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Psychology

<OpenstaxParagraph>
	While our sensory receptors are constantly collecting information from the environment, it is ultimately how we interpret that information that affects how we interact with the world. <OpenstaxTerm>Perception</OpenstaxTerm> refers to the way sensory information is organized, interpreted, and consciously experienced. Perception involves both bottom-up and top-down processing. <OpenstaxTerm>Bottom-up processing</OpenstaxTerm> refers to sensory information from a stimulus in the environment driving a process, and <OpenstaxTerm>top-down processing</OpenstaxTerm> refers to knowledge and expectancy driving a process, as shown in <a href="#Figure_05_01_topbot">Figure 5.2</a> (Egeth &amp; Yantis, 1997; Fine &amp; Minnery, 2009; Yantis &amp; Egeth, 1999).
</OpenstaxParagraph>
<OpenstaxFigure id="Figure_05_01_topbot" src="https://openstax.org/apps/archive/20240226.174525/resources/1b006097c67b6af1baf4f215c9b6f15090f715eb" alt="The figure includes two vertical arrows. The first arrow comes from the word “Top” and points downward to the word “Down.” The explanation reads, “Top-down processing occurs when previous experience and expectations are first used to recognize stimuli.” The second arrow comes from the word “bottom” and points upward to the word “up.” The explanation reads, “Bottom-up processing occurs when we sense basic features of stimuli and then integrate them.”" mediaType="image/jpg" width="649" height="265" />
<OpenstaxFigureText width="649">
	Figure 5.2 Top-down and bottom-up are ways we process our perceptions.
</OpenstaxFigureText>
<OpenstaxParagraph>
	Imagine that you and some friends are sitting in a crowded restaurant eating lunch and talking. It is very noisy, and you are concentrating on your friend’s face to hear what they are saying, then the sound of breaking glass and clang of metal pans hitting the floor rings out. The server dropped a large tray of food. Although you were attending to your meal and conversation, that crashing sound would likely get through your attentional filters and capture your attention. You would have no choice but to notice it. That attentional capture would be caused by the sound from the environment: it would be bottom-up.
</OpenstaxParagraph>
<OpenstaxParagraph>
	Alternatively, top-down processes are generally goal directed, slow, deliberate, effortful, and under your control (Fine &amp; Minnery, 2009; Miller &amp; Cohen, 2001; Miller &amp; D'Esposito, 2005). For instance, if you misplaced your keys, how would you look for them? If you had a yellow key fob, you would probably look for yellowness of a certain size in specific locations, such as on the counter, coffee table, and other similar places. You would not look for yellowness on your ceiling fan, because you know keys are not normally lying on top of a ceiling fan. That act of searching for a certain size of yellowness in some locations and not others would be top-down—under your control and based on your experience.
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<OpenstaxParagraph>
	One way to think of this concept is that sensation is a physical process, whereas perception is psychological. For example, upon walking into a kitchen and smelling the scent of baking cinnamon rolls, the <OpenstaxEm>sensation</OpenstaxEm> is the scent receptors detecting the odor of cinnamon, but the <OpenstaxEm>perception</OpenstaxEm> may be “Mmm, this smells like the bread Grandma used to bake when the family gathered for holidays.”
</OpenstaxParagraph>
<OpenstaxParagraph>
	Although our perceptions are built from sensations, not all sensations result in perception. In fact, we often don’t perceive stimuli that remain relatively constant over prolonged periods of time. This is known as <OpenstaxTerm>sensory adaptation</OpenstaxTerm>. Imagine going to a city that you have never visited. You check in to the hotel, but when you get to your room, there is a road construction sign with a bright flashing light outside your window. Unfortunately, there are no other rooms available, so you are stuck with a flashing light. You decide to watch television to unwind. The flashing light was extremely annoying when you first entered your room. It was as if someone was continually turning a bright yellow spotlight on and off in your room, but after watching television for a short while, you no longer notice the light flashing. The light is still flashing and filling your room with yellow light every few seconds, and the photoreceptors in your eyes still sense the light, but you no longer perceive the rapid changes in lighting conditions. That you no longer perceive the flashing light demonstrates sensory adaptation and shows that while closely associated, sensation and perception are different.
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<OpenstaxParagraph>
	There is another factor that affects sensation and perception: attention. Attention plays a significant role in determining what is sensed versus what is perceived. Imagine you are at a party full of music, chatter, and laughter. You get involved in an interesting conversation with a friend, and you tune out all the background noise. If someone interrupted you to ask what song had just finished playing, you would probably be unable to answer that question.
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<OpenstaxNote>
	<OpenstaxNoteTitle> Link to Learning </OpenstaxNoteTitle> 
	<OpenstaxParagraph>
		See for yourself how inattentional blindness works by checking out this <a href="http://openstax.org/l/blindness">selective attention test</a> from Simons and Chabris (1999).
	</OpenstaxParagraph>
</OpenstaxNote>
<OpenstaxParagraph>
	One of the most interesting demonstrations of how important attention is in determining our perception of the environment occurred in a famous study conducted by Daniel Simons and Christopher Chabris (1999). In this study, participants watched a video of people dressed in black and white passing basketballs. Participants were asked to count the number of times the team dressed in white passed the ball. During the video, a person dressed in a black gorilla costume walks among the two teams. You would think that someone would notice the gorilla, right? Nearly half of the people who watched the video didn’t notice the gorilla at all, despite the fact that he was clearly visible for nine seconds. Because participants were so focused on the number of times the team dressed in white was passing the ball, they completely tuned out other visual information. <OpenstaxTerm>Inattentional blindness</OpenstaxTerm> is the failure to notice something that is completely visible because the person was actively attending to something else and did not pay attention to other things (Mack &amp; Rock, 1998; Simons &amp; Chabris, 1999).
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<OpenstaxParagraph>
	In a similar experiment, researchers tested inattentional blindness by asking participants to observe images moving across a computer screen. They were instructed to focus on either white or black objects, disregarding the other color. When a red cross passed across the screen, about one third of subjects did not notice it (<a href="#Figure_05_01_Cross">Figure 5.3</a>) (Most, Simons, Scholl, &amp; Chabris, 2000).
</OpenstaxParagraph>
<OpenstaxFigure id="Figure_05_01_Cross" src="https://openstax.org/apps/archive/20240226.174525/resources/349f368d469ab5bb95ae67fbaa4c053390cb92c2" alt="A photograph shows a person staring at a screen that displays one red cross toward the left side and numerous black and white shapes all over." mediaType="image/jpg" width="488" height="292" />
<OpenstaxFigureText width="488">
	Figure 5.3 Nearly one third of participants in a study did not notice that a red cross passed on the screen because their attention was focused on the black or white figures. (credit: Cory Zanker)
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<OpenstaxParagraph>
	Motivation can also affect perception. Have you ever been expecting a really important phone call and, while taking a shower, you think you hear the phone ringing, only to discover that it is not? If so, then you have experienced how motivation to detect a meaningful stimulus can shift our ability to discriminate between a true sensory stimulus and background noise. The ability to identify a stimulus when it is embedded in a distracting background is called <OpenstaxTerm>signal detection theory</OpenstaxTerm>. This might also explain why a mother is awakened by a quiet murmur from her baby but not by other sounds that occur while she is asleep. Signal detection theory has practical applications, such as increasing air traffic controller accuracy. Controllers need to be able to detect planes among many signals (blips) that appear on the radar screen and follow those planes as they move through the sky. In fact, the original work of the researcher who developed signal detection theory was focused on improving the sensitivity of air traffic controllers to plane blips (Swets, 1964).
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<OpenstaxParagraph>
	Our perceptions can also be affected by our beliefs, values, prejudices, expectations, and life experiences. As you will see later in this chapter, individuals who are deprived of the experience of binocular vision during critical periods of development have trouble perceiving depth (Fawcett, Wang, &amp; Birch, 2005). The shared experiences of people within a given cultural context can have pronounced effects on perception. For example, Marshall Segall, Donald Campbell, and Melville Herskovits (1963) published the results of a multinational study in which they demonstrated that individuals from Western <OpenstaxTerm>cultures</OpenstaxTerm> were more prone to experience certain types of visual illusions than individuals from non-Western cultures, and vice versa. One such illusion that Westerners were more likely to experience was the <OpenstaxTerm>Müller-Lyer</OpenstaxTerm> illusion (<a href="#Figure_05_01_MullerLyer">Figure 5.4</a>): The lines appear to be different lengths, but they are actually the same length.
</OpenstaxParagraph>
<OpenstaxFigure id="Figure_05_01_MullerLyer" src="https://openstax.org/apps/archive/20240226.174525/resources/0d2804857055bce20ec9439c22807e4078666ec2" alt="Two vertical lines are shown on the left in (a). They each have V–shaped brackets on their ends, but one line has the brackets angled toward its center, and the other has the brackets angled away from its center. The lines are the same length, but the second line appears longer due to the orientation of the brackets on its endpoints. To the right of these lines is a two-dimensional drawing of walls meeting at 90-degree angles. Within this drawing are 2 lines which are the same length, but appear different lengths. Because one line is bordering a window on a wall that has the appearance of being farther away from the perspective of the viewer, it appears shorter than the other line which marks the 90 degree angle where the facing wall appears closer to the viewer’s perspective point." mediaType="image/jpg" width="731" height="366" />
<OpenstaxFigureText width="731">
	Figure 5.4 In the Müller-Lyer illusion, lines appear to be different lengths although they are identical. (a) Arrows at the ends of lines may make the line on the right appear longer, although the lines are the same length. (b) When applied to a three-dimensional image, the line on the right again may appear longer although both black lines are the same length.
</OpenstaxFigureText>
<OpenstaxParagraph>
	These perceptual differences were consistent with differences in the types of environmental features experienced on a regular basis by people in a given cultural context. People in Western cultures, for example, have a perceptual context of buildings with straight lines, what Segall’s study called a carpentered world (Segall et al., 1966). In contrast, people from certain non-Western cultures with an uncarpentered view, such as the Zulu of South Africa, whose villages are made up of round huts arranged in circles, are less susceptible to this illusion (Segall et al., 1999). It is not just vision that is affected by cultural factors. Indeed, research has demonstrated that the ability to identify an odor, and rate its pleasantness and its intensity, varies cross-culturally (Ayabe-Kanamura, Saito, Distel, Martínez-Gómez, &amp; Hudson, 1998).
</OpenstaxParagraph>
<OpenstaxParagraph>
	Children described as thrill seekers are more likely to show taste preferences for intense sour flavors (Liem, Westerbeek, Wolterink, Kok, &amp; de Graaf, 2004), which suggests that basic aspects of personality might affect perception. Furthermore, individuals who hold positive attitudes toward reduced-fat foods are more likely to rate foods labeled as reduced fat as tasting better than people who have less positive attitudes about these products (Aaron, Mela, &amp; Evans, 1994).
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5.1.2 Perception

1 Introduction to Psychology

1.1 What Is Psychology?

1.1.1 Why Study Psychology?

1.2 History of Psychology

1.2.1 Wundt and Structuralism

1.2.2 Functionalism

1.2.3 Freud and Psychoanalytic Theory

1.2.4 Wertheimer, Koffka, Köhler, and Gestalt Psychology

1.2.5 Pavlov, Watson, Skinner, and Behaviorism

1.2.6 Maslow, Rogers, and Humanism

1.2.7 The Cognitive Revolution

1.2.8 Multicultural And Cross-Cultural Psychology

1.2.9 Women in Psychology

1.3 Contemporary Psychology

1.3.1 Biopsychology and Evolutionary Psychology

1.3.2 Sensation and Perception

1.3.3 Cognitive Psychology

1.3.4 Developmental Psychology

1.3.5 Personality Psychology

1.3.6 Social Psychology

1.3.7 Industrial-Organizational Psychology

1.3.8 Health Psychology

1.3.9 Sport and Exercise Psychology

1.3.10 Clinical Psychology

1.3.11 Forensic Psychology

1.4 Careers in Psychology

1.4.1 Other Careers in Academic Settings

1.4.2 Career Options Outside of Academic Settings

2 Psychological Research

2.1 Why Is Research Important?

2.1.1 Use of Research Information

2.1.2 NOTABLE RESEARCHERS

2.1.3 The Process of Scientific Research

2.2 Approaches to Research

2.2.1 Clinical or Case Studies

2.2.2 Naturalistic Observation

2.2.3 Surveys

2.2.4 Archival Research

2.2.5 Longitudinal and Cross-Sectional Research

2.3 Analyzing Findings

2.3.1 Correlational Research

2.3.2 Causality: Conducting Experiments and Using the Data

2.3.3 Reliability and Validity

2.4 Ethics

2.4.1 Research Involving Human Participants

2.4.2 Research Involving Animal Subjects

3 Biopsychology

3.1 Human Genetics

3.1.1 Genetic Variation

3.1.2 Gene-Environment Interactions

3.2 Cells of the Nervous System

3.2.1 Neuron Structure

3.2.2 Neuronal Communication

3.2.3 Neurotransmitters and Drugs

3.3 Parts of the Nervous System

3.3.1 Peripheral Nervous System

3.4 The Brain and Spinal Cord

3.4.1 The Spinal Cord

3.4.2 The Two Hemispheres

3.4.3 Forebrain Structures

3.4.4 Midbrain and Hindbrain Structures

3.4.5 Brain Imaging

3.5 The Endocrine System

3.5.1 Major Glands

4 States of Consciousness

4.1 What Is Consciousness?

4.1.1 Biological Rhythms

4.1.2 Problems With Circadian Rhythms

4.2 Sleep and Why We Sleep

4.2.1 What is Sleep?

4.2.2 Why Do We Sleep?

4.3 Stages of Sleep

4.3.1 NREM Stages of Sleep

4.3.2 REM Sleep

4.4 Sleep Problems and Disorders

4.4.1 Insomnia

4.4.2 Parasomnias

4.4.3 Sleep Apnea

4.4.4 Narcolepsy

4.5 Substance Use and Abuse

4.5.1 Substance Use Disorders

4.5.2 Drug Categories

4.6 Other States of Consciousness

4.6.1 Hypnosis

4.6.2 Meditation

5 Sensation and Perception

5.1 Sensation versus Perception

5.1.1 Sensation

5.2 Waves and Wavelengths

5.2.1 Amplitude and Wavelength

5.2.2 Light Waves

5.2.3 Sound Waves

5.3 Vision

5.3.1 Anatomy of the Visual System

5.3.2 Color and Depth Perception

5.4 Hearing

5.4.1 Anatomy of the Auditory System

5.4.2 Pitch Perception

5.4.3 Sound Localization

Question	Answer
system in which perceptions are built from sensory input	bottom-up processing
failure to notice something that is completely visible because of a lack of attention	inattentional blindness
way that sensory information is interpreted and consciously experienced	perception
not perceiving stimuli that remain relatively constant over prolonged periods of time	sensory adaptation
change in stimulus detection as a function of current mental state	signal detection theory
interpretation of sensations is influenced by available knowledge, experiences, and thoughts	top-down processing