Sequence learning is the cognitive faculty enabling everyday skill acquisition. In the lab, it is typically measured in speed of response to sequential stimuli, whereby faster responses are taken to indicate improved anticipation. However, response speed is an indirect measure of anticipation, that can provide only limited information on underlying processes. As a result, little is known about what is learned during sequence learning, and how that unfolds over time. In this work, eye movements that occurred before targets appeared on screen in an ocular serial reaction time (O-SRT) task provided an online indication of where participants anticipated upcoming targets. When analyzed in the context of the stimuli preceding them, oculomotor anticipations revealed several simultaneous learning processes. These processes influenced each other, as learning the task grammar facilitated acquisition of the target sequence. However, they were dissociable, as the grammar was similarly learned whether a repeating sequence inhabited the task or not. Individual differences were found in how the different learning processes progressed, allowing for similar performance to be produced for different latent reasons. This study provides new insights into the processes subserving sequence learning, and a new method for high-resolution study of it.
Information stored in visual short-term memory is used ubiquitously in daily life; however, it is forgotten rapidly within seconds. When more items are to be remembered, they are forgotten faster, potentially suggesting that stronger memories are forgotten less rapidly. Here we tested this prediction with three experiments that assessed the influence of memory strength on the rate of forgetting of visual information without manipulating the number of items. Forgetting rate was assessed by comparing the accuracy of reports in a delayed-estimation task following relatively short and long retention intervals. In the first experiment, we compared the forgetting rate of items that were directly fixated, to items that were not. In Experiments 2 and 3 we manipulated memory strength by extending the exposure time of one item in the memory array. As expected, direct fixation and longer exposure led to better accuracy of reports, reflecting stronger memory. However, in all three experiments, we did not find evidence that increased memory strength moderated the forgetting rate.
Working memory (WM) is known to be impaired in patients with stroke experiencing unilateral spatial neglect (USN). Here, we examined in a systematic manner three WM components: memory of object identity, memory of object location, and binding between object identity and location. Moreover, we used two different retention intervals to isolate maintenance from other mnemonic and perceptual processes. Fourteen USN first-event stroke patients with right-hemisphere damage were tested in two different WM experiments using long and short retention intervals and an analog response scale. Patients exhibited more identification errors for items displayed on the contralesional side. Localization errors were also more prominent in the contralesional side, especially after a long retention interval. These localization errors were often a result of swap errors, that is, erroneous localizations of correctly identified contralesional objects in correctly memorized locations of ipsilesional objects. We conclude that a key WM deficit in USN is a lateralized impairment in binding between the identity of an object and its spatial tag.
Two of the dominating tasks in the visual working memory (VWM) literature are the Delayed Estimation (DE) task and the Change Detection (CD) task. However, there are no studies that directly compared how participants' expectation to be tested in these tasks impacts memory formation. Here, three experiments interspersed DE and CD trials with identical displays until the reporting stage. During each session, the frequency of trials of each task was altered to manipulate expectations of which task would be required. Expectation of a DE task led to an increase in the number of fixations during encoding and to more precise estimation. By contrast, expectation of a CD trial did not modulate CD accuracy. These results suggest that the precision with which information is encoded into VWM differs between these two tasks. This has implications for current theoretical debates on VWM and underscores the importance of the typically overlooked effect of task type on memory performance.
Public Significance StatementThe temporal retention and manipulation of visual information is typically termed visual working memory (VWM). Performance in VWM tasks is predictive of success in various real-life aspects such as educational achievements. The current study demonstrates the flexible and efficient nature of VWM-a task that requires more precision recruits more resources. The findings underscore the vast and largely overlooked role of task demands on working memory performance. Thus, caution should be exercised when making theoretical conclusions without taking into account task effects.
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