Unit 4a (Module 16-18) Study Guide

17-2 List the claims of ESP, and discuss the conclusions of most research psychologists after putting these claims to the test

*Parapsychology* is the study of paranormal phenomena, including *extrasensory perception (ESP)* and psychokinesis. The three most testable forms of ESP are telepathy (mind-to-mind communication), clairvoyance (perceiving remote events), and precognition (perceiving future events). Skeptics argue that (1) to believe in ESP, you must believe the brain is capable of perceiving without sensory input, and (2) researchers have been unable to replicate ESP phenomena under controlled conditions.

17-1 Explain how our expectations, contexts, emotions, and motivation influence our perceptions

*Perpetual set* is a mental predisposition that functions as a lens through which we perceive the world. Our learned concepts (schemas) prime us to organize and interpret ambiguous stimuli in certain ways. Our physical and emotional context, as well as our motivation, can create expectations and color our interpretation of events and behaviors.

16-1 Contrast sensation and perception, and explain the difference between bottom-up and top-down processing

*Sensation* is the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment. *Perception* is the process of organizing and interpreting this information, enabling recognition of meaningful events. Sensation and perception are actually parts of one continuous process. *Bottom-up processing* is sensory analysis that begins at the entry level, with information flowing from the sensory receptors to the brain. *Top-down processing* is information processing guided by high-level mental processes, as when we construct perceptions by filtering information through our experience and expectations.

16-5 Explain the function of sensory adaptation

*Sensory adaptation* (Our diminished sensitivity to constant or routine odors, sights, sounds, and touches) focuses our attention on informative changes in our enviornment.

18-2 Describe how the eye and brain process visual information.

After processing by bipolar and ganglion cells in the eyes' retina, neural impulses travel through the *optic nerve*, to the thalamus, and on to the visual cortex. In the visual cortex, *feature detectors* respond to specific features of the visual stimulus. Supercell clusters in other critical brain areas respond to more complex patterns. Through *parallel processing*, the brain handles many aspects of vision (color, movement, form, and depth) simultaneously. Other neural teams integrate the results, comparing them with stored information and enabling perceptions.

16-4 Distinguish between absolute and difference thresholds, and discuss whether we can sense and be affected by stimuli below the absolute threshold

Our *absolute threshold* for any stimulus is the minimum stimulation necessary for us to be consciously aware of it 50 percent of the time. *Signal detection theory* predicts how and when we will detect a faint stimulus amid background noise. Individual absolute thresholds vary, depending on the strength of the signal and also on our expectations, experience, motivation, and alertness. Our *difference threshold* is the difference we can discern between two stimuli 50 percent of the time. *Weber's law* states that two stimuli must differ by a constant percentage (not a constant amount) to be perceived as different. *Priming* shows that we can process some information from stimuli below our absolute threshold for conscious awareness. But the effect is too fleeting to enable people to expolit us with *subliminal* messages.

16-3 Identify the three steps that are basic to all our sensory systems

Our senses (1) receive sensory stimulation (often using specialized receptor cells); (2) transform that stimulation into neural impulses; and (3) deliver the neural information to the brain. *Transduction* is the process of converting one form of energy into another. Researchers in *psychophysics* study the relationships between stimuli's physical characteristics and our pyschological expiriences of them.

18-3 Discuss the theories that help us understand color vision

The *Young-Helmholtz trichromatic (three-color) theory* proposed that the retina contains three types of color receptors. Contemporary research has found three types of cones, each most sensitive to the wavelengths of one of the three primary colors of light (red, green, or blue). Hering's *opponent-process theory* proposed three additional color processes (red-versus-green, blue-versus-yellow, black-versus-white). Contemporary research has confirmed that, en route to the brain, neurons in the retina and the thalamus code the color-related information from the cones into pairs of opponent colors. These two theories, and the research supporting them, show that color processing occurs in two stages.

18-1 Describe the characteristics of visible light, and explain the process by which the eye transforms light energy into neural messages

The *hue* we perceive in light depends on its *wavelength*, and its brightness depends on its *intensity*. After entering the eye and being focused by the *lens*, light energy particles (from a thin slice of the broad spectrum of electromagnetic energy) strike the eye's inner surface, the *retina* The retina's light-sensitive *rods* and color-sensitive *cones* convert the light energy into neural impulses.

16-2 Discuss how much information we can consciously attend to at once

We *selectively attend* to, and process, a very limited portion of incoming information, blocking out much and often shifting the spotlight of our attention from one thing to another. Focused intently on one task, we often display *inattentional blindness* (Including change blindness) to other events and changes around us.