Perception - Chapter 3 Lecture Notes PDF

Chapter 3 Perception Some Questions to Consider Why can two different people experience different perceptions in response to the same stimulus? How does perception depend on a person’s knowledge about characteristics of the environment? How does the brain become...

Chapter 3 Perception Some Questions to Consider Why can two different people experience different perceptions in response to the same stimulus? How does perception depend on a person’s knowledge about characteristics of the environment? How does the brain become tuned to respond best to things likely to appear in the environment? What is the connection between perception and action? Are there neurons in the visual system that might help us understand other people’s actions? Syracuse University 2  Definitions Sensation: absorbing raw energy (e.g., light waves, sound waves) through our sensory organs Transduction: conversion of this energy to neural signals Attention: concentration of mental energy to process incoming information Perception: selecting, organizing, and interpreting these signals Syracuse University 3  Overview: Sensation and Perception Energy contains information about the world (usually incomplete, full of noise, and distorted) Accessory structure modifies energy Receptor transduces energy into a neural response Sensory nerve transmits the coded activity to the central nervous system Thalamus processes and relays the neural response Relayed to specialized areas of the cortex Perception of the world is created Syracuse University 4 Perception Is… (1 of 2) 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 Syracuse University 5 Adapted from https://www.tes.com/lessons/TxQsIJJuBMquog/the-interactive-lecture Perception Is… (2 of 2) 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. Syracuse University 6 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 Syracuse University 7 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 Constructive perception theories – Top-down processing – People actively construct perceptions using information based on expectations Syracuse University 8 The Complexity of Perception (1 of 2) 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 Syracuse University 9 The Complexity of Perception (2 of 2) Figure 3.11 “Multiple personalities of a blob.” What we expect to see in different contexts influences our interpretation of the identity of the “blob” inside the circles. Goldstein, Cognitive Psychology, 5th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or Syracuse University 10 duplicated, or posted to a publicly accessible website, in whole or in part. Hearing Words in a Sentence (1 of 2) – 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 Syracuse University 11 Hearing Words in a Sentence (2 of 2) – 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 Syracuse University 12 Helmholtz’s Unconscious Inference Figure 3.14 The display in (a) is usually interpreted as being (b) a blue rectangle in front of a red rectangle. It could, however, be (c) a blue rectangle and an appropriately positioned six-sided red figure. Goldstein, Cognitive Psychology, 5th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or Syracuse University 13 duplicated, or posted to a publicly accessible website, in whole or in part. 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 Figure 3.15 According to structuralism, a number of sensations (represented by the dots) add up to create our perception of the face. Goldstein, Cognitive Psychology, 5th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or Syracuse University 14 duplicated, or posted to a publicly accessible website, in whole or in part. Gestalt Principles of Perceptual Organization (1 of 6) – Principle of good continuation – Lines tend to be seen as following the smoothest path Figure 3.18 (a) Rope on the beach. (b) Good continuation helps us perceive the rope as a single strand. Goldstein, Cognitive Psychology, 5th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or Syracuse University 15 duplicated, or posted to a publicly accessible website, in whole or in part. Gestalt Principles of Perceptual Organization (2 of 6) – Law of pragnanz – (Principle of simplicity or good figure) – Every stimulus pattern is seen so the resulting structure is as simple as possible Figure 3.19 The Olympic symbol is perceived as five circles (a), not as the nine shapes in (b). Goldstein, Cognitive Psychology, 5th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or Syracuse University 16 duplicated, or posted to a publicly accessible website, in whole or in part. Gestalt Principles of Perceptual Organization (3 of 6) – Principle of similarity – Similar things appear grouped together Figure 3.20 (a) This pattern of dots is perceived as horizontal rows, vertical columns, or both. (b) This pattern of dots is perceived as vertical columns. Goldstein, Cognitive Psychology, 5th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or Syracuse University 17 duplicated, or posted to a publicly accessible website, in whole or in part.  Gestalt Principles of Perceptual Organization (4 of 6) Principle of familiarity – Things are more likely to form groups if the groups appear familiar or meaningful Caption: The Forest Has Eyes by Bev Doolittle (1985). Can you find 13 faces in this picture? (Source: “The Forest Has Eyes” 1984 Bev Doolittle, courtesy of The Greenwich Workshop, Inc.) Syracuse University 18 Gestalt Principles of Perceptual Organization (5 of 6) Figure 3.21 This photograph, Waves, by Wilma Hurskainen, was taken at the exact moment that the front of the white water aligned with the white area on the woman’s clothing. Similarity of color causes grouping; differently colored areas of the dress are perceptually grouped with the same colors in the scene. Also notice how the front edge of the water creates grouping by good continuation across the woman’s dress. Goldstein, Cognitive Psychology, 5th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or Syracuse University 19 duplicated, or posted to a publicly accessible website, in whole or in part. Gestalt Principles of Perceptual Organization (6 of 6) – 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. Syracuse University 20 Regularities of the Environment: Physical (1 of 3) – Common physical properties of the environment – Oblique effect – We perceive verticals and horizontals more easily than other orientations Figure 3.22 In these two scenes from nature, horizontal and vertical orientations are more common than oblique orientations. These scenes are special examples, picked because of the large proportion of verticals. However, randomly selected photos of natural scenes also contain more horizontal and vertical orientations than oblique orientations. This also occurs for human made buildings and objects. Goldstein, Cognitive Psychology, 5th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or Syracuse University 21 duplicated, or posted to a publicly accessible website, in whole or in part. Regularities of the Environment: Physical (2 of 3) – 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 Syracuse University 22 Regularities of the Environment: Physical (3 of 3) Figure 3.23 (a) Indentations made by people walking in the sand. (b) Turning the picture upside down turns indentations into rounded mounds. (c) How light from above and to the left illuminates an indentation, causing a shadow on the left. (d) The same light illuminating a bump causes a shadow on the right. Goldstein, Cognitive Psychology, 5th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or Syracuse University 23 duplicated, or posted to a publicly accessible website, in whole or in part. 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. – 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? Syracuse University 24 Comparing Conceptions of Object Perception – Top-down processing – Unconscious inference – Environmental regularities – Bayesian inference – Bottom-up processing – Gestalt principles Syracuse University 25 Neurons, Knowledge, and the Environment (1 of 2) – 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 Syracuse University 26 Neurons, Knowledge, and the Environment (2 of 2) Figure 3.27 (a) Greeble stimuli used by Gauthier. Participants were trained to name each different Greeble. (b) Magnitude of FFA responses to faces and Greebles before and after Greeble training. Goldstein, Cognitive Psychology, 5th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or Syracuse University 27 duplicated, or posted to a publicly accessible website, in whole or in part. 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. Figure 3.28 Three views of a “horse.” Moving around an object can reveal its true shape. Goldstein, Cognitive Psychology, 5th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or Syracuse University 28 duplicated, or posted to a publicly accessible website, in whole or in part. The Interaction of Perception and Action – Constant coordination occurs in the brain as we perceive stimuli while also taking action toward them. Figure 3.29 Picking up a cup of coffee: (a) perceiving and recognizing the cup; (b) reaching for it; (c) grasping and picking it up. This action involves coordination between perceiving and action that is carried out by two separate streams in the brain, as described in the text. Goldstein, Cognitive Psychology, 5th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or Syracuse University 29 duplicated, or posted to a publicly accessible website, in whole or in part. Perception and Action: (1 of 6) – 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) Syracuse University 30  Perception and Action: Using Dissociation Logic (2 of 6) If you are trying to understand a complex system, you can logically deduce conclusions from “malfunctions” Damage to different areas of the brain cause very different deficits – We can conclude that a specific area is necessary for a specific function Brain Ablation method allows scientists to damage specific areas of otherwise normal brains (usually in monkeys or cats) – Controlled damage allows for clear conclusions to be drawn Syracuse University 31  Perception and Action: Dissociation Logic (3 of 6) Single dissociation – One function is lost, another remains ▪ Example: Monkey A has damage to temporal lobe. This monkey is no longer able to identify objects (what) but can still identify locations (where) – Therefore, what and where rely on different mechanisms, although they may not operate totally independent of one another Syracuse University 32  Perception and Action: Dissociation Logic (4 of 6) Double dissociation – Requires two individuals with different damage and opposite deficits ▪ Example: Monkey A with temporal lobe damage has intact where but impaired what; Monkey B with parietal lobe damage has intact what but impaired where – Therefore, what and where streams must have different mechanisms AND operate independently of one another Syracuse University 33 Perception and Action: What and Where (5 of 6) Figure 3.30 The two types of discrimination tasks used by Ungerleider and Mishkin. (a) Object discrimination: Pick the correct shape. Lesioning the temporal lobe (purple-shaded area) makes this task difficult. (b) Landmark discrimination: Pick the food well closer to the cylinder. Lesioning the parietal lobe makes this task difficult. Goldstein, Cognitive Psychology, 5th Edition. © 2019 Cengage. All Rights Reserved. May not be scanned, copied or Syracuse University 34 duplicated, or posted to a publicly accessible website, in whole or in part. Perception and Action: What and Where (6 of 6) – 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 Syracuse University 35  Caption: (a) Alice can’t name objects but can accurately reach for them; (b) Bert can name objects, but has trouble accurately reaching for them. This illustrates a double dissociation. Syracuse University 36 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. Syracuse University 37