Elke B. Lange

Activation and Binding in Verbal Working Memory: A Dual-Process Model for the Recognition of Nonwords.

The article presents a mathematical model of short-term recognition based on dual-process models and the three-component theory of working memory [Oberauer, K. (2002). Access to information in working memory: Exploring the focus of attention. Journal of Experimental Psychology: Learning, Memory, and Cognition, 28, 411-421]. Familiarity arises from activated representations in long-term memory, ignoring their relations; recollection retrieves bindings in the capacity-limited component of working memory. In three experiments participants encoded two short lists of nonwords for immediate recognition, one of which was then cued as irrelevant. Probes from the irrelevant list were rejected more slowly than new probes; this was also found with probes recombining letters of irrelevant nonwords, suggesting that familiarity arises from individual letters independent of their relations. When asked to accept probes whose letters were all in the relevant list, regardless of their conjunction, participants accepted probes preserving the original conjunctions faster than recombinations, showing that recollection accessed feature bindings automatically. The model fit the data best when familiarity depended only on matching letters, whereas recollection used binding information.

Overwriting of phonemic features in serial recall

We tested two explanations of the phonological similarity effect in verbal short‐term memory: The confusion hypothesis assumes that serial positions of similar items are confused. The overwriting hypothesis states that similar items share feature representations, which are overwritten. Participants memorised a phonologically dissimilar list of CVC‐trigrams (Experiment 1) or words (Experiment 2 and 3) for serial recall. In the retention interval they read aloud other items. The material of the distractor task jointly overlapped one item of the memory list. The recall of this item was impaired, and the effect was not based on intrusions from the distractor task alone. The results provide evidence for feature overwriting as one potential mechanism contributing to the phonological similarity effect.

No Age Differences in Complex Memory Search : Older Adults Search as Efficiently as Younger Adults

In 2 experiments, the authors investigated age differences in memory search under 4 conditions: forward search, backward search, random search, and fixed irregular search. Both search slopes and serial position curves were investigated. Mixing conditions led to smaller age differences than blocking conditions, suggesting that younger adults have an advantage over older adults when strategies can be applied to memory scanning. All age differences in scanning rates, however, disappeared when age differences in a magnitude-judgment control task were controlled for, showing that age differences in memory scanning tasks are not because of the scanning process per se, but because of attention, sensorimotor speed, and decision processes. In both experiments, the serial position curves of older adults echoed those of younger adults closely, demonstrating that younger and older adults use the same scanning processes.

Ease of Access to List Items in Short-Term Memory Depends on the Order of the Recognition Probes

We report data from 4 experiments using a recognition design with multiple probes to be matched to specific study positions. Items could be accessed rapidly, independent of set size, when the test order matched the study order (forward condition). When the order of testing was random, backward, or in a prelearned irregular sequence (reordered conditions), the classic Sternberg result was obtained: Response times were slow and increased linearly with set size. A number of explanations for forward-condition facilitation were ruled out, such as the predictability of the study order (Experiment 2), the predictability of the probe order (Experiment 1), the covariation of study and test orders (Experiments 1, 2, and 4), processes of probe encoding and perception that did not rely on STM access (Experiments 1, 2, and 4), specific support of the forward condition by articulatory processes (Experiment 3), or condition-dependent strategic differences (Experiment 4). More detailed analyses demonstrated that fast forward responses could not be accounted for by the effects of input position and output position that modulated random responses, effects that did account for the slower responses of the reordered conditions (Experiments 1, 3, and 4). A final analysis of probe-to-probe transitions as a function of encoding distance revealed a sizeable single-step benefit in the random condition. We concluded that STM representations were serial rather than spatial and that forward probes benefited from their serial adjacency.

Differentiating between verbal and spatial encoding using eye-movement recordings

Visual information processing is guided by an active mechanism generating saccadic eye movements to salient stimuli. Here we investigate the specific contribution of saccades to memory encoding of verbal and spatial properties in a serial recall task. In the first experiment, participants moved their eyes freely without specific instruction. We demonstrate the existence of qualitative differences in eye-movement strategies during verbal and spatial memory encoding. While verbal memory encoding was characterized by shifting the gaze to the to-be-encoded stimuli, saccadic activity was suppressed during spatial encoding. In the second experiment, participants were required to suppress saccades by fixating centrally during encoding or to make precise saccades onto the memory items. Active suppression of saccades had no effect on memory performance, but tracking the upcoming stimuli decreased memory performance dramatically in both tasks, indicating a resource bottleneck between display-controlled saccadic control and memory encoding. We conclude that optimized encoding strategies for verbal and spatial features are underlying memory performance in serial recall, but such strategies work on an involuntary level only and do not support memory encoding when they are explicitly required by the task.

From pre-attentive processes to durable representation: An ERP index of visual distraction

Visual search and oddball paradigms were combined to investigate memory for to-be-ignored color changes in a group of 12 healthy participants. The onset of unexpected color change of an irrelevant stimulus evoked two reliable ERP effects: a component of the event-related potential (ERP), similar to the visual mismatch negativity response (vMMN), with a latency of 120-160 ms and a posterior distribution over the left hemisphere and Late Fronto-Central Negativity (LFCN) with a latency of 320-400 ms, apparent at fronto-central electrodes and some posterior sites. Color change of that irrelevant stimulus also slowed identification of a visual target, indicating distraction. The amplitude of this color-change vMMN, but not LFCN, indexed this distraction effect. That is, electrophysiological and behavioral measures were correlated. The interval between visual scenes approximated 1s (611-1629 ms), indicating that the brains sensory memory for the color of the preceding visual scenes must persist for at least 600 ms. Therefore, in the case of the neural code for color, durable memory representations are formed in an obligatory manner.

Capture of the gaze does not capture the mind

Sudden visual changes attract our gaze, and related eye movement control requires attentional resources. Attention is a limited resource that is also involved in working memory—for instance, memory encoding. As a consequence, theory suggests that gaze capture could impair the buildup of memory respresentations due to an attentional resource bottleneck. Here we developed an experimental design combining a serial memory task (verbal or spatial) and concurrent gaze capture by a distractor (of high or low similarity to the relevant item). The results cannot be explained by a general resource bottleneck. Specifically, we observed that capture by the low-similar distractor resulted in delayed and reduced saccade rates to relevant items in both memory tasks. However, while spatial memory performance decreased, verbal memory remained unaffected. In contrast, the high-similar distractor led to capture and memory loss for both tasks. Our results lend support to the view that gaze capture leads to activation of irrelevant representations in working memory that compete for selection at recall. Activation of irrelevant spatial representations distracts spatial recall, whereas activation of irrelevant verbal features impairs verbal memory performance.

Dual representation of item positions in verbal short-term memory: Evidence for two access modes

Memory sets of N=1 ~ 5 digits were exposed sequentially from left-to-right across the screen, followed by N recognition probes. Probes had to be compared to memory list items on identity only (Sternberg task) or conditional on list position. Positions were probed randomly or in left-to-right order. Search functions related probe response times to set size. Random probing led to ramped, “Sternbergian” functions whose intercepts were elevated by the location requirement. Sequential probing led to flat search functions—fast responses unaffected by set size. These results suggested that items in STM could be accessed either by a slow search-on-identity followed by recovery of an associated location tag, or in a single step by following item-to-item links in study order. It is argued that this dual coding of location information occurs spontaneously at study, and that either code can be utilised at retrieval depending on test demands.

Microsaccade-rate indicates absorption by music listening

The power of music is a literary topos, which can be attributed to intense and personally significant experiences, one of them being the state of absorption. Such phenomenal states are difficult to grasp objectively. We investigated the state of musical absorption by using eye tracking. We utilized a load related definition of state absorption: multimodal resources are committed to create a unified representation of music. Resource allocation was measured indirectly by microsaccade rate, known to indicate cognitive processing load. We showed in Exp. 1 that microsaccade rate also indicates state absorption. Hence, there is cross-modal coupling between an auditory aesthetic experience and fixational eye movements. When removing the fixational stimulus in Exp. 2, saccades are no longer generated upon visual input and the cross-modal coupling disappeared. Results are interpreted in favor of the load hypothesis of microsaccade rate and against the assumption of general slowing by state absorption.