Chapter 1 Perception PDF

Chapter 1.0 and 1.1 Perception is something you experience constantly, knowing about how it works is interesting in its own right. To appreciate why, consider what you are experiencing right now. If you touch the page of this book or look out at what’s around you, you might get the feeling that you...

Chapter 1.0 and 1.1 Perception is something you experience constantly, knowing about how it works is interesting in its own right. To appreciate why, consider what you are experiencing right now. If you touch the page of this book or look out at what’s around you, you might get the feeling that you are perceiving exactly what is “out there” in the environment. The first Perceptron (created by psychologist Frank Rosenblatt in 1958) - Room-sized five-ton computer that could teach itself to distinguish between basic images, such as cards with markings on the left vs right - Rosenblatt claimed that it could learn to recognize between similarities or identities between patterns of optical, electrical, or tonal information in processes similar to the brain - Could in fact not do this well since it took 50 trials to learn the simple task of telling whether a card had a mark on the left or right and was unable to carry more complex tasks - An issue with it is that the computer doesn’t have the huge amount of information humans accumulate as soon as they are born - When identifying an image, it can dedicate similar looking items but will not always be accurate - This Idea did lay the groundwork for a resurgence of interest in perception Perception: Experiences that result from stimulation of the senses - Perception depends on the properties of the sensory receptors - If you didn’t have certain receptors you would feel nothing or something different from what you feel now Chapter 1.2 Sensation: Involving simple “elementary” processes that occur right at the beginning of a sensory system - I.e., When light reaches the eye, sounds waves enter the ear , food touches your tongue Perception: Complex processes that involve higher-order mechanisms such as interpretation and memory that involved activity in the brain - I.e., identifying the food you’re eating and remembering the last time you ate it Sensation comes first, then perception comes after - Certain experiences depend heavily on the beginning of a sensory system - While others depend on interpretation and past experiences A stimulus as simple as a black dot on a white background or a hole in a piece of white paper? Now that interpretation is involved, does this experience become perception? Sensation is rarely used in modern research papers, mainly in taste and touch sensations, while perception is extremely common, and most perception researchers don't differentiate between the two. Chapter 1.3 Perceptual Process: - Begins with a stimulus in the environment (tree as example) - Ends with with conscious experiences of perceiving the tree, recognizing the tree, taking action with respect to the tree Perceptual Process Stages: 1. Distal Stimuli - Stimuli from the environment - Is only the rough shape of the stimuli and has not fully activated perception; only sensation (sensation of the tree as the example) 2. Proximal Stimuli - Representation of the stimuli is present - The stimuli is “in proximity” to the receptors - Principle of transformation: Stimuli and responses created by stimuli are transformed, or changed, between the distal stimulus and perception - Principle of representation: Everything a person perceives is based not on direct contact with stimuli but on representations of stimuli formed on the receptors and the resulting activity nervous system 3. Receptor Processes - Sensory receptors: Cells specialized to respond to mental energy, with each sensory system’s receptors specialized to respond to specific energies - Visual receptors respond to light - Auditory receptors to pressure changes in the air - Touch receptors to pressure transmitted through the skin - Smell and taste receptors to chemicals entering the nose and mouth - Sensory receptors do two thing when they receive information from the environment - Transform environmental energy to electrical energy - Shape perception the way they respond to different properties of the stimuli - Transduction: Transformation of environmental energy to electrical energy - A bridge between the external sensory world and your internal (neural) representation of that world Perceptual Process Stages cont. 4. Neural Processing - When the stimuli gets represented by electrical signals from the sensory receptors, they travel through a vast interconnected network that - Transmit signals from the receptors to the brain and then within the brain - Change (or process) these signals as they are transmitted - These occur because of the interactions between neurons as the signals travel from the receptors to the brain - The processing can also cause some signals to become reduce or prevent them from getting through; while also are amplified so they arrive at the brain with added strength - Neural Processing: Changes in the signals that occur as they are transmitted through the maze of neurons - Electrical signals created through transduction are often sent to a sense’s primary receiving area in the cerebral cortex (different senses have different areas - Cerebral cortex: 2-mm thick layer that contains the machinery for creating perception, as well as other functions like language, memory, emotions, and thinking - Occipital Lobe: Primary receiving area for vision - Temporal Lobe: Primary receiving area for hearing - Parietal Lobe: Primary receiving area for touch, temperature, pain - When signals reach the primary receiving area, they are then transmitted to other structure of the brain - For example, the frontal lobe receives signals from all of the senses, and it plays an important role in perceptions that involve the coordination of information received through two or more senses. 5. Conscious Experience of perception 6. Recognition - Placing an object in a category and then giving it meaning - Visual form agnosia: Inability to recognize objects due to brain tumor. - Dr P case where he mistakenglove as a continous surface unfolded on itself that appears to have five outpouchings 7. Taking Action - Motor Activities in response to the stimulus  - Some researchers see this as an important outcome since it is important for survival Perception is a continuously changing process - I.e., Visual and Auditory representations of the tree change every time the person moves his body relative to the tree, since it might look and sound different from different angle. - Thus, although we can describe the perceptual process as a series of steps that “begins” with the distal stimulus and “ends” with perception, recognition, and action, the overall process is dynamic and continually changing. Knowledge: Any information that the perceiver brings to a situation - I.e., Prior experience, expectations - It can affect a number of steps in the perceptual process - Rat-Man Demonstration: Shows how recently acquired knowledge can influence perception - Categorize: To place objects into categories - Bottom-up Processing (Data-based processing): Processing based on the stimuli reaching the receptors - Top-down Processing (Knowledge-based processing): Processing based on knowledge - “Very often” involved in perception - As stimuli become more complex, the role of top-down processing increases - our past experiences, can play an important role in determining what we perceive. Chapter 1.4 To study the perceptual process, we split the 7 steps into three major components - Stimulus (Steps 1-2) - Physiology (Steps 3-4) - Behavior (Steps 5-7) The goal of perceptual research is to understand the relationships between these three components The Stimulus-Behavior Relationships: Relates stimuli to behavioral responses such as perception, recognition, action - The main relationship measured during the first 100 years of the study of perception - Stimulus-Behavior Relationship Relationship beyween Stimulus and Behavior = Pressure on the shoulder, causing sensation and reaction (behaviour). Relationship between stimulus and physiology: Pressure on the shoulder leads to neural firing (physiology). Relationship between Physiology and Behavior: Neural firing results in shoulder feeling (physiology). - Psychophysics: Measures the relationships between the physical (stimulus) and the psychological (behavioral response) - Oblique effect: Presenting black and white striped stimuli called grating and measuring grating acuity - Grating acuity: The smallest width of line that participants can detect  - When grating acuity is assessed at different orientations, the results show that acuity is best for gratings oriented vertically or horizontally, rather than obliquely (A) The Stimulus-Physiology Relationships: Relationships between stimuli and physiological responses like neurons firing - Often studied by measuring brain activity - David Coppola and coworkers (1998) measured the oblique effect physiologically using a technique called optical brain imaging - Found out that horizontal and vertical orientations caused larger brain responses in visual brain areas than oblique orientations The Physiology-behavior Relationship: Relates physiological responses and behavioral responses - Christpher Furmanski and Stephen Engel (2000) determined physiology-behavior relationship for different grating orientations by measuring both the brain response and behavioral sensitivity - The physiological measurements were made using fMRI - Showed larger brain responses to vertical and horizontal gratings than oblique gratings Chapter 1.5 The grating acuity experiment measured the absolute threshold for seeing fine lines - Absolute threshold: Smallest stimulus level that can just be detected - I.e., Smallest amount of salt you need to be able to taste, intensity of a whisper that you can just barely hear - Thresholds measure the limits of the sensory systems - They also have an important place in the history of perceptual psychology Gustav Fechner (1801-1887, Professor of physics at the University of Leipzig) introduced a number of ways of measuring threshold - Back then, people saw the body as something physical (could be seen, measured and studied and the mind as not physical (could not be seen, measured, studied) - Fechner thought of the body and mind as two sides of a single reality - He proposed the mind could be studied by measuring the relationship between changes in physical stimulation (the body part) and a person’s experience (the mind part) - Based on the observation that as physical stimulation is increased, the person’s perception also increases - I.e., by increasing the intensity of a light, the person’s perception of the light also increases Classical Psychophysical methods: - Method of limits - Experimenter presented stimuli in either ascending or descending order - Procedure is repeated a number of times; threshold is determined by calculating the average of all the crossover points - Method of constant stimuli - Different stimulus intensities are presented one at a time, and the participant must respond whether they perceive it on each trial - Threshold is defined by the intensity that results detection on 50% of trials - Method of adjustment - The participant adjusts the stimulus intensity continuously - barely audible intensity is taken as the threshold - Repeated numerous times; threshold is determined by taking the average setting Choice among the three methods is determined by the degree of accuracy needed and amount of time available - The method of constant stimuli is the most accurate because it involves many observations and stimuli are presented in random order but is time-consuming  - The method of adjustment is faster because participants can determine their thresholds Difference threshold: The smallest difference between two stimuli that enables us to tell the difference between them - I.e., You make a second batch of stew where you start with the same amount of salt you need to add to the second batch to detect a difference in salt content between the two batched Fechner and Weber’s methods made it possible to measure the ability to detect stimuli and also determine mechanisms responsible for experiences. - Examines how vision het better in the dark as their vision adapted this is caused by the decrease in threshold as your eyes stay in the dark - Changes view from we see better when we spend time in the dark to providing a quantitative description of what is happening as a person’s ability to see improves. Measuring Perception Above Threshold - Magnitude Estimation - Fechner created a mathematical formula relating physical stimuli and perception of their magnitude (big and small or loud or soft) - How it works is that - Experimenter first creates a “standard” stimulus to the participant - Participant hears sounds of different intensities - Asked to assign a number to each of the sounds proportional to the loudness of the original sound - The number of the “loudness” is the perceived magnitude of the stimulus - Recognition Testing - Tests for recognition across different spectrums (Visual, Touch, Taste, Smell) - Process of categorizing - For example = people can identify rapidly flashed pictures. - Recognition is not only visual; it can also include hearing (“that’s a car revving its engine”), touch (“that feels like an apple”), taste (“mmm, chocolate”), and smell (“that’s a rose”). - Reaction Time - Time between presentation of a stimulus and the person’s reaction to it - For example measuring a person reaction time when seeing an object while paying attention to the middle.  - Phenomenological Report - Describing what you see around you - Physical Tasks and Judgement - Tests more on the 7th stage of the perceptual process - How we take action within our environment Distinction between physical and perceptual - There is not a one-to-one relationship between the physical intensity of light and our perceptual response to light - People might judged the light that are twice as bright as just two levels above the normal brightness - Electromagnetic spectrum: Band of energy ranging from gamma rays at the short-wave end of the spectrum to AM radio and AC circuits at the long-wave end. - Human see just the small band of energy called visible light, sandwiched between the ultraviolet and infrared energy bands. - We are blind to ultraviolet and shorter wavelengths. - perception is psychology, not physics, and perceptual responses are not necessarily the same as the responses of physical measuring devices.