The Chapter 5 slides are relevant to APA Outcome 1.2a(3). Specific slides are additionally relevant to other outcomes as noted on the notes page associated with the relevant slide.
Figure 5.2. To build an internal representation of the outside world, the brain solves three fundamental adaptive problems for each of its sensory systems. (a) It translates messages from the environment into the language of the nervous system; (b) it identifies the elementary components of the messages, such as colors, sounds, simple forms, and patterns of light and dark; and (c) it builds a stable interpretation of those components once they’ve been extracted.
Figure 5.3. Visible light is actually only a small part of the electromagnetic spectrum, which includes such other energy forms as X rays and radio and TV waves. Changes in the wavelength of light from about 400 nanometers to 700 nanometers are experienced as changes in color; short wavelengths are seen as violets and blues; medium wavelengths as yellows and greens; and long wavelengths as reds.
Figure 5.4. Light enters the eye through the cornea, pupil, and lens. As the lens changes shape in relation to the distance of the object, the reflected light is focused at the back of the eye where, in the retina, the visual message is translated.
Figure 5.5. Rods and cones send signals to other cells in the retina. Ganglion cells in the fovea, which receive input from cones, tend to have smaller receptive fields than cells located in the sides of the retina, which receive input from rods. This helps to explain why we see fine detail better in the fovea and why we see better out of the sides of our eyes when light levels are low.
Figure 5.6. Receptive fields in the retina often have a center-surround arrangement. Light falling in the center of the field has an opposite effect from light falling in the surround. (a) Light in the center of the field produces an excitatory response (green). (b) Light falling in the surround produces an inhibitory response (purple). (c) When light falls equally in both regions, there is no net increase in the cell’s activity compared to its no-light baseline activity level. This kind of receptive field helps the brain detect edges.
Figure 5.8. Your eyes gradually adjust to the dark and become more sensitive; that is, you can detect light at increasingly low levels of intensity. The rods and cones adapt at different rates and reach different final levels of sensitivity. The dark adaptation curve represents the combined adaptation of the two receptor types. At about the 8-minute mark there is a point of discontinuity; this is where further increases in sensitivity are due to the functioning of the rods.
Figure 5.9. Input from the left visual field falls on the inside half of the left eye and the outside half of the right eye and projects to the right hemisphere of the brain; input from the right visual field projects to the left hemisphere. Visual processing occurs at several places along the pathway, ending in the visual cortex, where highly specialized processing takes place.
Figure 5.10. Hubel and Wiesel discovered feature detectors in the brains of cats and monkeys. Feature detectors increase their firing rates to specific bars of light presented at particular orientation.
Figure 5.11. Blue-sensitive cones are most likely to respond to short wavelengths of light; green-sensitive cones respond best to medium wavelengths; red-sensitive cones respond best to long wavelengths. Notice that rods are not sensitive to long wavelengths of light. (Based on Jones & Childers, 1993.)
Figure 5.12. Stare closely at the middle of this face for about a minute. Then focus on the black dot on the right. What do you see now? The demo works better in a brightly lit environment.
Figure 5.13. Whether you detect meaningful images in (a) and (b) depends on how much prior knowledge you bring to perceptual interpretation. (From Coren, Ward, & Enns, 1994.)
Figure 5.15. We have a natural tendency to divide any visual scene into a discernible “figure” and “background.” This task can be difficult, as with the “hidden faces” painting (a); or it can be easy but ambiguous (b): Which do you see - a vase or a pair of profiles?
This slide relates to 1.2b, as the Gestalt school is a historical perspective in psychology.
Figure 5.17. Notice all the changes in the image of a door as it moves from closed to open. Yet we perceive it as a constant rectangular shape.
Figure 5.18. We see these three planters as matching in size and shape partly because of depth cues in the environment: Each covers three tiles in length and three in width.
Figure 5.19. The girl on the right appears to be much larger than the girl on the left. But this is an illusion, induced by the belief that the room is rectangular. In fact, the sloping ceiling and floors provide misleading depth cues. To the viewer looking through the peephole the room appears perfectly normal. This famous illusion was designed by Adelbert Ames.
This slide is relevant to Outcomes 1.2c and 1.2d(1): the influence of experience and culture on psychological processes.
Figure 5.23. Sound enters the auditory canal and causes the tympanic membrane to vibrate in a pattern that is then transmitted through three small bones in the middle ear to the oval window. The oval window vibrates, causing fluid inside the cochlea to be displaced, which moves the basilar membrane. The semicircular canals contribute to our sense of balance.
Outcome 3.1 (using critical thinking effectively) may be seen as relevant to this slide as it evaluates popular claims students may have heard regarding pheromones.
Psychophysics, described on this slide and the next four, concerns the relationship between the objective world of reality and the subjective one of appearance, a persisting issue in psychology. Objective 1.2d(4) is relevant.
Figure 5.25. The more intense the stimulus, the greater the likelihood that it will be detected. The absolute threshold is the intensity level at which we can detect the presence of the stimulus 50% of the time.
Figure 5.26. There are four possible outcomes in a signal detection experiment: (a) If the stimulus is present and correctly detected, it’s called a hit . (b) If the stimulus is absent but the observer claims it’s present, it’s a false alarm . (c) A miss is when the stimulus is present but not detected; and (d) A correct rejection is when the observer correctly recognizes that the stimulus was not presented.
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