Hockenbury Discovering Psychology 5th txtbk

Introduction: What Are Sensation and Perception?89In this chapter, we will explore the overlapping processes of sensation and perception.Sensation refers to the detection and basic sensory experience of environmentalstimuli, such as sounds, images, and odors. Perception occurs when we integrate, organize,and interpret sensory information in a way that is meaningful. Here’s a simpleexample to contrast the two terms. Your eyes’ physical response to light, splotchesof color, and lines reflects sensation. Integrating and organizing those sensations sothat you interpret the light, splotches of color, and lines as a painting, a flag, or someother object reflects perception. Mike’s visual world reflects this distinction. Althoughhis eye was accurately transmitting visual information from his environment (sensation),his brain was unable to make sense out of the information (perception).Where does the process of sensation leave off and the process of perceptionbegin? There is no clear boundary line between the two processes as we actuallyexperience them. In fact, many researchers in this area of psychology regard sensationand perception as a single process.Although the two processes overlap, we will present sensation and perceptionas separate discussions. In the first half of the chapter, we’ll discuss the basics ofsensation—how our sensory receptors respond to stimulation and transmit thatinformation in usable form to the brain. In the second half of the chapter, we’llexplore perception—how the brain actively organizes and interprets the signalssent from our sensory receptors.Basic Principles of SensationKey Theme• Sensation is the result of neural impulses transmitted to the brain fromsensory receptors that have been stimulated by physical energy from theexternal environment.Key Questions• What is the process of transduction?• What is a sensory threshold, and what are two main types of sensorythresholds?• How do sensory adaptation and Weber’s law demonstrate that sensation isrelative rather than absolute?Experiencing the World Through OurSenses Imagine biting into a crisp, redapple. All your senses are involved in yourexperience—vision, smell, taste, hearing,and touch. Although we’re accustomed tothinking of our differ ent senses as beingquite distinct, all forms of sensation involvethe stimulation of specialized cellscalled sensory receptors.We’re accustomed to thinking of the senses as being quite different from one another.However, all our senses involve some common processes. All sensation is aresult of the stimulation of specialized cells, called sensory receptors, by some formof energy.Imagine biting into a crisp, red apple. Your experience of hearing the applecrunch is a response to the physical energy of vibrations in the air, or sound waves.The sweet taste of the apple is a response to the physical energy of dissolvable chemicalsin your mouth, just as the distinctive sharp aroma of the apple is a response toairborne chemical molecules that you inhale through your nose. The smooth feel ofthe apple’s skin is a response to the pressure of the apple against your hand. And themellow red color of the apple is a response to the physical energy of light wavesreflecting from the irregularly shaped object into which you’ve just bitten.Sensory receptors convert these different forms of physical energy into electricalimpulses that are transmitted via neurons to the brain. The process by which a formof physical energy is converted into a coded neural signal that can be processedby the nervous system is called transduction. These neural signals are sent tothe brain, where the perceptual processes of organizing and interpreting the codedmessages occur. Figure 3.1 on the next page illustrates the basic steps involved in sensationand perception.We are constantly being bombarded by many different forms of energy. Forinstance, at this very moment radio and television waves are bouncing around thesensationThe process of detecting a physical stimulus,such as light, sound, heat, or pressure.perceptionThe process of integrating, organizing, andinterpreting sensations.sensory receptorsSpecialized cells unique to each sense organthat respond to a particular form of sensorystimulation.transductionThe process by which a form of physicalenergy is converted into a coded neuralsignal that can be processed by thenervous system.