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Chapter 5

Psychological Science - Third Canadian Edition - Chapter Five Notes.docx

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University of Toronto St. George

INTRODUCTION TO PSYCHOLOGY (CHAPTER 5) SENSATION = the sense organs’ responses to external stimuli and the transmission of these responses to the brain PERCEPTION = the processing, organization, and interpretation of sensory signals; it results in an internal representation of the stimulus TRANSDUCTION = a process by which sensory receptors produce neural impulses when they receive physical or chemical stimulation ABSOLUTE THRESHOLD = the minimum intensity of stimulation that must occur before you experience a sensation DIFFERENCE THRESHOLD = the just noticeable difference between two stimuli; the minimum amount of change required to detect a difference SIGNAL DETECTION THEORY = a theory on perception based on the idea that the detection of a faint stimulu requires a judgment – it is not an all-or-none process SENSORY ADAPTATION = the decrease in sensitivity to a constant level of stimulation GUSTATION = the sense of taste TASTE BUDS = sensory receptors that transduce taste information HOW WE TASTE:  When you bite into something, molecules dissolve in fluid on your tongue  Are received by taste receptors in taste buds, on the tongue, mouth and throat  They transmit that signal along a cranial nerve through the thalamus to other areas of your brain  As a result, you know taste is good or bad OLFACTION = the sense of smell, which occurs when receptors in the nose respond to chemicals OLFACTORY EPITHELIUM = the thin layer of tissue, within the nasal cavity, that is embedded with smell receptors OLFACTORY BULB = the brain centre for smell, located below the frontal lobes HOW WE SMELL:  When you smell something, odorants pass into your nose and nasal cavity  Olfactory receptors, in the olfactory epithelium, transmit the signal to the olfactory bulb  The bulb transmits the signal along the olfactory nerve to areas of the cortex and amygdala  As a result, you smell HAPTIC SENSE = the sense of touch HOW WE TOUCH:  When you touch something, your skin registers the temperature and the pressure  Temperature and pressure receptors in your skin transmit the signal along the trigeminal nerve or the spinal nerve, through the thalamus to other areas of the brain  As a result, you touch HOW WE EXPERIENCE PAIN:  When you touch something painful, you register pain with two type of receptors  Fast fibres (with myelination) register sharp, fast pain  Slow fibres (w/o myelination) register duller, more diffuse pain  According to the gate control theory, neural gates in the spinal cord allow signals through and those gates can be closed when information about touch is being transmitted (rubbing sore spot) or by distraction AUDITION = the sense of sound perception SOUND WAVE = the pattern of the changes in air pressure through time that results in the percept of a sound EARDRUM (TYMPANIC MEMBRANE) = a thin membrane, which sound waves vibrate, that marks the beginning of the middle ear HOW WE HEAR:  Variations in air pressure produce sound waves that arrive at the ear  These sound waves move through the outer ear and make the eardrum vibrate  Signal moves through the middle ear, causing the ossicles to vibrate  The ossicles’ vibration causes the oval window to vibrate, creating pressure in waves in the inner ear’s fluid that bend hair cells and cause neurons on the basilar membrane to fire neural signals  These signals travel along the auditory nerve to the brain’s primary auditory cortext  As a result you hear CORNEA = the clear outer covering of the eye RETINA = the thin inner surface of the back of the eyeball; the retina contains the photoreceptors that transduce light into neural signals PUPIL = the small opening in the eye; lets in light waves IRIS = the coloured muscular circle on the surface of the eye; changes shape to let in more or less light RODS = retinal cells that respond to low levels of illumination and result in black-and-white perception CONES = retinal cells that respond to higher levels of illumination and result in colour perception FOVEA – the centre of the retina where cones are densely packed HOW WE SEE:  Image’s light waves have to strike the eye  The light waves enter the eyeball through the pupil, which determines how much light enters  The size of the pupil is controlled by the iris  Two types of photoreceptors on the retina, rods and cones, convert the light waves into electrical impulses  Signals are processed by the bipolar, amacrine and horizontal cells  Information from those cells is passed to ganglion cells, which generate action potentials that are transmitted by the optic nerve  Signals from the left visual field go to the right portion of each retina, follow along the optic nerve to the optic chiasm, and then travel though the right thalamus to the right visual cortex  Signals from the right visual field go to the left portion of each retina, follow along the optic nerve to the optic chiasm, and then travel through the left thalamus to the left visual cortex  As a result, you see RECEPTIVE FIELD = the region of visual space to which neurons in the primary visual cortex are sensitive LATERAL INHIBITION = a visual process in which adjacent photoreceptors tend to inhibit one another KINESTHETIC SENSE = perception of our limbs in space VESTIBULAR SENSE = perception of balance BINOCULAR DEPTH CUES = cues of depth perception that arise from the fact that people have 2 eyes MONOCULAR DEPTH CUES = cues of depth perception that are available to each eye alone PERCEPTUAL CONSTANCY = people correctly perceive objects as constant in their shape, size, colour, and lightness, despite raw sensory data that could mislead perception WHAT ARE THE BASIC SENSORY PROCESSES:  All the senses share similar processes.  Each has receptors that respond to different physical or chemical stimuli by transducing them into some pattern of brain activity.  Typically, different receptors respond to different types of stimuli, and most sensory systems integrate signals from these different receptors into an overall sensation.  This system allows a relatively small number of receptors to code a wide variety of stimuli.  For example, the visual system can interpret the entire range of colours with only three cone types, and all the taste sensations are produced by five primary taste receptors.  These various sensory receptors help the perceptual system receive important information that assists in solving adaptive problems.  Sensory information, although obtained from the outside world, is processed entirely in the brain to produce sensory experience through perception. WHAT ARE THE BASIC PERCEPTUAL PROCESSES:  The perceptual system is intelligent.  It takes ambiguous sensory information and constructs rich and meaningful experiences that allow us to navigate the world around us.  All perception occurs in the brain, where various perceptual processes take incoming sensations and construct them into meaningful perceptions.  Information first arrives in primary sensory regions, such as V1 for vision and A1 for audition, but multiple brain regions contribute to our unified perceptual experience.  The perceptual system uses cues from the person’s environment to help interpret sensory information.  For instance, visual cues help provide information about what objects are and where they are located, as well as information about depth and motion.  Contemporary theorists emphasize that perceptions are not faithful reproductions of the physical world but rather are constructed through multiple processes that allow us to taste, smell, touch, hear, and see. SENSATION = involves the detection of external stimuli (light, pressure, odours) responses to those stimuli and the transmission of these responses to the brain; Stimuli needs to be translated into chemical or electrical signals for brain to understand them TRANSDUCTION = process by which sensory receptors pass impulses to connecting neurons when they receive stimulation; Most of this info goes first to the thalamus except for smell before being directed to part of the cortex for further processing SENSORY THRESHOLD: 1. Absolute – the minimum intensity of stimulation that must occur before you experience a sensation; ex: quietest whisper you could hear half the time 2. Difference – the ju
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