Invitation to Psychology

(Barry) #1
UFO sightings seem to be on the increase
just about everywhere. In February, a boy on a
passenger jet bound for Massachusetts was film-
ing another jet flying some distance away when
his camera recorded an unidentified object whiz-
zing by his window. In January, someone posted
a video of at least eight objects flying across
the sky in Mexico. Sightings have increased off
the coast of Cape Town, South Africa, and there
have even been reports that a UFO was spotted
moving across the sky near the International

Space Station, which orbits about 250 miles
above the Earth.
One of the earliest UFO accounts occurred
in the late 1940s, when a rancher noticed
some strange objects strewn about his property
near Roswell, New Mexico. When the Air Force
quickly blocked off and cleared the site, sto-
ries circulated that a spacecraft had crashed
and that alien corpses had been recovered.
Thousands of believers in UFOs still flock to the
International UFO Museum in Roswell.

W


hy do some people insist that they have


seen UFOs despite the skepticism of


others, who scoff and dismiss these objects


as planes and planets in the night sky? The


answer is that our sensations often deceive


us, and not just when we are looking up at


mysterious objects in the sky. “I saw it with


my own eyes!” people exclaim, as they tell of


seeing an image of Jesus on a garage door,


Osama bin Laden’s face in smoke billowing


from the doomed World Trade Center, the


Virgin of Guadalupe in a tortilla, or Mother


Teresa’s face in a cinnamon bun. These illu-


sions seem perfectly real to the people who


see them. Why do such reports turn up all


over the world, often with specific details?


In this chapter, we will answer these


questions by exploring how our senses take


in information from the environment and


how our brains use this information to con-


struct a model of the world. We will focus


on two closely connected sets of processes


that enable us to know what is happening


both inside our bodies and in the world


beyond our own skins. The first, sensation,


is the detection of physical energy emitted


or reflected by physical objects. The cells


that do the detecting are located in the


sense organs—the eyes, ears, tongue, nose,


skin, and internal body tissues. Sensory


processes produce an immediate awareness


of sound, color, form, and other building


blocks of consciousness. Without sensation,


we would lose touch—literally—with reality.


But to make sense of the world imping-


ing on our senses, we also need perception, a


set of mental operations that organizes sen-


sory impulses into meaningful patterns. Our


sense of vision produces a two- dimensional


image on the back of the eye, but we per-


ceive the world in three dimensions. Our


sense of hearing brings us the sound of a


C, an E, and a G played simultaneously on


the piano, but we perceive a C-major chord.


Sometimes, a single sensory image produces


two alternating perceptions, and the result is


an image that keeps changing, as illustrated


by the two examples on the next page.


Sensation and perception are the foun-


dation for learning, thinking, and acting.


Findings about these processes are often


put to practical use, as in the design of


industrial robots and in the training of as-


tronauts, who must make crucial decisions


based on what they sense and perceive.


An understanding of sensation and percep-


tion can also help us think more critically


about our own experiences and encourages


in us a certain humility: Usually we are


sure that what we sense and perceive must


be true, yet sometimes we are just plain


wrong. As you read this chapter, you will


sensation The detection
of physical energy emit-
ted or reflected by physi-
cal objects; it occurs
when energy in the exter-
nal environment or the
body stimulates receptors
in the sense organs.

perception The pro-
cess by which the brain
organizes and interprets
sensory information.
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