MCAT Social and Behavioral Sciences : Perceptual Concepts and Organization
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Example Question #3 : Principles Of Sensation
Perception is the process that occurs when the brain processes sensory stimuli and translates them in a way that a person can understand. Perception is not usually a conscious process; furthermore, sensing a particular stimulus is a different process than the interpretation (i.e. perception) of that stimulus.
A team of perception researchers decided to test the difference between sensation and perception by testing the reading speed of a paragraph in three conditions. In the first condition, the researchers correctly spelled the words in the sentences. In the second condition, they had the same words with the letters randomly jumbled within each word; however, the first and last letter of each word remained in the correct position. In the third condition, researchers used the same words and randomly jumbled every letter in each word, including the first and last letters. Sample sentences from the paragraphs are below:
1). Mary crossed the street to purchase a cookie after lunch.
2). Mray csorsed the sretet to pruachse a ckooie atfer lnuch.
3). Rmya rsocsed het teerst to curaepshs a okocei feart culhn.
The researchers timed how long it took for the participants to correctly say a sentence fluently. They found that participants in condition three took significantly more time to read the sentence fluently, whereas they found no significant difference in the average amount of time it took participants to read the passage in condition one compared to condition two.
Suppose the researchers were also interested in the amount of time it took the participants in each condition to read each letter fluently (as opposed to each word). In order to test this phenomenon, participants across conditions were instructed to read each letter aloud as quickly and as correctly as possible. They found no group differences in letter reading speed or accuracy. Based on these results, the researchers would most likely conclude which of the following?
It is unlikely that participants in condition three were reading the words more slowly in the initial experiment due to poor reading ability.
For reading, perceptual processes involve more than decoding individual letters.
All of these
For reading, top-down processes are more often used than bottom-up processes.
All of these
If participants in all three conditions did not differ in letter reading speed, but they differed in word reading speed, then it suggests that reading is not just decoding letters. In other words, top-down processes are at play. In a top-down process, the brain uses a-priori knowledge of the world to form percepts or mental impressions about what a stimulus might be.
Given that participants in condition three were reading slower, it could be that their reading ability was poorer to begin with (i.e. a confounding variable); however, because they can read letters just as fluently as the other groups, it is unlikely that the groups differ in reading ability.
Example Question #4 : Principles Of Sensation
Perception is the process that occurs when the brain processes sensory stimuli and translates them in a way that a person can understand. Perception is not usually a conscious process; furthermore, sensing a particular stimulus is a different process than the interpretation (i.e. perception) of that stimulus.
A team of perception researchers decided to test the difference between sensation and perception by testing the reading speed of a paragraph in three conditions. In the first condition, the researchers correctly spelled the words in the sentences. In the second condition, they had the same words with the letters randomly jumbled within each word; however, the first and last letter of each word remained in the correct position. In the third condition, researchers used the same words and randomly jumbled every letter in each word, including the first and last letters. Sample sentences from the paragraphs are below:
1). Mary crossed the street to purchase a cookie after lunch.
2). Mray csorsed the sretet to pruachse a ckooie atfer lnuch.
3). Rmya rsocsed het teerst to curaepshs a okocei feart culhn.
The researchers timed how long it took for the participants to correctly say a sentence fluently. They found that participants in condition three took significantly more time to read the sentence fluently, whereas they found no significant difference in the average amount of time it took participants to read the passage in condition one compared to condition two.
The observation that participants did not differ in reading time between conditions one and two illustrates that humans rely on which of the following principles when reading?
Phi phenomenon
Inattentional blindness
Bottom-up processing
Top-down processing
Top-down processing
Top-down and bottom-up processing are both examples of feature analysis, which allows us to detect specific elements and assemble them into a more complex visual form. A top-down process is a progression from the whole to the details (in this case, from the whole word to the individual letters). Bottom-up processing is the opposite; it is the progression from individual elements to the whole. Because participants in condition two were still reading as quickly as those in condition one, it suggests that in reading, humans process the whole word rather than each individual letter (i.e. top-down process).
The Phi Phenomenon is the illusion of movement created by presenting visual stimuli in rapid succession (e.g. a cartoon flip book). Inattentional blindness occurs when someone is hyper-focused on one stimulus and unable to take in other information.
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