Study Psych Final PDF

Sensation and Perception Sensation ◦ The process by which (objective) stimuli are detected, transduced into nerve impulses, and sent to the brain. Perception ◦ The brain’s interpretation of raw sensory inputs. Transduction ◦ The process of converting an external energy or substance into el...

Sensation and Perception Sensation ◦ The process by which (objective) stimuli are detected, transduced into nerve impulses, and sent to the brain. Perception ◦ The brain’s interpretation of raw sensory inputs. Transduction ◦ The process of converting an external energy or substance into electrical activity within neurons. Sense Receptor ◦ Specialized cell responsible for converting external stimuli into neural activity for a specific sensory system. Sensory Adaptation ◦ Activation is greatest when a stimulus is first detected and then declines in responsiveness over time. ◦ Also called neural adaptation. Psychophysics ◦ The study of how we perceive sensory stimuli based on their physical characteristics. Absolute Threshold ◦ The lowest level of a stimulus needed for the nervous system to detect a change 50% of the time. Just Noticeable Difference (JND) ◦ The smallest change in the intensity of a stimulus that we can detect. Weber’s Law ◦ There is a constant proportional relationship between the JND and original stimulus intensity. ◦ I = Intensity of the stimulus. ◦ K = Constant Signal-to-noise ratio ◦ The ratio of the power of a signal to the power of background noise. ◦ Signal = Stimulus to be perceived. ◦ Noise = Everything else Increased sensitivity to the signal causes hits and correct rejections to occur more often. Decreased sensitivity to the signal causes misses and false alarms to occur more often. Differences in sensitivity are measured with a statistic called d′ (“d-prime”). ◦ A measure of the stimulus’ salience. ◦ i.e., increases in d′ represent improved detection. ◦ Plotted using ROC curves (Receiver Operating Characteristic Curves) False Alarm Probability Observer with d′ = 0 (random guessing) Observer with d′ > 0 (ROC curve) Perceptions is determined by three basic elements: ◦ What is currently in the sensory field. ◦ What was in the sensory field a moment ago. ◦ What we have experienced in the past. Parallel Processing ◦ The ability to attend to many sense modalities simultaneously. Bottom Up-Processing ◦ Processing in which a whole is constructed from parts. Top-Down Processing ◦ Conceptually driven processing influenced by beliefs and prior learning. Bottom-up and Top-down processing are not mutually exclusive. Woman’s Face Perceptual Set ◦ A set formed when expectations influence perceptions. Perceptual Constancy ◦ The process by which we perceive stimuli consistently across varied conditions. Perceptual sets and constancy are just concepts which describe patterns of behaviour in relation to sets of stimuli. They do not provide an explanation for that pattern of behaviour. E.g., Viewing all three doors as equivalent is an example of perceptual constancy. A person doesn't not view all three doors as equivalent because of perceptual constancy. Selective Attention ◦ The process of selecting one sensory channel and ignoring or minimizing others. ◦ Assumed to be controlled by the reticular activating system (RAS) and higher cortical regions. Filter ‘Theory’ of Attention ◦ Attention is a “bottle neck” through which information passes. ◦ Dichotic Listening: a research design in which subjects have a message delivered to each ear independently through headphones. Both messages are delivered simultaneously, but only the attended ear’s message is able to be accurately recalled. inattentional Blindness ◦ Failure to detect stimuli that are in plain sight when our attention is focused elsewhere. Change Blindness ◦ Failure to detect changes in a visual stimulus. Can you spot what is changing in this image? Perception of events outside the known channels of sensation. ◦ Precognition ◦ Predicting events before they occur through paranormal means (i.e. don’t rely on standard scientific mechanism ◦ E.g., What card will appear? ◦ Telepathy ◦ Reading other people’s minds. ◦ E.g., What card is the person next to you thinking of? ◦ Clairvoyance ◦ Detecting the presence of objects or people hidden from view. ◦ E.g., What symbol is on the other side of the card? Why do people believe in ESP? ◦ Illusory Correlations ◦ People underestimate the frequency of coincidences. ◦ The Birthday Problem: ◦ Q: How large must a group of people be before the probability of two people sharing the same birthday exceeds 50 percent? ◦ A: 23 Visible Light: ◦ Electromagnetic radiation between 400 and 700 nanometers. Hue ◦ The colour of light. The Cornea ◦ Part of the eye containing transparent cells that focus light on the retina. ◦ Myopia (nearsightedness): ◦ Cornea is too long causing the focus of light to occur in front of the retina. ◦ Can only see close objects well. ◦ Hyperopia (farsightedness): ◦ Cornea is too flat causing the focus of light to occur behind the retina. ◦ Can only see far objects well. The Lens ◦ Part of the eye that changes curvature to keep images in focus. ◦ Contains transparent cells (i.e., light passes through them). ◦ Accommodation : ◦ Changing the shape of the lens to focus on objects near or far. The Retina ◦ Membrane at the back of the eye responsible for converting light into neural activity. ◦ Rods ◦ Photoreceptor cells in the retina allowing us to see in low levels of light. ◦ Approx. 92 million per eye. ◦ Dark Adaptation: Time in dark before rods regain maximum light sensitivity. ◦ Cones ◦ Photoreceptor cells in the retina allowing us to see in colour. ◦ Approx. 6 – 7 million per eye. The Retina ◦ Membrane at the back of the eye responsible for converting light into neural activity. ◦ Photopigments ◦ Protein molecules within the rods and cones whose chemical reactions when absorbing light result in nerve impulses being generated. ◦ Optic Nerve ◦ Nerve (technically a bundle of ganglion cells’ axons) that travels from the retina to the brain. Blind Spot ◦ Part of the visual field we can’t see because of an absence of rods and cones (i.e., optic nerve’s location). Shape and Contour ◦ Hubel and Wiesel ◦ Recorded electrical activity of V1 area of visual cortex in cats. ◦ Discovered feature detector cells: ◦ Cells that detect lines and edges. ◦ At later levels of visual processing (e.g., V2) cells begin to detect more complex shapes and movements. The Principles of Gestalt Psychology ◦ A German school of psychology that emphasized the natural organization of perceptual elements into wholes, or patterns. ◦ “Gestalt” ≈ “whole” ◦ Psychology should be focused on how the “whole” is created from its basic parts. ◦ Main Figures: ◦ Max Wertheimer ◦ Wolfgang Kohler ◦ Kurt Koffka Kanizsa Square ◦ Proximity: ◦ Objects physically close to each other tend to be perceived as unified wholes. Similarity : ◦ Similar objects will be seen as being grouped together or related. Continuity: ◦ We perceive lines as continuous movement while discounting abrupt changes. ◦ Also called “good continuation” The Principles of Gestalt Psychology ◦ Closure: ◦ The tendency to view incomplete figures or forms as complete objects. The Principles of Gestalt Psychology ◦ Symmetry: ◦ Symmetrically arranged objects are perceived as wholes. Figure-Ground Segregation: ◦ The tendency to separate elements of an image into a foreground (figure) and background (ground). Trichromatic Theory: ◦ Idea that colour vision is based on our sensitivity to the three primary colours. ◦ Fits with later findings that three types of cone cells are present that respond maximally at different wavelengths. ◦ Short ◦ Medium ◦ Long ◦ Relies on additive colour mixing. ◦ Can’t account for afterimages. S M L Opponent Process Theory: ◦ Theory that we perceive colors in terms of three pairs of opponent colors: ◦ red or green ◦ blue or yellow ◦ black or white ◦ Dual-Process Theory ◦ The modern color vision theory that posits that cones are sensitive to red, green, and blue, as well as opponent processes at the level of ganglion cells. Colour Blindness ◦ Inability to see some or all colours. ◦ Usually due to genetic abnormalities that cause the absence/reduction in a specific cone type. ◦ Monochromats – have only one type of cone (very rare = 0.0007% of the population). ◦ Dichromats - have two types of cone. ◦ Brain damage to cortical areas responsible for vision can also produce colour blindness Depth Perception: ◦ Ability to judge distance and three-dimensional relations. ◦ Monocular Cues: ◦ Stimuli that enable us to judge depth using only one eye. ◦ Binocular Cues: ◦ Stimuli that enable us to judge depth using both eyes. Monocular Cues ◦ Relative Size: ◦ All things being equal, more distant objects look smaller than closer objects. Monocular Cues ◦ Texture Gradient ◦ The texture of objects becomes less apparent as objects move farther away. nterposition ◦ Close objects block the view of distant objects. Depth Perception ◦ Monocular Cues ◦ Linear Perspective ◦ The outlines of objects converge as distance increases. Height in plane ◦ Here distant objects tend to appear higher, and nearer objects appear lower. Light and Shadow ◦ The casting of shadows gives objects a 3-D form. Motion Parallax ◦ When objects moving across a field of view appear to move more/faster the closer they are to an observer. Binocular Cues ◦ Binocular Disparity ◦ Depth information is obtained by comparing the difference in image location of the left and right eyes. Binocular Convergence ◦ The degree to which your eyes converge inward gives provides information to estimate distance. Blindness (Vision Loss) ◦ The inability to see due to problems with the eye and its related structures. ◦ Vision is less than or equal to 20/200 (20/20 is considered normal vision). ◦ Rely more on other senses (touch, hearing, etc.). ◦ Visual cortex’s function changes due to neural plasticity. Motion Blindness ◦ A neurological disorder in which a person is not able to perceive motion. ◦ Also known as “Cerebral Akinetopsia” ◦ Often caused by... ◦ Brain damage ◦ Alzheimer's disease Visual Agnosia ◦ An failure to recognize visually presented objects. ◦ Not due to impairments in memory or intelligence. ◦ Often due to damage to peripheral regions of occipital cortex near the parietal and temporal lobes. ◦ Different types: ◦ Prosopagnoisa : failure to recognize faces. ◦ Anosognosia : failure to recognize illness ◦ Finger agnosia : failure to recognize fingers ◦ Topographical disorientation : failure to recognize places. Blindsight: ◦ The ability of individuals with blindness to detect and respond to visual stimuli despite lacking awareness of having seen anything. ◦ Often the result of damage to V1 area of visual cortex