1989 — 1992 |
Wixted, John |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Serial Memory @ University of California-San Diego
Dr. Wixted's research project is designed to enhance our understanding of memory in animals and to advance the comparative analysis of animal and human memory. Specifically, this project will investigate how well pigeons can remember a series of visual images presented in rapid succession. This procedure is analogous to one often used in human-memory studies in which people are asked to remember a list of words. Of primary concern is whether animals, like humans, remember items at the beginning or end of a series better than they remember middle items. In studies with human subjects, these "primacy" and "recency" effects are so commonly observed that they may be regarded as lawful properties of human short-term memory. In studies with animals, however, some researchers have obtained a robust primacy effect while others have reported its conspicuous absence. One explanation of these inconsistent findings appeals to the concept of "interference." According to this view, animals become confused when given many lists to remember in a single session because some of the items appear over and over again on different lists. Indeed, the only study to observe a primacy effect in birds arranged the experiment in such a way that items were never repeated within a session. An alternative explanation for the inconsistent findings appeals to differences between studies in temporal variables, such as delay of reward. Dr. Wixted will independently vary interference and delay of reward in an effort to clarify the conditions under which a primacy effect may be observed in animals. In addition to the immediate goal of helping to resolve apparently conflicting empirical findings, the results of Dr. Wixted's investigation may eventually facilitate the study of short-term memory disorders in humans by establishing the groundwork for relevant animal models.
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0.915 |
1992 — 1996 |
Wixted, John |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Reinforcement-Based Models of Delayed Matching-to-Sample Performance @ University of California-San Diego
Dr. Wixted's research is designed to enhance our understanding of the principles that govern animal memory. If successful, the results may help to solve the far more complex puzzle of how memory operates, and sometimes goes awry, in humans. The basic procedure used throughout these experiments involves presenting a series of trials, during each of which a color (e.g., red) is shown to a pigeon in a center window for a few seconds, the color is removed for a period of time, and then the pigeon is given a choice between two colors (red vs. green) in two side windows. A response to the matching color (in this case, red) is rewarded with food while a response to the nonmatching color simply ends the trial. Dr. Wixted will carry out three sets of experiments that address different, but related, issues. The first set is concerned with the question of how short-term and long-term memory compete to determine the pigeon's choice on a given trial. More specifically, the choice between red and green may involve a competition between short-term memory for the previous color (red) and long-term memory for the choice color that generally provides the greater number of rewards. The second set of experiments is concerned with identifying the psychological variables that cause a stimulus to become more (or less) memorable. The principle under investigation holds that a stimulus associated with a short delay to a biologically significant event (e.g., food) is more memorable than one associated with a long delay. Finally, the third set of experiments investigates the variables that influence memory for nonoccurrence. That is, under what conditions will an animal remember that no stimulus appeared in the center window on a particular trial? Together, the results of these experiments will help to identify the principles that underlie animal and, ultimately perhaps, human memory.
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0.915 |
1996 — 2003 |
Wixted, John T |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Signal Detection Theory and Memory For Asymmetric Events @ University of California San Diego
DESCRIPTION (provided by applicant): The proposed research is designed to test a variety of theories that have been advanced to explain memory for the duration of an event in animals. The core phenomenon of interest is known as the "choose-short" effect. The choose-short effect refers to the fact that, no matter which duration was actually presented, pigeons tend to remember the duration as having been short. One well-known theory holds that the increasing tendency to report that the short sample occurred as the retention interval increases implies that the remembered duration of an event shrinks with the passage of time. Three other accounts of this phenomenon assume that the result stems from the fact that an event that is short in duration is more like "nothing" than an event that is long in duration. As such, when memories eventually fade to nothing (as they do when the retention interval is long), birds tend to select the better of the two available options (i.e., they report that the short sample was presented). Yet another explanation is that birds have the capacity to transform a nominal discrimination task into a signal detection task. The signal-detection framework has been used to interpret findings from studies on human recognition memory for more than two decades, but its relevance to animal memory has not been widely investigated. Because detection theory offers a theoretical framework common to both species, it could help to facilitate the development of relevant animal models of memory impairment in humans.
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1 |
1997 — 1998 |
Wixted, John T |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Signal Detection Theory &Memory For Asymmetric Events @ University of California San Diego
DESCRIPTION (Adapted from applicant's abstract): The proposed research is designed to test a theoretical analysis of animal memory for asymmetric events on signal detection theory. Most animal memory procedures require a delayed discrimination between two events of roughly equal salience, but several seemingly unrelated lines of research have arranged memory tests for inherently unequal events. Examples include (a) memory for the presence vs. absence of an event, (b) memory for event duration (e.g., short vs. long), and memory for stimuli from different sensory modalities (e.g., tone vs. light). The proposed research tests a new theory of animal memory that attempts to provide a unified explanation for an interesting pattern of results common to each of these areas. That analysis may offer a general theory of memory for asymmetric events. The basic methodology used in most of the proposed experiments involves presenting one of two events that differ in salience, followed by a delay, followed by the presentation of two alternatives (red and green choice stimuli). A response to one color is reinforced with food on trials beginning with the less salient sample while a response to the other color is reinforced on trials beginning with the more salient sample. The discriminations to be tested include presence vs. absence, short vs. long duration, and tone vs. light. The signal detection analysis assumes that, in each case, the less salient stimulus is more like "nothing" than the more salient event. Several experiments are proposed to test this and related ideas. Additional experiments will investigate the mathematical form of the receiver operating characteristic (ROC) function. This approach has been used extensively in the human perception and human memory literatures to test the signal detection framework against competing accounts, and the same strategy is warranted here. The signal detection framework has been used to interpret findings from other studies on human recognition memory for more than two decades, but the use of this approach in the study of animal memory is comparatively rare. Identifying similarities and differences between animal and human memory is complicated by the absence of a coherent theoretical framework common to both species. Signal detection theory may offer one such framework, thereby facilitating the development of relevant animal models of memory impairment in humans.
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1 |
2009 — 2011 |
Wixted, John T |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
On the Nature of Recollection @ University of California San Diego
DESCRIPTION (provided by applicant): Recognition memory is thought to be based on two processes, recollection and familiarity. The proposed research will investigate contrasting views of one of these two processes, namely, the recollection process. The question of how best to conceptualize recollection is of fundamental importance to computational models and neuropsychological models of memory. One view, which is by far the most common view, holds that recollection is a threshold process in that whenever it occurs, it carries with it high confidence that an item was seen before. This idea is explicit in some models, but it is also implicit in the thinking that underlies the popular Remember/Know procedure. An alternative view is that recollection is a continuous process (i.e., recollection comes in degrees, including very small degrees). This account is compatible with signal-detection theory, and it holds that recollection can be associated with low, medium or high degrees of confidence (and accuracy), depending on the degree of recollection associated with the test item. The resolution of high-profile debates in the cognitive neuroscience literature hinges to a large extent on a resolution of this question concerning the nature of the recollection process. Behavioral methods, including ROC analysis, relational memory procedures, and variations of the Remember/Know procedure will be used to address this problem. In several of these experiments, the crux of the issue is whether recollection occurs even when accuracy is low, confidence is low, and subjects claim that recollection absent. PUBLIC HEALTH RELEVANCE: Memory deficits are now recognized to be a core feature of several mental illnesses, especially schizophrenia. The methods that are typically used to further our understanding of these memory deficits are almost exclusively based on a model of memory that may not be valid. The proposed work tests that model of memory against an alternative and long-standing model known as signal-detection theory.
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1 |
2012 — 2014 |
Wixted, John Mickes, Laura (co-PI) [⬀] |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Signal Detection Theory and Eyewitness Memory @ University of California-San Diego
The purpose of the proposed research is to link a longstanding framework for understanding how recognition memory decisions are made to the forensically relevant question of how witnesses make a recognition memory decision when faced with a lineup. In the field of experimental psychology, our understanding of how recognition memory decisions are made has been effectively guided by signal-detection theory since Egan's (1958) seminal report was published more than 50 years ago. By contrast, in the applied literature, signal-detection-based efforts to understand decision-making on recognition memory tasks are virtually nonexistent. The wide chasm separating experimental and applied investigations of recognition memory is surprising because issues that may be informed by signal-detection theory (e.g., the relationship between confidence and accuracy) are of considerable interest in both fields. In the applied literature, it has been repeatedly noted that signal-detection theory could inform eyewitness memory but, to date, no signal-detection model of lineup-based recognition memory has been seriously pursued.
The goal of the proposed research is to produce a simple signal-detection framework that will be useful for helping to understand a variety of empirical phenomena that have been investigated in the applied literature, including the relationship between confidence and accuracy. Our strategy will be to test the viability of a signal-detection-based model of eyewitness memory using tasks that are in some ways similar to standard list-memory tasks (e.g., each subject studies a list of items) but that have been modified to be more forensically relevant (e.g., the stimuli will consist of faces, and the recognition tests will involve lineups). After testing and developing a simple signal-detection model using those relatively convenient laboratory procedures, we plan to then test the model using more forensically relevant methods that are commonly used in the applied literature (e.g., where each subject is drawn from a diverse population, views one simulated crime, and provides one recognition decision). The results should help scientists to better inform policymakers about how to improve police lineup procedures.
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0.915 |
2015 — 2017 |
Wixted, John |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
The Role of Diagnostic Vs. Non-Diagnostic Facial Features in Eyewitness Identification @ University of California-San Diego
The problem of innocent suspects being mistakenly convicted of a crime they did not commit and the parallel problem of guilty suspects being mistakenly released into society are attributable in no small part to the fallibility of eyewitness memory. A great deal of eyewitness memory research has focused on reducing false identifications of innocent suspects (thereby reducing the chances that they will be wrongly convicted). However, methods that reduce that unfortunate error often have the effect of increasing the complementary error, namely, the error of failing to identify guilty suspects. That tradeoff might be considered acceptable, but a better approach would involve reducing both errors simultaneously. To date, very little research has been conducted with that goal in mind, but it is the goal of the research proposed here. In particular, this research asks what can be done to enhance eyewitness discriminability (i.e., the ability to tell the difference between innocent and guilty suspects). To answer this question, the research is guided by a new theory of eyewitness identification: the diagnostic feature-detection hypothesis. Enhancing the discriminability of eyewitness memory procedures has significant broader impacts because it would decrease misidentifications of the innocent while at the same time increasing identifications of the guilty.
This project will focus on three widely used eyewitness identification procedures: the traditional simultaneous lineup (in which 6 faces are shown to the witness simultaneously), the newer sequential lineup (in which the 6 faces are shown to the witness one at a time), and the showup procedure (in which only one face is shown to a witness for a yes/no decision). Virtually all police departments make use of the showup procedure (because it is often the only possibility in a fast-moving investigation), and nearly 30% of police departments have switched from the simultaneous lineup procedure to the sequential procedure. However, contrary to what was previously believed, recent work has found that both the showup and the sequential lineup are inferior to the simultaneous procedure (i.e., the simultaneous procedure can reduce false identifications of innocent suspects while at the same time increasing correct identifications of guilty suspects compared to the other two procedure). Given the common and likely continued use of the showup procedure and sequential lineup, this research proposes a series of experiments to investigate simple and convenient ways to enhance the diagnostic accuracy of these eyewitness identification procedures.
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0.915 |
2019 — 2021 |
Leutgeb, Jill K (co-PI) [⬀] Miller, Cory T [⬀] Wixted, John T |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Neural Basis of Memory in Primate Medial Temporal Lobe @ University of California, San Diego
Project Summary The medial temporal lobe (MTL) plays a critical role in the rapid formation of episodic memories in human and nonhuman primates, while research performed in freely-moving rodents has likewise identified these same structure as being pivotal for spatial navigation. Each of these lines of work reflect powerful research traditions that have significantly contributed to our understanding of medial temporal lobe function, but questions remain about how to reconcile their considerable data sets. One compelling hypothesis is that the same neural mechanisms that support the role of MTL in spatial navigation also support the formation of episodic memories. We propose an innovative set of experiments designed to directly test this hypothesis Our approach involves recording neural activity from the same neurons in the medial temporal lobe of marmoset monkeys in two contexts. One involves head-restrained subjects performing a recognition memory task typical of human experiments while in the other freely-moving subjects navigate spatial environments commonly used in studies of rodents. Our innovative approach will allow us to test ? for the first time - whether the same neurons in primate medial temporal lobe support behaviors performed in tasks representative of these two research traditions. Aim 1 seeks to characterize recognition memory in marmosets using a task that ? like spatial navigation ? relies on incidental memory formation. Experiments in Aim 2 examine the role of the hippocampal CA fields and entorhinal cortex in spatial navigation, including the putative existence of place cells and grid cells, respectively. Aim 3 directly tests the principal question of this proposal by recording from the identical neurons while subjects perform the recognition memory task in Aim 1 and navigate spatial environments similar to studies in Aim 2.
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