Neural pattern similarity underlies the mnemonic advantages for living words

Continuous goal representations: Distance in representational space affects goal switching

Theorists across all fields of psychology consider goals crucial for human action control. Still, the question of how precisely goals are represented in the cognitive system is rarely addressed. Here, we explore the idea that goals are represented as distributed patterns of activation that coexist within continuous mental spaces. In doing so, we discuss and extend popular models of cognitive control and goal-directed behavior, which implicitly convey an image of goals as discrete representational units. To differentiate empirically between discrete and continuous formats of goal representation, we employed a set-shifting paradigm in which participants switched between color goals that varied systematically in their distance in representational space. Across three experiments, we found that previous goals biased behavior during goal switches and that the extent of this bias decreased gradually with the previous goal's distance in color space from color information in the current trial. These graded effects of goal distance on performance are difficult to reconcile with the assumption that goals are discrete representational entities. Instead, they suggest that goals are represented as distributed, partly overlapping patterns of activation within continuous mental spaces. Moreover, the monotonous effects of distance in representational space on performance observed across all conditions in all experiments imply that the spreading of goal activation in representational space follows a monotonous (e.g., bell-shaped) distribution and not a nonmonotonous (e.g., Mexican-hat shaped) one. Our findings ask for a stronger consideration of the continuity of goal representations in models and investigations of goal-directed behavior.

The animacy (bias) effect in recognition: testing the influence of intentionality of learning and retrieval quality

The animacy effect, a memory advantage for animate/living over inanimate/non-living items, is well-documented in free recall, but unclear in recognition memory. This might relate to the encoding tasks that have been used and/or to an unequal influence of animacy on the processes underlying recognition (recollection or familiarity). This study reports a recognition memory experiment, coupled with a remember/know procedure. An intentional and two incidental learning conditions (one animacy-related and one animacy-unrelated) were used. No animacy effect was found in discriminability (A') irrespectively of the encoding condition. Still, different mechanisms in incidental and intentional conditions conducted to said result. Overall, animates (vs. inanimates) elicited more hits and also more false alarms. Moreover, participants tended to assign more remember responses to animate (vs. inanimate) hits, denoting higher recollection for the former. These findings are suggestive of an animacy bias in recognition, which was stronger in the animacy-related encoding condition. Ultimate and proximate mechanisms underlying the animacy effect are examined.

A direct replication and extension of Popp and Serra (2016, experiment 1): better free recall and worse cued recall of animal names than object names, accounting for semantic similarity

Introduction

Free recall tends to be better for names of animate concepts such as animals than for names of inanimate objects. In Popp and Serra's 2016 article, the authors replicated this "animacy effect" in free recall but when participants studied words in pairs (animate-animate pairs intermixed with inanimate-inanimate pairs) and were tested with cued recall, performance was better for inanimate-inanimate pairs than for animate-animate pairs ("reverse animacy"). We tested the replicability of this surprising effect and one possible explanation for the effect (semantic similarity).

Methods

Our Experiment 1 was a preregistered direct replication (N = 101) of Popp and Serra's Experiment 1 (mixed-lists condition). In a second preregistered experiment conducted in four different samples (undergraduate N = 153, undergraduate N = 143, online Prolific N = 101, online Prolific/English-as-a-first-language N = 150), we manipulated the within-category semantic similarity of animal and object wordlists.

Results

AIn Experiment 1, just as in Popp and Serra, we observed an animacy effect for free recall and a reverse animacy effect for cued recall. Unlike Popp and Serra, we found that controlling for interference effects rendered the reverse animacy effect non-significant. We took this as evidence that characteristics of the stimulus sets (e.g., category structure, within-category similarity) may play a role in animacy and reverse animacy effects. In Experiment 2, in three out of our four samples, we observed reverse animacy effects when within-category similarity was higher for animals and when within-category similarity was equated for animals and objects.

Discussion

Our results suggest that the reverse animacy effect observed in Popp and Serra's 2016 article is a robust and replicable effect, but that semantic similarity alone cannot explain the effect.

Identifying causal subsequent memory effects

Over 40 y of accumulated research has detailed associations between neuroimaging signals measured during a memory encoding task and later memory performance, across a variety of brain regions, measurement tools, statistical approaches, and behavioral tasks. But the interpretation of these subsequent memory effects (SMEs) remains unclear: if the identified signals reflect cognitive and neural mechanisms of memory encoding, then the underlying neural activity must be causally related to future memory. However, almost all previous SME analyses do not control for potential confounders of this causal interpretation, such as serial position and item effects. We collect a large fMRI dataset and use an experimental design and analysis approach that allows us to statistically adjust for nearly all known exogenous confounding variables. We find that, using standard approaches without adjustment, we replicate several univariate and multivariate subsequent memory effects and are able to predict memory performance across people. However, we are unable to identify any signal that reliably predicts subsequent memory after adjusting for confounding variables, bringing into doubt the causal status of these effects. We apply the same approach to subjects' judgments of learning collected following an encoding period and show that these behavioral measures of mnemonic status do predict memory after adjustments, suggesting that it is possible to measure signals near the time of encoding that reflect causal mechanisms but that existing neuroimaging measures, at least in our data, may not have the precision and specificity to do so.

A cautionary note on the studies using the picture-word interference paradigm: the unwelcome consequences of the random use of "in/animates"

The picture-word interference (PWI) paradigm allows us to delve into the process of lexical access in language production with great precision. It creates situations of interference between target pictures and superimposed distractor words that participants must consciously ignore to name the pictures. Yet, although the PWI paradigm has offered numerous insights at all levels of lexical representation, in this work we expose an extended lack of control regarding the variable animacy. Animacy has been shown to have a great impact on cognition, especially when it comes to the mechanisms of attention, which are highly biased toward animate entities to the detriment of inanimate objects. Furthermore, animate nouns have been shown to be semantically richer and prioritized during lexical access, with effects observable in multiple psycholinguistic tasks. Indeed, not only does the performance on a PWI task directly depend on the different stages of lexical access to nouns, but also attention has a fundamental role in it, as participants must focus on targets and ignore interfering distractors. We conducted a systematic review with the terms "picture-word interference paradigm" and "animacy" in the databases PsycInfo and Psychology Database. The search revealed that only 12 from a total of 193 PWI studies controlled for animacy, and only one considered it as a factor in the design. The remaining studies included animate and inanimate stimuli in their materials randomly, sometimes in a very disproportionate amount across conditions. We speculate about the possible impact of this uncontrolled variable mixing on many types of effects within the framework of multiple theories, namely the Animate Monitoring Hypothesis, the WEAVER++ model, and the Independent Network Model in an attempt to fuel the theoretical debate on this issue as well as the empirical research to turn speculations into knowledge.

Within-pair factors might explain the inconsistent effects of animacy on paired-associates recall

The tendency for people to have better memory for animate (living) concepts than inanimate (nonliving) concepts in memory tasks involving free recall and recognition suggests that animacy status can be an important predictor of memory. To date, however, the effect of animacy on paired-associates recall has been mixed: Some studies have found an animacy advantage, some have found an animacy disadvantage, and some have found no difference by animacy. We tested the hypothesis that the within-pair relationship of the two words in a pair matters more for cued recall than animacy itself. In two experiments, college students studied animate and inanimate English word pairs for a cued-recall test. We varied whether the pairs involved two typical exemplars from the same category (e.g., SALMON-TROUT; FORK-SPOON), one typical and one atypical exemplar from the same category (e.g., DOCTOR-SCIENTIST; HOUSE-IGLOO), or two unrelated words from different categories (e.g., SERGEANT-COBRA; MAGAZINE-PLIERS). Respectively, these pair types produced an animacy disadvantage, an animacy advantage, and no difference by animacy in both experiments. We then examined several measures of within-pair similarity for the items. All were positively associated with paired-associates recall, but animacy had no effect on cued recall above and beyond the relationship of these measures to recall. These results suggest that the within-pair relationship matters more for cued recall than does animacy. Uneven variation in within-pair relationships for animate versus inanimate pairs-rather than animacy itself-might therefore produce the apparently inconsistent effects of animacy on paired-associates recall.

Analyzing the structure of animacy: Exploring relationships among six new animacy and 15 existing normative dimensions for 1,200 concrete nouns

Animacy is an important word variable (especially for episodic memory), yet no norms exist in the literature. We present a complete, usable normative data set of 1,200 relatively concrete nouns normed on 15 existing dimensions (concreteness, familiarity, imagery, availability, valence, arousal, dominance, age of acquisition, length, orthographic neighborhood, phonographic neighborhood, number of syllables, and subtitle frequency/contextual diversity) and six new animacy dimensions (a general living/non-living scale, ability to think, ability to reproduce, similarity to a person, goal-directedness, and movement likelihood). Principal component analysis of these 21 dimensions revealed that animacy scales were conceptually different from extant word variables. Further, factor analysis of the six new scales revealed these animacy norms may be separable into two dimensions: a "Mental" component related to animates' ability to think and have goals, and a "Physical" component related to animates' general resemblance to living things. These data provide useful theoretical insight into the structure of the animacy dimension, an important factor in many cognitive processes. The norms are accessible at https://osf.io/4t3cu .

Stability of neural encoding moderates the contribution of sleep and repeated testing to memory consolidation

There is evidence suggesting that online consolidation during retrieval-mediated learning interacts with offline consolidation during subsequent sleep to transform memory. Here we investigate whether this interaction persists when retrieval-mediated learning follows post-training sleep and whether the direction of this interaction is conditioned by the quality of encoding resulting from manipulation of the amount of sleep on the previous night. The quality of encoding was determined by computing the degree of similarity between EEG-activity patterns across restudy of face pairs in two groups of young participants, one who slept the last 4 h of the pre-training night, and another who slept 8 h. The offline consolidation was assessed by computing the degree of coupling between slow oscillations (SOs) and spindles (SPs) during post-training sleep, while the online consolidation was evaluated by determining the degree of similarity between EEG-activity patterns recorded during the study phase and during repeated recognition of either the same face pair (i.e., specific similarity) or face pairs sharing sex and profession (i.e., categorical similarity) to evaluate differentiation and generalization, respectively. The study and recognition phases were separated by a night of normal sleep duration. Mixed-effects models revealed that the stability of neural encoding moderated the relationship between sleep- and retrieval-mediated consolidation processes over left frontal regions. For memories showing lower encoding stability, the enhanced SO-SP coupling was associated with increased reinstatement of category-specific encoding-related activity at the expense of content-specific activity, whilst the opposite occurred for memories showing greater encoding stability. Overall, these results suggest that offline consolidation during post-training sleep interacts with online consolidation during retrieval the next day to favor the reorganization of memory contents, by increasing specificity of stronger memories and generalization of the weaker ones.

Animacy and threat in recognition memory

Animate items are better remembered than inanimate items, suggesting that human memory has evolved to prioritize information related to survival. The proximate mechanisms for the animacy effect are not yet known, but one possibility is that animate items are more likely to capture attention, which then leads to better memory for those items. The first experiment independently manipulated the animacy and perceived threat of studied items and found that both target recognition and false-alarm recognition were higher for animate items compared to inanimate items and for threatening items compared to non-threatening items. The effects were eliminated when d' scores were calculated. The second experiment used a response signal delay (RSD) manipulation where participants were forced to respond after a short (500 ms) or long (2,000 ms) time delay during the recognition test. Similar to the first experiment, the effects of animacy and threat for target recognition and false-alarm recognition persisted and did not interact with the RSD manipulation. Taken together, the results of the studies suggest that the animacy and threat effects in memory are robust and that attention capture might be at least partly responsible for the animacy effect.

Of Beavers and Tables: The Role of Animacy in the Processing of Grammatical Gender Within a Picture-Word Interference Task

Grammatical gender processing during language production has classically been studied using the so-called picture-word interference (PWI) task. In this procedure, participants are presented with pictures they must name using target nouns while ignoring superimposed written distractor nouns. Variations in response times are expected depending on the congruency between the gender values of targets and distractors. However, there have been disparate results in terms of the mandatory character of an agreement context to observe competitive gender effects and the interpretation of the direction of these effects in Romance languages, this probably due to uncontrolled variables such as animacy. In the present study, we conducted two PWI experiments with European Portuguese speakers who were asked to produce bare nouns. The percentage of animate targets within the list was manipulated: 0, 25, 50, and 100%. A gender congruency effect was found restricted to the 0% list (all targets were inanimate). Results support the selection of gender in transparent languages in the absence of an agreement context, as predicted by the Gender Acquisition and Processing (GAP) hypothesis (Sá-Leite et al., 2019), and are interpreted through the attentional mechanisms involved in the PWI paradigm, in which the processing of animate targets would be favored to the detriment of distractors due to biological relevance and semantic prioritization.

Neural pattern similarity across concept exemplars predicts memory after a long delay

The irregularities of the world ensure that each interaction we have with a concept is unique. In order to generalize across these unique encounters to form a high-level representation of a concept, we must draw on similarities between exemplars to form new conceptual knowledge that is maintained over a long time. Two neural similarity measures - pattern robustness and encoding-retrieval similarity - are particularly important for predicting memory outcomes. In this study, we used fMRI to measure activity patterns while people encoded and retrieved novel pairings between unfamiliar (Dutch) words and visually presented animal species. We address two underexplored questions: 1) whether neural similarity measures can predict memory outcomes, despite perceptual variability between presentations of a concept and 2) if pattern similarity measures can predict subsequent memory over a long delay (i.e., one month). Our findings indicate that pattern robustness during encoding in brain regions that include parietal and medial temporal areas is an important predictor of subsequent memory. In addition, we found significant encoding-retrieval similarity in the left ventrolateral prefrontal cortex after a month's delay. These findings demonstrate that pattern similarity is an important predictor of memory for novel word-animal pairings even when the concept includes multiple exemplars. Importantly, we show that established predictive relationships between pattern similarity and subsequent memory do not require visually identical stimuli (i.e., are not simply due to low-level visual overlap between stimulus presentations) and are maintained over a month.

A set of 750 words in Spanish characterized in two survival-related dimensions: avoiding death and locating nourishment

With the aim of finding quantitative indicators of the survival relevance for a set of concrete concepts, a subjective rating task was administered to a large sample of college students (N = 300). In the rating task, participants used a five-point scale to rate 750 concepts in one of two survival-relevant dimensions, providing their own judgment about the relevance of each concept in a situation in which either avoiding death (AD) or obtaining food (OF) was of importance. The subjective ratings showed high stability and reliability and showed varied patterns of association to potentially relevant concept-defining variables, with correlational analyses showing both commonalities and differences between the two rated dimensions. Regression analyses indicated that, while not likely to modulate word accessibility, survival ratings were related to certain conceptual properties that could be especially sensitive for threat detection. The collected data set provides normative information that can be of use in manipulating and controlling verbal stimuli in future research focusing on adaptive properties of episodic memory and other aspects of the human cognitive system. The complete norms are available for downloading at Open Science Framework ( https://osf.io/sf9mb/ ).

Animacy effects extend to working memory: results from serial order recall tasks

Words that represent animate entities (e.g., dog) are recalled from long-term memory more accurately than words representing inanimate entities (e.g., pan). In this research, we examined whether the animacy effect extends to working memory (WM). The potential roles of WM maintenance strategies (rehearsal and directed attention) were also examined. Participants performed serial order recall tasks with sets of 3, 4, 5 or 6 words that were either animate or inanimate. In stage 1 of Experiment 1, participants received no instructions regarding how to maintain the words. In stage 2, participants received either no instructions, sub-vocal rehearsal or directed attention instructions. In all instruction groups and at both stages, significant animacy effects were observed at set sizes of 4, 5 and 6 but not set size 3. The animacy effect was larger at set size 5 than other set sizes. In Experiment 2, participants completed the task with and without articulatory suppression. In both conditions, animacy effects were observed at set sizes 4, 5 and 6, but not at set size 3. The magnitude of the animacy effect declined as set size increased from 4 to 6. Animacy appears to enhance serial recall, but the effect is not dependent on rehearsal.

The Emotional Facet of Subjective and Neural Indices of Similarity

Emotional similarity refers to the tendency to group stimuli together because they evoke the same feelings in us. The majority of research on similarity perception that has been conducted to date has focused on non-emotional stimuli. Different models have been proposed to explain how we represent semantic concepts, and judge the similarity among them. They are supported from behavioural and neural evidence, often combined by using Multivariate Pattern Analyses. By contrast, less is known about the cognitive and neural mechanisms underlying the judgement of similarity between real-life emotional experiences. This review summarizes the major findings, debates and limitations in the semantic similarity literature. They will serve as background to the emotional facet of similarity that will be the focus of this review. A multi-modal and overarching approach, which relates different levels of neuroscientific explanation (i.e., computational, algorithmic and implementation), would be the key to further unveil what makes emotional experiences similar to each other.

Episodic memory for natural and transformed food

It has been proposed that the conceptual knowledge of food and its putative subdivision into natural (i.e., fruit/vegetables) and transformed (i.e., food that underwent thermic or non-thermic processing) may follow the living/non-living distinction. In the present study, we investigated whether the advantage for living things compared to non-living things observed in episodic memory (the so-called animacy effect) extends to natural foods and transformed foods respectively. We pursued this issue in two experiments. In Experiment 1, we measured episodic memory for natural and transformed foods in young participants. In Experiment 2, we enrolled dementia-free centenarians, patients with Alzheimer's disease (DAT), Progressive primary aphasia (PPA), and healthy controls whose episodic memory was also tested for living/non-living things. Results showed that young participants had better recognition memory for transformed foods compared to natural foods. This difference disappeared in centenarians and patients. However, centenarians and PPA exhibited enhanced levels of false alarms (FA) with natural food, and DAT patients with both natural and transformed food. As far as the living/non-living distinction is concerned, the episodic memory for the living category appears more resilient to the decline compared to the non-living category in patients, particularly those with PPA. In conclusion, our study shows that transformed food is better remembered than natural food, suggesting that it is more salient and possibly relevant from an evolutionary perspective. The natural/transformed distinction appears susceptible to erosion only in the presence of a high degree of episodic memory impairment. These results offer novel insight on episodic memory of food, and also extend the current knowledge on the animacy effect in episodic memory.

Animals Do Not Induce or Reduce Attentional Blinking, But They Are Reported More Accurately in a Rapid Serial Visual Presentation Task

Evolutionary psychologists have suggested that modern humans have evolved to automatically direct their attention toward animal stimuli. Although this suggestion has found support in several attentional paradigms, it is not without controversy. Recently, a study employing methods customary to studying the attentional blink has shown inconclusive support for the prioritization of animals in attention. This showed an advantage for reporting animals as second targets within the typical window of the attentional blink, but it remained unclear whether this advantage was really due to a reduction of the attentional blink. We reassessed for the presence of a reduced attentional blink for animals compared with artifacts by using three disparate stimuli sets. A general advantage for animals was found but no indication of a reduction of the attentional blink for animals. There was no support for the prediction that animal distractors should lead to spontaneous inductions of attentional blinks when presented as critical distractors before single targets. Another experiment with single targets still showed that animals were reported more accurately than artifacts. A final experiment showed that when animals were first target, they did not generate stronger attentional blinks. In summary, we did find a general advantage for animal images in the rapid serial visual presentation task, but animal images did not either induce or reduce attentional blinks. This set of results is in line with conclusions from previous research showing no evidence for a special role of animals in attention.

Neural Pattern Similarity in the Left IFG and Fusiform Is Associated with Novel Word Learning

Previous studies have revealed that greater neural pattern similarity across repetitions is associated with better subsequent memory. In this study, we used an artificial language training paradigm and representational similarity analysis to examine whether neural pattern similarity across repetitions before training was associated with post-training behavioral performance. Twenty-four native Chinese speakers were trained to learn a logographic artificial language for 12 days and behavioral performance was recorded using the word naming and picture naming tasks. Participants were scanned while performing a passive viewing task before training, after 4-day training and after 12-day training. Results showed that pattern similarity in the left pars opercularis (PO) and fusiform gyrus (FG) before training was negatively associated with reaction time (RT) in both word naming and picture naming tasks after training. These results suggest that neural pattern similarity is an effective neurofunctional predictor of novel word learning in addition to word memory.