A computer simulation model of rats’ place navigation in the Morris water maze

Rats rapidly learn to swim from a variety of starting locations, including novel ones, to a small invisible platform submerged in a pool of cool opaque liquid. A computer simulation based on a simple perceptual memory-matching model successfully mimics this ability. The model assumes that the rat, when it successfully reaches the platform, notes the distance to prominent extramaze landmarks and stores this perceptual information in memory. When placed in the pool on subsequent trials, the simulated rat attempts to match perceived distance between itself and the landmarks to the remembered distances from the platform to the landmark. The model accounts for many of the known facts about rats’ behavior in the swimming pool and makes some interesting predictions that could be easily tested experimentally. The model has the advantage, relative to other cognitive map models, of specifying how spatial information is represented in memory and how this information guides behavior.     

Reconsidering ‘spatial memory’ and the Morris water maze

The Morris water maze has been put forward in the philosophy of neuroscience as an example of an experimental arrangement that may be used to delineate the cognitive faculty of spatial memory (e.g., Craver and Darden, Theory and method in the neurosciences, University of Pittsburgh Press, Pittsburgh, 2001; Craver, Explaining the brain: Mechanisms and the mosaic unity of neuroscience, Oxford University Press, Oxford, 2007). However, in the experimental and review literature on the water maze throughout the history of its use, we encounter numerous responses to the question of “what” phenomenon it circumscribes ranging from cognitive functions (e.g., “spatial learning”, “spatial navigation”), to representational changes (e.g., “cognitive map formation”) to terms that appear to refer exclusively to observable changes in behavior (e.g., “water maze performance”). To date philosophical analyses of the water maze have not been directed at sorting out what phenomenon the device delineates nor the sources of the different answers to the question of what. I undertake both of these tasks in this paper. I begin with an analysis of Morris’s first published research study using the water maze and demonstrate that he emerged from it with an experimental learning paradigm that at best circumscribed a discrete set of observable changes in behavior. However, it delineated neither a discrete set of representational changes nor a discrete cognitive function. I cite this in combination with a reductionist-oriented research agenda in cellular and molecular neurobiology dating back to the 1980s as two sources of the lack of consistency across the history of the experimental and review literature as to what is under study in the water maze.     

How do room and apparatus cues control navigation in the Morris water task? Evidence for distinct contributions to a movement vector

The present study compared the relative influence of location and direction on navigation in the Morris water task. Rats were trained with a fixed hidden or cued platform, and probe trials were conducted with the pool repositioned such that the absolute spatial location of the platform was centered in the opposite quadrant of the pool. Rather than swimming to the platform location, rats swam in the direction that was reinforced during training, resulting in navigation to the relative location of the platform in the pool and search at the appropriate distance from the pool wall. Pool relocation tests revealed disruptions in cued navigation if the cued platform remained at the absolute location, whereas no disruption was observed if the platform remained at the relative location (same direction). The results indicate that direction holds greater influence than does location and further demonstrate that this observation is not altered by the amount of training or time on the platform. The authors propose that navigation in the water task involves a movement vector in which the distal cues and apparatus provide direction and distance information, respectively.     

Does syntax contribute to the function of duets in a parrot, Amazona auropalliata?

Complex acoustic signals in many animal species are characterized by a syntax that governs how different notes are combined, but the importance of syntax to the communicative function of signals is not well understood. Mated pairs of yellow-naped amazons, Amazona auropalliata, produce coordinated vocal duets that are used for territory maintenance and defense. These duets follow rules that specify the ordering of notes within duets, such as a strict alternation of sex-specific notes and a defined progression of note types through each duet. These syntactical rules may function to define sex-specific roles, improve coordination, and allow individuals to combine calls into meaningful sequences. As a first step toward understanding the functional significance of syntax, we conducted two separate audio playback experiments in which we presented nesting pairs with normal duets and duets with broken syntax (i.e., one of the syntactic rules was broken). In Experiment One, we reversed the order of female and male notes within note pairs while retaining the typical progression of note types through a duet. In Experiment Two we reversed the order of note types across a whole duet while retaining the typical female-male ordering within note pairs. We hypothesized that duets with broken syntax would be less-effective signals than duets with normal syntax and predicted that pairs would respond less to broken syntax than to normal duets. Contrary to predictions, we did not observe differences in response between treatments for any variables except latency to approach the speaker. After we combined data across experiments post hoc, we observed longer latencies to approach the speakers after playbacks of broken syntax duets, suggesting that pairs could differentiate between playbacks. These responses suggest that breaking one rule of duet syntax at a time does not result in detectable loss of signal efficacy in the context of territorial intrusions.     

Does retrieval fluency contribute to the underconfidence-with-practice effect?

Judgments of learning (JOLs) made during multiple study-test trials underestimate increases in recall performance across those trials, an effect that has been dubbed the underconfidence-with-practice (UWP) effect. In 3 experiments, the authors examined the contribution of retrieval fluency to the UWP effect for immediate and delayed JOLs. The UWP effect was demonstrated with reliable underconfidence on Trial 2 occurring for both kinds of JOL. However, in contrast to a retrieval-fluency hypothesis, fine-grained analyses indicated that the reliance of JOLs on retrieval fluency contributed minimally to the UWP effect. Our discussion focuses on the status of the retrieval-fluency hypothesis for the UWP effect.     

Does order of letter analysis contribute to the parafoveal identification asymmetry?

A parafoveally presented target character usually is identified more accurately when flanked by a nontarget character to its foveal side than when flanked by one to its peripheral side. An outside-in process of analysis produced by uncertainty about the target's position could contribute to this asymmetry. Current results revealed a greater asymmetry with relative target position blocked than with it mixed over trials, suggesting that target position uncertainty leads to inside-out, rather than outside-in, analysis.     

Does a cognitive map guide choices in the radial-arm maze?

Fifteen rats performed in a standard radial-arm maze task (Experiment 1) and in a modified task with a set of forced choices and a 15-min retention interval prior to completion of the maze (Experiment 2). In addition to the standard measure of choice in the radial-arm maze, orientation toward arms was measured and considered to constitute go-no-go "microchoice" decisions. Rats investigated but rejected many arms. A model of choice was developed in which it was assumed that choice decisions about arms were made independently and that microchoices were not selectively guided toward baited arms. The model performed nearly as well as the rats. These results place important limitations on the theory that choice behavior in the radial-arm maze is guided by a cognitive map.     

Does imagery contribute to metaphoric quality?

With metaphoric quality divided into an appropriateness and novelty component, college-student subjects rated 75 metaphoric sentences on those components and on imageability. Different subjects were assigned to each of the three rating conditions (n=45 in each). Correlations based on mean ratings of the metaphors indicated that imageability was negatively related to novelty and positively related to appropriateness. A composite of the novelty and appropriateness ratings (deemed to reflect metaphoric quality) proved to be independent of imageability. Examination of metaphors with the highest and lowest imagery ratings suggested that imagery was facilitated by perceptual-configural linkages and inhibited by remote conceptual linkages between topic and vehicle. This configural-conceptual distinction appears to be of greater importance than quality in influencing the extent to which a metaphor is imaged.An earlier version of this paper was presented by the first author at the Annual Meeting of the Eastern Psychological Association, New York City, April 1981. This research was funded in part by a doctoral fellowship from the Social Sciences and Humanities Research Council of Canada to the first author, who is now affiliated with the University of Illinois.     

Does the thought of death contribute to the memory benefit of encoding with a survival scenario?

Four studies tested whether the thought of death contributes to the survival processing advantage found in memory tests (i.e., the survival effect). In the first study, we replicated the “Dying To Remember” (DTR) effect identified by Burns and colleagues whereby activation of death thoughts led to better retention than an aversive control situation. In Study 2, we compared an ancestral survival scenario, a modern survival scenario and a “life-after-death” scenario. The modern survival scenario and the dying scenario led to higher levels of recall than the ancestral scenario. In Study 3, we used a more salient death-thought scenario in which people imagine themselves on death row. Results showed that the “death-row” scenario yielded a level of recall similar to that of the ancestral survival condition. We also collected ratings of death-related thoughts (Studies 3 and 4) and of survival-related and planning thoughts (Study 4). The ratings indicated that death-related thoughts were induced more by the dying scenarios than by the survival scenarios, whereas the reverse was observed for both survival-related and planning thoughts. The findings are discussed in the light of two contrasting views of the influence of mortality salience in the survival effect.     

Can linguistics contribute to the study of verbal behavior?

A number of publications during the last decade reveal a growing interest in linguistics and psycholinguistics among some radical behaviorists, who have proposed a direct rapprochement between a formal analysis of language and a functional account. It is argued that whereas function has to do with the circumstances under which verbal behavior is emitted, structure has to do with its "internal organization," the ways in which sentences or parts thereof are presumably interrelated. These are said to be different dimensions of verbal behavior; together they should lead toward a coherent psychology of language. But psychologists bent on incorporating techniques from linguistics should be aware of its underlying assumptions, lest their work be deflected in essentially unproductive directions. The line between rapprochement and subservience is thin indeed, as the extant literature shows. This paper traces the development of mainstream contemporary psycholinguistics and examines the linguist's assumptions about the subject matter in the light of a behavioral analysis. The possibility of an effective reconciliation seems to be a long way off.     

Does the radial arm maze necessarily test spatial memory?

Since its design 25 years ago (Olton & Samuelson, 1976), the eight-arm radial maze has become very popular and is now widely used to assess spatial memory in rodents. Two versions of the full-baited maze protocol are present in the literature: with or without confinement between the visit of each arm. The confinement was introduced by Olton himself as early as 1977 (Olton, Collison, & Werz, 1977) to eliminate stereotypic behaviors that he had previously observed. It is widely regarded that the confinement prevents rodents from developing these response patterns, and as such it is considered an improved procedure to test spatial memory. Surprisingly, to the best of our knowledge, no study has been especially designed to demonstrate the efficacy of the confinement in blocking the stereotypic behaviors of the animals. The present study compares the strategies of rats trained with or without a confinement procedure. The results show that, after nine days of training, rats submitted to a 5- or a 10-s confinement reach the same level of performance as rats without confinement. The confinement totally prevents stereotypic behaviors like clockwise serial searching strategies which are often observed without confinement. Even a 0-s confinement is sufficient to prevent clockwise strategies, but rats seem to develop other stratagems which do not imply spatial memory. Furthermore, rats previously trained without confinement are unable to perform the task when confinement is introduced on a test day. In contrast, rats previously trained with confinement perform the task correctly when the confinement is no longer present. Thus, without confinement, good levels of performance can be achieved without precise spatial representations.     

Does the distance between us matter? Influences of physical proximity to others on consumer choice

Individuals’ physical closeness to one another can either increase or decrease their preference for distinctive products. When individuals perceive their proximity to others to be voluntary, they are likely to interpret it as an indication of their affiliation motivation. Consequently, in a product choice task, they choose options that others consider desirable. When people perceive that their close proximity to others results from circumstances beyond their control, however, they feel that their personal space is violated and experience a need for to express their individuality. In this case, they are more likely to choose products that distinguish themselves from others.     

Does mediator use contribute to the spacing effect for cued recall? Critical tests of the mediator hypothesis

When study is spaced across sessions (versus massed within a single session), final performance is greater after spacing. This spacing effect may have multiple causes, and according to the mediator hypothesis, part of the effect can be explained by the use of mediator-based strategies. This hypothesis proposes that when study is spaced across sessions, rather than massed within a session, more mediators will be generated that are longer lasting and hence more mediators will be available to support criterion recall. In two experiments, participants were randomly assigned to study paired associates using either a spaced or massed schedule. They reported strategy use for each item during study trials and during the final test. Consistent with the mediator hypothesis, participants who had spaced (as compared to massed) practice reported using more mediators on the final test. This use of effective mediators also statistically accounted for some – but not all of – the spacing effect on final performance.     

Does response interference contribute to face composite effects?

Holistic processing of faces can be measured as a failure of selective attention to one face-half under instructions to ignore the other face-half in a naming or same/different matching task. But is interference from the irrelevant half due to response interference rather than to holistic processing? Here, participants learned to name two faces “Fred” and two “Bob.” At test, composites were created from top and bottom halves of different learned faces or of a novel face, and composites were either aligned or misaligned. Naming was slower when the irrelevant half was from a different face as opposed to the same face, regardless of whether it was associated with the same name, a different name, or no name, suggesting holistic processing. Interference was eliminated when composite halves were misaligned. These results suggest that, unlike Stroop effects, composite effects are not due to response interference.     

How do the internal details of the object contribute to recognition?

Object recognition becomes difficult when the main axis of the object is foreshortened. It has previously been reported that this so-called foreshortened disadvantage is larger when the silhouette of the object is presented than when the line drawing of the object is presented. The pronounced foreshortened disadvantage in silhouette recognition indicates that the internal details of the object, which are absent in the silhouette, provide useful information, particularly when the main axis is foreshortened. But the role of these internal details remains controversial. One account for the pronounced disadvantage is that the internal details contribute to the derivation of the main axis. The other account is that internal details provide the distinctive features that are directly matched to the object represented in memory. The aim in the present study was to determine which of these two explanations best accounts for the differential foreshortened disadvantage between line drawings and silhouettes. To reduce the uncertainty regarding the axis orientation, a 3-D arrow indicating the orientation of the main axis was presented as a cue before the object itself was presented. As a result, the difference in the foreshortened disadvantage between silhouettes and line drawings disappeared. This indicated that the pronounced foreshortened disadvantage for silhouettes was caused by a lack of axis information. In other words, the internal details provided the information necessary for axis derivation when the axis was foreshortened.     

To share or not to share? Explaining willingness to share in the context of social distance

Sharing can help make goods available to many people who would otherwise have no access to them. In the effort of motivating more people to participate in the sharing economy, it is useful to know the variables that influence the willingness to share (WTS). Our study aims to identify these variables. Applying field theory, we conducted an experiment based on nonmonetary sharing situations. Complementing existing research directed towards users of goods, we focused on the providers of goods, thus broadening the understanding of sharing contexts. We demonstrate that WTS can be explained by several variables. In particular, a low social distance increases individuals' WTS their belongings with others. Product involvement is also a predictor of whether or not people are willing to share. In contrast, consumer characteristics such as materialism, altruism, and interpersonal trust have no impact on sharing intentions. Our findings provide significant implications for consumer research and for the marketing of sharing organizations.     

On the validity of Raven’s matrices test: Does spatial ability contribute to performance?

The paper reports on an investigation of the convergent and discriminant validity of Raven’s matrices in considering reasoning and spatial abilities. Raven’s advanced progressive matrices (APM) and four scales representing reasoning, visualization, mental rotation and closure were applied to a sample of N = 280 university students. The data were investigated by means of structural equation modeling. The results demonstrated convergent validity of APM with respect to reasoning. In contrast, in investigating discriminant validity substantial correlations of moderate size between APM and the scales representing spatial abilities were observed. However, the investigation of the structure of the prediction of APM revealed that the scales representing spatial abilities did not improve the prediction based on the reasoning scale alone at the latent level. Consequently, it is suggested that Raven’s matrices show good convergent validity and slightly impaired discriminant validity.     

How does the hippocampus contribute to memory?

Recently, Wirth et al. reported that hippocampal neurons signal the acquisition of new associations by altering the selectivity of their responses to crucial stimuli. The course of these changes was gradual, with some neurons recruited before, others at the time of, and yet others shortly after learning. These observations suggest the hippocampus might contribute to memory by identifying consistencies across experiences that constitute important new associations.     

Does rate of processing determine ease of target detection?

In a complex target identification task, Krumhansl (1982) reported that ease of target detection was inversely related to the exposure duration of contextual elements in the display. This relationship held at brief exposures of the contextual elements. However, in Krumhansl's design, brightness and duration covaried. Hence, the results cannot be ascribed unambiguously to the effect of duration alone. In the present two experiments, brightness and duration were varied independently. The outcome showed that brightness differences were both a necessary and a sufficient condition for producing the relationships observed by Krumhansl. In fact, when brightness was equalized across all durations the relationship was reversed. Although unable to account for the effects of duration, Krumhansl's formal model remains viable as a predictor of the effects of brightness.     

Does the Subject of Experience Exist in the World?

In this paper I attempt to show, by considering a number of sources, including Wittgenstein, Sartre, Thomas Nagel and Spinoza, but also adding something crucial of my own, that it is impossible to construe the subject of experience as an object among other objects in the world. My own added argument is the following. the subject of experience cannot move in time along with material events and processes or it could not be aware of the passage of time, hence neither of change nor of motion. the subject cannot therefore be identified with any neural process, function, or location since whatever goes on in the CNS is necessarily objective and part of the temporal flux. However this does not imply any form of dualism for experiences exist only for the subject whose experiences they are and hence they have no objective reality.