Sensory Perception: Vision, Sensory Receptors, and Perception Depth, Assignments of Psychology

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General Psychology-online Fall 2019

SENSATION AND

PERCEPTION

Chapter 4

Chapter 4

Sensation and Perception

I. Sensation – define/explain what it is. Sensation is the process of detection of internal or external stimuli. An individual can sense the environment through his or her sense organs: skin for touch, taste buds in the tongue for taste, olfactory receptors in the nose for smell, auditory receptors in the ears for sound, and the retina of the eyes for sight. Internal sensations can also occur. For example: a physical change such as temperature alteration or pain. These detections are sent to the brain for their initial processing. A. Principles of Sensation

1. Transduction or translation - creating a neural code When the body detects or picks up a sensation, it must travel to the brain to be processed. For that to happen, the sensation must be first converted into an electrical signal or a neural impulse. The process of the conversion from the physical stimuli to an electrical signal is called transduction. The electrical signals are sent to the brain to be interpreted when the neural code is presented. The neural code is how the neurons are representing the electrical signals to the brain, a pattern of neural firing, which is transformed into a more purposeful language for the body. Sensory receptors The sensory receptors are the specialized structures (cells) that make transduction possible. There are many different types of receptors, each one specialized in a type of stimulus. For example: Receptor name Specialized stimulus Photoreceptors Visible light Thermoreceptors Temperature Chemoreceptors Chemical stimuli Proprioceptors Sense of position Mechanoreceptor Mechanical stress 2. Thresholds A threshold refers to the intensity level to be exceeded, in this case, of a stimulus for it to be detected.  Absolute threshold Lowest level of a stimulus’ intensity that can be detected by an organism in at least half of the time that it is presented. It is obtained by experimenting with different levels of intensity and it varies from person to person. Vision, hearing, touch, smell, and taste are included in the stimuli’s threshold to be measured. For example: to measure the taste’s absolute threshold of an individual, a researcher presents different amounts of water where he added a drop of a bitter substance or a spoon of sugar to be tasted by the subject and identify if there is any change in the water’s flavor. It can take many trials before the absolute threshold can be determined. General Psychology

Chapter 4 that the neural impulses are taking is the optic nerve. This nerve is part of the nervous system and it is made from the long axons of the ganglion cells. Somewhere along the optic nerve route some nerve fibers cross over, allowing both sides of the brain to receive signals from both eyes. The signal arrives to the visual centers of the brain. The occipital cortex can be found at the back of the brain and it is divided in five different areas. The very first stop in the occipital cortex is in the primary visual cortex or Brodmann area. This area aids the brain to determine location, spatial information, and color data.

2. Next, describe what happens in the association pathways shown below, wherein sensation becomes perception: Association pathways are fiber pathways that connect a part of the cerebral cortex to another within the same hemisphere. These paths allow intercommunication between different areas of the brain. Our senses follow very similar routes to communicate with the brain. Energy, a stimulus which is converted into a neural impulse, then the impulse is transduced into information for the brain, and the receptors send the information to the cerebral cortex for it to be interpreted. Once the information arrives to the occipital lobe, the visual’s neural impulse would need to be sorted and managed for a better interpretation. This happens due to the lobe receiving perspectives from two sources, or different information from each eye. In the cortex this information must be integrated into a single image to be processed. The integration occurs via two paths, the where and the what path.  “WHAT” pathway: occipital  temporal The what path works together with the temporal lobe which is involved in memory processes. The role of this path, and the cortexes involved, is to deal with shapes, colors, and textures to help determine what an object is.  “WHERE” pathway: occipital  parietal The where path works in conjunction with the parietal lobe that is related to mapping the visual world. These structures work to locate objects in space, motion, and depth. The brain is always working and in constant communication with other structures. While visual information processing is happening, other senses, brain structures, and processes are also happening. Sensation is only the physical input of information that our sensory receptors are catching. The integration of the stimuli, the organization of information in the brain, its interpretation and evaluation, and the use of memory recall would allow a person to perceive. Perception makes the individual aware of events and objects in the world. General Psychology

Chapter 4 II. Perception – define/ explain what it is. When sensory information is interpreted, organized, selected, comprehended, and given a meaning it has become a perception. Perception is different in every person, not everyone would respond the same way to any given sensory input. For example: an initial olfactory sensation of a smell coming from the kitchen. When the brain had put in all the work into giving that smell a meaning, a person’s final perception could be the brain recognizing that the smell is their favorite dessert being prepared. A. Perceptual Organization (P.O.) Define/ explain what it is The perceptual organization groups visual aspects together into logical units. This organization is seen as a short-cut that helps make sense of what we see in a more rapidly manner. For example: if a person goes into an emergency room full of people, the first thing he or she is going to perceive is that most of that people is sick. Perceptual organization is mostly intended for speed and because of this, we sometimes make mistakes and can experience something totally different from reality. Like when a person is in a dark room and he or she looks at the corner and perceives that what is being seen is the shape of a stranger standing there, when it could just be a pile of laundry.

1. Form perception: The Gestalt Laws of P.O Explain each of the following Gestalt Laws/ Principle of PO: The Gestalt laws of perceptual organization imply that elements closely gathered in a common space most likely tend to be grouped together. These laws are around because of the mind’s ingrained disposition to perceive patterns.  Figure-ground Figure-ground is the differentiation made between a figure and a ground, or the ability to separate objects on different layer depths. That is why most printed information will use dark ink on a white background. Another example: while browsing on the internet and all the pop-up adds appear on the screen, you can close each of them layer by layer because you can recognize them as separated elements.  Simplicity The whole is better than the sum of its parts. instead of trying to figure out a way to describe various shapes as one odd figure, people tend to perceive everything in its simplest form because it takes less time to process. Designers usually take advantage of these law when they want to use uncomplicated shapes.  Closure Law of perception which states that when people see an incomplete or unfinished image, they disregard the incompleteness of it and fill in the gaps, perceiving it as a complete unit. If too much information in the image is missing, the elements would be interpreted as separate rather than whole. General Psychology

Chapter 4 Motion parallax is the perception of the speed at which an object is moving in relation to the distance it is located at. This can be applied whether the observer or the object is moving. The closer the object, the faster it appears to be moving. For example: when riding in a car, objects that are closer to you, such as road signs, buildings, or trees appear to go by quickly. Objects that are farther away will seem to move much more slowly, like the mountains in the background.

3. Perceptual constancy - define/ explain what it is, e.g., constancy of an object’s size and shape. Perceptual constancy refers to the propensity to perceive a familiar object as always being the same, or for it to have perpetual characteristics like shape, size, and color, regardless of the stimuli changes that occur (like a change in the level of illumination). For example: when walking away or towards your car, in the visual field it would look smaller or bigger, these changes in size would not be surprising to you due that you are familiar with the actual size of your car (constancy of size). B. Perceptual Interpretation (P.I.): define/ explain what it is. The word perceptual means: having the ability to create an opinion about something by using your senses. Perceptual interpretation refers to having the capacity of produce a meaningful interpretation from sensory experience. 1. Gibson’s theory of “direct perception” – define/ explain it. James J. Gibson, an important American psychologist, proposed in his theory that the mind perceives stimuli from the environment in a direct way. This perception is obtained without the need of any further mental process. Thus, perception can be explained entirely in terms of the environment. - Explain the “visual cliff” phenomenon The visual cliff phenomenon refers to an experiment created to determine if the depth perception in infants was a learned behavior or if it was innate. The researchers created a fall-like or cliff illusion using a sheet of plexiglass. An infant is placed on the edge in the beginning of the cliff and the baby’s caregiver is standing on the other side at the end of it. If the baby’s depth perception had already been developed, the baby would be able to notice the cliff and be afraid to move towards the caregiver. It he baby crawled towards the caregiver without paying attention to the cliff, it was granted that he or she lacked depth perception. The conclusion at the end of the experiment was that a person can perceive depth at around the time they start to crawl, when they experience getting hurt when slipping or bumping into other objects. General Psychology

Chapter 4

2. Psychological influences on P.I. a. Context – explain how it influences perception The word context indicates the words utilized in a written or spoken statement that influence the meaning of such statement. It also refers to the circumstances linked to situations that can affect how a person interprets it. Thus, context influences the way a person interprets and reacts to a stimulus, especially visual and tactile. b. Expectations or schemas – explain what they are. Describe an example of how they are involved in perception. In general, a schema is a mental portrayal, a pattern of thinking that allows a person to categorically organize their knowledge. It helps to understand new incoming information. This organization works as a short-cut for a speedy perception. On the other hand, schemas can be responsible for reducing and limiting the way we think, resulting in a stereotyping thinking. Some schemas can include: expectations, beliefs, emotions, needs, etc. For example: in children, schemas are very important for their development. A child can learn that when mom feeds him a red, round fruit (an apple), that it has a particularly sweet and good flavor. The baby has created a schema for an apple. Next time he sees a round and red food he will expect it to taste like the apple he was fed before, but this time it was a tomato. He might think that something is wrong with this new apple, until he is explained that it is a different fruit called a tomato. Therefore, a new schema will be created for the new fruit. Schemas are created through experience, they are constantly modified, and can go wrong because they can open a window for prejudice and stereotypes. c. Motivations – give an example of how our motivations can influence P.I. Motivation is the desire and action towards reaching a goal. It explains why somebody does something. Motivation can affect the way a person perceives the environment. For example: when a person has a basic physiological need, like thirst, he or she will be more aware or motivated while walking down the street to locate a water fountain. Or if this person is at home watching tv, he or she will be strongly influenced to go get a drink if there is a beverage commercial. **The food deprivation experiment****. Describe what happened in this classic experiment in terms of:

• what was manipulated (independent variables),** The I.V. is the lapse of time that the groups went without consuming any food: 24 hours, 10 hours, and right before the experiment started. - what was measured (dependent variable) D.V. is the effects of food and water deprivation on the identification of neutral, and food related words. - what the results were a) The three groups did not differ in their responses to the neutral words. General Psychology

Chapter 4 D. Cultural/Environmental Influences on Perception The Muller-Lyer Illusion – explain how it demonstrates the influence of culture on perception based on how people of different cultures either experience or don’t experience this illusion. The Muller-Lyer illusion is a famous optical illusion where two lines of the same length seem to be different. This is because of the design of the overall figures, the main line and the fins, or the angular lines that are added for this illusion. Our brains process the figure, if the fins are pointing away from the main line, the figure appears to be longer. If they point inwards, it appears to be shorter. Thus, these depth cues lead us to assume that the main line in both figures are of different lengths. People of different cultures either experience or don’t experience this illusion. This is believed to happen because of the environment in which they live and interact. If they live in a place where there isn’t an interaction with angles, different sized buildings, and such, they won’t be able to perceive this illusion. They don’t have enough experience with this type of cues linked to the Muller-Lyer illusion. General Psychology