Cognitive Neuroscience: Perception and Action PDF

COGNITIVE NEUROSCIENCE  OBJECTIVES BY THE END OF THIS CHAPTER, YOU SHOULD BE ABLE TO: 1. Describe the challenges involved in visual perception in humans and in computer-vision systems. 2. Distinguish between bottom-up (data-based) and top-down (knowledge-based) processing. 3. Describ...

COGNITIVE NEUROSCIENCE  OBJECTIVES BY THE END OF THIS CHAPTER, YOU SHOULD BE ABLE TO: 1. Describe the challenges involved in visual perception in humans and in computer-vision systems. 2. Distinguish between bottom-up (data-based) and top-down (knowledge-based) processing. 3. Describe evidence demonstrating the existence of separate brain pathways for visually perceiving objects and for physically interacting with those objects. THE NATURE OF PERCEPTION Perception is..... Experience resulting from stimulation of the senses Basic concepts Perceptions can change based on added information Involves a process similar to reasoning or problem solving Perceptions occur in conjunction with actions THE NATURE OF PERCEPTION Perception is..... It is possible that true human perceptual processes are unique to humans. Attempts to create artificial forms of perception (machines) have been met with limited success and each time have had problems that could not be solved WHY CAN’T MACHINES PERCEIVE LIKE HUMANS? Inverse Projection Problem Refers to the task of determining the object responsible for a particular image on the retina Involves starting with the retinal image and then extending outward to the source of that image Objects can be hidden or blurred People can often identify objects that are obscured and therefore incomplete, or in some cases objects that are blurry WHY CAN’T MACHINES PERCEIVE LIKE HUMANS? Objects look different from different viewpoints Viewpoint invariance Scenes contain high-level information Scenes are more complex INFORMATION USED IN HUMAN PERCEPTION The human perceptual system uses two types of information: Environmental energy stimulating the receptors Knowledge and expectations the observer brings to the situation APPROACHES TO UNDERSTAND PERCEPTION Direct perception theories Bottom-up processing Perception comes from stimuli in the environment Parts are identified and put together, and then recognition occurs APPROACHES TO UNDERSTAND PERCEPTION Constructive perception theories Top-down processing People actively construct perceptions using information based on expectations THE COMPLEXITY OF PERCEPTION Bottom-up processing Perception may start with the senses Incoming raw data Energy registering on receptors Top-down processing Perception may start with the brain Person’s knowledge, experience, and expectations HEARING WORDS IN A SENTENCE Top-down processing influences our perception of language based on our individual experience with the language Speech segmentation The ability to tell when one word ends and another begins Transitional probabilities Knowing which sound will likely follow another in a word HEARING WORDS IN A SENTENCE Top-down theory Some perceptions are the results of unconscious assumptions we make about the environment We use our knowledge to inform our perceptions We infer much of what we know about the world Likelihood principle We perceive the world in the way that is “most likely” based on our past experiences CONCEPTIONS OF OBJECT PERCEPTION CONCEPTIONS OF OBJECT PERCEPTION Perceptual Organization “Old” view—structuralism Perception involves adding up sensations “New” view—Gestalt principles The mind groups patterns according to intrinsic laws of perceptual organization CONCEPTIONS OF OBJECT PERCEPTION Gestalt Principles of Perceptual Organization Principle of good continuation Lines tend to be seen as following the smoothest path CONCEPTIONS OF OBJECT PERCEPTION Gestalt Principles of Perceptual Organization Law of Pragnanz (Principle of simplicity or good figure) Every stimulus pattern is seen so the resulting structure is as simple as possible CONCEPTIONS OF OBJECT PERCEPTION Gestalt Principles of Perceptual Organization Principle of similarity Similar things appear grouped together CONCEPTIONS OF OBJECT PERCEPTION Gestalt Principles of Perceptual Organization Principle of similarity Similar things appear grouped together CONCEPTIONS OF OBJECT PERCEPTION Gestalt Principles of Perceptual Organization Perception is determined by specific organizing principles, not just dark and light stimuli activating the retina. Role of experience is minor compared to these intrinsic, “built in” principles. Experience can influence perception but is not the key driver. CONCEPTIONS OF OBJECT PERCEPTION Regularities of the Environment: Physical Common physical properties of the environment Oblique effect We perceive verticals and horizontals more easily than other orientations CONCEPTIONS OF OBJECT PERCEPTION Regularities of the Environment: Physical Light-from-above assumption We assume light comes from above because this is common in our environment We perceive shadows as specific information about depth and distance CONCEPTIONS OF OBJECT PERCEPTION Regularities of the Environment: Semantic The meaning of a given scene is related to what happens within that scene. Semantic regularities are the characteristics associated with functions carried out in different types of scenes. CONCEPTIONS OF OBJECT PERCEPTION Regularities of the Environment: Semantic Scene schema It is knowledge of what a given scene ordinarily contains. In the jewelry case at Tiffany’s, would you expect to see a plate of fish and chips or diamond rings? CONCEPTIONS OF OBJECT PERCEPTION Bayesian Inference One’s estimate of the probability of a given outcome is influenced by two factors: The prior probability The likelihood of a given outcome CONCEPTIONS OF OBJECT PERCEPTION NEURONS AND KNOWLEDGE ABOUT THE ENVIRONMENT Some neurons respond best to things that occur regularly in the environment Neurons become tuned to respond best to what we commonly experience. Horizontals and verticals Experience-dependent plasticity NEURONS AND KNOWLEDGE ABOUT THE ENVIRONMENT PERCEPTION AND ACTION: BEHAVIOR Movement Facilitates Perception As observers, our movement adds complexity to perception compared to if we remain static but moving around a stimulus offers us more views to create accurate perceptions. PERCEPTION AND ACTION: BEHAVIOR PERCEPTION AND ACTION: BEHAVIOR The Interaction of Perception and Action Constant coordination occurs in the brain as we perceive stimuli while also taking action toward them. PERCEPTION AND ACTION: BEHAVIOR PERCEPTION AND ACTION: PSYCHOLOGY What pathway Determining the identity of an object Ventral pathway (lower part of the brain) Where pathway Determining the location of an object Dorsal pathway (upper part of the brain) PERCEPTION AND ACTION: PSYCHOLOGY Milner and Goodale (1995) Perception pathway: From visual cortex to temporal lobe Corresponds to the what pathway Action pathway: From visual cortex to parietal lobe Corresponds to the where pathway Also called the how pathway PERCEPTION AND ACTION: PSYCHOLOGY Mirror Neurons These neurons respond while a subject watches an action being performed in the same way as if the subject was performing the action. fMRI research has found evidence of a mirror neuron system in the brain. Iacoboni (2005) found higher rate of mirroring if the subject’s intention to perform the action was greater.