Nonhuman Memory Research Articles

Evaluating evidence from animal models of episodic memory.

A fundamental question in comparative cognition concerns the ability to remember back in time to an earlier event or episode. This ability is referred to as episodic memory. Whether nonhumans can be used to model human episodic memory has engendered much interest and debate for over 2 decades. The central hypothesis of an animal model of episodic memory is that, at the moment of the memory assessment, the animal remembers back in time to a specific earlier event or episode. I describe (a) an approach for evaluating evidence of episodic memory in animal models (b) what aspects of episodic memory are being modeled in animals (c) what standards ought to be applied to a candidate model of episodic memory in nonhumans (d) the first evidence of episodic memory in nonhumans, and (e) a brief overview of the diversity of approaches that are now available. The remainder of the article focuses on the development of a robust model of episodic memory in rats. Converging lines of evidence suggest that rats provide a good model for exploring episodic memory. This evidence includes studies that focus on (a) what-where-when memory (b) source memory (c) binding of episodic memories (d) memory of multiple Items in context using episodic memory (e) replay of episodic memories (f), recollection, and (g) answering an unexpected question after incidental encoding. In each of these domains, I describe evidence for episodic memory in the absence of nonepisodic judgments of familiarity. I end with some consideration of future directions. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Comparative cognition-Conceptual and methodological advancements.

This special issue originally placed a Call for Papers that emphasized the importance of "Conceptual and Methodological" advances in the field of Comparative Cognition. Represented here is a collection of 14 papers that helps to display some of the diversity of ideas and approaches within this flourishing research area. The first paper in this issue, by Gazes and Lazareva (2021), discusses transitive inference learning from the perspectives of: identifying the problems of contextual variables in studying different species; whether associative processes can or cannot fully account for the behavior and, if not, what alternative representational mechanisms might be at work; and, finally, how ecological considerations may support comparative research by suggesting novel theoretical and empirical questions. The next paper, by Loy et al. (2021) investigates questions related to the complexity of learning in invertebrate species, single-celled organisms, and plants. The paper by Rawlings et al. (2021) reviews the literature on cumulative cultural evolution, primarily in nonhuman primate species, and critically evaluates the importance of identifying the essential conceptual and methodological issues in what many have deemed to be a uniquely human form of behavior. The paper by Goto and Watanabe (2021) explores whether the mouse visual system is sensitive to Gestalt principles, using operant discrimination learning tasks similar to those used previously to document Gestalt processing in chimpanzees and humans. Qadri and Cook (2021) use the innovative approach of "adaptive genetic algorithms" to assess the relative importance of different features of a stimulus in controlling organisms' discrimination learning performance. Wittek et al. (2021) introduce a novel method for studying the importance of visual accumulation processes in pigeons when information is presented to a single hemisphere at a time. The paper by Cowie et al. (2021) focuses on a misallocation model of two-step sequence learning in young children and explores from a behavioranalytic viewpoint the implications of assuming that reinforcement might be misattributed to a misremembered response at the beginning of the behavioral sequence. The paper by López-Tolsa and Pellón (2021) explores whether the opportunity to display schedule-induced drinking as an early response within a behavioral sequence might alter the accuracy of temporal control in different-length fixed-interval schedule tasks with rats. Crystal (2021) reviews the literature examining episodic memory in nonhuman species and considers a variety of criteria and methods thought to be crucial for establishing empirical evidence for episodic memory in nonhumans, in general, and rats, in particular. Vila et al. (2021) discuss the use a novel 'hide-and-seek' task in preschool age children to study episodic-like memory; their work illustrates how memory dynamics can change over time in a manner not very unlike what has been demonstrated in other nonhuman research paradigms. The paper by Krichbaum et al. (2021) discusses some of the methodological difficulties one faces in studying spatial cognition in canines. The paper by Castro et al. (2021) uses a complex categorization learning task in which different sets of display features are diagnostic, or not, of category mastery depending upon context. The paper by Vernouillet et al. (2021) explores the formation of same/different concept learning in two species of corvids (pinyon jays and California scrub jays). The final paper, by Lazarowski et al. (2021) examines the possibility of abstract same/different learning in canines using a trial-unique training matching-to-sample procedure with olfactory stimuli. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Episodic memory in nonhuman animals?

Experimental psychologist Jonathan Crystal and evolutionary psychologist Thomas Suddendorf debate with nonhuman animals experience human-like episodic memory.

Morgan's canon is not evidence.

Mahr & Csibra's (M&C's) account of the communicative function of episodic memory relies more heavily on the case against episodic memory in nonhumans than their description suggests. Although the communicative function of episodic memory may be accurate as it pertains to human behaviour, we question whether Morgan's canon is a suitable foundation on which to build theories of supposedly human-specific traits.

Validation of the human odor span task: effects of nicotine.

Amongst non-smokers, nicotine generally enhances performance on tasks of attention, with limited effect on working memory. In contrast, nicotine has been shown to produce robust enhancements of working memory in non-humans. To address this gap, the present study investigated the effects of nicotine on the performance of non-smokers on a cognitive battery which included a working memory task reverse-translated from use with rodents (the odor span task, OST). Nicotine has been reported to enhance OST performance in rats and the present study assessed whether this effect generalizes to human performance. Thirty non-smokers were tested on three occasions after consuming either placebo, 2mg, or 4mg nicotine gum. On each occasion, participants completed a battery of clinical and experimental tasks of working memory and attention. Nicotine was associated with dose-dependent enhancements in sustained attention, as evidenced by increased hit accuracy on the rapid visual information processing (RVIP) task. However, nicotine failed to produce main effects on OST performance or on alternative measures of working memory (digit span, spatial span, letter-number sequencing, 2-back) or attention (digits forward, 0-back). Interestingly, enhancement of RVIP performance occurred concomitant to significant reductions in self-reported attention/concentration. Human OST performance was significantly related to N-back performance, and as in rodents, OST accuracy declined with increasing memory load. Given the similarity of human and rodent OST performance under baseline conditions and the strong association between OST and visual 0-back accuracy, the OST may be particular useful in the study of conditions characterized by inattention.

Episodic-like Memory in the Rat

A fundamental question in comparative cognition is whether animals remember unique, personal past experiences. It has long been argued that memories for specific events (referred to as episodic memory) are unique to humans. Recently, considerable evidence has accumulated to show that food-storing birds possess critical behavioral elements of episodic memory, referred to as episodic-like memory in acknowledgment of the fact that behavioral criteria do not assess subjective experiences. Here we show that rats have a detailed representation of remembered events and meet behavioral criteria for episodic-like memory. We provided rats with access to locations baited with distinctive (e.g., grape and raspberry) or nondistinctive (regular chow) flavors. Locations with a distinctive flavor replenished after a long but not a short delay, and locations with the nondistinctive flavor never replenished. One distinctive flavor was devalued after encoding its location by prefeeding that flavor (satiation) or by pairing it with lithium chloride (acquired taste aversion), while the other distinctive flavor was not devalued. The rats selectively decreased revisits to the devalued distinctive flavor but not to the nondevalued distinctive flavor. The present studies demonstrate that rats selectively encode the content of episodic-like memories.

Episodic-like memory in a gorilla: A review and new findings

The current paper examines if gorillas ( Gorilla gorilla gorilla) possess an episodic memory system. Episodic memory, in humans, is a neurocognitive system that stores information about the personal past. Unique to episodic memory is its palinscopic or past-focused orientation; most memory systems serve to provide the organism with up to date knowledge of the current state of the world. We review four operational definitions that have been used to address issues of episodic memory in non-humans and review the literature with a focus on the studies previously done on gorillas. We describe two new studies with King, an adult male western lowland gorilla. We show that King can remember the order of past events (Experiment 1) and that King can remember where events occurred (Experiment 2). We conclude by discussing alternate explanations of our findings and speculate on future directions.

Episodic memory in primates.

Episodic memory refers to a system of memory with the capacity to recollect specific events from an individual's life. Some psychologists have suggested that episodic memory is a uniquely human phenomenon. We challenge that idea and present evidence that great apes and other primates may possess episodic-like memory. We review criteria developed to assess episodic-like memory in nonhumans, and how they apply to primates. In particular, we discuss the criteria of Clayton et al. [2001], who stated that episodic-like memory is based on the retrieval of multiple and integrated components of an event. We then review eight studies examining memory in great apes and apply the Clayton et al. criteria to each of them. We summarize the evidence that is compatible with the existence of episodic-like memory, although none of the data completely satisfy the Clayton et al. criteria. Morover, feelings of pastness and feelings of confidence, which mark episodic memory in humans, have not been empirically addressed in nonhuman primates. Future studies should be directed at these aspects of memory in primates. We speculate on the functional significance of episodic memory in nonhuman primates.