Sensation and Perception PDF

SENSATION AND PERCEPTION COMPARISON SENSATION Perception is the way we interpret these sensations and therefore make sense of everything around us. A mental process (such as seeing, hearing, or smelling)...

SENSATION AND PERCEPTION COMPARISON SENSATION Perception is the way we interpret these sensations and therefore make sense of everything around us. A mental process (such as seeing, hearing, or smelling) The act or faculty of perceiving, or resulting from the immediate apprehending by means of the senses external stimulation of a sense or of the mind; cognition; organ often as distinguished understanding. from a conscious awareness of the sensory process PERCEPTION 2  SENSATION Sensation can be explained as Sensory receptors are specialized the process by which one form neurons that respond to specific of energy is converted into types of stimuli. When sensory information is detected by a another form. For example, light sensory receptor, sensation has is converted into neural impulses occurred. For example, light that by which we code sensory events enters the eye causes chemical in our system that can be changes in cells that line the back processed by our brain. The of the eye. These cells relay messages in the form of action sensory systems process potentials to the central nervous information reaching to the system. The conversion from brain. The motor systems sensory stimulus energy to action process information going out of potential is known as the brain to muscles and glands. transduction. 3  PERCEPTION Perception refers to the way How we interpret those sensory information is organized, sensations is influenced by our interpreted, and consciously available knowledge, our experienced. experiences, and our thoughts. This is called top-down processing. One way to think of this concept is that sensation is a physical process, whereas perception is psychological. 4 PERCEPTION 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 sensory adaptation. 5 ABSOLUTE THRESHOLD The minimum amount of stimulus energy that must be present for the stimulus to be detected 50% of the time. Another way to think about this is by asking how dim can a light be or how soft can a sound be and still be detected half of the time. The sensitivity of our sensory receptors can be quite amazing. It has been estimated that on a clear night, the most sensitive sensory cells in the back of the eye can detect a candle flame 30 miles away (Okawa & Sampath, 2007). Under quiet conditions, the hair cells (the receptor cells of the inner ear) can detect the tick of a clock 20 feet away (Galanter, 1962). 6 ABSOLUTE THRESHOLD It is also possible for us to get messages that are presented below the threshold for conscious awareness—these are called subliminal messages. A message below that threshold is said to be subliminal where we receive it, but we are not consciously aware of it. Research evidence shows that in laboratory settings, people can process and respond to information outside of awareness. (Kunst-Wilson & Zajonc, 1980; Rensink, 2004; Nelson, 2008; Radel, Sarrazin, Legrain, & Gobancé, 2009; Loersch, Durso, & Petty, 2013). 7 FACTOR THAT AFFECTS SENSATION AND PERCEPTION ATTENTION MOTIVATION EXPERIENCE BELIEFS Attention plays a significant If you have been expecting a Individuals who are deprived The shared experiences of role in determining what is really important phone call of the experience of binocular people within a given cultural sensed versus what is while taking a shower and you vision during critical periods of context can have pronounced perceived think you hear the phone development have trouble effects on perception. ringing but in reality it is not, perceiving depth (Fawcett, then you have experienced Wang, & Birch, 2005). that motivation to detect a meaningful stimulus can shift our ability to discriminate between a true sensory stimulus and background noise. 8 WAVES AND WAVELENGTHS VISUAL AND AUDITORY STIMULI WAVES AND WAVELENGTHS Visual and auditory stimuli both occur in the form of waves. Although the two stimuli are very different in terms of composition, wave forms share similar characteristics that are especially important to our visual and auditory perceptions. Two physical characteristics of a wave are amplitude and wavelength. 10  SOUND The amplitude of a wave is the Wavelength is directly related to height of a wave as measured the frequency of a given wave from the highest point on the form. Frequency refers to the wave (peak or crest) to the number of waves that pass a lowest point on the wave given point in a given time (trough). period and is often expressed in terms of hertz (Hz), or cycles per second. Longer wavelengths will Wavelength refers to the length have lower frequencies, and of a wave from one peak to the shorter wavelengths will have next. higher frequencies.. 11  LIGHT WAVES The visible spectrum is the The visible spectrum in humans is portion of the larger associated with wavelengths that electromagnetic spectrum that range from 380 to 740 nm—a very small distance, since a nanometer we can see. As the image shows, (nm) is one billionth of a meter. the electromagnetic spectrum Other species can detect other encompasses all of the portions of the electromagnetic electromagnetic radiation that spectrum. For instance, honeybees occurs in our environment and can see light in the ultraviolet range (Wakakuwa, Stavenga, & includes gamma rays, x-rays, Arikawa, 2007), and some snakes ultraviolet light, visible light, can detect infrared radiation in infrared light, microwaves, and addition to more traditional visual radio waves. light cues (Chen, Deng, Brauth, Ding, & Tang, 2012; Hartline, Kass, & Loop, 1978). 12  LIGHT WAVES In humans, light wavelength is associated with perception of color. Within the visible spectrum, our experience of red is associated with longer wavelengths, greens are intermediate, and blues and violets are shorter in wavelength. (An easy way to remember this is the mnemonic ROYGBIV: red, orange, yellow, green, blue, indigo, violet.) The amplitude of light waves is associated with our experience of brightness or intensity of color, with larger amplitudes appearing brighter. 13  SOUND WAVES The frequency of a sound wave is As was the case with the visible associated with our perception spectrum, other species show of that sound’s pitch. High- differences in their audible frequency sound waves are ranges. For instance, chickens perceived as high-pitched have a very limited audible sounds, while low-frequency range, from 125 to 2000 Hz. Mice sound waves are perceived as have an audible range from 1000 low-pitched sounds. The audible to 91000 Hz, and the beluga range of sound frequencies is whale’s audible range is from between 20 and 20000 Hz(The 1000 to 123000 Hz. Our pet dogs hertz (symbol: Hz) is the unit of and cats have audible ranges of frequency), with greatest about 70–45000 Hz and 45– sensitivity to those frequencies 64000 Hz, respectively (Strain, that fall in the middle of this 2003). range. 14  SOUND WAVES The loudness of a given sound However, there is the is closely associated with the potential for hearing damage amplitude of the sound wave. from about 80 dB to 130 dB: Higher amplitudes are These are sounds of a food processor, power lawnmower, associated with louder heavy truck (25 feet away), sounds. Loudness is measured subway train (20 feet away), in terms of decibels (dB), a live rock music, and a logarithmic unit of sound jackhammer. The threshold intensity. A typical for pain is about 130 dB, a jet conversation would correlate plane taking off or a revolver with 60 dB; a rock concert firing at close range (Dunkle, might check in at 120 dB. 1982). 15  SOUND WAVES Amplitude is the relative strength of Although wave amplitude is sound waves (transmitted vibrations), generally associated with which we perceive as loudness or loudness, there is some volume. Amplitude is measured in interaction between decibels (dB), which refer to the sound frequency and amplitude in pressure level or intensity. our perception of loudness within the audible range. For example, a 10 Hz sound wave Frequency is the rate at which current is inaudible no matter the changes direction per second. It is amplitude of the wave. A measured in hertz (Hz), an 1000 Hz sound wave, on the international unit of measure where 1 other hand, would vary hertz is equal to 1 cycle per second. dramatically in terms of Hertz (Hz) = One hertz is equal to one perceived loudness as the cycle per second amplitude of the wave increased. 16  CHEMICAL AND OTHER SENSES In this section, we will explore our chemical senses (taste and smell) and our body senses (touch, temperature, pain, balance, and body position). 17  THE CHEMICAL SENSES Taste (gustation) and For example, when we describe the flavor of a given food, we are smell (olfaction) are really referring to both gustatory and olfactory properties of the called chemical senses food working in combination. You because both have have learned since elementary school that there are four basic sensory receptors that groupings of taste: sweet, salty, sour, and bitter. Research respond to molecules demonstrates, however, that we have at least six taste groupings. in the food we eat or in Umami is our fifth taste. Umami is the air we breathe. actually a Japanese word that roughly translates to yummy, and There is a pronounced it is associated with a taste for monosodium glutamate interaction between (Kinnamon & Vandenbeuch, 2009). our chemical senses. 18  THE CHEMICAL SENSES Molecules from the food Taste buds have a life cycle of and beverages we ten days to two weeks, so consume dissolve in our even destroying some by burning your tongue won’t saliva and interact with have any long-term effect; taste receptors on our they just grow right back. tongue and in our mouth Taste molecules bind to and throat. Taste buds receptors on this extension are formed by groupings and cause chemical changes of taste receptor cells within the sensory cell that result in neural impulses with hair-like extensions being transmitted to the brain that protrude into the via different nerves, central pore of the taste depending on where the bud. receptor is located. 19  THE CHEMICAL SENSES Olfactory receptor cells are There is tremendous variation in the located in a mucous membrane sensitivity of the olfactory systems of at the top of the nose. Small different species. We often think of dogs as having far superior olfactory hair-like extensions from these systems than our own, and indeed, receptors serve as the sites for dogs can do some remarkable things odor molecules dissolved in the with their noses. There is some mucus to interact with chemical evidence to suggest that dogs can receptors located on these “smell” dangerous drops in blood extensions. Once an odor glucose levels as well as cancerous tumors (Wells, 2010). Dogs’ molecule has bound a given extraordinary olfactory abilities may be receptor, chemical changes due to the increased number of within the cell send signals to the functional genes for olfactory olfactory bulb, a bulb-like receptors (between 800 and 1200), structure at the tip of the frontal compared to the fewer than 400 observed in humans and other lobe where the olfactory nerves primates (Niimura & Nei, 2007). begin 20  THE CHEMICAL SENSES Taste information is transmitted to the medulla, thalamus, and limbic system, and to the gustatory cortex, which is tucked underneath the overlap between the frontal and temporal lobes (Maffei, Haley, & Fontanini, 2012; Roper, 2013). From the olfactory bulb, information is sent to regions of the limbic system and to the primary olfactory cortex, which is located very near the gustatory cortex (Lodovichi & Belluscio, 2012; Spors et al., 2013). 21  TOUCH, THERMOCEPTION, AND NOCICEPTION A number of receptors are distributed throughout the skin to respond to various touch- related stimuli. These receptors include Meissner’s corpuscles, Pacinian corpuscles, Merkel’s disks, and Ruffini corpuscles. Meissner’s corpuscles respond to pressure and lower frequency vibrations, and Pacinian corpuscles detect transient pressure and higher frequency vibrations. Merkel’s disks respond to light pressure, while Ruffini corpuscles detect stretch (Abraira & Ginty, 2013). 22  TOUCH, THERMOCEPTION, AND NOCICEPTION In addition to the receptors located in the skin, there are also a number of free nerve endings that serve sensory functions. These nerve endings respond to a variety of different types of touch- related stimuli and serve as sensory receptors for both thermoception (temperature perception) and nociception (a signal indicating potential harm and maybe pain) (Garland, 2012; Petho & Reeh, 2012; Spray, 1986). Sensory information collected from the receptors and free nerve endings travels up the spinal cord and is transmitted to regions of the medulla, thalamus, and ultimately to somatosensory cortex, located in the postcentral gyrus of the parietal lobe. 23  PAIN PERCEPTION Pain is an unpleasant experience that involves both physical and psychological components. Feeling pain is quite adaptive because it makes us aware of an injury, and it motivates us to remove ourselves from the cause of that injury. In addition, pain also makes us less likely to suffer additional injury because we will be gentler with our injured body parts. 24  THE VESTIBULAR SENSE, PROPRIOCEPTION, AND KINESTHESIA The vestibular sense contributes When these hair cells are to our ability to maintain balance stimulated, they send signals to and body posture. As the image the brain via the vestibular shows, the major sensory organs nerve. Although we may not be (utricle, saccule, and the three consciously aware of our semicircular canals) of this vestibular system’s sensory system are located next to the information under normal cochlea in the inner ear. The circumstances, its importance is vestibular organs are fluid-filled apparent when we experience and have hair cells, similar to the ones found in the auditory motion sickness and/or dizziness system, which respond to related to infections of the inner movement of the head and ear (Khan & Chang, 2013). gravitational forces. 25  THE VESTIBULAR SENSE, PROPRIOCEPTION, AND KINESTHESIA These sensory systems also In addition to maintaining gather information from balance, the vestibular system receptors that respond to stretch collects information critical for and tension in muscles, joints, controlling movement and the skin, and tendons (Lackner & reflexes that move various parts DiZio, 2005; Proske, 2006; Proske of our bodies to compensate for & Gandevia, 2012). changes in body position. Proprioceptive and kinesthetic Therefore, information travels to the brain both proprioception (perception via the spinal column. Several of body position) cortical regions in addition to the and kinesthesia (perception of cerebellum receive information the body’s movement through from and send information to space) interact with information the sensory organs of the provided by the vestibular proprioceptive and kinesthetic system. systems. 26 CHART Statistics here 6 5 4 3 2 1 0 Category 1 Category 2 Category 3 Category 4 Series 1 Series 2 Series 3 27 THE PRINCIPLES OF PERCEPTION  Everyday different stimuli around us will be stimulating our sense organs. many of these stimuli are received by our sense organs and are converted into sensations. These sensations are transmitted to the concerned parts of the brain. In turn the brain will interpret these sensations. it is only after such interpretation we understand what the stimulus is. Hence in understanding the world around us, attention occurs first, followed by sensation and finally, interpretation by brain.  PERCEPTION In the perceptual process we The process of interpretation of select a particular stimulus with stimulus is known as perception. our attention and interpret it. In Perception may be defined as “a the same way whenever it is process of interpretation of a necessary many discrete stimuli in our visual field are organized into a present stimulus on the basis of form and perceived more past experience”. Perception is meaningfully than they appear. not simple; it is an integrated This phenomenon was well approach. It is a synthetic explained by Gestalt psychologists. process where different They believed that the brain creates a coherent perceptual physiological and psychological experience by perceiving a processes are involved. These stimulus as a whole than processes include the accuracy perceiving discrete entities. This is of sense organs, clarity of more meaningfully stated in the sensations and mental set of an gestalt principle as ‘the whole is better than sum total of its parts’. individual. 30  SUB-PRINCIPLES OF PERCEPTION: FIGURE-GROUND RELATIONSHIP According to this principle any figure can be perceived more meaningfully in a background and that figure cannot be separated from that background. For example, letters written with a white chalk piece are perceived clearly in the background of a blackboard. 31  SUB-PRINCIPLES OF PERCEPTION: GROUPING OF STIMULI IN PERCEPTUAL ORGANIZATION According to gestalt principle, the objects can be perceived meaningfully when they are grouped together. There are some principles which are followed by us in order to make our perception more meaningful. Example Proximity which means nearness.. 32  SUB-PRINCIPLES OF PERCEPTION: PERCEPTUAL CONSTANCY This refers to stableness in perception. We have a tendency to perceive the objects as relatively stable and unchanging in shape and size, in spite of a change in the image that we receive. 33  SUB-PRINCIPLES OF PERCEPTION: DEPTH PERCEPTION. Ability of a person to perceive the distance is known as depth perception. This is very important ability to judge the distance between us and other people, objects and vehicles moving particularly when we are on roads. This is also known as third dimension. The other two dimensions are left and right, and above and below. 34  SUB-PRINCIPLES OF PERCEPTION: PERCEPTION OF MOVEMENT When a particular object appears in different places at different times, we understand that the object is in movement. This process is called perception of movement. Such an ability to perceive movement is gained from birth itself as a natural process. This is a most important ability. It is only by this ability the organism can understand the world around and can perceive the dangers / threats in the movement, so that it can easily escape from such dangers. Sometimes we perceive that the objects are moving while in fact the objects are stationary, i.e. they will not be moving. Hence the perception of an object which is not moving, as an object moving is an illusion. 35 THANK YOU !