Proactive interference of visual working memory chunks implicates long-term memory.

Visual working memory (VWM) is a limited cognitive resource that can be functionally expanded through chunking (Miller, 1956). For example, participants can hold an increasing number of colours in mind as they learn to chunk reliably paired combinations (Brady et al., 2009). We investigated whether this benefit is mediated through the in situ compression of VWM representations (Brady et al., 2009) or the offloading of chunks to long-term memory (LTM; Huang & Awh, 2018; Ngiam et al., 2019) by asking if a vulnerability of LTM - proactive interference - influences VWM performance. We adapted previous designs using deterministic (Experiment 1, N = 60) and probabilistic pairings (Experiments 2 and 3, N = 64 and 80, respectively), to include colour pairings that swapped in sequence along with pairings that were consistent in sequence. Generally, participants reported colours from consistent pairs more accurately than from swapping pairs, which we designed to drive interference in LTM (Experiments 1 and 2). The error profiles also pointed to proactive interference between swapping pairs in all three experiments. Moreover, participants who had explicit awareness of frequent colour pairings had higher VWM accuracy, and their errors reflected more proactive interference than their unaware counterparts (Experiment 3). This pattern of long-term proactive interference in a VWM task lends support for accounts of VWM chunking that propose LTM offloading.

Retrieval-induced forgetting of spatial position depends on access to multiple shared features within categories.

Retrieval-induced forgetting (RIF) is typically observed in verbal memory tasks, although a few studies have observed RIF in visual spatial tasks. This leaves an open question as to whether RIF depends on semantic identity to link across semantic properties of objects, or whether RIF depends on access to the perceptual features of objects. To explore RIF of spatial positions, we report three experiments utilizing a continuous measure of the accessibility and precision for objects that were distinguished by their shape, color, and spatial region. After a study phase, half of the objects in a single-color category were selectively practiced for their spatial position, by requiring the object to be placed in the exact spatial position seen previously. Finally, all objects were probed for their spatial position at test. No RIF occurred for objects that shared only one color feature but were located within the same spatial region (in Experiment 1) or when objects shared the same color, but were located within different spatial regions (in Experiment 3). However, RIF did occur when objects shared the same spatial region and the same color (Experiment 2). Overall, the interim recall of the spatial positions of cue-objects impairs access to the position of other cue-objects within the same color category, but only when these groups had sufficient overlapping and competing features. The finding that RIF only occurs to the accessibility of spatial positions, not the precision of visual spatial memory, was interpreted as consistent with inhibitory theories of forgetting.

Cumulative semantic cost without successful naming.

Accessing semantic information has negative consequences for successive recovering attempts of similar information. For instance, in the course of picture-naming tasks, the time required to name an object is determined by the total number of items from the same category that have already been named; naming latencies increase proportionally to the total number of semantically related words named previously. This phenomenon is called cumulative semantic cost (or interference). Two picture-naming experiments with children (4-11 years old, 229 participants) investigate whether having successfully named the previous within-category items is a necessary condition for the cumulative semantic cost to appear. We anticipated that younger children would have a larger rate of nonresponses compared with older children, reflecting the fact that younger children have not yet consolidated many lexical representations. Our results confirmed this prediction. Critically, we also observed that cumulative semantic cost was independent of having successfully retrieved previous within-category lexical items. Furthermore, picture trials for which the previous within-category item elicited a nonresponse showed the same amount of cost as those picture trials for which the previous within-category item elicited a correct naming event. Our findings indicate that it is the attempt to retrieve a lexical unit, and not the successful retrieval of a specific lexical unit, that causes semantic cost in picture naming. This cost can be explained by a mechanism of weakening the semantic-to-lexical mappings of semantic coordinate words. The findings are also discussed in the context of retrieval-induced forgetting effects in memory recall research.

Effects of proactive interference on non-verbal working memory.

Working memory (WM) is a cognitive system responsible for actively maintaining and processing relevant information and is central to successful cognition. A process critical to WM is the resolution of proactive interference (PI), which involves suppressing memory intrusions from prior memories that are no longer relevant. Most studies that have examined resistance to PI in a process-pure fashion used verbal material. By contrast, studies using non-verbal material are scarce, and it remains unclear whether the effect of PI is domain-general or whether it applies solely to the verbal domain. The aim of the present study was to examine the effect of PI in visual WM using both objects with high and low nameability. Using a Directed-Forgetting paradigm, we varied discriminability between WM items on two dimensions, one verbal (high-nameability vs. low-nameability objects) and one perceptual (colored vs. gray objects). As in previous studies using verbal material, effects of PI were found with object stimuli, even after controlling for verbal labels being used (i.e., low-nameability condition). We also found that the addition of distinctive features (color, verbal label) increased performance in rejecting intrusion probes, most likely through an increase in discriminability between content-context bindings in WM.

Do learners predict a shift from recency to primacy with delay?

The shift from recency to primacy with delay reflects a fundamental observation in the study of memory. As time passes, the accessibility of earlier-learned representations tends to increase relative to the accessibility of later-learned representations. In three experiments involving participants' memory for text materials, we examined whether participants understood that there might be such a shift with retention interval. In marked contrast to their actual performance, participants predicted recency effects at both shorter and longer retention intervals. Our findings add to the evidence that the storage and retrieval dynamics of the human memory system, though adaptive overall from a statistics-of-use standpoint, are both complex and poorly understood by users of the system.