The Effects of Training Under Working Memory Load on Performance During Testing

In 2 experiments, subjects trained in a data entry task, typing one 4-digit number at a time. At training subjects either typed the numbers immediately after they appeared or typed the previous number while holding the current number in working memory. In Experiment 2, either nothing or a physical space was inserted between the second and third digits. Subjects completed a 5-min distractor task after training and then completed the test, which consisted of the same data entry task but with all subjects typing the 4-digit numbers immediately as they appeared. The results indicated little benefit for training using working memory on performance at test; however, a component analysis of each keystroke revealed different strategies for each training condition. The results from Experiment 1 suggested an advantage at test for typing numbers that had been presented during training, but only for subjects who were trained to type the numbers as they appeared, and only for the third keystroke. Experiment 2 showed no advantage overall for having a space between the numbers, and analyses for each keystroke revealed that the extra working memory requirement during training slowed entering the last 3 digits of the number and the concluding keystroke at test. TRAINING UNDER WORKING MEMORY LOAD 3 The Effects of Training Under Working Memory Load on Performance During Testing Working memory is a short-term memory with limited capacity that is flexible based on the task at hand. For example, consider a person remembering a grocery list that he or she forgot to write down. As the person finds a food item in the grocery store, he or she discards it from working memory, never to be remembered again. Suppose the person remembers an item that he or she initially forgot to include in the mental list. The person adds the new item to the working memory store until he or she finds the new item and then discards it from the mental list. The items in working memory change according to which task a person selectively attends. The purpose of the current study is to test whether having to use working memory during a training session affects performance on a test. Principles of Training Researchers have studied training in order to see changes in performance over time, and to determine if training transfers across different circumstances. Several studies have manipulated the type of training, the stimuli presented during training, the length of time between training and testing, and the test itself. However, an explanation of the neural processes thought to underlie training is in order. Recent studies in neuroscience have found possible neural processes to explain why training is effective. Neuroscientists think that when a well-established memory is retrieved, it is vulnerable to degradation by molecular processes. Forming a memory increases the strength of a synapse (the connection between two neurons) and all of the important activities that help store the memory. By default, neurons want to go back to their base state, with the help of protein degradation processes, which would cancel out the increased activity that formed the memory. When a memory is retrieved, the strengthened synapse is vulnerable to the protein degradation TRAINING UNDER WORKING MEMORY LOAD 4 process. However, in a process called reconsolidation, the act of activating the memory also signals the activities that formed the memory to reactivate, hence the synapse stays strong. Some scientists argue that retrieving a memory does not only make the memory vulnerable to degradation, but that it makes the memory vulnerable to modification (Lee, 2009). In other words, it is possible for the memory to disappear if the reconsolidation process is disrupted, but it is also possible to strengthen the memory to make it stronger than it was originally (Lee, 2009). Reconsolidation relates to training in that each trial of training strengthens the relevant synapses so that they become stronger after each trial (Lee, 2008). Lee found that training animals in a fear context, followed by more training, strengthened the fear memory, but only after the protein degradation processes had started to destabilize the synapse. When the protein degradation processes were blocked artificially, no reconsolidation was necessary and the strength of the synapse remained the same (Lee, 2008). Another study found that training working memory strengthened the connection between different lobes in the brain and that it increased the efficiency with which attentional resources were distributed in short-term memory (Kundu, Sutterer, Emrich, & Postle, 2013). In other words, training to improve working memory strengthened communication between major lobes of the brain, making short-term memory more efficient and creating less demand on the memory system. In order to determine what type of training is effective, researchers have manipulated the stimuli within the training sessions and tested the amount of transfer to a testing condition. One study found that when subjects trained in a specific condition and switched to a different training condition, there was no transfer of skill from one condition to another (Healy, Wohldmann, Sutton, & Bourne, 2006). The conditions involved training with one or more computer mouse directions reversed, so that subjects had to acclimate to one or more mouse directions going in TRAINING UNDER WORKING MEMORY LOAD 5 the opposite direction than they were familiar. The only transfer found was when the training and testing conditions a subject could encounter had some similarity, so that the processes involved in training were a subset of those involved in testing (Healy et al., 2006). Another study used a data entry task similar to the task used in the current study, except varying the presentation of the numbers. Buck-Gengler and Healy (2001) used a data entry task to train four-digit numbers in different formats. One format was presented as numerals (1234) and the other format was presented as words (one two three four). In both conditions, subjects typed the numbers using the 10-keypad. The test consisted of a mixture of old and new four-digit numbers, or numbers that had been presented during training and numbers that had not been presented. The format of the numbers also varied, as in the training session. The results were that subjects who trained with numbers presented as numerals typed slower and made more mistakes on the test than subjects who trained with numbers presented as words. Buck-Gengler and Healy (2001) believe that having to process the words during training led to better retention than seeing a number as numerals and typing it using the same format. Varying the presentation of the training stimuli is one way to test training and transfer, but there have been hypotheses put forward for the results seen from training and transfer. The specificity of training hypothesis states that training on a specific task in a specific way does not create transfer to a different task. The only transfer that occurs is if the test or other task is the same as what was trained. Chein and Morrison (2010) found that training working memory did not transfer to tasks of reasoning or fluid intelligence, which is the ability to solve problems in new situations separate from an individual's current knowledge and experience. Their experiment, in part, supports the specificity of training concept in that improving working memory during training did not improve performance on different tasks based on reasoning. TRAINING UNDER WORKING MEMORY LOAD 6 Healy et al. (2006) found specificity of training effects when a particular reversal condition during training did not transfer to a different reversal condition, but within the same condition subjects became faster. Not only did subjects not display transfer from one condition to another, they showed improvement when the conditions were the same. In an experiment that also used reversing a direction on a specific plane, subjects were faster when they tested on the same targets as the ones they trained for initiation time (Wohldmann, Healy, & Bourne, 2008). The experimenters reasoned that initiation, the first keystroke in the data entry task, includes formulating a motor plan as well as making the first move, so when subjects were faster on initiation when they trained and tested on the same targets, it suggested that initiation is specific to the targets that were trained (Wohldmann et al., 2008). This explanation is aligned with the specificity of training hypothesis, at least for making the first movement. In the field of neuroscience, Kundu et al. (2013) speculated that transfer from training to testing “may be contingent on the degree to which the training task and transfer task share common neural architectures” (p. 8714). The idea that transfer from training to testing is based on shared parts of the brain suggests a neural basis for the specificity of training hypothesis. In contrast to specificity of training, another concept that has been described as an explanation of what goes on between training and testing is contextual interference. Contextual interference is the idea that randomizing the order of presented stimuli during training leads to better retention because the processing demand is greater than training the same stimuli over and over in a block. In addition, constantly changing training induces thinking of different strategies for completing the trials, and thus increases the amount of transfer from one task to another. According to contextual interference, subjects who train in a more difficult setting should TRAINING UNDER WORKING MEMORY LOAD 7 perform worse during training, but better during testing because of the beneficial retention and transfer effects. Shea and Morgan (1979) found evidence for the benefit of training in a random condition compared to training in a blocked condition. The subjects who had trained in