Posters: Memory I

In tests of working memory with verbal or spatial materials repeating the same memory sets across trials leads to improved memory performances. This well-established “Hebb repetition effect” could not be shown for visual materials. This absence of the Hebb effect can be explained in two ways: either, persons fail to acquire a long-term memory representation of the repeated memory sets over the course of repetitions, or they acquire such long-term memory representations, but fail to use them during the to be processed working memory task. With the present study (N = 30), we aimed to decide between these two possibilities by manipulating the long-term memory knowledge of some of the memory sets used in a change-detection task. Before the change-detection test, the participants had to complete an explicit learning phase where they had to memorize three arrays of colors until a satisfying memory performance was reached. Subsequently, the participants were tested with the change-detection paradigm, which contained both previously learned and new color arrays. The previously learned arrays were continuously repeated across trials, whereas the new arrays were randomly generated. Change detection performance was better on previously learned compared to new arrays, showing that long-term memory is used in change detection. Memory for the previously learned arrays did not improve further during change detection, showing no evidence for further learning through repetition.

Forgetting of outdated information can be examined by means of list-method directed forgetting. In this task, people study a list of words and then receive a forget or a remember cue for this first list before studying a second list. Typical results show list-1 forgetting in response to forget cues. At least for short retention intervals, forgetting of list 1 only appears when new material is encoded after the forget cue. This finding is consistent with the involvement of an inhibitory control process that regulates between-list interference by reducing access to list 1. Recent work indicates that list-1 forgetting can be long-lasting, but it is unclear if such persistent forgetting depends on list-2 learning, too. We examined this question by manipulating not only the cue after list-1 study (remember vs. forget) but also the presence of list 2 (with vs. without) and the delay between studying and a free recall test (30 sec vs. 20 minutes). Results showed list-1 forgetting after short and longer delay in the presence of list-2 encoding, but no such forgetting in the absence of list 2. These findings demonstrate a critical role of post-cue encoding for persistent list-1 forgetting. They are consistent with predictions derived on the basis of the inhibition account of list-method directed forgetting, suggesting that between-list interference may be a necessary component for long-lasting forgetting to arise.

Our memories are broken up into discrete events, even though we experience the world in a continuous manner. The Event Horizon Model (EHM; Radvansky, 2012) explains the discreteness of events in memory based on online segmentation or event shifts. One prediction of the EHM is that recently encountered information is more difficult to access in memory following an event shift. Previous experiments have shown larger rates of forgetting following spatial shifts, even when retention time was held constant; this is referred to as the Location Updating Effect (LUE). In two experiments we aimed to discover whether more basic changes in the environment would lead to similar effects as the LUE. In Experiment 1 subjects incidentally learned a list of words (with a task requiring a response to font style) and each list was followed by a memory probe for one of the words. On half of the trials the background color changed during the presentation of the list. Based on the EHM, we expected worse memory for words in trials with the color change. We found a nonsignificant trend supporting our prediction. In Experiment 2, which is still ongoing, we aimed to make the shift more salient by requiring a change in response keys to font style following a color change. As in Experiment 1, we predict larger rates of forgetting on trials with a background color shift. Furthermore, given the extra change (the response) we predict that the effects will be larger than those found in Experiment 1.

Previous studies have shown detrimental effects of interruptions on the execution of interrupted (primary) tasks in laboratory settings and work environments. Aim of this study was to examine effects of different cognitive demands of interruptions on the post-interruption performance in a primary task. The primary task was a verbal procedural task with sequential constraints, simulating a typical procedural task like performing a checklist from memory. While performing this primary task, 44 participants were interrupted for 30s at different steps by an interruption task varying in memory demand (2-back vs. 1-back task) and processing code (verbal vs. spatial). Resumption times (how fast the primary task is resumed) and sequence errors (resuming the primary task at the wrong step) were analyzed. Assuming that interruptions demanding more memory resources and the same processing code as the primary task are more disruptive, worse post-interruption performance was expected for the 2-back interruption tasks compared to the 1-back tasks, and for verbal compared to spatial interruptions. As expected, high memory demand of interruption task lead to longer resumption times and more sequence errors at post-interruption step, compared to the interruptions posing low memory demand. Verbal interruptions lead to longer resumption times at post-interruption step than spatial ones, while no effect was found on sequence errors. The results reveal additive effects of the two factors in resumption times, and suggest that both memory and processing code demands are relevant properties of interruptions which can influence the post-interruption performance.

Studies showed that a brief period of wakeful resting after learning boosts the retention of new memories, whereas task-related cognition after learning weakens memory retention. In extension to existing wakeful resting studies, we explored the impact of social media usage after learning on memory retention. We tested healthy young adults who were required to learn and immediately recall two vocabulary lists. After recalling the first list, participants were asked to wakefully rest (eyes closed, relaxed) for several minutes and after recalling the second list, they were asked to use Instagram or Facebook for several minutes. Memories for both vocabulary lists were tested again at the end of the experimental session. Our results showed that social media usage after learning had detrimental effects on memory retention compared to wakeful resting. Findings are discussed in the light of existing wakeful resting and social media studies.

In old age (>60 years), episodic long-term memory (LTM) formation becomes increasingly impaired due to age-related healthy and sometimes pathological atrophy of the medial temporal lobe, especially the hippocampus. On the other hand, recent evidence from neuroimaging and lesion studies suggests that learning novel information coherent with prior knowledge can tremendously reduce or even circumvent the role of the hippocampus in LTM formation via means of the medial prefrontal cortex (mPFC) inhibiting the hippocampus’ novelty response. We could show repeatedly that a special kind of learning, that is, when a semantic association is very suddenly comprehended (via insight or Aha!), learning is hippocampus-independent and instead relies more on midline structures such as the mPFC and precuneus. Here, we present a behavioral study on learning from insight that compared memory performance for learning from insight, using a German version of the Compound Remote Associate Task. We compared performance on insight problem solving and later memory performance for young adults between the age of 18 and 30 years (n = 30) with adults age 60 to 80 (n = 30). Based on this work, we aim to develop learning strategies that employ learning from insight to help compensate age-related decline of episodic LTM formation.

To examine influences of context changes between encoding and retrieval of motor sequences, we varied a number of encoding and retrieval features. Participants learned two sets of three-finger movements at two different PCs, all enacted with fingers of the right hand. We varied keyboard and display orientation, stimuli, background color, response keys, position of the hand, and the used PC between the two set. A final free recall test comprised either the same context features as present during study of the first item set or the ones present during study of the second item set or novel test context features. Results showed significant differences in overall recall performance between test conditions, indicating that context features of study episodes guided retrieval of motor sequences. In addition, the number of recalled items varied as a function of output position. Context features of the set-1 study episode were associated with initially lower but subsequently increasing recall performance, whereas features of the set-2 study episode were associated with initially higher and subsequently decreasing recall performance. This implies that a context reinstatement for list-1 items during the test phase does not immediately enhance accessibility of those items. However, access is subsequently facilitated over the course of retrieval attempts.