Lesson 5 Sensation and Perception Handouts PDF

INTRODUCTION TO PSYCHOLOGY SENSATION AND PERCEPTION Introduction Thanks to the nose, ears, eyes, tongue, and skin, we can imagine a day at the beach: glimmering blue sky, salty water, warm sand, and crying seagulls. Our knowledge of the world depends on the senses: vision, hearing, taste, smell, p...

INTRODUCTION TO PSYCHOLOGY SENSATION AND PERCEPTION Introduction Thanks to the nose, ears, eyes, tongue, and skin, we can imagine a day at the beach: glimmering blue sky, salty water, warm sand, and crying seagulls. Our knowledge of the world depends on the senses: vision, hearing, taste, smell, position, movement, balance, and touch. If someone bounces a basketball, our eyes and ears pick up stimuli such as light and sound waves and send neural signals to the brain. This process called sensation occurs when physical energy from objects in the world or in the body stimulates the sense organs. The Senses Sensation is the process by which physical energy from objects in the world or in the body stimulates the sense organs, and stimulation of sensory receptors and the transmission of sensory information to the central nervous system. The brain interprets and organizes this sensory information in a process called perception. Psychologists assess the acuity of the senses in three ways: 1. Measuring the absolute threshold 2. Measuring the difference threshold 3. Applying signal detection theory The absolute threshold is the minimum amount of stimulation required for a person to detect the stimulus 50 percent of the time. The difference threshold is the smallest difference in stimulation that can be detected 50 percent of the time. The difference threshold is sometimes called the just noticeable difference (jnd), and it depends on the strength of the stimulus. Example: If someone were comparing two weak stimuli, such as two very slightly sweet liquids, he’d be able to detect quite a small difference in the amount of sweetness. However, if he were comparing two intense stimuli, such as two extremely sweet liquids, he could detect only a much bigger difference in the amount of sweetness. Sensory Adaptation When people walk into a restaurant, they probably notice food smells right away. However, as they sit in the restaurant, the smells gradually become less noticeable. This phenomenon occurs because of sensory adaptation. Sensory adaptation is the decrease in sensitivity to an unchanging stimulus. The smells don’t disappear—the people just become less sensitive to them. Development of the Senses Babies have all the basic sensory abilities and many perceptual skills, but these abilities develop and grow more sensitive over time. Babies can recognize the difference between a human voice and other sounds, and they can locate a sound’s origin. They can recognize the difference between smells and, very early on, can recognize their mother’s particular smell. As for taste, they can differentiate between sweet and salty. Babies also have fairly adept visual abilities. Soon after birth, they can distinguish objects of different colors and sizes. When they are just a few weeks old, they begin to differentiate among contrasts, shadows, and patterns, and they can perceive depth after just a few months. Sensitive Periods Even innate perceptual skills need the right environment to develop properly. A lack of certain experiences during sensitive periods of development will impair a person’s ability to perceive the world. Example: People who were born blind but regain their vision in adulthood usually find the visual world confusing. Since these adults were blind in infancy, they missed the sensory experiences necessary for their visual system to develop fully. Vision Structure of the Eye The process of vision cannot be understood without some knowledge about the structure of the eye: The cornea is the transparent, protective outer membrane of the eye. The iris, the colored part of the eye, is a ring of muscle.  The iris surrounds an opening called the pupil, which can get bigger or smaller to allow different amounts of light through the lens to the back of the eye. In bright light, the pupil contracts to restrict light intake; in dim light, the pupil expands to increase light intake. Pupils Dilates - When a person enters a dark room, to allow lighter to enter their eyes. Example: People can often see a star in the night sky if they look a little to the side of the star instead of directly at it. Looking to the side utilizes peripheral vision and makes the image of the star fall onto the periphery of the retina, which contains most of the rods. The lens, which lies behind the pupil and iris, can adjust its shape to focus light from objects that are near or far away. This process is called accommodation. Light passing through the cornea, pupil, and lens falls onto the retina at the back of the eye. The retina is a thin layer of neural tissue. The image that falls on the retina is always upside down. The center of the retina, the fovea, is where vision is sharpest. This explains why people look directly at an object they want to inspect. This causes the image to fall onto the fovea, where vision is clearest. Rods and Cones The retina has millions of photoreceptors called rods and cones. Photoreceptors are specialized cells that respond to light stimuli. There are many more rods than cones. The long, narrow cells, called rods, are highly sensitive to light and allow vision even in dim conditions. There are no rods in the fovea, which is why vision becomes hazy in dim light. However, the area just outside the fovea contains many rods, and these allow peripheral vision. Because rods are so sensitive to light, in dim lighting conditions peripheral vision is sharper than direct vision. Visual Processing in the Brain After being processed in the thalamus and different areas of the brain, visual signals eventually reach the primary visual cortex in the occipital lobe of the brain’s cerebrum. Form Perception The ability to see separate objects or forms is essential to daily functioning. Suppose a girl sees a couple in the distance with their arms around each other. If she perceived them as a four-legged, two-armed, two-headed person, she’d probably be quite disturbed. People can make sense of the world because the visual system makes sensible interpretations of the information the eyes pick up. Depth Perception Depth perception is your ability to see objects in three dimensions, including their size and how far away they are from you. It’s made possible by lots of parts in your eyes and your brain working together to process information, estimate their location and create the images you see. (Ex. Having a pencil and a mug on the desk and being able to tell which one is closer, and threading a needle) Gestalt psychology, a school of thought that arose in Germany in the early twentieth century, explored how people organize visual information into patterns and forms. Gestalt Principles Gestalt psychologists described several principles people use to make sense of what they see. These principles include figure and ground, proximity, closure, similarity, continuity, and simplicity: Figure and ground: One of the main ways people organize visual information is to divide what they see into figure and ground. Figure is what stands out, and ground is the background in which the figure stands. People may see an object as figure if it appears larger or brighter relative to the background. They may also see an object as figure if it differs noticeably from the background or if it moves against a static environment.  Proximity: When objects lie close together, people tend to perceive the objects as a group. For example, in the graphic, people would probably see these six figures as two groups of three. Closure: People tend to interpret familiar, incomplete forms as complete by filling in gaps. People can easily recognize the following figure as the letter k in spite of the gaps. Similarity: People tend to group similar objects together. In the next figure, people could probably distinguish the letter T because similar dots are seen as a group. Continuity: When people see interrupted lines and patterns, they tend to perceive them as being continuous by filling in gaps. The next figure is seen as a circle superimposed on a continuous line rather than two lines connected to a circle. Simplicity: People tend to perceive forms as simple, symmetrical figures rather than as irregular ones. This figure is generally seen as one triangle superimposed on another rather than a triangle. with an angular piece attached to it. Hearing Hearing, or audition, depends on the presence of sound waves, which travel much more slowly than light waves. Sound waves are changes in pressure generated by vibrating molecules. The physical characteristics of sound waves influence the three psychological features of sound: loudness, pitch, and timbre. Loudness depends on the amplitude, or height, of sound waves. The greater the amplitude, the louder the sound perceived. Amplitude is measured in decibels. The absolute threshold of human hearing is defined as 0 decibels. Loudness doubles with every 10-decibel increase in amplitude. A Whisper to a Scream The loudness of normal human conversation is about sixty decibels. A whisper is about twenty decibels. A shout right into someone’s ear is about 115 decibels. Being exposed to sounds that are over 120 decibels, even for brief periods, can damage the auditory system. The Structure of the Ear Knowing the basic structure of the ear is essential to understanding how hearing works. The ear has three basic parts: the outer ear, the middle ear, and the inner ear. The visible part of the ear is the pinna, which collects sound waves and passes them along the auditory canal to a membrane called the eardrum. When sound waves hit the eardrum, it vibrates. The eardrum transmits the vibration to three bones, or ossicles, in the middle ear, which are called the hammer, the anvil, and the stirrup. The diagram of the ear shows how they got these names: they actually look like a hammer, an anvil, and a stirrup. In response to the vibration, these ossicles move one after another. Their function is to amplify the sound vibrations. From the ossicles, vibrations move through a membrane called the oval window to the cochlea of the inner ear. The cochlea is a coiled, fluid-filled tunnel. Inside the cochlea are receptors called cilia or hair cells that are embedded in the basilar membrane. The basilar membrane runs along the whole length of the coiled cochlea. Vibrations that reach the inner ear cause the fluid in the cochlea to move in waves. These waves in turn make the hair cells move. The movement triggers impulses in neurons that connect with the hair cells. The axons of these neurons come together to form the auditory nerve, which sends impulses from the ear to the brain. In the brain, the thalamus and the auditory cortex, which is in the temporal lobe of the cerebrum, receive auditory information. Frequency and Amplitude - Sounds that have many cycles per second are high-frequency, or high-pitch, while sounds that have fewer cycles per second are low-frequency, or low-pitch. - Wave frequency is to pitch as wave amplitude is to loudness. Taste and Smell Taste and smell are chemical senses. As light waves stimulate vision and sound waves stimulate sound, chemicals stimulate taste and smell. Taste Taste, or gustation, happens when chemicals stimulate receptors in the tongue and throat, on the inside of the cheeks, and on the roof of the mouth. These receptors are inside taste buds, which in turn are inside little bumps on the skin called papillae. Taste receptors have a short life span and are replaced about every ten days. For a long time, researchers believed in the existence of four tastes: salty, sweet, sour, and bitter. Recently, researchers have suggested the presence of a fifth taste called umami. The spice monosodium glutamate (MSG) has an umami taste, as do many protein-rich foods. Taste is also strongly influenced by smell. Smell Smell, or olfaction, happens when chemicals in the air enter the nose during the breathing process. Smell receptors lie in the top of the nasal passage. They send impulses along the olfactory nerve to the olfactory bulb at the base of the brain. Researchers theorize that there are a great many types of olfactory receptors. People perceive particular smells when different combinations of receptors are stimulated. Remembrance of Smells Past The sense of smell is closely connected with memory. Most people have had the experience of smelling something, maybe a certain perfume or spice, and suddenly experiencing a strong emotional memory. Researchers don’t know exactly why this happens, but they theorize that smell and memory trigger each other because they are processed in neighboring regions of the brain. Bodily True Organ Location Stimulus Sensory Receptors Experience or Discrimination Eye Rods and Cones Retina Light Waves Visual Perceptions Ear Tectorial Cells Cochlea Sound Waves Tones, Noise, music, speech Nose Olfactory Bulbs Olfactory Gaseous Smell (fruity, Epithelium Substances flowery, smoky)  Tongue Taste Buds Surface and Liquid Sweet, salty, sour, Edge of the substances bitter tongue Skin Meissner Layers of the skin Touch Warmth, pressure, Corpuscles cold and pain Errors in Perception 1. Illusion – is an impression from experience which does not correctly represent the objective situation outside the observer. It maybe used to denote error in immediate perception and in meaning. 2. Hallucinations – false perceptions occurring in the absence of sensory experience. 3. Delusions – are false beliefs organized from both perception and memory, in an individual may misinterpret his own identity or misinterpret the actions of others. Extrasensory perception—ESP Extrasensory perception—ESP—is defined by parapsychologists as the acquisition by a human or animal mind of information it could not have received by normal, sensory means. Some researchers, however, take issue with the term "extrasensory perception." They protest that the phenomena may not be "perception" at all, as the receiver of this information does not know if the knowledge is right or wrong when he or she first perceives it. Here are brief definitions of the areas of ESP that are studied by parapsychologists: Clairvoyance is the awareness, without physical aids or normal sensory means, of what is going on elsewhere. In recent years, clairvoyance has sometimes been called remote viewing. Out-of-body experience (also called astral projection) is the apparent projection of the mind from the body, often with the seeming ability to travel great distances in a matter of seconds. Precognition (premonition) is the obtaining of information about the future that could not have been gained through normal means. Psychokinesis (telekinesis) is the movement of objects, seemingly caused by some force unknown to physical science. The direct action of mind on matter is the parapsychologists' current nominee as the energy involved in poltergeist cases—those bizarre occurrences when bottles and crockery float through the air, fires break out on living room tables, or disembodied voices cackle threats and obscenities. Kinesthesis – Also referred to as kinesthesia or kinesthetic sense. It is a Sense of movement and body position Telepathy is the transference of thought from one mind to another. Distance and time seem unable to affect this phenomenon.