In large part, perceiving is something that people learn to do. We begin to learn about the world as infants and continue throughout our lives. If our visual abilities are damaged or limited when we are infants, we could continue to experience deficiencies in adulthood, despite any physical remedies.
Perceptual Set
It is clear that our own subjective beliefs can and do influence our perceptions. We all have ideas about the world around us that help us make sense of it and give meaning to ambiguous stimuli. This helps us understand why some people can look at a picture and see something scary, while others see something neutral.
Visual Illusions
Two diagrams are labeled Muller-Lyer Illusion.
Image Description
A visual illusion can occur when the subjective perceptual experience is different from what is really there. An example of a visual illusion is the "Muller-Lyer illusion." The slanted lines cause horizontal line segment AB to appear longer than line segment CD. The two line segments actually are the same length.
A diagram labeled Ponzo illusion is shown. Thirteen lines converge at a single point. At the bottom of the diagram, a horizontal line intersects the middle three lines. At the top of the diagram, a horizontal line intersects all lines.
In the "Ponzo illusion," the top horizontal line seems longer than the lower horizontal line, even though the two lines are equal in length. Such illusions are natural artifacts of the way our visual systems work. As a result, illusions provide important insights into the functioning of the visual system. In addition, visual illusions are fun to experience.
Size constancy allows us to perceive far away objects in their normal size, even though the image they create on our eyes is very small.
Depth Perception
Depth perception is the ability to view the external world in three dimensions while also being able to perceive distance. In order to identify an object, we need to know both what it is and where it is. In order to accomplish this, we rely on binocular cues and convergence. Binocular cues are essentially visual cues for depth that require two eyes. Convergence refers to the turning inward of the eyes when they focus on an object that is nearby. We can also use monocular cues, which are visual depth cues that may be used by only one eye. When an object is up to 50 feet away, we will use binocular cues, but when an object is farther away, we use monocular cues. Research on the visual cliff revealed that many species perceive the world in three dimensions at, or very soon after, birth.
Perceptual Constancy
Having perceived an object as a coherent figure and having located it in space, how then do we recognize it—despite the varying images that it may cast on our retinas? Size, shape, and lightness constancies describe how objects appear to have unchanging characteristics regardless of their distance, shape, or motion. These constancies explain several of the well-known visual illusions.
Color constancy states that perception of the color of an object remains the same, despite any changes in lighting. This is closely related to lightness constancy, but the focus is on color. For example, an apple will look red whether you view inside your kitchen or outside on your deck. When calculating the color of a particular object, the brain will take all wavelengths in the visual field into account.
Brightness constancy states that objects maintain the same brightness, even though the amount of light reflected by them changes. For example, you will view snow as white on a sunny or cloudy day.
Shape constancy states that objects are perceived as having a constant shape, despite changes in point of view or orientation. For example, imagine that you are holding a dinner plate in front of you at arm's length. If you are looking at the plate straight-on, it will appear to have the shape of a circle. Now rotate the plate in some way so that you are not looking at it straight-on; it will still appear to be round, even though the image on your retina is in the shape of an oval. This is an example of shape constancy.
Size constancy is the tendency to perceive objects as staying the same size (within a certain range) despite changes in our distance from them. For example, as a friend is walking toward you on the street, he or she does not appear to be growing in size. A car driving away from you does not appear to be getting smaller. The size of the objects remain fixed, despite the small image on our retina.
Form Perception
Gestalt Principles — To make sense of the world, humans need to know where one thing begins and another ends. In order to recognize an object, it first needs to be observed and perceived as distinct from its surroundings. In other words, it needs to be seen as a figure different from the background. The figure also needs to be organized so that our brain can recognize it and give it meaning. Some Gestalt principles used in the process of object recognition include closure, continuity, proximity, and similarity.
Closure — The human brain will often fill in gaps in order to make sense of disjointed pieces and view them as a complete form. For example, the image below is a series of unattached lines. However, your brain fills in the gaps and recognizes the image as a duck.
A drawing of a duck is shown. The lines do not fully connect.
Continuity — Continuity occurs when patterns and lines are perceived as continuing in space and time. Look at the drawing below. The drawing on the left could very well be composed of the two separate pieces that are on the right. But since we do not see a clear delineation between the pieces, our brains assume that they are continuous. Instead of two distinct objects, we see a straight line with a curved line running through it.
Several arcs and horizontal lines are shown.
Proximity — The law of proximity states that things that are close together will tend to be grouped together. In the drawing below, we tend to perceive four groups of two boxes, rather than eight individual boxes.
Eight blocks are shown. They are arranged in a line in patterns of two. Each block has a gradiant color scheme.
Similarity — Items that are alike in some way, be it color, shape, or size, will tend to be perceived as belonging together. In the drawing below, we perceive rows of objects instead of other layouts or groupings like columns.
Four rows and five columns of dots are shown. The top and third rows are a lighter shade than the second and fourth rows.
Figure Ground Perception
One of the most important findings of Gestalt psychologists is that people tend to consistently organize the visual field into figure and ground. The figure will stand out from the rest of the environment. For example, when you look at your computer monitor, the wall behind it becomes the background. The object, or figure, is closer to you, and the background, or wall, is farther away.
Gestalt psychologists also found that selective attention is involved in this process. Selective attention refers to the ability to concentrate and focus on some areas and stimuli and filter out other areas. This gives some control over what we see and perceive as figure and ground. To support the idea that the whole is different from the sum of its parts, Gestalt psychologists have also developed some ambiguous figure ground images. In these images, the figure and ground can be reversed depending on where the person is focusing at a given moment in time. Consider the image at the top of this page (Rubin vase) as an excellent depiction of figure-ground perception. You may see a white vase as the figure, in which case you will see it displayed on a dark ground. However, you may also see two dark faces that point toward one another. Notice that when you do so, the white area of the figure becomes the ground. Even though your perception may alternate between these two possible interpretations, the parts of the illustration are constant. Thus, the illustration supports the Gestalt position that the whole is not determined solely by its parts. The Dutch artist M.C. Escher was intrigued by ambiguous figure-ground relationships.
Perception
Perceptual Organization
Sensation occurs when energy in the external environment stimulates the sensory receptors in sensing organs such as the ears, eyes, nose, skin, and tongue. Perception is the process by which the brain interprets and organizes sensory information. In practice, sensation and perception are virtually impossible to separate, because they are part of one continuous process.
Transforming sensory information into meaningful perceptions involves cognition, a set of mental activities that includes thinking, knowing, and remembering. Knowledge and experience are extremely important for perception, because they help us make sense of the input to our sensory systems.
"Gestalt" is a German word that means pattern or configuration. Gestalt psychologists focus on how people perceive patterns or parts as a meaningful whole. The early Gestalt psychologists were impressed with the seemingly innate way we organize fragments of sensory data into whole perceptions. Our minds structure the information that comes to us in several demonstrable ways.
Question: Transforming sensory information into meaningful perceptions involves cognition.
ONLY using this information above, answer the following questions:
1. Describe the structure of a neuron and explain the function of each of its major parts.
2. Explain the interaction between the central nervous system and the peripheral nervous system.
3. If the corpus callosum is severed, how might this affect the way that we perceive the world?
4. How might modern brain imaging techniques be useful to psychologists?
5. Explain the difference between absolute threshold and difference threshold.
1 answer
The information provided above does not directly address the specific questions regarding the structure of a neuron, the central and peripheral nervous systems, the effects of severing the corpus callosum, modern brain imaging techniques, or the differences between absolute threshold and difference threshold. However, I can provide general answers based on common knowledge in the fields of neuroscience and psychology.
Structure of a Neuron and Its Functions:
Dendrites: These are branching extensions at the beginning of a neuron that receive signals from other neurons and transmit them to the cell body.
Cell Body (Soma): This part contains the nucleus and is responsible for maintaining the life of the neuron. It processes signals received from the dendrites.
Axon: This is a long, slender projection that conducts electrical impulses away from the cell body to other neurons or muscles. The axon can be covered by a myelin sheath, which speeds up signal transmission.
Axon Terminals (Synaptic Terminals): Located at the end of the axon, these terminals release neurotransmitters into the synaptic cleft, transmitting signals to other neurons.
Interaction Between the Central Nervous System and Peripheral Nervous System:
The central nervous system (CNS), comprising the brain and spinal cord, processes information and coordinates actions. The peripheral nervous system (PNS) connects the CNS to the rest of the body, comprising all peripheral nerves. The PNS is further divided into the somatic and autonomic systems, with the former controlling voluntary movements and the latter regulating involuntary bodily functions. Communication occurs through sensory input from the PNS to the CNS, with subsequent motor output from the CNS back to the PNS to initiate responses.
Effects of Severing the Corpus Callosum on Perception:
The corpus callosum connects the left and right hemispheres of the brain, facilitating communication between them. If it is severed, a condition known as split-brain syndrome can occur. This may lead to different perceptions and responses from each hemisphere. For example, the left hemisphere typically processes language and verbal tasks, while the right hemisphere is more involved in spatial and visual processing. A person may have difficulty naming objects that are only processed by the right hemisphere or may exhibit conflicting behaviors if one hemisphere perceives something differently than the other.
Usefulness of Modern Brain Imaging Techniques in Psychology:
Modern brain imaging techniques, such as fMRI (functional Magnetic Resonance Imaging) and PET (Positron Emission Tomography), allow psychologists to visualize brain activity in real-time. These techniques can help in understanding brain functions related to perception, cognition, and emotion. They allow researchers to correlate specific mental processes with brain regions, examine brain abnormalities, and study how various factors (like experience and learning) influence brain activity.
Difference Between Absolute Threshold and Difference Threshold:
Absolute Threshold refers to the smallest amount of stimulus energy needed for a person to detect a stimulus 50% of the time (e.g., the minimum sound level that can be heard).
Difference Threshold, also known as the Just Noticeable Difference (JND), is the smallest amount of change in a stimulus that can be detected 50% of the time (e.g., the smallest change in weight that can be sensed when lifting). The difference threshold is relative to the original stimulus level, often described by Weber's law.
While the questions draw from areas not directly covered by the provided text, these general explanations are consistent with basic concepts in psychology and neuroscience.
1 answer