Psychology in Everyday Life: How Understanding Sensation and Perception Can Save Lives
Human factors is the field of psychology that uses psychological knowledge, including the principles of sensation and perception, to improve the development of technology. Human factors has worked on a variety of projects, ranging from nuclear reactor control centers and airplane cockpits to cell phones and websites (Proctor & Van Zandt, 2008). For instance, modern televisions and computer monitors were developed on the basis of the trichromatic color theory, using three color elements placed close enough together so that the colors are blended by the eye. Knowledge of the visual system also helped engineers create new kinds of displays, such as those used on notebook computers and music players, and better understand how using cell phones while driving may contribute to automobile accidents (Lee & Strayer, 2004).
Human factors also has made substantial contributions to airline safety. About two thirds of accidents on commercial airplane flights are caused by human error (Nickerson, 1998). During takeoff, travel, and landing, the pilot simultaneously communicates with ground control, maneuvers the plane, scans the horizon for other aircraft, and operates controls. The need for a useable interface that works easily and naturally with the pilot’s visual perception is essential.
Psychologist Conrad Kraft (1978) hypothesized that as planes land, with no other distance cues visible, pilots may be subjected to a type of moon illusion, in which the city lights beyond the runway appear much larger on the retina than they really are, deceiving the pilot into landing too early. Kraft’s findings caused airlines to institute new flight safety measures, where copilots must call out the altitude progressively during the descent, which has probably decreased the number of landing accidents.
Figure 4.38 presents the design of an airplane instrument panel before and after it was redesigned by human factors psychologists. On the left is the initial design in which the controls were crowded and cluttered, in no logical sequence, each control performing one task. The controls were more or less the same in color, and the gauges were not easy to read. The redesigned digital cockpit (right on Figure 4.38) shows a marked improvement in usability. More of the controls are color-coded and multifunctional so that there is less clutter on the dashboard. Screens make use of LCD and 3-D graphics. Text sizes are changeable—increasing readability—and many of the functions have become automated, freeing up the pilots concentration for more important activities.
One important aspect of the redesign was based on the principles of sensory adaptation. Displays that are easy to see in darker conditions quickly become unreadable when the sun shines directly on them. It takes the pilot a relatively long time to adapt to the suddenly much brighter display. Furthermore, perceptual contrast is important. The display cannot be so bright at night that the pilot is unable to see targets in the sky or on the land. Human factors psychologists used these principles to determine the appropriate stimulus intensity needed on these displays so that pilots would be able to read them accurately and quickly under a wide range of conditions. The psychologists accomplished this by developing an automatic control mechanism that senses the ambient light visible through the front cockpit windows and that detects the light falling on the display surface, and then automatically adjusts the intensity of the display for the pilot (Silverstein, Krantz, Gomer, Yeh, & Monty, 1990; Silverstein & Merrifield, 1985).
· Sensory interaction occurs when different senses work together, for instance, when taste, smell, and touch together produce the flavor of food.
· Selective attention allows us to focus on some sensory experiences while tuning out others.
· Sensory adaptation occurs when we become less sensitive to some aspects of our environment, freeing us to focus on more important changes.
· Perceptual constancy allows us to perceive an object as the same, despite changes in sensation.
· Cognitive illusions are examples of how our expectations can influence our perceptions.
· Our emotions, motivations, desires, and even our culture can influence our perceptions.
EXERCISES AND CRITICAL THINKING
1. Consider the role of the security personnel at the APEC meeting who let the Chaser group’s car enter the security area. List some perceptual processes that might have been at play.
2. Consider some cases where your expectations about what you think you might be going to experience have influenced your perceptions of what you actually experienced.
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4.6 Chapter Summary
Sensation and perception work seamlessly together to allow us to detect both the presence of, and changes in, the stimuli around us.
The study of sensation and perception is exceedingly important for our everyday lives because the knowledge generated by psychologists is used in so many ways to help so many people.
Each sense accomplishes the basic process of transduction—the conversion of stimuli detected by receptor cells into electrical impulses that are then transported to the brain—in different, but related, ways.
Psychophysics is the branch of psychology that studies the effects of physical stimuli on sensory perceptions. Psychophysicists study the absolute threshold of sensation as well as the difference threshold, or just noticeable difference (JND). Weber’s law maintains that the JND of a stimulus is a constant proportion of the original intensity of the stimulus.
Most of our cerebral cortex is devoted to seeing, and we have substantial visual skills. The eye is a specialized system that includes the cornea, pupil, iris, lens, and retina. Neurons, including rods and cones, react to light landing on the retina and send it to the visual cortex via the optic nerve.
Images are perceived, in part, through the action of feature detector neurons.
The shade of a color, known as hue, is conveyed by the wavelength of the light that enters the eye. The Young-Helmholtz trichromatic color theory and the opponent-process color theory are theories of how the brain perceives color.
Depth is perceived using both binocular and monocular depth cues. Monocular depth cues are based on gestalt principles. The beta effect and the phi phenomenon are important in detecting motion.
The ear detects both the amplitude (loudness) and frequency (pitch) of sound waves.
Important structures of the ear include the pinna, eardrum, ossicles, cochlea, and the oval window.
The frequency theory of hearing proposes that as the pitch of a sound wave increases, nerve impulses of a corresponding frequency are sent to the auditory nerve. The place theory of hearing proposes that different areas of the cochlea respond to different frequencies.
Sounds that are 85 decibels or more can cause damage to your hearing, particularly if you are exposed to them repeatedly. Sounds that exceed 130 decibels are dangerous, even if you are exposed to them infrequently.
The tongue detects six different taste sensations, known respectively as sweet, salty, sour, bitter, piquancy (spicy), and umami (savory).
We have approximately 1,000 types of odor receptor cells and it is estimated that we can detect 10,000 different odors.
Thousands of nerve endings in the skin respond to four basic sensations: Pressure, hot, cold, and pain, but only the sensation of pressure has its own specialized receptors. The ability to keep track of where the body is moving is provided by the vestibular system.
Perception involves the processes of sensory interaction, selective attention, sensory adaptation, and perceptual constancy.
Although our perception is very accurate, it is not perfect. Our expectations and emotions color our perceptions and may result in illusions.