The late positive event-related potential component is time locked to the decision in recognition memory tasks.

Two event-related potential (ERP) components are commonly observed in recognition memory tasks: the Frontal Negativity (FN400) and the Late Positive Component (LPC). These components are widely interpreted as neural correlates of familiarity and recollection, respectively. However, the interpretation of LPC effects is complicated by inconsistent results regarding the timing of ERP amplitude differences. There are also mixed findings regarding how LPC amplitudes covary with decision confidence. Critically, LPC effects have almost always been measured using fixed time windows relative to memory probe stimulus onset, yet it has not been determined whether LPC effects are time locked to the stimulus or the recognition memory decision. To investigate this, we analysed a large (n = 132) existing dataset recorded during recognition memory tasks with old/new decisions followed by post-decisional confidence ratings. We used ERP deconvolution to disentangle contributions to LPC effects (defined as differences between hits and correct rejections) that were time locked to either the stimulus or the vocal old/new response. We identified a left-lateralised parietal LPC effect that was time locked to the vocal response rather than probe stimulus onset. We also isolated a response-locked, midline parietal ERP correlate of confidence that influenced measures of LPC amplitudes at left parietal electrodes. Our findings demonstrate that, contrary to widespread assumptions, the LPC effect is time locked to the recognition memory decision and is best measured using response-locked ERPs. By extension, differences in response time distributions across conditions of interest may lead to substantial measurement biases when analysing stimulus-locked ERPs. Our findings highlight important confounding factors that further complicate the interpretation of existing stimulus-locked LPC effects as neural correlates of recollection. We recommend that future studies adopt our analytic approach to better isolate LPC effects and their sensitivity to manipulations in recognition memory tasks.

Greater target or lure variability? An exploration on the effects of stimulus types and memory paradigms.

In recognition memory, the variance of the target distribution is almost universally found to be greater than that of the lure distribution. However, these estimates commonly come from long-term memory paradigms where words are used as stimuli. Two exceptions to this rule have found evidence for greater lure variability: a short-term memory task (Yotsumoto et al., Memory & Cognition, 36, 282-294 2008) and in an eyewitness memory paradigm (Wixted et al., Cognitive Psychology, 105, 81-114 2018). In the present work, we conducted a series of recognition memory experiments using different stimulus (faces vs. words) along with different paradigms (long-term vs. short-term paradigms) to evaluate whether either of these conditions would result in greater variability in lure items. Greater target variability was observed across stimulus types and memory paradigms. This suggests that factors other than stimuli and retention interval might be responsible for cases where variability is less for targets than lures.

Modelling orthographic similarity effects in recognition memory reveals support for open bigram representations of letter coding.

A variety of letter string representations has been proposed in the reading literature to account for empirically established orthographic similarity effects from masked priming studies. However, these similarity effects have not been explored in episodic memory paradigms and very few memory models have employed orthographic representation of words. In the current work, through two recognition memory experiments employing word and pseudoword stimuli respectively, we empirically established a set of key orthographic similarity effects for the first time in recognition memory - namely the substitution effect, transposition effect and reverse effect in recognition memory of words and pseudowords, and a start-letter importance in recognition memory of words. Subsequently, we compared orthographic representations from the reading literature including slot coding, closed-bigram, open-bigram and the overlap model. Each of these representations was situated in a global matching model and fitted to recognition performance via Luce's choice rule in a hierarchical Bayesian framework. Model selection results showed support for the open-bigram representation in both experiments.

Integrating word-form representations with global similarity computation in recognition memory.

In recognition memory, retrieval is thought to occur by computing the global similarity of the probe to each of the studied items. However, to date, very few global similarity models have employed perceptual representations of words despite the fact that false recognition errors for perceptually similar words have consistently been observed. In this work, we integrate representations of letter strings from the reading literature with global similarity models. Specifically, we employed models of absolute letter position (slot codes and overlap models) and relative letter position (closed and open bigrams). Each of the representations was used to construct a global similarity model that made contact with responses and RTs at the individual word level using the linear ballistic accumulator (LBA) model (Brown & Heathcote Cognitive Psychology, 57 , 153-178, 2008). Relative position models were favored in three of the four datasets and parameter estimates suggested additional influence of the initial letters in the words. When semantic representations from the word2vec model were incorporated into the models, results indicated that orthographic representations were almost equally consequential as semantic representations in determining inter-item similarity and false recognition errors, which undermines previous suggestions that long-term memory is primarily driven by semantic representations. The model was able to modestly capture individual word variability in the false alarm rates, but there were limitations in capturing variability in the hit rates that suggest that the underlying representations require extension.

Modeling the continuous recognition paradigm to determine how retrieval can impact subsequent retrievals.

There are several ways in which retrieval during a memory test can harm memory: (a) retrieval can cause an increase in interference due to the storage of additional information (i.e., item-noise); (b) retrieval can decrease accessibility to studied items due to context drift; and (c) retrieval can result in a trade in accuracy for speed as testing progresses. While these mechanisms produce similar outcomes in a study-test paradigm, they are dissociated in the 'continuous' recognition paradigm, where items are presented continuously and a participant's task is to detect a repeat of an item. In this paradigm, context drift results in worse performance with increasing study-test lag (the lag effect), whereas increasing item-noise is evident in a decrease in performance for later test trials in the sequence (the test position effect [TPE]). In the present investigation, we measured the influences of item-noise, context drift, and decision-related factors in a novel continuous recognition dataset using variants of the Osth et al. (2018) global matching model. We fit both choice and response times at the single trial level using state-of-the-art hierarchical Bayesian methods while incorporating crucial amendments to the modeling framework, including multiple context scales and sequential effects. We found that item-noise was responsible for producing the TPE, context drift decreased the magnitude of the TPE (by diminishing the impact of item-noise), and speed-accuracy changes had some minor effects that varied across participants.

The spatiotemporal gradient of intrusion errors in continuous outcome source memory: Source retrieval is affected by both guessing and intrusions.

Previous research has characterized source retrieval as a thresholded process, which fails on a proportion of trials and leads to guessing, as opposed to a continuous process, in which response precision varies across trials but is never zero. The thresholded view of source retrieval is largely based on the observation of heavy tailed distributions of response errors, thought to reflect a large proportion of "memoryless" trials. In this study, we investigate whether these errors might instead reflect systematic intrusions from other list items which can mimic source guessing. Using the circular diffusion model of decision making, which accounts for both response errors and RTs we found that intrusions account for some, but not all, errors in a continuous-report source memory task. We found that intrusion errors were more likely to come from items studied in nearby locations and times, and were well-described by a spatiotemporal gradient model, but not from semantically or perceptually similar cues. Our findings support a thresholded view of source retrieval but suggest that previous work has overestimated the proportion of guesses which have been conflated with intrusions.

Novelty rejection in episodic memory.

Episodic memory theories have postulated that in recognition, a probe is accepted or rejected on the basis of its global similarity to studied items. Mewhort and Johns (2000) directly tested global similarity predictions by manipulating the feature compositions of probes-novelty rejection was facilitated when probes contained novel features even when other features strongly matched, an advantage dubbed the extralist feature effect, which greatly challenged global matching models. In this work, we conducted similar experiments using continuously valued separable- and integral-dimension stimuli. Analogs of extralist lures were constructed where one stimulus dimension contained a value that was more novel than the other dimensions, whereas overall similarity was equated to another class of lures. Facilitated novelty rejection for lures with extralist features was only found for separable-dimension stimuli. While integral-dimension stimuli were well described by a global matching model, the model failed to account for extralist feature effects with separable-dimension stimuli. We applied global matching models-including variants of the exemplar-based linear ballistic accumulator-that employed different means of novelty rejection afforded by separable-dimension stimuli, including decisions based on the global similarity of the individual dimensions and selective attention being directed toward novel probe values (a diagnostic attention model). While these variants produced the extralist feature effect, only the diagnostic attention model succeeded in providing a sufficient account of all of the data. The model was also able to account for extralist feature effects in an experiment with discrete features similar to those from Mewhort and Johns (2000). (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Do item-dependent context representations underlie serial order in cognition? Commentary on Logan (2021).

Logan (2021) presented an impressive unification of serial order tasks including whole report, typing, and serial recall in the form of the context retrieval and updating (CRU) model. Despite the wide breadth of the model's coverage, its reliance on encoding and retrieving context representations that consist of the previous items may prevent it from being able to address a number of critical benchmark findings in the serial order literature that have shaped and constrained existing theories. In this commentary, we highlight three major challenges that motivated the development of a rival class of models of serial order, namely positional models. These challenges include the mixed-list phonological similarity effect, the protrusion effect, and interposition errors in temporal grouping. Simulations indicated that CRU can address the mixed-list phonological similarity effect if phonological confusions can occur during its output stage, suggesting that the serial position curves from this paradigm do not rule out models that rely on interitem associations, as has been previously been suggested. The other two challenges are more consequential for the model's representations, and simulations indicated the model was not able to provide a complete account of them. We highlight and discuss how revisions to CRU's representations or retrieval mechanisms can address these phenomena and emphasize that a fruitful direction forward would be to either incorporate positional representations or approximate them with its existing representations. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Sources of Interference in Memory Across Development.

Episodic memory involves remembering not only what happened but also where and when the event happened. This multicomponent nature introduces different sources of interference that stem from previous experience. However, it is unclear how the contributions of these sources change across development and what might cause the changes. To address these questions, we tested 4- to 5-year-olds (n = 103), 7- to 8-year-olds (n = 82), and adults (n = 70) using item- and source-recognition memory tasks with various manipulations (i.e., list length, list strength, word frequency), and we decomposed sources of interference using a computational model. We found that interference stemming from other items on the study list rapidly decreased with development, whereas interference from preexperimental contexts gradually decreased but remained the major source of interference. The model further quantified these changes, indicating that the ability to discriminate items undergoes rapid development, whereas the ability to discriminate contexts undergoes protracted development. These results elucidate fundamental aspects of memory development.

Does source memory exist for unrecognized items?

In episodic memory research, there is a debate concerning whether decision-making in item recognition and source memory is better explained by models that assume all-or-none retrieval processes or continuous underlying strengths. One aspect in which these classes of models tend to differ is their predictions regarding the ability to retrieve contextual details (or source details) of an experienced event, given that the event itself is not recognized. All-or-none or high-threshold models predict that when items are unrecognized, source retrieval is not possible and only guess responses can be elicited. In contrast, models assuming continuous strengths predict that it is possible to retrieve the source of unrecognized items, albeit with low accuracy. Empirically, there have been numerous studies reporting either chance accuracy or above-chance accuracy for source memory in the absence of recognition. Crucially, studies presenting recognition and source judgements for the same item in immediate succession (simultaneous design) have revealed chance-level accuracy, while studies presenting a block of recognition judgements followed by a block of source judgements (blocked design) have revealed slightly above-chance accuracy. Across three sets of experiments involving multiple design manipulations, the present investigation demonstrated: (a) that source memory for unrecognized items is indeed higher in blocked designs; (b) that evidence for the effect in blocked designs is likely artifactual due to item memory changing between blocks; and (c) that the effect does exist in simultaneous designs, but is highly subtle and is more easily detected when uncertainty in the participant-level data is low or is accounted for in a hierarchical Bayesian model. It is suggested that findings of a null effect in the prior literature may be attributable to design elements that hinder source memory as a whole, and to high degrees of uncertainty in the participant-level source data when conditioned on unrecognized items. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

How do recall requirements affect decision-making in free recall initiation? A linear ballistic accumulator approach.

Models of free recall describe free recall initiation as a decision-making process in which items compete to be retrieved. Recently, Osth and Farrell (Psychological Review, 126, 578-609, 2019) applied evidence accumulation models to complete RT distributions and serial positions of participants' first recalls in free recall, which resulted in some novel conclusions about primacy and recency effects. Specifically, the results of the modeling favored an account in which primacy was due to reinstatement of the start-of-the-list, and recency was found to be exponential in shape. In this work, we examine what happens when participants are given alternative recall instructions. Prior work has demonstrated weaker primacy and greater recency when fewer items are required to report (Ward & Tan, Memory & Cognition, 2019), and a key question is whether this change in instructions qualitatively changes the nature of the recall process, or merely changes the parameters of the recall competition. We conducted an experiment where participants studied six- or 12-item lists and were post-cued as to whether to retrieve a single item, or as many items as possible. Subsequently, we applied LBA models with various assumptions about primacy and recency, implemented using hierarchical Bayesian techniques. While greater recency was observed when only one item was required for output, the model selection did not suggest that there were qualitative differences between the two conditions. Specifically, start-of-list reinstatement and exponential recency functions were favored in both conditions.

A circular diffusion model of continuous-outcome source memory retrieval: Contrasting continuous and threshold accounts.

A circular analogue of the diffusion model adapted for continuous response tasks is applied to a continuous-outcome source memory task. In contrast to existing models of source retrieval that attribute all of the variability in responding to memory, the circular diffusion model decomposes noise into variability arising from memory and from decision processes. We compared three models: (1) a single diffusion process with trial-to-trial variability in drift rate, (2) a mixture of two diffusion processes, one with positive drift that does not vary from trial-to-trial, and a second zero-drift process that represents discrete guessing, and (3) a hybrid model that mixed positive and zero-drift processes with trial-to-trial variability in the positive drift process. Comparison of model fits to joint response error and response-time (RT) data suggest that a memory strength threshold under which no information is retrieved appears to underlie responding in a continuous-report source memory task. Additionally, we also conditioned participants' source responding on their confidence in an old/new recognition task, ruling out the possibility that participant guessing was only due to unrecognized items. Overall, our findings support an all-or-none or some-or none view of source memory retrieval and pose a challenge to continuous models of source memory.

A dynamic model of deciding not to choose.

We propose a dynamic theory of decisions not to choose which of 2 options is correct. Such "do not-know" judgments are of theoretical and practical importance in domains ranging from comparative psychology, psychophysics, episodic memory, and metacognition to applied areas including educational testing and eyewitness testimony. However, no previous theory has provided a detailed quantitative account of the time it takes to make both definitive and do not-know responses and their relative frequencies. We tested our theory, the multiple threshold race (MTR), in 1 recognition memory experiment where participants had to pick a previously studied target out of 2 similar faces and another where targets and lures were tested 1 at a time. In both experiments we manipulated similarity through face morphing. High similarity made decisions difficult, encouraging do not-know responses. We also tested the MTR's ability to account for other manipulations that aimed to affect the speed and probability of do not-know responses, including increasing penalties for making an error (with no penalty for a do not-know response) and emphasizing either response speed or accuracy. We found that there were marked individual differences in do not-know use, and that the MTR was able to account for the intricate pattern of effects associated with our manipulations, both on average and in terms of individual differences. We discuss how estimates of MTR's parameters illuminate the psychological mechanisms that govern the interplay between definitive and do not-know responding. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Two processes are not necessary to understand memory deficits.

Bastin et al. propose a dual-process model to understand memory deficits. However, results from state-trace analysis have suggested a single underlying variable in behavioral and neural data. We advocate the usage of unidimensional models that are supported by data and have been successful in understanding memory deficits and in linking to neural data.

Privacy versus open science.

Pervasive internet and sensor technologies promise to revolutionize psychological science. However, the data collected using these technologies are often very personal-indeed, the value of the data is often directly related to how personal they are. At the same time, driven by the replication crisis, there is a sustained push to publish data to open repositories. These movements are in fundamental conflict. In this article, we propose a way to navigate this issue. We argue that there are significant advantages to be gained by ceding the ownership of data to the participants who generate the data. We then provide desiderata for a privacy-preserving platform. In particular, we suggest that researchers should use an interface to perform experiments and run analyses, rather than observing the stimuli themselves. We argue that this method not only improves privacy but will also encourage greater compliance with good research practices than is possible through open repositories.

Are associations formed across pairs? A test of learning by temporal contiguity in associative recognition.

In models such as the search of associative memory (SAM: Gillund & Shiffrin, Psychological Review, 91(1), 1-67 1984) model, associations in paired-associate tasks are only formed between the pair of to-be-remembered items. The temporal context model (TCM: Howard & Kahana, Journal of Mathematical Psychology, 46, 268-299 2002) deviates from SAM by positing that long-range associations are formed between the current item and all previously presented items, even in paired-associate tasks, where cross-pair associations are formed in addition to within-pair associations (Davis, Geller, Rizzuto, & Kahana, Psychonomic Bulletin & Review, 15, 64-69 2008). We tested this proposal in an associative recognition task by constructing rearranged pairs where the distance in within-list serial position between the two pair members was manipulated between one and five pairs. Models such as TCM would predict that FAR should be highest for rearranged pairs that are constructed from pair members that were adjacent to each other on the study list, whereas models such as SAM predict that FAR should be equal for rearranged pairs regardless of whether they are constructed from adjacent or remote pairs. Results from our experiment and from three archival datasets found that FAR for rearranged pairs did not depend on whether the constituent items came from nearby or remote pairs, suggesting that participants were not forming associations across pairs of items in the task.

Using response time distributions and race models to characterize primacy and recency effects in free recall initiation.

Primacy and recency effects are common benchmarks for models of free recall and episodic memory. In this work, we show that RT distributions carry diagnostic information about how items enter into competition for recall, and how that competition impacts on the dynamics of recall and leads to novel conclusions about the forms of primacy and recency effects. We jointly fit RT distributions and serial position functions for free recall initiation with both a racing diffusion model and the linear ballistic accumulator (LBA: Brown & Heathcote, 2008). The models were fit in a hierarchical Bayesian framework, factorially varying different assumptions of how primacy and recency are generated. Recency functions were either exponential or power law in shape. Primacy was treated either as a strength boost to the early list items so that both primacy and recency items jointly compete to be retrieved; a mixture of primacy and recency gradients reflecting the usage of different retrieval cues; or a primacy-as-recency account in which primacy items are functionally recent due to the contribution of rehearsal. Although serial position curves do not distinguish between these accounts, they make distinct predictions about how RT distributions vary across serial positions. Results from a number of data sets strongly favor an exponential recency function along with a mixture model of primacy and recency gradients. These results suggest that complete RT distributions can provide informative constraints on models of free recall. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Modeling the dynamics of recognition memory testing with an integrated model of retrieval and decision making.

A robust finding in recognition memory is that performance declines monotonically across test trials. Despite the prevalence of this decline, there is a lack of consensus on the mechanism responsible. Three hypotheses have been put forward: (1) interference is caused by learning of test items (2) the test items cause a shift in the context representation used to cue memory and (3) participants change their speed-accuracy thresholds through the course of testing. We implemented all three possibilities in a combined model of recognition memory and decision making, which inherits the memory retrieval elements of the Osth and Dennis (2015) model and uses the diffusion decision model (DDM: Ratcliff, 1978) to generate choice and response times. We applied the model to four datasets that represent three challenges, the findings that: (1) the number of test items plays a larger role in determining performance than the number of studied items, (2) performance decreases less for strong items than weak items in pure lists but not in mixed lists, and (3) lexical decision trials interspersed between recognition test trials do not increase the rate at which performance declines. Analysis of the model's parameter estimates suggests that item interference plays a weak role in explaining the effects of recognition testing, while context drift plays a very large role. These results are consistent with prior work showing a weak role for item noise in recognition memory and that retrieval is a strong cause of context change in episodic memory.

A diffusion decision model analysis of evidence variability in the lexical decision task.

The lexical-decision task is among the most commonly used paradigms in psycholinguistics. In both the signal-detection theory and Diffusion Decision Model (DDM; Ratcliff, Gomez, & McKoon, Psychological Review, 111, 159-182, 2004) frameworks, lexical-decisions are based on a continuous source of word-likeness evidence for both words and non-words. The Retrieving Effectively from Memory model of Lexical-Decision (REM-LD; Wagenmakers et al., Cognitive Psychology, 48(3), 332-367, 2004) provides a comprehensive explanation of lexical-decision data and makes the prediction that word-likeness evidence is more variable for words than non-words and that higher frequency words are more variable than lower frequency words. To test these predictions, we analyzed five lexical-decision data sets with the DDM. For all data sets, drift-rate variability changed across word frequency and non-word conditions. For the most part, REM-LD's predictions about the ordering of evidence variability across stimuli in the lexical-decision task were confirmed.

Likelihood ratio sequential sampling models of recognition memory.

The mirror effect - a phenomenon whereby a manipulation produces opposite effects on hit and false alarm rates - is benchmark regularity of recognition memory. A likelihood ratio decision process, basing recognition on the relative likelihood that a stimulus is a target or a lure, naturally predicts the mirror effect, and so has been widely adopted in quantitative models of recognition memory. Glanzer, Hilford, and Maloney (2009) demonstrated that likelihood ratio models, assuming Gaussian memory strength, are also capable of explaining regularities observed in receiver-operating characteristics (ROCs), such as greater target than lure variance. Despite its central place in theorising about recognition memory, however, this class of models has not been tested using response time (RT) distributions. In this article, we develop a linear approximation to the likelihood ratio transformation, which we show predicts the same regularities as the exact transformation. This development enabled us to develop a tractable model of recognition-memory RT based on the diffusion decision model (DDM), with inputs (drift rates) provided by an approximate likelihood ratio transformation. We compared this "LR-DDM" to a standard DDM where all targets and lures receive their own drift rate parameters. Both were implemented as hierarchical Bayesian models and applied to four datasets. Model selection taking into account parsimony favored the LR-DDM, which requires fewer parameters than the standard DDM but still fits the data well. These results support log-likelihood based models as providing an elegant explanation of the regularities of recognition memory, not only in terms of choices made but also in terms of the times it takes to make them.