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Sensations and Perceptions. Sensations and Perceptions. Sensations can be defined as the passive process of bringing information from the outside world into the body and to the brain. The process is passive in the sense that we do not have to be consciously engaging in a "sensing" process. .
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Sensations and Perceptions • Sensations can be defined as the passive process of bringing information from the outside world into the body and to the brain. The process is passive in the sense that we do not have to be consciously engaging in a "sensing" process.
Sensations and Perceptions • Perception can be defined as the active process of selecting, organizing, and interpreting the information brought to the brain by the senses.
HOW THEY WORK TOGETHER • 1) Sensation occurs: • a) Sensory organs absorb energy from a physical stimulus in the environment. • b) Sensory receptors convert this energy into neural impulses and send them to the brain.
How They Work Together • 2) Perception follows: • a) The brain organizes the information and translates it into something meaningful.
Selective Attention • 1) Selective Attention - process of discriminating between what is important & is irrelevant (Seems redundant: selective-attention?), and is influenced by motivation.
Perceptual Expectancy • 2) Perceptual Expectancy - how we perceive the world is a function of our past experiences, culture, and biological makeup.
Psychophysics • Psychophysics can be defined as,the study of how physical stimuli are translated into psychological experience. • In order to measure these events, psychologists use.
THRESHOLDS • 1) Threshold - a dividing line between what has detectable energy and what does not. • For example - many classrooms have automatic light sensors. When people have not been in a room for a while, the lights go out. However, once someone walks into the room, the lights go back on. For this to happen, the sensor has a threshold for motion that must be crossed before it turns the lights back on. So, dust floating in the room should not make the lights go on, but a person walking in should.
THRESHOLDS • 2) Difference Threshold - the minimum amount of stimulus intensity change needed to produce a noticeable change. • The greater the intensity (ex., weight) of a stimulus, the greater the change needed to produce a noticeable change. • For example, when you pick up a 5 lb weight, and then a 10 pound weight, you can feel a big difference between the two. However, when you pick up 100 lbs, and then 105 lbs, it is much more difficult to feel the difference.
Signal-Detection Theory • 3) Signal-Detection Theory - detection of a stimulus involves some decision making process as well as a sensory process. Additionally, both sensory and decision making processes are influenced by many more factors than just intensity. • a) Noise - how much outside interference exists. • b) Criterion - the level of assurance that you decide must be met before you take action. Involves higher mental processes. You set criterion based on expectations and consequences of inaccuracy.
Signal-Detection Theory • For example - at a party, you order a pizza...you need to pay attention so that you will be able to detect the appropriate signal (doorbell), especially since there is a lot of noise at the party. But when you first order the pizza, you know it won't be there in 2 minutes, so you don't really pay attention for the doorbell. As the time for the pizza to arrive approaches, however, your criterion changes...you become more focused on the doorbell and less on extraneous noise.
SIGHT/VISION • A) The visual system works on sensing and perceiving light waves. Light waves vary in their length and amplitude: • a) Wave length (also referred to as frequency, since the longer a wave, the less often/quickly it occurs) - affects color perception (ex., red=approx 700, yellow approx 600) • b) Wave amplitude (this is the size/height of the wave) - affects brightness perception.
Structure of the Eye • 1) Cornea - the round, transparent area that allows light to pass into the eye. • 2) Lens - the transparent structure that focuses light onto the retina. • 3) Retina - inner membrane of the eye that receives information about light using rods and cones. The functioning of the retina is similar to the spinal cord - both act as a highway for information to travel on. • 4) Pupil - opening at the center of the iris which controls the amount of light entering the eye. Dilates and Constricts. • 5) Rods & Cones - many more rods (approximately 120 million) than cones (approx 6.4 million).
Rods and Cones • a) Cones - visual receptor cells that are important in daylight vision and color vision. • The cones work well in daylight, but not in dim lighting. This is why it is more difficult to see colors in low light. • most are located in the center of the retina...called the FOVEA, which is a tiny spot in the center of the retina that contains ONLY cones...visual acuity is best here. • SO...when you need to focus on something you attempt to bring the image into the fovea.
Rods and Cones • b) Rods - visual receptor cells that are important for night vision and peripheral vision. • The rods are better for night vision because they are much more sensitive than cones. • In addition, the rods are better for peripheral vision because there are many more on the periphery of the retina. The cones are mostly in and around the fovea but decrease as you go out. • To see best at night, look just above or below the object...this keeps the image on the rods.
Color and Vision • C) Seeing In Color - we can see many colors, but only have 3 types of cones that receive information about color. We have cones that pick up light waves for red, green, and blue.
Color Vision Theories • 1) Trichromatic Theory - this theory indicates that we can receive 3 types of colors (red, green, and blue) and that the cones vary the ratio of neural activity (Like a projection T.V.). The ratio of each color to the other then determines the exact color that we see.
Color Vision Theories • 2) Opponent-Process Theory - color perception depends on the reception of pairs of antagonist colors. Each receptor can only work with one color at a time so the opponent color in the pair is blocked out. Pairs = red-green, blue-yellow, black- white (light-dark).
PERCEPTION • Much of our understanding of how and why we perceive things comes from Gestalt Psychology • For example - one of the most well known Gestalt principles is the Phi Phenomenon, which is the illusion of movement from presenting stimuli in rapid succession. When you see a cartoon or running Christmas lights, you see movement (although none actually exists) because of this principle.
PERCEPTION • A) Gestalt Principles of Perceptual Organization • 1) figure-ground - this is the fundamental way we organize visual perceptions. When we look at an object, we see that object (figure) and the background (ground) on which it sits. For example, when I see a picture of a friend, I see my friends face (figure) and the beautiful Sears brand backdrop behind my friend (ground).
Simplicity/Pragnanz • simplicity/pragnanz (good form) - we group elements that make a good form. However, the idea of "good form" is a little vague and subjective. Most psychologists think good form is what ever is easiest or most simple.
Proximity • 3) Proximity - nearness=belongingness. Objects that are close to each other in physical space are often perceived as belonging together.
Similarity • 4) Similarity—As you probably guessed, this one states that objects that are similar are perceived as going together. For example, if I ask you to group the following objects: (* * # * # # #) into groups, you would probably place the asterisks and the pound signs into distinct groups.
Continuity • Continuity - we follow whatever direction we are led. Dots in a smooth curve appear to go together more than jagged angles. This principle really gets at just how lazy humans are when it comes to perception.
Closure • Closure - we tend to complete a form when it has gaps.
Common Fate • Common fate - elements that move together tend to be grouped together. For example, when you see geese flying south for the winter, they often appear to be in a "V" shape.
Illusions • Reversible Figures - ambiguous sensory information that creates more than 1 good form. For example, the picture of two faces looking toward each other that is also a vase.
Illusions • Impossible Figures - objects that can be represented in 2-dimensional pictures but can not exist in 3-dimensional space despite our perceptions. You know the artist, Escher who draws the pictures like...the hands drawing each other, the waterfall that goes down and stays level at the same time, etc...
THE PERCEPTION OF PAIN • Pain is an unpleasant yet important function for survival: warning system (but not all pain is needed for survival). • There are two different pathways to the brain on which pain can travel - information brought from free nerve endings in the skin to the brain via two different systems: • 1) Fast pathways - registers localized pain (usually sharp pain) and sends the information to the cortex in a fraction of a second. EX. - cut your finger with a knife.
THE PERCEPTION OF PAIN • Slow pathways - sends information through the limbic system which takes about 1-2 seconds longer than directly to the cortex (longer lasting, aching/burning).
