What is the difference between sensation and perception?

As biological mechanisms, sensation occurs when cells at the periphery of the body detect physical stimuli, and perception occurs when systems in the brain process these signals and produce conscious awareness of sensory inputs.

How are physical events translated into psychological events?

In transduction, physical stimuli reaching the body activate receptor cells in the body’s nervous system; these cells then send nerve impulses toward the brain. Processing of the signals in the brain itself gives rise to perceptual and sensory experience.

How are we able to perceive depth even with one eye closed?

We rely on monocular cues such as converging vertical lines, variations in visual texture, occlusion, shading, clarity, and environmental context.

What are the advantages of having two eyes?

Binocularity’s advantages include a “spare” eye, a wider visual field, and more accurate depth perception. The superior depth perception occurs thanks to two binocular cues to depth: stereopsis and convergence.

How does the visual system enable us to perceive motion?

Your visual system delivers information about the movement of an object in the environment (with respect to you, who are not moving), such that you can detect immediately not only that an object is moving, however slightly, but also where it’s going and how fast. It also delivers information about your own movement through an environment (which is not moving).

How do past experiences and current context influence perception of shape?

There are several examples of this. One is that in the context of the numbers 12 and 14, a vertical line next to a curved letter “m” shape on its side looks like the number 13. In the context of letters, that same shape looks like a B. Another example concerns cultural contexts. As seen in this chapter’s Cultural Opportunities, Japanese students, raised in a culture that values holistic thinking, were better at reproducing the relative (versus absolute) length of a line. North American students, raised in a culture that values analytic thinking, showed the opposite pattern of perception.

What does it take for us to notice whether someone dimmed the lights?

A just noticeable difference’s (JND’s) value depends on how much light is already in the environment. If a lot of light is present, then a larger change in illumination is needed for us to notice the change in brightness.

How does our attention to the overall environment enable us to experience color?

The psychological experience of color is determined not only by the wavelength of light, but also by our ability to mentally compute how changes in illumination in the environment will affect perception; this ability is responsible for color constancy.

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Do colors have opposites?

Yes. For example, you can imagine a reddish brown but not a reddish green because red and green are opposites, as are yellow and blue. Opponent processes in perception create visual experiences that consist of these opposing color pairs. Biological mechanisms involved in perceiving one color weaken over time, which causes mechanisms that perceive the opposite color to dominate your perceptual experience.

Through what biological process are we able to convert light energy into information that is sent to the brain?

The cornea focuses light, which passes through the pupil, whose size is controlled by the iris. The lens further focuses incoming light, which is projected onto the retina, which contains two types of photoreceptors: rods and cones. The retina picks up most of its visual information during visual fixations, which occur between saccades.

How is visual information processed once it reaches the brain?

Rods and cones send information via ganglion cells, which form the optic nerve. These visual signals cross at the optic chiasm. After crossing, signals reach the lateral geniculate nucleus, which perform “computations” on these signals.

Given the complexity of visual information, how are we able to perceive objects accurately?

Visual properties such as the shape, brightness, texture, and color of objects influence one another, due to complex information processing in the cortex that integrates information about these perceptual features. This integration produces more accurate perception of objects.

What are the qualities of sound?

They are loudness, pitch, timbre, and location.

How do we know where a sound is coming from?

We use cues based on timing (how long it takes a sound to reach your right or left ear) and differences in pressure created by sound waves on our right and left ears. These cues can make right/left localization easy but can make front/back localization difficult. Up/down localization is made possible by the asymmetrical shape of the ear.

What psychological processes enable you to not only hear sounds, but also recognize them?

Auditory recognition—that is, recognizing sounds—requires you to maintain a sound in short-term memory, to activate knowledge of sounds stored in long-term memory, and to compare the two (the incoming sound and the sound stored in memory).

Through what biological process are we able to convert sound waves into meaningful information?

The outer ear captures sound waves and directs them down the auditory canal. In the middle ear, motion of the eardrum causes motion in ossicles, which, in turn, creates activity in the inner ear. Transduction occurs in the cochlea, which contains auditory hair cells whose movement triggers neural impulses that travel via the auditory nerve to the brain’s auditory cortex, in the temporal lobe. Signals from the left ear reach the right side of the brain and vice versa. The auditory cortex is organized systematically according to pitch; similar sound wave frequencies are processed in neighboring areas. In addition, specialized regions of the auditory cortex process information about the location of sounds, the source of sounds, and vocalizations by members of one’s own species.

What are some types of stimuli we can smell?

We can smell food, pheromones (though not as well as other species), and disease.

Through what biological process are we able to convert airborne chemical signals into information that is sent to the brain?

Signals from the receptor cells (activated by odorants, pheromones, and disease-related molecules in the air) are sent to the olfactory bulbs, which send information to the olfactory cortex, where the processing of the signals that allow you to recognize smells is completed.

Why are some people more sensitive to odors than others?

Researchers have been able to link genetic variations that produce variations in the number and diversity of receptors to individual differences in olfaction.

Besides salty and sweet, what are the other types of tastes we can detect? What the heck is umami?

Humans perceive five distinct taste qualities: sweet, salty, bitter, sour, and umami. Umami is a recently discovered quality; it corresponds to the taste sensation we usually call “savory.”

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Why don’t all salty foods taste the same?

Even when two foods share a quality, such as saltiness, there are four other dimensions that can influence their taste. Hedonics refers to how much you like the taste. Localization is perception of where within the mouth a taste is experienced. Onset/aftertaste describes whether a taste will linger or vanish. Intensity describes the strength of the gustatory experience. Two foods might both be salty, but one could have a much greater intensity of saltiness than the other and perhaps a longer aftertaste, too.

What is the difference between flavor and taste?

When you eat, some of the perceptual information you gather comes from taste and some of it comes from smell. The combination of two perceptual systems—gustation and olfaction—contributes to its flavor.

What is a supertaster?

Supertasters are people whose have greater sensitivity to tastes than others.

Through what biological process are we able to convert gustatory information from our mouths to our brains?

When taste receptors, bundled together in taste buds, are stimulated by food chemicals, they release neurotransmitters that begin the process of transmitting gustatory information to the brain. Signals from taste receptors travel along neural pathways to the brain stem and then to the gustatory cortex, which is highly connected to other regions of the brain. This means that taste perception is affected by other sensory inputs and the overall state of the body. As we saw in This Just In, five distinct regions of the cortex process each of the five types of gustatory signals: sweet, salty, bitter, sour and umami.

On what parts of the body is touch perceived most accurately?

The greatest acuity is found at the fingers. The lowest is found at the shoulder, back, and areas of the leg.

How do hand and finger movements deliver information about texture, temperature, and hardness?

When you move your fingertips back and forth across the surface of an object, you acquire information about texture. To get temperature information, you hold your fingers still on an object’s surface. Pressing against the surface of an object tells you how hard it is.

How do we detect mass?

We detect mass by holding objects and moving them around. Size influences judgments of weight; when given two objects of the same weight but different size, people judge the larger object to be lighter.

Through what biological process are we able to convert haptic information from our skin to our brains?

Cutaneous receptors convert physical stimulation into nervous-system impulses, which send impulses that travel to your spinal cord and then to your brain.

What is our sixth sense?

Our sixth sense is the kinesthetic system, the perceptual system that delivers information about the orientation of your body and its various parts.

What explains pain?

Nociceptors send electrical signals to the brain when activated by harmful stimuli, such as a cut or burn. Nociceptors send fast signals, which produce sudden, sharp pain, as well as slow signals, which produce prolonged, lingering, dull pain. According to the gate control theory of pain, the spinal cord contains a biological mechanism that acts like a gate. When it’s closed, pain signals can’t get past the spinal cord to the brain, so people don’t feel pain even though their nociceptors have fired.

Why are we so good at recognizing faces?

Across the course of evolution, the ability to recognize others would have been critical to survival, reproduction, and the survival of offspring. Natural selection thus would have favored the evolution of this ability.

Does motivation—one’s goals and desires—influence perception?

Yes. One example of research providing initial evidence on this question came from a study in which children estimated the size of either of two objects: (1) coins or (2) cardboard disks of the same size as coins. The children judged that the coins—a desired object—were larger than the disks, especially if the children were poor.

Do people hear only what they want to hear?

People can, in fact, selectively attend to some auditory information while simultaneously tuning out other information, although some unattended information can still grab attention.

Do people see only what they want to see?

People can, in fact, selectively attend to some visual information and simultaneously miss unexpected information. Our perceptions—including what we see—are guided at least in part by current motives.

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