Psych: Chapter 3: Sensation and Perception

PRESENTATION

Chapter 3:

Sensation and Perception

Welcome to the chapter content

Index

Sensation (vision, hearing, taste, smell, touch)

Perceptual Illusions

Perception

The Effects of Experience on Perceptual Interpretations

Closing

Definitions

Perception (Interpret)

Sensation (Detect)

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Absolute/Difference Threshold

Sensory Receptors

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The Basic Steps of Sensation and Perception

How a Pit Viper Sees a Bird at Night

Does the world look different to other species? In many cases, yes. Each species has evolved a unique set of sensory capabilities. Pit vipers see infrared light, which we sense only as warmth. The bird here has been photographed through an infrared viewer. The image shows how a pit viper uses its infrared vision to detect warm-blooded prey at night (Van Dyke & Grace, 2010). Similarly, many insect and bird species can detect ultraviolet light, which is invisible to humans.

The Electromagnetic Spectrum

The Path of Light in the Human Eye Pg. 79

Demonstration of the Blind Spot

Hold this image a few feet in front of you. Close your right eye and stare at the spider with your left eye. Slowly bring the image toward your face. At some point, the moth will disappear because you have focused it on the part of your retina where the blind spot is located. Notice, however, that you still perceive the spider web. That's because your brain has filled in information from the surrounding area.

Color Blindness

Hearing

Audition- the scientific term for the sense of hearing Soundwaves- Physical stimuli that produce sensory sound experience

Path of Sound Through the Human Ear

Restoring Hearing

• Cochlear implants convert sound into electrical impulses that directly stimulate the auditory nerve via electrodes implanted in the cochlea.
• Do not restore normal hearing (Farris-Trimble et al., 2014)
• Use can allow hearing-impaired individuals to perceive speech and other everyday sounds (Clark et al., 2013; O’Donoghue, 2013)

Smell(Olfaction)

Taste (Gustation)

• Taste buds- Specialized sensory receptors for taste that are located on the tongue and inside the mouth and throat.
• Is it true that different tastes are detected on different parts of your tongue?

Touch

• Skin- the largest and heaviest sense organ; also the largest organ in the human body overall. Many different kinds of sensory receptors in the skin which respond to stimuli
• Sensory receptors- distributed unevenly among different areas of the body. Hands, face, and lips are much more sensitive to touch than your back, arms, and legs.
• Pain- the unpleasant sensory and emotional experience associated with actual or potential bodily damage

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Summary Table of the Senses

Perception: the process of integrating, organizing, and interpreting sensory information into meaningful representations

Top-Down Processing

Bottom-up Processing

Emphasized sensory receptors in detecting the basic features of a stimulus; attention focuses on the parts of the pattern before moving to the whole

Emphasizes the observer’s experience in arriving at meaningful perceptions; attention moves from the whole to part of the pattern

Hallucination

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false or distorted perception that seems vividly real to the person experiencing it. Are perceptions that are not grounded in a real sensation–someone perceives something that isn’t there

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Figure-Ground Relationship/Reversal

What image do you see first?

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Perception

Monocular Cues:

Depth Perception:

The use of visual cues to perceive the distance or the three-dimensional characteristics of an object.

Distance or depth cues that can be processed by either eye alone.

Size and Shape constancy:

Binocular Cues:

The perception that a familiar object remains the same shape regardless of the image produced on our retinas

Distance or depth cues that require the use of both eyes.

The Delboeuf Illusion

Does one of the black dots appear to be larger than the other?

The Moon Illusion

Why does the moon appear to be much larger when it is viewed on the horizon then when it is viewed higher in the sky? Part of the explanation has to do with our perception of the distance of objects at different locations on the horizon– here the runner, the trees, and the moon itself. People perceive objects on the horizon as farther away then objects that are directly overhead in the sky, leading to misjudging size.

The Perceptul Illusion

• Underscores the idea that we actively construct our perceptual representations of the world according to psychological principles.
• The misperception of the true characteristics of an object or an image

• The Müller-Lyer Illusion
• Famous visual illusion involving the misperception of the identical length of two lines, one with arrows pointed inward, one with arrows pointed outward
• Inward arrows mean the line is close and smaller for its retinal image.

Culture and Human Behavior and the Muller-Lyer Illusion

• Carpentered-world hypothesis
• People in industrialized societies are far more susceptible to the Müller-Lyer illusion than are people in some nonindustrialized societies.
• This may be due to the carpentered-world hypothesis (Seagall, 1963, 1966), which posits that people living in urban, industrialized environments have a great deal of perceptual experience in judging lines, corners, edges, and other rectangular objects.

Effects of Experience on Perceptual Interpretations

There is a tendency to perceive objects or situations from a particular frame of reference (perceptual set).Perceptual sets usually lead to accurate conclusions. The human tendency to see faces in ambiguous stimuli may contribute to false positives. Can you explain why?

What questions/comments do you have

Thank you for your time and attention in this chapter!!

Specialized cells unique to each sense organ that respond to a particular form of sensory stimulation.

• Absolute Threshold- the smallest possible strength of a stimulus that can be detected half the time.
• Difference threshold- Smallest possible difference between two stimuli that can be detected half the time; also called just noticeable difference.

The process of detecting a physical stimulus, such as light, sound, heat, or pressure.

The process of integrating, organizing, and interpreting sensations

Sensitivity of Different Body Areas to Pain

Source: Information from Geldard (1972)

Individual Differences in Pain Perception and Tolerance

People respond to pain differently:

• Women tend to have a lower pain threshold than men, but rate pain as more unpleasant and display more intense physiological responses to painful stimuli (Casale et al., 2021; Jarrett, 2011).
• Women are more likely to than men to experience pain-related diseases; and when they do they are more likely to have a more severe case. It is not clear why the differences exist. Some argue that we need to move past “an overreliance on binary categories to fully understand how and why sex and gender impact on pain” (Keogh, 2022, p. S108).
• Ethnicity, race, and culture also influence the response to pain (Jarrett, 2011).
• Research has documented stereotype-driven differences in treatment of pain with many doctors showing higher empathy and a higher likelihood of treatment for White people than for Black people, despite the fact that Black people, often report higher levels of pain than White people (Morales & Young, 2021; Tait & Chibnall, 2014).

How do Hallucinations Occur?

Researchers suggest that some may be due to bottom-up processing, in which actual sensations are misperceived (the wind blows and feels like a touch). While some may be due to top-down processing, perceptions based on expectations (smelling food when walking by a closed restaurant)

Hallucinations

Why do so many perceive something that isn’t there? Research suggests that hallucinations may offer an evolutionary advantage, contributing to survival. Hallucinations have been documented as “warning signs,” such as hearing sirens or children crying, smelling smoke, or feeling hands. So hallucinations may mean that we are attuned to our environment in ways that might protect us.

Figure-Ground Relationship- A Gestalt principle stating that a perception is automatically separated into the figure, which is the main element of the scene, and the ground, which is its background. Figure-Ground Reversal- Illustrate the psychological nature of our ability to perceptually sort a scene into the main element and the background. If you perceive the white area as the figure and the dark area as the ground, you’ll perceive a vase. If you perceive the dark area as the figure, you’ll perceive two faces.