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PSYCH 101 Unit IV Sensation & Perception

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University of Waterloo
Richard Ennis

PSYCH 101 Unit IV: Sensation & Perception Two Inseparable Processes: Sensation & Perception • Sensation: o The physical sensing of the environment o Physiological o Relatively objective o Learning and experience NOT required • Perception: o Mental interpretation of the environment o Psychological o Relatively subjective (based on one’s own experience) o Learning and experience ARE required The Process of Sensation: • Occurs in as 3 steps: 1. Reception – external forces (e.g. light, heat, sound etc.) from the environment are received by the sensory receptor cells 2. Transduction – the external force/energy is converted into neural impulses 3. Transmission – Delivering the neural information to the brain to be processed Random Facts about the Nose: • *The nose is the only place with a direct link between the environment and the brain • Smell was our first sense • Every living organism has the ability to sense chemicals in the environment • Chemical process are the only ones that replace/replenish neurons (every 1-2 months) • Human nose is one of the least sensitive in the animal kingdom Smell: Odor Receptors • Humans actually have a rather poor sense of smell for an animal • But despite this, we still have 350 types of smell receptors allowing us to detect 10000 odors The Thalamus & Other Senses: • The Thalamus is the relay center of the brain o It job is to look at incoming messages and determine what type of sensation it is o It then is able to direct the signal to the specific part of the brain that is able to process and make sense of the signal • However, the Thalamus has no jurisdiction over the sense of smell The Limbic System & Smell: • Instead of the thalamus, smell is under the control of the limbic system. • The limbic system is linked to our memory and emotion • Therefore, smell has a very unique ability to invoke powerful emotions and memories The “Right” Chemistry: • Breast-fed infants: o Infants will begin to identify and associated the smell of the mother’s breast at a very young age, especially since the sense of smell is the first sense to develop • Signature smells: o Humans can actually have the ability to identify smells of other people, especially those who are important in our lives • Sexual turn ons and turn offs (for men and women) o Female:  The most powerful smell to increase female sexual arousal was a combination of liquorish and cucumber • A close second was baby powder • Third was lavender and pumpkin pie  Turns offs, however, include the smell of men’s cologne, the smell of charcoal BBQ, and the smell of cherry o Males:  Men are aroused by the smell of liquorish and lavender • Other smells: o Scent of lemon/peppermint makes a person more alert o Scent of spiced apples makes a person more relaxed o Vanilla is said to reduce anxiety o The smell of coffee and cookies increases the motivation of people to help ESP (Extrasensory Perception): • Frank Gilovich defines ESP as “the experience of, or response to, a target object, state, or event, or influence without sensory contact” o 80% of Canadian college students believe in ESP o 50% of the US population believes in ESP • Types of ESP: o Precognition:  The accurate prediction of future events (i.e. “knowing” the future) o Clairvoyance:  Knowing the state of affairs of something, but the information cannot directly be assessed by you  E.g. having a vision about where a kidnapper is hiding their hostage, but not necessarily being able to go there o Telepathy:  Involving 2 or more people being able to communicate with one another using communication that is between one mind and another (i.e. mind- reading messages from one another) The Evidence for ESP: • Anecdotal evidence (personal accounts/stories) • Biased reporting (reporting things that did not happen because it was reported improperly) • No replication • No identified energy sources or sensory process • The will to believe • No scientific support despite 150 years of research Further Readings from the Textbook From Module 17: Basic Principles of Sensation and Perception Making Sense of the World: Top-down vs. Bottom-up Processing • Top-down processing: o Using models, ideas, and experiences to interpret sensory information o E.g. asking yourself “is that something I’ve seen before?” • Bottom-up processing: taking in sensory information that we have not experienced and analyzing it by integration with higher order processing o Taking sensory information o E.g. what am I seeing? Thresholds: • The absolute threshold refers to the minimum level of stimulus intensity needed to detect a stimulus half the time • Anything less than this is considered “subliminal” o Subliminal stimuli is something that is below our threshold for being able to consciously detect • Subliminal detection: o Although we cannot learn complex knowledge from subliminal stimuli, we can be subtly influenced by them unconsciously  E.g. when a slide flashes a nude image, we are more likely to look longer at the slide • Weber’s Law: o The principle stating that in order for 2 stimuli to be perceived as independently different, they must differ by a given percentage (rather than a given amount) Sensory Adaptation: • Refers to becoming less aware of a constantly exposed stimuli because our nerve less fire less frequently o In order words, the human brain will tune out that particular stimuli because the brain has deemed it consistent and unchanging, so the brain does not bother with it • We often do not notice this because our eyes are constantly moving Perceptual Set: • Defined as what we EXPECT to see, which influences what we DO see o This is an example of top-down processing, since we are relying on experience that we have been sensitized before to interpret sensory information Context Effects: • A given stimulus may be perceived as radically different because of the immediate context o Example: two dots that are the same size are drawn in the middle, but the first dot has 4 larger ones around it, making it appear smaller, while the other dot has 4 smaller ones around it making it appear bigger: Emotion and Motivation: • Not only are perceptions influenced by top-down processing and context effects, they are also influenced by emotion and motivation as well • Experiments have shown that: o Destinations seem farther when you’re tired o A target looks farther when your crossbow is heavier o A hill looks steeper with a heavy backpack, after sad music, or when you’re walking alone o Something that you desire appears to be closer From Module 18: Vision and Perceptual Organization and Interpretation Vision: • Human eyes receive light energy and transduce (i.e. transform) that light energy into neural messages that the brain can process o The brain ultimately turns this light energy wave sensations into colours o Granted, the human eye is only capable of picking up some of these waves • Colour/Hue and Brightness: o Humans can perceive the wavelength/frequency of the electromagnetic waves as colour/hue  Hue = the dimension of colour that is determined by the length of a wavelength of light  Wavelength = the distance from the peak of one light/sound wave to the peak of the next o We perceive the height/amplitude of these waves as intensity or brightness (e.g. how loud or bright something is)  Intensity = the amount of energy in a light or sound wave as determined by the wavelength’s amplitude The Eye: • Light enters the eye though the cornea and the pupil, and becomes focused and inverted by the lens. o The lens of the eyes are not rigid and can perform “accommodation” by changing shape to focus on objects that are near or far away • The light will travel to the retina, where it begins to be transduced into neural impulses that are sent to the optic nerve o The optic nerve is the carrier of neural impulses from the eye to the brain • Other parts of the eye: o Iris – the ring of muscle tissue that forms the coloured portion of the eye around the pupil and controls the size of the pupil opening o Rods – retinal receptors that detect black, white, and gray; rods function in darker/twilight time periods o Cones – retinal receptors that detect fine detail allowing colour sensations; cones function in daylight/well-lit areas o Fovea – the central point of the retina where the eye’s cones cluster • Also keep into consideration that the eye cannot see everything o This is known as a “blind-spot” which is a point where the optic nerve leaves the eye, creating a spot that has no vision since there are no receptor cells located there Visual Information Processing: • Some ganglion cells in the eye send signals directly to the visual cortex in response to certain features o Features may include: visual patterns, certain edges, lines, or movements • Supercells, which are in and around the visual cortex, integrate these feature signals to recognize more complex forms o An example of a more complex form requiring the integration of feature signals are faces of people Colour Vision: The Young-Helmholtz Trichromatic (i.e. Three
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