Midterm II Study Guide Chapter 6 Visual Attention o Selective o Shiftable o Divisible Attention the brain s most powerful tool to allocate mental resources to sensory and perceptual information in the environment Attention is Divided Attention the limited ability of paying attention to more than one thing at a time Example driving and texting don t mix Selective Attention focusing on specific objects and filtering out others o Visual system constructed this way Too much information for the retina to handle Fovea helps achieve selection Eye movements take in different parts of a scene o Saccades small rapid eye movements o Fixations pauses indicating where the person pays attention o 3 fixations second Factors determining location of fixations o Stimulus Salience areas of a scene that attract attention because of shape color size or orientation Saliency maps show these properties are fixed on o Scene Schema prior knowledge about what is found in typical scenes Influence on task Stimulus saliency overridden Saccades and fixations linked to action o Effects of Past Experience example detecting stop signs at intersections and stopping there Perception without focused attention experiment by Reddy et al o Central task letters flashed in center of the screen are the same 80 90 performance o Peripheral task faces flashed to the side of the screen are male or female o Dual task same as peripheral task but determine color of disk Faces 90 performance Discs 54 performance o Results Gender determined without focused attention while color of disc couldn t o Conclusion faces have meaning and are perceived as whole objects Inattentional blindness stimulus not perceived even when the person directly looks at it o Passing around ball experiment 46 of people didn t see gorilla Change blindness a change in a stimulus not perceived after interruptions in visual field o Scene presented blank screen slightly changed scene presented o Subjects noticed changes more quickly when pointed out to them o Real objects in the environment change which is why we don t notice them as much Binding process by which features are combined to create perception of coherent objects o Example a rolling ball activates a number of different areas of the cortex that deal with say form color depth motion and location These signals combine to form a unified percept Feature Integration Theory Preattentive Stage features of objects separated Focused Attention Stage features combined into coherent perception Attention is glue for what and where streams Illusory Conjunctions features associated with one object become incorrectly associated with another o Balint s Syndrome damage to parietal lobe causes inability to focus attention on individual objects and results in incorrect combinations or features Visual Search conjunction search find target with two or more features o Parietal lobe where stream o Parietal lobe damage no conjunction search Physiological Approach to Binding Synchrony Hypothesis neurons firing to the same object or different qualities of the object synchronize with each other o Same firing pattern o Attention may help synchronize neural firing Physiology of Attention Colby et al experiment o Monkey fixates on dot while peripheral light flashed on the right Fixation only condition keep eyes fixated and release lever when dot dimmed Fixation and attention condition keep eyes fixated and release lever when peripheral light dimmed Recordings from neuron in parietal lobe that responded to peripheral light made o Results Neuron fired well when monkey attended to peripheral light Neuron fired poorly when monkey wasn t attending to peripheral light Response was due to attention Chapter 7 Taking Action Ecological Approach to Perception Look for information in the environment that provides information for perception Stresses relationship between o Organism and environment o Perception and action Information optic array structure created by surfaces textures and contours in the environment o Optic flow appearance of object as the observer moves past them Two characteristics Flow is more rapid near the moving observer Gradient of flow difference in speed of flow dependent on distance from observer No flow at the destination toward which the observer is moving Focus of Expansion point in distance where there is no flow Invariant Information properties that remain constant while observer is moving Self produced information flow is created by the movement of the observer o Skilled actions establish connection between sensory and motor systems o Example gymnasts can t perform with eyes closed Vision very important in balance o 13 16 month old children put in swinging room where floor stationary but walls and ceilings swung o Children swayed back and forth o Adults showed the same result o Result vision has a powerful effect on balance and overrides other senses Navigating Through the Environment Land and Lee Study gaze of driver o Method car fitted with measurement tools for angle of steering wheel speed and o Experiment when driving straight driver looks ahead and not at focus of expansion When turning a curve driver looks at tangent point at the side of the road Suggests noting position of car in relation to centerline or side of the road Physiology of Navigation flow patterns straight Optic Flow Neurons neurons in the medial superior temporal area MST respond to Experiment monkeys trained to respond to direction of flow of dots on screen left right or o As task done MST stimulated that respond to specific direction of flow patterns o o Result stimulation increased judgment of movement in a direction Judgments shifted in direction of stimulated neuron Experiment London cab drivers given destination on map and midway the destination was changed They also heard a statement unrelated to their destination fMRI monitored brain activity o o Results showed link between brain activation and specific navigation tasks Activation of visual cortex and PPA for inspecting buildings Activation of hippocampus and PPA for planning routes Acting on Objects Affordance of object information indicating what an object is used for Indicate potential for action as part of our perception o o Certain types of brain damage cannot name but can still pick up object and use it o Tea cup experiment of not recognizing it unless it had a handle Physiology of Reaching and Grasping o Experiment neurons in parietal lobe silent when monkey does not act fire