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Depth perception—the ability to judge the distance of objects.

Monocular cues—clues about distance based on the image of one eye.

Monocular cues include interposition or overlap, relative size, aerial perspective or relative clarity, texture gradient, relative height or elevation, linear perspective, relative brightness, motion parallax, and accommodation.

Binocular cues—clues about distance requiring two eyes.

Binocular cues include the more important retinal disparity and convergence.

Optical or visual illusions—discrepancies between the appearance of a visual stimulus and its physical reality. Common examples of visual illusions include reversible figures, illusory contours, the Muller-Lyer illusion, Ponzo illusion, and moon illusion.

Schemas—concepts or frameworks that organize and interpret information.

ESP (extrasensory perception)—the controversial claim that perception can occur apart from sensory input.

Parapsychology—the study of paranormal events that investigates claims of ESP, including telepathy, clairvoyance, precognition, and telekinesis or psychokinesis.

CHAPTER 9

States of Consciousness

IN THIS CHAPTER

Summary: While you are reading this book you may find yourself daydreaming as irrelevant thoughts surface, images of other situations come into view, and you create inner, private realities unconnected to this topic. Daydreams provide stimulation when your interest is flagging and lets you experience positive emotions. Although we hope not, you may even doze off. If so, you are experiencing different states of consciousness. In the late 1800s, early structuralists like Wilhelm Wundt, followed by Edward Titchener, examined consciousness in order to learn about the structure of the mind, and functionalists like William James considered consciousness as essential for adapting to the environment. During the first half of the 1900s, behaviorists discounted and ignored consciousness. By the 1950s, cognitive psychologists returned to the examination of consciousness, especially the phenomenon of attention. Attention is a state of focused awareness. What you pay attention to is what you process into perceptions, thoughts, and experiences.

Consciousness is your awareness of the outside world and yourself, including your own mental processes, thoughts, feelings, and perceptions. Your consciousness is selective, subjective and unique to you, always changing, and central to your sense of self.

This chapter examines variations in consciousness, some which you commonly experience and others which you don’t.

Key Ideas

Levels of consciousness

Sleep and dreaming

Sleep disorders

Hypnosis

Meditation

Psychoactive drugs—Depressants, Narcotics, Stimulants, Hallucinogens

Levels of Consciousness

Although your current level of consciousness is basically limited to what is relevant to you and what you notice, other events can either become conscious or influence your conscious experience. Your preconscious is the level of consciousness that is outside of awareness but contains feelings and memories that you can easily bring into conscious awareness. For example, if asked what you ate for dinner last night, you could easily remember and tell. Your nonconscious is the level of consciousness devoted to processes completely inaccessible to conscious awareness, such as blood flow, filtering of blood by kidneys, secretion of hormones, and lower level processing of sensations, such as detecting edges, estimating size and distance of objects, recognizing patterns, etc. For psychoanalysts, also known as psychodynamic psychologists, the unconscious, sometimes called the subconscious, is the level of consciousness that includes often unacceptable feelings, wishes, and thoughts not directly available to conscious awareness. According to cognitive psychologists, the unconscious is the level of consciousness that processes information of which you are unaware. The unconscious operates whenever you feel or act without being aware of what’s influencing you, whether it’s a stimulus from the current