Retention-error patterns in complex alphanumeric serial-recall tasks

Great minds think alike: New measures to quantify the similarity of recalls

Given the recent interest in how memory operates in social contexts, it is more important than ever to meaningfully measure the similarity between recall sequences of different individuals. Similarity of recall sequences of different individuals has been quantified using primarily order-agnostic and some order-sensitive measures specific to memory research without agreement on any one preferred measure. However, edit distance measures have not been used to quantify the similarity of recall sequences in collaborative memory studies. In the current study, we review a broad range of similarity measures, highlighting commonalities and differences. Using simulations and behavioral data, we show that edit distances do measure a memory-relevant factor of similarity and capture information distinct from that captured by order-agnostic measures. We answer illustrative research questions which demonstrate potential applications of edit distances in collaborative and individual memory settings and reveal the unique impact collaboration has on similarity.

Extended trajectory of spatial memory errors in typical and atypical development: The role of binding and precision

Spatial reconstruction, a method for evaluating how individuals remember the placement of objects, has traditionally been evaluated through the aggregate estimation of placement errors. However, this approach may obscure the nature of task errors. Specifically, recent data has suggested the importance of examining the precision of responses, as well as absolute performance on item-context bindings. In contrast to traditional analysis approaches based on the distance between the target and the reconstructed item, in this study we further explored three types of errors (swap error, global error, and local distance) that may all contribute to the distance, with particular emphasis on swap errors and local distance due to their associations with item-context bindings and memory precision, respectively. We examined these errors in children aged 3-18 years, making comparisons between children with typical development (TD) and children with Down syndrome (DS), a population with known memory challenges. As expected, older children outperformed younger children in terms of overall memory accuracy. Of importance is that we measured uneven maturational trajectories of memory abilities across the various error types. Specifically, both remembered locations (irrespective of object identity) and swap errors (object-location binding errors) align with the overall memory accuracy. Memory precision, as measured by local distance in simpler set size 2 trials, mirrored overall memory accuracy. However, for more complex set size 3 trials, local distance remained stable before age 8 and showed age-related change thereafter. The group with DS showed reduced precision compared to a TD matched group, and measures of precision, and to a lesser extent binding errors, correlated with standard neuropsychological outcomes. Overall, our study contributed to a fine-grained understanding of developing spatial memory ability in a large sample of typical developing children and a memory impaired population. These findings contribute to a growing body of research examining precision as a key factor in memory performance.

Can compression take place in working memory without a central contribution of long-term memory?

Information is easier to remember when it is recognized as structured. One explanation for this benefit is that people represent structured information in a compressed form, thus reducing memory load. However, the contribution of long-term memory and working memory to compression are not yet disentangled. Previous work has mostly produced evidence that long-term memory is the main source of compression. In the present work, we reveal two signatures of compression in working memory using a large-scale naturalistic data set from a science museum. Analyzing data from more than 32,000 memory trials, in which people attempted to recall briefly displayed sequences of colors, we examined how the estimated compressibility of each sequence predicted memory performance. Besides finding that compressibility predicted memory performance, we found that greater compressibility of early subsections of sequences predicted better memory for later subsections, and that mis-recalled sequences were simpler than the originals. These findings suggest that (1) more compressibility reduces memory load, leaving space for additional information; (2) memory errors are not random and instead reflect compression gone awry. Together, these findings suggest that compression can take place in working memory. This may enable efficient storage on the spot without direct contributions from long-term memory. However, we also discuss ways long-term memory could explain our findings.

An easy way to improve scoring of memory span tasks: The edit distance, beyond "correct recall in the correct serial position"

For researchers and psychologists interested in estimating a subject's memory capacity, the current standard for scoring memory span tasks is the partial-credit method: subjects are credited with the number of stimuli that they manage to recall correctly in the correct serial position. A critical issue with this method, however, is that intrusions and omissions can radically change the scores depending on where they occur. For example, when recalling the sequence ABCDE, "ABCD" is worth 4 points but "BCDE" is worth 0 points. This paper presents an improved scoring method based on the edit distance, meaning the number of changes required to edit the recalled sequence into the target. Edit-distance scoring gives results close to partial-credit scoring, but without the corresponding vulnerability to positional shifts. A reanalysis of memory performance in two large datasets (N = 1093 and N = 758) confirms that in addition to being more logically consistent, edit-distance scoring demonstrates similar or better psychometric properties than partial-credit, with comparable validity, a small increase in reliability, and a substantial increase of test information (measurement precision in the context of item response theory). Test information was especially improved for harder items and for subjects with ability in the lower range, whose scores tend to be severely underestimated by partial-credit scoring. Code to compute edit-distance scores with various software is made available at https://osf.io/wdb83/ .

Examining the limits of Memory-Guided Planning in 3- and 4-year olds

Stored memories may be drawn upon when accomplishing goals. In two experiments, we investigated limits on the ability to use episodic memories to support planning in 3- and 4-year-old children. We designed a new memory-guided planning task that required children to both retrieve memories and apply those memories to accomplish multiple, nested goals. We manipulated the difficulty of the task by varying the number of steps required to achieve the goals, and examined the impact of this manipulation on both memory retrieval and planning. We found that, overall, 4-year-olds outperformed 3-year-olds, but as task difficulty increased, all children made more errors. Analysis of these errors suggested that retrieval and planning processes might impose separate limits on memory-guided planning in early childhood, but that these limits may ease across early childhood.

Chunking and redintegration in verbal short-term memory

Memory for verbal material improves when words form familiar chunks. But how does the improvement due to chunking come about? Two possible explanations are that the input might be actively recoded into chunks, each of which takes up less memory capacity than items not forming part of a chunk (a form of data compression), or that chunking is based on redintegration. If chunking is achieved by redintegration, representations of chunks exist only in long-term memory (LTM) and help to reconstructing degraded traces in short-term memory (STM). In 6 experiments using 2-alternative forced choice recognition and immediate serial recall we find that when chunks are small (2 words) they display a pattern suggestive of redintegration, whereas larger chunks (3 words), show a pattern consistent with data compression. This concurs with previous data showing that there is a cost involved in recoding material into chunks in STM. With smaller chunks this cost seems to outweigh the benefits of recoding words into chunks. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Simple and Complex Working Memory Tasks Allow Similar Benefits of Information Compression

Complex working memory span tasks were designed to engage multiple aspects of working memory and impose interleaved processing demands that limit the use of mnemonic strategies, such as chunking. Consequently, the average span is usually lower (4 ± 1 items) than in simple span tasks (7 ± 2 items). One possible reason for the higher span of simple span tasks is that participants can take advantage of the spare time to chunk multiple items together to form fewer independent units, approximating 4 ± 1 chunks. It follows that the respective spans of these two types of tasks could be equal (at around 4 ± 1) if stimulus lists exclusively used nonchunkable stimulus items. To manipulate the chunkability of the stimulus lists, our method involved a measure of their compressibility, i.e., the extent to which a pattern exists that can be detected and used as a basis of chunk formation. We predicted an interaction between the types of tasks and chunkability/compressibility, supporting a single higher span for the condition in which a simple span task was combined with chunkable items. The three other conditions were predicted to prevent chunking processes, either because the interleaved processing task did not allow any chunking process to occur or because the noncompressible material inherently limited the chunkability of information. The prediction that chunking is important solely in simple spans was not confirmed: Effects of information compression contributed to performance levels to a similar extent in both tasks according to a theoretically-based metric. This result suggests that i) complex span tasks might overestimate storage capacity in general, and ii) the difference between simple and complex span performance levels must rest in some mechanism other than prevention of a chunking strategy by the interleaved processing task in complex span tasks.

Compression in Working Memory and Its Relationship With Fluid Intelligence

Working memory has been shown to be strongly related to fluid intelligence; however, our goal is to shed further light on the process of information compression in working memory as a determining factor of fluid intelligence. Our main hypothesis was that compression in working memory is an excellent indicator for studying the relationship between working-memory capacity and fluid intelligence because both depend on the optimization of storage capacity. Compressibility of memoranda was estimated using an algorithmic complexity metric. The results showed that compressibility can be used to predict working-memory performance and that fluid intelligence is well predicted by the ability to compress information. We conclude that the ability to compress information in working memory is the reason why both manipulation and retention of information are linked to intelligence. This result offers a new concept of intelligence based on the idea that compression and intelligence are equivalent problems.

Developmental Abilities to Form Chunks in Immediate Memory and Its Non-Relationship to Span Development

Both adults and children –by the time they are 2–3 years old– have a general ability to recode information to increase memory efficiency. This paper aims to evaluate the ability of untrained children aged 6–10 years old to deploy such a recoding process in immediate memory. A large sample of 374 children were given a task of immediate serial report based on SIMON®, a classic memory game made of four colored buttons (red, green, yellow, blue) requiring players to reproduce a sequence of colors within which repetitions eventually occur. It was hypothesized that a primitive ability across all ages (since theoretically already available in toddlers) to detect redundancies allows the span to increase whenever information can be recoded on the fly. The chunkable condition prompted the formation of chunks based on the perceived structure of color repetition within to-be-recalled sequences of colors. Our result shows a similar linear improvement of memory span with age for both chunkable and non-chunkable conditions. The amount of information retained in immediate memory systematically increased for the groupable sequences across all age groups, independently of the average age-group span that was measured on sequences that contained fewer repetitions. This result shows that chunking gives young children an equal benefit as older children. We discuss the role of recoding in the expansion of capacity in immediate memory and the potential role of data compression in the formation of chunks in long-term memory.