On specification and the senses. Behavioral and Brain Sciences, 24 2 , — Trappey, C. A meta-analysis of consumer choice and subliminal advertising. Psychology and Marketing, 13 , — Weiskrantz, L. Consciousness lost and found: A neuropsychological exploration. Wickens, T. Elementary signal detection theory. Figure 5. Skip to content Chapter 5. Sensing and Perceiving. Learning Objectives Review and summarize the capacities and limitations of human sensation.
Explain the difference between sensation and perception and describe how psychologists measure sensory and difference thresholds. As the intensity of a stimulus increases, we are more likely to perceive it. Stimuli below the absolute threshold can still have at least some influence on us, even though we cannot consciously detect them. Key Takeaways Sensation is the process of receiving information from the environment through our sensory organs. Perception is the process of interpreting and organizing the incoming information so that we can understand it and react accordingly.
Transduction is the conversion of stimuli detected by receptor cells to electrical impulses that are transported to the brain. Although our experiences of the world are rich and complex, humans — like all species — have their own adapted sensory strengths and sensory limitations. Sensation and perception work together in a fluid, continuous process.
Our judgments in detection tasks are influenced by both the absolute threshold of the signal as well as our current motivations and experiences. Signal detection analysis is used to differentiate sensitivity from response biases. Research has found that stimuli can influence behaviour even when they are presented below the absolute threshold i. The effectiveness of subliminal advertising, however, has not been shown to be of large magnitude.
Exercises and Critical Thinking Leaf through a magazine or watch several advertisements on television and pay attention to the persuasive techniques being used. What impact are these ads having on your senses? Based on what you know about psychophysics, sensation, and perception, what are some of the reasons why subliminal advertising might be banned in some countries?
B But what does "meaningful" mean? How do we know what information is important and should be focused on? For example - students in class should focus on what the teachers are saying and the overheads being presented. Students walking by the classroom may focus on people in the room, who is the teacher, etc. But someone from a different country with different experiences and history may not have any idea what to expect and thus be surprised when they see cars go driving by.
Another example - you may look at a painting and not really understand the message the artist is trying to convey. But, if someone tells you about it, you might begin to see things in the painting that you were unable to see before. C Psychophysics can be defined as, the study of how physical stimuli are translated into psychological experience.
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.
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 lbs, and then lbs, it is much more difficult to feel the difference. Additionally, both sensory and decision making processes are influenced by many more factors than just intensity.
Involves higher mental processes. You set criterion based on expectations and consequences of inaccuracy. For example - at a party, you order a pizza 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 A the visual system works on sensing and perceiving light waves. Light waves vary in their length and amplitude:. The functioning of the retina is similar to the spinal cord - both act as a highway for information to travel on. Dilates and Constricts. Bottom-up processing refers to the fact that perceptions are built from sensory input, stimuli from the environment. On the other hand, how we interpret those sensations is influenced by our available knowledge, our experiences, and our thoughts related to the stimuli we are experiencing.
This is called top-down processing. One way to think of this concept is that sensation is a physical process, whereas perception is psychological. When we see our professor speaking in the front of the room, we sense the visual and auditory signals coming from them and we perceive that they are giving a lecture about our psychology class. Although our perceptions are built from sensations, not all sensations result in perception. This is known as sensory adaptation.
Imagine entering a classroom with an old analog clock. Upon first entering the room, you can hear the ticking of the clock; as you begin to engage in conversation with classmates or listen to your professor greet the class, you are no longer aware of the ticking. The clock is still ticking, and that information is still affecting sensory receptors of the auditory system.
The fact that you no longer perceive the sound demonstrates sensory adaptation and shows that while closely associated, sensation and perception are different. Additionally, when you walk into a dark movie theater after being outside on a bright day you will notice it is initially extremely difficult to see. If you are wondering why it takes so long to adapt to darkness, in order to change the sensitivity of rods and cones, they must first undergo a complex chemical change associated with protein molecules which does not happen immediately.
Now that you have adapted to the darkens of the theater, you have survived marathon watching the entire Lord of the Rings series, and you are emerging from the theater a seemly short ten hours after entering the theater, you may experience the process of light adaptation, barring it is still light outside.
During light adaptation, the pupils constrict to reduce the amount of light flooding onto the retina and sensitivity to light is reduced for both rods and cones which takes usually less than 10 minutes Ludel, So why is the process of raising sensitivity to light to adapt to darkness more complex than lowering sensitivity to adapt to light? Caruso has suggested that a more gradual process is involved in darkness adaptation due to humans tendency over the course of evolution to slowly adjust to darkness as the sun sets over the horizon.
There is another factor that affects sensation and perception: attention. Attention plays a significant role in determining what is sensed versus what is perceived. Imagine you are at a party full of music, chatter, and laughter. You get involved in an interesting conversation with a friend, and you tune out all the background noise. If someone interrupted you to ask what song had just finished playing, you would probably be unable to answer that question.
One of the most interesting demonstrations of how important attention is in determining our perception of the environment occurred in a famous study conducted by Daniel Simons and Christopher Chabris In this study, participants watched a video of people dressed in black and white passing basketballs.
Participants were asked to count the number of times the team in white passed the ball. During the video, a person dressed in a black gorilla costume walks among the two teams. You would think that someone would notice the gorilla, right? Because participants were so focused on the number of times the white team was passing the ball, they completely tuned out other visual information.
Failure to notice something that is completely visible because of a lack of attention is called inattentional blindness. More recent work evaluated inattention blindness related to cellphone use. Participants were not aware that while they walked through the square a unicycling clown would ride right in front of them. See for yourself how inattentional blindness works by checking out this selective attention test from Simons and Chabris :. One of the most interesting demonstrations of how important attention is in determining our perception of the environment occurred in a famous study conducted by Daniel Simons and Christopher Chabris In this study, participants watched a video of people dressed in black and white passing basketballs.
Participants were asked to count the number of times the team in white passed the ball. During the video, a person dressed in a black gorilla costume walks among the two teams. You would think that someone would notice the gorilla, right?
Because participants were so focused on the number of times the white team was passing the ball, they completely tuned out other visual information. Failure to notice something that is completely visible because of a lack of attention is called inattentional blindness. In a similar experiment, researchers tested inattentional blindness by asking participants to observe images moving across a computer screen.
They were instructed to focus on either white or black objects, disregarding the other color. Motivation can also affect perception. Have you ever been expecting a really important phone call and, while taking a shower, you think you hear the phone ringing, only to discover that it is not?
If so, then you have experienced how motivation to detect a meaningful stimulus can shift our ability to discriminate between a true sensory stimulus and background noise. The ability to identify a stimulus when it is embedded in a distracting background is called signal detection theory. This might also explain why a mother is awakened by a quiet murmur from her baby but not by other sounds that occur while she is asleep. Signal detection theory has practical applications, such as increasing air traffic controller accuracy.
Controllers need to be able to detect planes among many signals blips that appear on the radar screen and follow those planes as they move through the sky. In fact, the original work of the researcher who developed signal detection theory was focused on improving the sensitivity of air traffic controllers to plane blips Swets, Our perceptions can also be affected by our beliefs, values, prejudices, expectations, and life experiences.
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