Sensation- The process of accepting the stimulus by the senses. Considered the mechanism of receiving information. In sensation there must be a stimulus and there must be a receptors that are sensitive to the stimulus. Stimulus is any form of energy that can cause awareness or change of consciousness. Defines any form of energy capable of exciting the nervous system like light waves, sound waves, and chemical energy that causes the sensation of taste and smell. Receptors are specialized cells responsible for detecting specific type of energy as a result of transduction. Specialized nerve ending capable of responding to energy. Transduction is the process of changing the stimulus sense into energy for neural activity Psychophysics is the relationship between the physical and psychological environment. It connects the external and internal world of an individual. Aims to examine the sensitivity of the individual to various stimuli. Then it determines the psychological perception on the stimulus. The process assess the presence and intensity of the stimulus. Furthermore the presence of stimulus depends on the cognition , experience, culture, personality and what the individual expects, desires and wants to perceive. the study of how physical stimuli are translated into psychological experience. Threshold - a dividing line between what has detectable energy and what does not. Absolute Threshold is the least quality and quantity of a stimulus that can be sensed and perceived consequently. It is the smallest intensity of energy that can be perceived 50 percent of the time. A person who can detect the weakest stimulus is said to be sensitive or with high threshold. For human senses to perceive or detect stimulus, it must depend on the background level or should be under idea condition. Absolute threshold on certain or same stimuli may cary depending on different people’s perception. SENSES ABSOLUTE TRESHOLD VISION A candle flame at 30 miles on a dark clear night. HEARING a tickling watch at 20 feet under quiet conditions TASTE a teaspoon of sugar dissolve in two gallons of water. SMELL one drop of perfume diffused throughout 3 rooms. TOUCH the wing of a fly falling on your cheek from distance of 1 centimeter. Difference Threshold or Just Noticeable Difference (JND) is the minimum difference in intensity between two stimuli when caused by a smallest change. It does not only determine the presence or absence of stimulus but also detect whether the two small stimuli are different or the same. Weber’s Law by Ernst Weber Regardless of magnitude, two stimuli must differ by a constant minimum percentage ( rather that a constant amount to be perceived as different. JND=KI, where I is the intensity of stimulus and K is the constant fraction which varies according to the different sensory systems for the different aspects of sensation. Senses K( constant fraction) Pitch .003 Brightness .017 Weight .020 Loudness .100 Pressure on skin .140 Saltiness of taste .200 Signal Detection Theory This theory states, sensitivity o stimuli depends on a variety of factors beeside the physical intensity of the stimulus and the sensory abilities of the observer. These factors include individual and contextual variations such as fatigue expectancy and the urgency of the moment. Fechner’s and Steven’s Law Since JND is the minimum detectable change, Frechner reasoned that constant increases in physical energy will result continuously to smaller increases in one’s onw magnitude. Gustav Frechner suggested that Weber’s Law can be utilized to understand the perception or psychological experience on the magnitude of stimulus. The tendency of JND is to grow larger, since JND has already the smallest K. For JND to progress larger it needs an increase of energy from the stimulus. The required stimulus becomes more intense and physical energy demands larger increase to detect a change of greater magnitude from the constant JND. Fechner’s law enables one to describe and judge differences of each sensory system. S.S. Steven found the late to generate accurae functions in estimation subjective relaive magnitude of any kind of stimulus of varying intensities. This law for activity reaches the photoreceptor (rod and cones). Photoreceptors contain photo pigmentes or chemicals that can respond to light. The light causes the photigmentes to separate resulting to electic potentials. This electric potential will then transmit the signal ( stimulus ) to the brain understanding why people have different perception on the same stimuli. Visual Sensation; Cornea, the transparent protective covering curved tissue in front of the eye. Behind the cornea, Aqueous Humor the light continues to the anterior front chamber which contains the watery liquid (aqueous humor ) to provide nutrients and keep the cornea moist. Pupil where the light enters through. A small hole at the center of the black circle of the eyes and behind the chamber. The pupil controls the amount of light by constricting ( closing ) on too much light and dilating ( opening ) under dark condition. Iris- is the colored muscles of the eye responsible for reducing *(constricting) or enlarging (dilating ) the size of the pupil. Lens is an elastic curved structure that bends light rays in order to focus a clear image to the retina. Retina is an intricate network of cells containing neurons, ganglion cells and photoreceptors. It is the retina where visual transduction takes place. This is the conversion of light energy into neural activity or electrical potential in the neurons so that the stimulus can be transmitted to the brain. After passing the neurons, the neural activity reaches the photoreceptor ( Rod and Cones) Rod and Cones photoreceptors contain photopigments or chemicals that can respond to light. Rod does not distinguish colors. Best for night time vision Cones best for daytime vision and in able us to see colors. Fovea is a minute area in the center of the retina where vision is at best. Contains only cones Blind Spots is the place on the retina where the optic nerve leaves the eye on its way to the brain. One cannot see anything that reaches only this part of the retina. COLOR VISION Wavelength of light the sun projects wavelength of light. Has a determined intensity that can sense a certain color. Hue the fundamental color, marked by the intensity of wavelength of the light. ( based on Wavelength content) Saturation is associated with the purity of color. ( based on purity ) Brightness conform to the total degree of all the wavelengths constituting light ( based on intensity ) Auditory Sensation Sound Waves are vibrations in the air that are processed by the auditory ( or hearing ) system. Inna composed of cartilage and has a relatively poor blood supply. Auditory canal contains lining of tiny hairs and wax gland which lubricate and subsequently protect bye trapping dirt and insects. Ear drum like a drum cause the sound waves to vibrate match the sound produced. The vibrated matched sound produced is conducted to the three smallest bones in the body named for their shape the malleus (hammer), incus (anvil) and the stapes ( stirrub). The three suspended chained tiny bones convert the action of sound pressure into mechanical movements. The increased pressure affects the oval window, a flexible membrane that amplifies the changes in resure developed by the former soundwaves. Cochlea where transduction happens. A snail shaped structure that is the sensory organ of hearing. The vibrational patterns that are initiated by vibration of the stapes footpleate sut up a traveling pattern within the cochlea. This wavelike pattern causes a shearing of the cilia of the outer and inner hair cells. This searing causes hair call depolarization resulting in all or none neural impulses that the brain interprets as sounds. Theories of Hearing. Goerg con Bekesy started on how frequency is coded. The place theory depends on the pitch ( highness/ lowness). Somatic Sensation Somatic sensation includes the skin senses of touch, temperature, pain and kinesthesia. The somatic senses are distributed throughout the body. The skin has several receptors which are specific to different types of stimulus. The skin has three layers: The skin has three layers: Epidermis (outermost) Dermis ( middle ) And the subcutaneous (lowest) In touch, individuals detect mechanical energy or pressure against the skin. The receptors for touch are Meissner’s corpuscles and Merkel’s disk. The pacinian corpuscles, receptors for pressure are responsible for pressure sensitivity. The most sensitive part are the lips and fingers. The back part of the body is insensitive. The more receptors, the more sensitive. Physiologic zero if the skin temperature is 32 degrees centigrade, no sensation is felt, neither hot or cold. The baseline temperature ranges from 20 degrees Celsius at the earlobe to about 37 degrees Celsius on the forearm. Thermoreceptors are located under the skin, which responds to increases and decreases in temperature. They come in two types warm and cold. Ruffini nerve ending receptor for hot Krause end bulbs for cold. Pain usually is the sensation that warns the individuals that damage to one’s body is occurring. Pain is usually on the skin surfaces. It is offen localized. Internal pains do occur and are hard to distinguish and determined. Pain is also a reflection of subjective judgment. Pain depends on one’s perception ( fear, thoughts, ideas, imagination etc.). the receptors for physical pain is the free nerve ending. Chemical Senses. Gustatory Sense (taste ) and olfactory sense ( smell) are referred to as chemicals senses. They relate closely in reacting to chemical substances in different stimuli. The receptors for gestation are the taste buds. Taste buds are grouped together to form the structure called papillae. The taste buds contained in the human tongue are about 10 000. These receptor cells are connected to nerve fibers that bring taste signal or information to the brain. They have four basic taste: sweet, sour, salty and bitter. Olfaction or the sense of smell is somehow considered to be one of the lower senses. Odors of gaseous state are sense in the upper part of the nose. Molecules enter through the nostrils ( opening) or from the back of the mouth ( oral cavity) into the nasal cavity. Hence olfaction is a dual sense; it can smell internally (oral cavity) and externally (nasal cavity).Between the oral cavity and nasal cavity lies the olfactory epithelium or SCHENEIDERIAN membrane. The nasal cavity contains the olfactory mucosa, a membrane providing moisture. The olfactory mucosa is lined with cilia ( hair like projections.). The olfactory mucosa and cilia together trap moleculres not needed and produce electrical signals. Electric signals are sent to the olfactory receptors, the olfactory bulb. According to Henning there are six basic smell that can be perceived or determined by the brain: Fragrant, fruity, spicy, putrial, resinous and burned. Stereochemical theory of Amoore states that there are seven basic odors: Ethera ( chemical ), Floral (flower), Minty (spearmint), pungent (vinegar), camphoraceous (mothball) musky (perfume), and putrial ( raw fish or meat) This theory ( odor receptor site) explains that smell receptors have specific shapes and reception sites, and that the molecules of different types of smell must fit into the particular shapes. Chromatographic Theory explains that different smells are perceived based on the distance traveled inside the nasal cavity and the place it landed on in the mucous lining. The Kinesthetic and Vestibular Senses provides information about movement, posture and orientation while the Vestibular sense provides information about balance and movement. The semicircular canal which are located in the inner ear contain sensory receptors that detect head motion that is caused when one tilts or move his/head and or body. Both of the kinesthetic and vestibular senses work together in order to coordinate proprioceptive feedback which informs about the position of one’s limbs and body parts in relation to other body parts. Summary Sense Organ Sensation Stimuli Sensitivity Receptors Eyes vision lightwaves intensity of rods and cones Wavelengths: (retina) Hue, saturation Brightness Ears audiion soundwaves intensity of organ of corti Frequency: (cochlea) Pitch, tone, Loudness Skin somatic mechanical cutaneous: Touch and thermal pain free nerve ending (tactile) temperature: Warm Ruffini’s ending Cold Krause end bulb Pressure pacinian corpuscles Touch Merkel’s disk Meissner’s corpuscles Peritrichial Tongue gustatory solid and salt, sweet taste buds (taste) liquid (soluble sour, bitter Substance) Nose olfactory gaseous state Henning’s olfactory bulb Basic smell Amoore’s Stereochemical Theory Ear (inner vestibular bodily balance end of hair cells in the Ear (balance) movements (equilibrium) semicircular canal Semicircular Canal) Muscles, Kinesthetic bodily posture never endings of Tendons , (sia) movements muscles, tendons Joints and joints Perception is the process of giving meaning to sensation. Perception refers to interpretation of what we take in through our senses. The way we perceive our environment is what makes us different from other animals and different from each other. Perception Attention involves focusing on a specific aspect of experience while ignoring others. Attention is not only selective it is also shiftable. Principles of perception includes those involving shape perception, depth perception, motion perception and perceptual constancy A. Shape is perceived because of marked off contour ( a location at which a sudden change of brightness occurs. Gestalt psychologists developed a number of principles of perceptual organization one of which are the figure ground relationship, closure, proximity and similarity. a. Figure ground is the principle by which individuals organized the perceptual field into stimuli hat stand out our better known as the figure and those that are leftover or known as the ground b. Closure when individual sees disconnected or incomplete figures they fill in the spaces and see them as complete figures. c. Proximity when individuals see objects that are near each other, they tend to be seen as a unit. d. Similarity when individuals see objects that are similar to each other they tend to be seen as a unit. B. Depth Perception is the ability to perceive objects three-dimensionally. In order to see a world depth, people tend to use binocular cues, such as retinal disparity and convergence and monocular cues such as linear perspective, texture gradient, relative size, interposition, shadowing and aerial perspective. a. Binocular cues are depth cues that are based on the combination of the images on the left and right eyes and on the way the two eyes work together. Because individuals have two eyes, they tend to get two views of the world, one from each eye. The disparity or difference of the image in the two eyes is the binocular cue the brain uses to determine the depth or distance of an object. Both images are combined in the brain and the disparity between the images of objects in the two eyes gives information about the three dimensionality of the world. The perception of debt disparity can be demonstrated using stereoscopic information from single ow dimensional image. b. Monocular Cues are depth cues that can be extracted from the image in one eye either the left or the right eye. Some examples of monocular cues are as follows: Aerial Perspective. Distant objects tend to appear hazy due to pollution and water vapor in the air that scatter light waves Familiar size. Is based on what individual have learned from experience about the standard sizes of objects. Height in the field of view. Objects that are higher in a picture are seen as father away. Linear Perspective is when the cue is based on the fact that objects farther away take up less space on the retina. As an object recedes into the distance, parallel lines in the scene appear converge. Overlap. An object that partially conceals or overlaps another object is perceived as closer. Shading. This cue involves changes in perception due to the position of the light and the position of the viewer. Size in the field view. All other things being equal, objects that are smaller are seen farther away. Texture Gradient. Texture becomes denser and finer, the farther away it is the from the viewer. c. Motion Perception. Focuses on both real movement and apparent movement ( occurs when an object is stationary but they tend to perceive it to be moving.) d. Perceptual Constancy this concepts includes size, shape and brightness constancy. Experience with object and distance helps individuals to see objects as unchanging. C. Illusions Illusions occur when two objects produce exactly the same retinal image but are perceived as different images. D. Extrasensory Perception. Parapsychology study of ESP Extrasensory Perception is a perception that occurs without the use of any known sensory process. Most psychologists do not believe in ESP; however, a few of them investigate it. There are four main categories of ESP. a. Telepathy involves the transfer of thought from one person to another b. Precognition involves knowing events before they happen c. Clairvoyance involves the ability to perceive remote events that are not in sight d. Psychokinesis is the mind-over-matter phenomenon of being able to move objects without touching them such as mentally getting a chair to rise off the floor or shattering a glass merely by staring at it.
Posted on: Wed, 21 Aug 2013 11:01:31 +0000
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