The Role of Attention in Behavior

     Attention is taking notice or focusing on a certain figure, conversation, or really anything in the world. Many people don't know, however, that there are different types of attention, such as selective attention and selective inattention. Selective attention is defined as "the focusing of conscious awareness on a particular stimulus." Of 11,000,000 bits of information our sense take in from the environment per second, only 40 are consciously processed. This is due to selective attention, which strongly affects behavior. Without the ability to block the 10,999,960 bits of stimuli that we don't process, we'd go insane trying to process every part of our world.
     Selective attention results in selective inattention, which is the part of the environmental stimulus that we do not consciously process. Inattentional blindness, a type of selective inattention, is when people fail to see visible objects when their attention is directed somewhere else. A form of inattentional blindness is called change blindness, when is when people fail to notice changes in the environment.
     In regards to behavior, our behavior heavily relies on what part of our environment we pay attention to. Focusing on negative experiences instead of positive ones will most likely mold a pessimistic person. Not paying attention to what your friend is saying will most likely make you ignorant when they bring the subject up again. So, how/what we consciously process shapes our behavior, even if we don't consciously know it.

Color and Motion Perception

Color Perception

• In the United States, red and white are used for emergency vehicles. I think red is used because people associate red with danger and chaos. The advantages of using red is that is easily detected under bright light. and is distinct from other vehicles. While under dim/dark lighting red is not as easily detectable, the flashing lights help with its visibility. White is a great color to use because it is very visible under dark light. However, white emergency vehicles could be mistaken for vans or buses.
• The color of an emergency vehicle greatly affects its visibility and ability to alert drivers and pedestrians. The experience of color depends on the context; our perception of the color of the emergency vehicle changes depending on whether we see the whole vehicle, or if we just see part of it. If we see part of the vehicle under changing lighting, the vehicle will seem to change color. But if we see the whole vehicle under changing lighting, it will remain the same color. This is known as color constancy. As the book said, "You and I see color thanks to our brains' computations of the light reflected by any object relative to its surrounding objects." So, our perception of color is determined by the object and its surroundings. In choosing the color for an emergency vehicle, they should choose a color that is distinctly different than its surroundings in order for it to retain color constancy in different lighting.
• One factor that affects how easy it is to see various colors is the context of the color, which depends on the brightness, relative luminance, lighting/wavelength shifts, and surrounding colors.

After looking at all of the different factors which affect color perception, I think emergency vehicles should use bright colors such as neon-ish red and yellow. Red will be obvious during the day, while yellow will be easily visible during the night. Also, since this combination of colors are not common, the emergency vehicles will be easily detectable and will stand out from the surroundings.

Motion Perception

• We rely on motion perception for everyday life, such as eating, walking, writing, or driving.
• In order to perceive motion, we rely on factors such as sizes of objects. As an object becomes smaller, we perceive it to be moving away from us. In contrast, as an object becomes bigger, we perceive it to be moving towards us. Also, our brains perceive large objects (such as trains) to be moving slower than small objects (such as cars), even if they are moving at the same speed. To form the perception of movement, brains use stroboscopic movement, a rapid series of slightly varying images.

Astronaut's Dilemma & More!

GESTALT: an organized whole

Gestalt Principles to group Stimuli and to form Perception...

• proximity: group nearby things together
• similarity: group similar figures together
• continuity: perceive smooth, continuous patterns instead of choppy, discontinuous patterns
• connectedness: group things that are uniform and linked
• closure: we fill in gaps to create a complete whole figure/object
• figure-ground: organization of the visual field into objects (figures) that stand out from their surroundings (ground)

Depth Perception: seeing objects in 3 dimensions and the ability to judge distance

Retinal disparity, a binocular cue, allows us to perceive depth and provides us with the ability to determine the relative distance of different objects. Retinal disparity while looking straight and far ahead is not very effective in judging distance, so we use monocular cues.

Motion Perception



Brains perceive motion as a rapid series of slightly varying images, a phenomenon known as stroboscopic movement.

Brain Processing:

• bottom-up: analysis which begins with sensory receptors and works up to the brain's integration of sensory information
• top-down: analysis guided by high-level mental processes, such as when perception construction or drawing on experiences/expectations; progression from a whole to its elements

When people see optical illusions, they first use top-down processing. So, they see the whole picture (instead of its several elements) and try to make sense of it, but it doesn't work. This is because optical illusions trick different parts of perception, such as depth perception and contours. Since top-down processing is guided by perception construction, top-down processing makes people very vulnerable to illusions.

Astronauts Dilemma:

     Top-down processing will be tricky but important for the astronauts. During top-down processing, the brain focuses on the whole first, and then works its way down to analyze the various details of the whole. This processing allows the brain to form perceptions. Top-down processing can be important for the astronauts, so they should be sharpening their depth and motion perception skills. These skills could be useful to an extent, considering depth and motion could be vastly different under conditions on different planets. Therefore, their perceptions would also be different. Top-down processing can harm the astronauts by making them vulnerable illusions too. If their perceptions are different than reality, due to illusions, their data could be affected by their perceptions. So, the astronauts should be wary of perceptions and need to focus on details first, using bottom-up processing.
     Possibly the most important Gestalt strategy is determining figure-ground relationships. Knowing how objects are organized in comparison to their surroundings will be really important for the astronauts to travel through the different planets. Also, the principles for grouping could be useful, but they also may be harmful if perceptions made by top-down processing are fooled by illusions. Grouping stimuli based on perceptions is tricky business, considering the human brain is always trying to create order out of patterns, even when there aren't any. So, the astronauts should be wary of Gestalt strategies for perceiving objects and patterns, because top-down processing can taint reality. However, they should focus on perceiving accurate figure-ground relationships.
     The astronauts should look for binocular and monocular cues to help with figure-ground segregation by forming depth perceptions. Binocular cues, such as retinal disparity, will help the astronauts determine the relative difference between objects. However, if objects are straight ahead, retinal disparity won't be very useful, so they should search for monocular cues, such as relative size, interposition, and light/shadowing. Relative size will help the astronauts perceive which objects are closest and which are farthest. Interposition allows the astronauts to determine how the objects are layered upon each other. Also, a brighter image is perceived as being close, while dimmer images are perceived as being far away. All of these cues will help the astronauts determine which objects are the figures, and which objects are the ground. So, they should look for these cues, while always being wary of illusions.

*more information about binocular and monocular cues can be found in the blog post "The Laws of Perception"

The Laws of Perception

Binocular Cues: depth cues that depend on using two eyes

• retinal disparity: the difference between the images from the retinas of each eye; by comparing these images, the brain perceives distance
• the larger the disparity, the closer the object
• 3-D movies exaggerate retinal disparity

Monocular Cues: depth cues that are available to either eye alone

• relative size: if two objects are similar in size, the larger object (with the greater retinal disparity) is perceived to be closer than the smaller object
• relative height: high objects are perceived to be far away
• texture gradient: as texture becomes less apparent and clear, we judge the surface to be going into the distance
• relative motion (motion parallax): as we move, for example in a car, closer objects seem to move past quickly in comparison to objects in the distance, which seem to move with us
• aerial perspective: far away objects appear to blurred or hazy due to the atmosphere
• linear perspective: parallel lines seem to converge in the distance; as they appear to converge more, the perceived distance grows
• interposition: when two objects overlap, the object that is being covered is perceived as being further away than the object that is covering it
• light and shadow: a shaded, dimmer object appears to be farther away than a bright object

phi phenomenon: an illusion of movement created when 2+ adjacent lights blink on and off quickly

perceptual constancy: despite changes in illumination and retinal images, we are able to perceive objects as unchanging with the same shape, size, color, and brightness

perceptual adaptation: our ability to adapt to changed visual input

perceptual set: a mental predisposition which influences (top-down) what we perceive and do not perceive

The Sensory Processes

VISION
In order to see, we transduce light energy (in the form of electromagnetic waves) into neural messages that our brain processes.

First, light passes through the cornea, which bends the light to focus. Then, the iris adjusts the amount of light that enters the pupil. Once through the pupil, the light travels through the lens, which focuses the light in an image on the retina. The retina has two types of receptor cells, rods (which enable peripheral vision, have a high sensitivity in dim light, and are located in the periphery of the retina) and cones (which have high color sensitivity/detail sensitivity and are located in the center of the retina). Chemical changes in the rods and cones activate bipolar cells, which activate ganglion cells. The axons of the ganglion cells form the optic nerve, which carries visual information to the thalamus. From there, the thalamus distributes the visual information to the visual cortex in the occipital lobe, where it will be processed. Feature detector cells in the visual cortex respond to different features of the image, and send this information to supercell clusters which respond to these complex patters and features. More generally, the brain divides the visual scene into several different aspects, such as color, motion, form, and depth. This is known as parallel processing.

 

HEARING

The stimulus energy of noise is sound waves. In order to hear, our ears transform sound waves into nerve impulses which our brain processes as sounds. Sound waves first travel through the outer ear's auditory canal, which leads the energy into the middle ear. In the middle ear, the sound waves meet the eardrum, which begins to vibrate. The vibrations pass through the piston, composed of the hammer, anvil, and stirrup. From there, the vibrations enter the cochlea, located in the inner ear. The cochlea's membrane and the fluid within begin to vibrate, creating ripples in the basilar membrane, which bends hair cells on its surface. The movement of hair cells creates impulses in nearby nerve cells, whose axons form the auditory nerve. Through the thalamus, neural messages are sent to the auditory cortex in the temporal lobes.

 

TOUCH

All skin sensations are various combinations of four basic sensations: pressure, warmth, cold, and pain. Some parts of skin are especially sensitive to one of the four basic sensations, making some sensations more strong. However, there are no specialized nerve endings for the specific sensations; there are only identifiable receptors for pressure. Touch is a bottom-up property of senses and a top-down product of expectations, because expectations effect how you respond to a sensation.

 

VESTIBULAR SENSE

The vestibular sense monitors position and movement of your head, basically your sense of equilibrium, using "biological gyroscopes" in your inner ear. Vestibular sacs, which connect the semicircular canals with the cochlea, are filled with fluid that moves when your head or body moves. When you move, hair-like receptors are activated and send neural messages to the cerebellum about your position. The cerebellum allows you to maintain balance.

 

KINESTHESIS

Kinesthesis is your sense of position and movement of your body parts. There are sensors in your joints, tendons, bones, ears, and even your skin which enable kinesthesis. It also interacts with vision; if you are in the dark or close your eyes, your sense of balance and position will become slightly compromised. Without kinesthesis, you wouldn't be able to sense the location or position of your limbs. Kinesthesis works with the vestibular sense.

 

PAIN

Pain varies depending on physiology, experiences, attention, and culture, much like other sensations. Unlike other sensations, however, there isn't just one stimulus that creates pain. Instead, there are many nocireceptors, which detect harmful sensations (high temperatures, burning chemicals, intense pressure). One theory of pain is the gate-control theory, which involves the fibers in the spinal cord that conduct signals to the brain. The gate-control theory says that during a painful experience (tissue damage), small fibers in the spinal cord become activated and open the "gate," allowing pain signals to be transferred to the brain to be processed. When large fibers in the spinal cord become activated, they close the "gate" and prevent pain signals from reaching the brain.

 

 

TASTE

Similar to touch, which has four basic sensations, taste has five basic sensations: sweet, salty, sour, bitter, and umami. All other tastes are a mixture of these five, basic taste sensations. Essentially, taste is a chemical sense. All over tongues are bumps, which each contain 200+ taste buds. Taste buds collect chemicals from the food eaten. Inside the taste buds are 50-100 receptor cells with hair-fibers that sense food molecules. Some receptors are more sensitive to a specific taste sensation, such as sour. Much like other sensations, taste varies based on expectations and experiences.

 

SMELL

Like taste, smell is a chemical sensation. Because the smell chemicals are so different, there are many receptor proteins which work together to detect these scents. When an odor molecule binds to a receptor, which are located on nasal cavity neurons, the olfactory receptor cells send electrical signals to high regions of the brain via the combined axons of the olfactory receptor cells.

 

                                    

Sensory Disorders

Visual Disorders:

 

Prospagnosia: face blindness; the inability to recognize faces/people

Color-Deficiency: lack proper functioning of red-sensitive or green-sensitive cones in the retina

Hearing Disorders:

Conduction Hearing Loss: caused by damage to the mechanical system that conducts sound waves to the cochlea

Sensorineural Hearing Loss: "nerve deafness"; damage to the hair cell receptors or associated nerves
          -people use cochlea implants, which translate sound into neural signals,            in order to restore hearing from this particular type of hearing loss

 

 

The Basic Principles of Sensory Transduction

     Each day, we experience countless sensations. A sensation is the process in which our sensory receptors and nervous system receive stimulus energies from our environment. The change of this stimulus energy into electrical energy that can be used in our body, specifically the brain, is known as signal transduction. However, the stimulus often doesn't have enough energy for us to be able to consciously recognize the stimulus. The minimum stimulation needed to detect a sensation 50% of the time is called the absolute threshold. This doesn't mean that if a stimulus is below your absolute threshold you won't detect it; it means that you are unlikely to detect it. The signal detection theory predicts when you will detect these weak signals, which is dependent upon experience, expectations, motivation, and alertness. This explains why each person responds to stimuli differently. A single person's response to the same stimuli can change as well, which is known as sensory adaption, the diminishing sensitivity to an unchanging stimulus. Due to constant exposure to a stimulus, our nerve cells fire less to the stimulus. However, our sight does not undergo sensory adaption because eyes are constantly moving. 

     Similar to the absolute threshold is the difference threshold, also known as the "just noticeable difference" (JND). The difference threshold is the minimum difference a person can detect between two different stimuli 50% of the time. This threshold increases as the size of the stimuli increases. For example, if one-ounce is added to five-ounces, you are likely to notice the difference. However, if one-ounce is added to fifty-ounces, you probably wouldn't be able to notice that one-ounce was added because the weight was already large. So, the difference threshold for the fifty-ounce example is large, meaning you would need to add a large amount, such as ten-ounces, in order to recognize that weight has changed. Weber's law explains this, stating that for their difference to be noticeable, the two stimuli must differ by a constant proportion, not amount.

 

 

This picture illustrates difference threshold and Weber's Law.