and the Perceiving Visual CortexAs you can see in Figure 5.7, “Anatomy of the Human Eye,” light enters theeye through thecornea,a clear covering that protects the eye and begins tofocus the incoming light.The light then passes through thepupil,a smallopening in the centre of the eye. The pupil is surrounded by theiris,thecoloured part of the eye that controls the size of the pupil by constricting ordilating in response to light intensity. When we enter a dark movie theatre ona sunny day, for instance, muscles in the iris open the pupil and allow morelight to enter. Complete adaptation to the dark may take up to 20 minutes.Behind the pupil is thelens,a structure that focuses the incoming light ontheretina,the layer of tissue at the back of the eye that containsphotoreceptor cells. As our eyes move from near objects to distant objects, aprocess known asvisual accommodationoccurs.Visualaccommodationisthe process of changing the curvature of the lens to keepthe light entering the eye focused on the retina.Rays from the top of the

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Term
Winter
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Depth perception

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