Comparison groups
But it clearly is not enough to observe how often ‘gold’ appeared in the lists. Many people, when asked to think of metals, would include gold, even without having it read to them while they slept. Researchers can overcome this type of problem by examining the difference between the performance of a comparison group or condition and an experimental group or condition. So Wood et al. (1992) made two comparisons. One comparison was between groups. Some participants were awake while the words were read to them, and some were asleep. Because people were randomly assigned to the groups, comparing how often the target words appeared in each of the groups showed whether people were more influenced by presentations while they were awake or by presentations while they were asleep. People who were awake during the presentations were more than twice as likely to report the target words as people who slept. This comparison shows that learning while awake is better than learning while asleep, but it does not rule out the possibility that the sleepers’ performance was influenced by the presentations. Multiple observations were made for each participant and then compared. There were actually two different lists of words – one included ‘a metal: gold’ and the other included ‘a flower: pansy’. Each participant was read only one of the lists, but all participants were tested on both categories. This allowed the experimenters to measure how often people produced words that had been read to them compared to words that had not been read to them.
There was no real difference between individuals’ subsequent reports of key words when the words had been read to them and when the words had not been read to them. The pair of bars furthest to the left provides the same comparison for people who were awake during the word presentations. It is pretty clear that if people were awake during word presentation, then the presentations of the lists had a big effect on subsequent memory for those key words.
But it clearly is not enough to observe how often ‘gold’ appeared in the lists. Many people, when asked to think of metals, would include gold, even without having it read to them while they slept. Researchers can overcome this type of problem by examining the difference between the performance of a comparison group or condition and an experimental group or condition. So Wood et al. (1992) made two comparisons. One comparison was between groups. Some participants were awake while the words were read to them, and some were asleep. Because people were randomly assigned to the groups, comparing how often the target words appeared in each of the groups showed whether people were more influenced by presentations while they were awake or by presentations while they were asleep. People who were awake during the presentations were more than twice as likely to report the target words as people who slept. This comparison shows that learning while awake is better than learning while asleep, but it does not rule out the possibility that the sleepers’ performance was influenced by the presentations. Multiple observations were made for each participant and then compared. There were actually two different lists of words – one included ‘a metal: gold’ and the other included ‘a flower: pansy’. Each participant was read only one of the lists, but all participants were tested on both categories. This allowed the experimenters to measure how often people produced words that had been read to them compared to words that had not been read to them.
There was no real difference between individuals’ subsequent reports of key words when the words had been read to them and when the words had not been read to them. The pair of bars furthest to the left provides the same comparison for people who were awake during the word presentations. It is pretty clear that if people were awake during word presentation, then the presentations of the lists had a big effect on subsequent memory for those key words.
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