Eric Legge | University of Alberta (original) (raw)
Papers by Eric Legge
Journal of Experimental Biology, 2013
Acta psychologica, 2012
The Method of Loci (MOL) is an ancient mnemonic strategy used to enhance serial recall. Tradition... more The Method of Loci (MOL) is an ancient mnemonic strategy used to enhance serial recall. Traditionally, the MOL is carried out by imagining navigating a familiar environment and "placing" the to-be-remembered items in specific locations. For retrieval, the mnemonist re-imagines walking through the environment, "looking" for those items in order. Here we test a novel MOL method, where participants use a briefly studied virtual environment as the basis for the MOL and applied the strategy to 10 lists of 11 unrelated words. When our virtual environments were used, the MOL was as effective, compared to an uninstructed control group, as the traditional MOL where highly familiar environments were used. Thus, at least for naïve participants, a highly detailed environment does not support substantially better memory for verbal serial lists.
Behavior research methods, 2013
We extend a Bayesian method for combining estimates of means and variances from independent cues ... more We extend a Bayesian method for combining estimates of means and variances from independent cues in a spatial cue-combination paradigm. In a typical cuecombination experiment, subjects estimate a value on a single dimension-for example, depth-on the basis of two different cues, such as retinal disparity and motion. The mathematics for this one-dimensional case is well established. When the variable to be estimated has two dimensions, such as location (which has both x and y values), then the one-dimensional method may be inappropriate due to possible correlations between x and y and the fact that the dimensions may be inseparable. A cue-combination task for location involves people or animals estimating xy locations under two single-cue conditions and in a condition in which both cues are combined. We present the mathematics for the two-dimensional case in an analogous manner to the one-dimensional case and illustrate them using a numeric example. Our example involves locations on maps, but the method illustrated is relevant for any task for which the estimated variable has two or more dimensions.
The Journal of experimental biology, 2013
Many animals -including insects -navigate visually through their environment. Solitary foraging d... more Many animals -including insects -navigate visually through their environment. Solitary foraging desert ants are known to acquire visual information from the surrounding panorama and use it to navigate along habitual routes or to pinpoint a goal such as the nest. Returning foragers that fail to find the nest entrance engage in searching behaviour, during which they continue to use vision. The characteristics of searching behaviour have typically been investigated in unfamiliar environments. Here we investigated in detail the nest-searching behaviour of Melophorus bagoti foragers within the familiar visual environment of their nest. First, by relating search behaviour to the information content of panoramic (360deg) images, we found that searches were more accurate in visually cluttered environments. Second, as observed in unfamiliar visual surrounds, searches were dynamic and gradually expanded with time, showing that nest pinpointing is not rigidly controlled by vision. Third, contrary to searches displayed in unfamiliar environments, searches observed here could be modelled as a single exponential search strategy, which is similar to a Brownian walk, and there was no evidence of a Lévy walk. Overall, our results revealed that searching behaviour is remarkably flexible and varies according to the relevance of information provided by the surrounding visual scenery.
PLOS One, 2012
Little is known about the strategies people use to effectively hide objects from others, or to se... more Little is known about the strategies people use to effectively hide objects from others, or to search for objects others have hidden. The present research extends a recent investigation of people's hiding and searching strategies in a simple room with 9 cache location. In the present studies, people hid and searched for three objects under more than 70 floor tiles in complex real and virtual rooms. Experiment 1 replicated several finding of Talbot et al within the more complex real and virtual environments. Specifically, people traveled further from origin and selected more dispersed locations when hiding than when searching. Experiments 2 and 3 showed that: 1) people were attracted to an area of darkness when searching and avoided locations close to a window when hiding, 2) when search attempts were limited to three choices, people searched farther from origin and dispersed their locations more when hiding than when searching, and 3) informing people that they would need to recover their hidden objects altered their hiding behavior and increased recovery accuracy. Across all experiments, consistencies in location preferences emerged, with more preference for the middle of the room during hiding and more preference for corners of the room during searching. Even though the same people participated in both the hiding and searching tasks, it appears that people use different strategies to select hiding places than to search for objects hidden by others.
Learning and Motivation, Jan 1, 2009
Adults searched for or cached three objects in nine hiding locations in a virtual room or a real-... more Adults searched for or cached three objects in nine hiding locations in a virtual room or a real-space room. In both rooms, the locations selected by participants differed systematically between searching and hiding. Specifically, participants moved farther from origin and dispersed their choices more when hiding objects than when searching for hidden objects. In addition, in both virtual and real-space rooms, prior experience in the hiding task increased the distance participants traveled from origin and the dispersion of their choices during searching. Furthermore, gender differences appeared in the virtual room but not in the real-space room. Specifically, during hiding females travelled farther from origin than males and during searching they dispersed their choices more than males. Overall, the results suggest that strategies used by adult humans for searching and caching are consistent with those seen in non-human animals and children.
Animal Cognition, Jan 1, 2010
Many ant species travel large distances to find food, sometimes covering distances that are up to... more Many ant species travel large distances to find food, sometimes covering distances that are up to one million times their body length. Even when these foraging trips follow convoluted paths, the ants usually find their way back to their nest with precision (Wehner et al. in J Exp Biol 199:129–140, 1996). Ants have been shown to use both compass cues in the sky (pattern of polarised light) and landmarks on Earth to return to their nest. We present two experiments conducted on a solitary foraging ant: Melophorus bagoti in their natural habitat in the central Australian desert. Ants were trained and tested in situ. We tested foragers’ ability to exit a circular arena which provided an undifferentiated panorama. Artificial visual landmarks were located near a small exit. On tests in which path integration information was not available, foragers did not use artificial landmarks as beacons. Instead, they oriented in the learned exit direction, whether or not it pointed to the nest. We suggest that M. bagoti foragers learned a context-specific local vector when cued by the context of the circular arena. Our findings present the first evidence that M. bagoti foragers learn context-specific compass directions to chart their initial path home.
Behavioural Processes, Jan 1, 2009
Redundant encoding of local and global spatial cues is a common occurrence in many species. Howev... more Redundant encoding of local and global spatial cues is a common occurrence in many species. However, preferential use of the each type of cue seems to vary across species and tasks. In the current study, pigeons (Columba livia) were trained in three experiments on a touch screen task which included redundant local positional cues and global spatial cues. Specifically, pigeons were required to choose the middle out of three choice squares, such that the position within the array provided local information and the location on the screen provided global information. In Experiment 1, pigeons were trained and tested on vertically aligned arrays. In Experiment 2, pigeons were trained and tested on horizontally aligned arrays, and in Experiment 3, pigeons were trained and tested with vertical, horizontal and diagonally aligned arrays. The results indicate that preference for cue type depends upon the type of spatial information being encoded. Specifically, on vertical and diagonally aligned arrays, pigeons preferred global cues, whereas on horizontally aligned arrays, pigeons preferred local cues.
Learning and Motivation, Jan 1, 2009
We investigated whether search accuracy of adult humans could be enhanced using differential rewa... more We investigated whether search accuracy of adult humans could be enhanced using differential reward contingencies in landmark-based spatial tasks conducted on a computer screen. We found that search accuracy was significantly enhanced by differential outcomes in a conditional spatial search task, in which the landmark-to-goal relationship depended on a previously presented sample object (Experiment 4). In contrast, no significant differential outcomes effect (DOE) was seen in several other variations of spatial search tasks. We interpret the pattern of significant and non-significant results in terms of the information value of outcome expectancies. To our knowledge this is the first report of a DOE in a landmark-based spatial localization task and is one of only a few demonstrations that differential outcomes can enhance memory performance in normal functioning adults.
Journal of Experimental Biology, 2013
Acta psychologica, 2012
The Method of Loci (MOL) is an ancient mnemonic strategy used to enhance serial recall. Tradition... more The Method of Loci (MOL) is an ancient mnemonic strategy used to enhance serial recall. Traditionally, the MOL is carried out by imagining navigating a familiar environment and "placing" the to-be-remembered items in specific locations. For retrieval, the mnemonist re-imagines walking through the environment, "looking" for those items in order. Here we test a novel MOL method, where participants use a briefly studied virtual environment as the basis for the MOL and applied the strategy to 10 lists of 11 unrelated words. When our virtual environments were used, the MOL was as effective, compared to an uninstructed control group, as the traditional MOL where highly familiar environments were used. Thus, at least for naïve participants, a highly detailed environment does not support substantially better memory for verbal serial lists.
Behavior research methods, 2013
We extend a Bayesian method for combining estimates of means and variances from independent cues ... more We extend a Bayesian method for combining estimates of means and variances from independent cues in a spatial cue-combination paradigm. In a typical cuecombination experiment, subjects estimate a value on a single dimension-for example, depth-on the basis of two different cues, such as retinal disparity and motion. The mathematics for this one-dimensional case is well established. When the variable to be estimated has two dimensions, such as location (which has both x and y values), then the one-dimensional method may be inappropriate due to possible correlations between x and y and the fact that the dimensions may be inseparable. A cue-combination task for location involves people or animals estimating xy locations under two single-cue conditions and in a condition in which both cues are combined. We present the mathematics for the two-dimensional case in an analogous manner to the one-dimensional case and illustrate them using a numeric example. Our example involves locations on maps, but the method illustrated is relevant for any task for which the estimated variable has two or more dimensions.
The Journal of experimental biology, 2013
Many animals -including insects -navigate visually through their environment. Solitary foraging d... more Many animals -including insects -navigate visually through their environment. Solitary foraging desert ants are known to acquire visual information from the surrounding panorama and use it to navigate along habitual routes or to pinpoint a goal such as the nest. Returning foragers that fail to find the nest entrance engage in searching behaviour, during which they continue to use vision. The characteristics of searching behaviour have typically been investigated in unfamiliar environments. Here we investigated in detail the nest-searching behaviour of Melophorus bagoti foragers within the familiar visual environment of their nest. First, by relating search behaviour to the information content of panoramic (360deg) images, we found that searches were more accurate in visually cluttered environments. Second, as observed in unfamiliar visual surrounds, searches were dynamic and gradually expanded with time, showing that nest pinpointing is not rigidly controlled by vision. Third, contrary to searches displayed in unfamiliar environments, searches observed here could be modelled as a single exponential search strategy, which is similar to a Brownian walk, and there was no evidence of a Lévy walk. Overall, our results revealed that searching behaviour is remarkably flexible and varies according to the relevance of information provided by the surrounding visual scenery.
PLOS One, 2012
Little is known about the strategies people use to effectively hide objects from others, or to se... more Little is known about the strategies people use to effectively hide objects from others, or to search for objects others have hidden. The present research extends a recent investigation of people's hiding and searching strategies in a simple room with 9 cache location. In the present studies, people hid and searched for three objects under more than 70 floor tiles in complex real and virtual rooms. Experiment 1 replicated several finding of Talbot et al within the more complex real and virtual environments. Specifically, people traveled further from origin and selected more dispersed locations when hiding than when searching. Experiments 2 and 3 showed that: 1) people were attracted to an area of darkness when searching and avoided locations close to a window when hiding, 2) when search attempts were limited to three choices, people searched farther from origin and dispersed their locations more when hiding than when searching, and 3) informing people that they would need to recover their hidden objects altered their hiding behavior and increased recovery accuracy. Across all experiments, consistencies in location preferences emerged, with more preference for the middle of the room during hiding and more preference for corners of the room during searching. Even though the same people participated in both the hiding and searching tasks, it appears that people use different strategies to select hiding places than to search for objects hidden by others.
Learning and Motivation, Jan 1, 2009
Adults searched for or cached three objects in nine hiding locations in a virtual room or a real-... more Adults searched for or cached three objects in nine hiding locations in a virtual room or a real-space room. In both rooms, the locations selected by participants differed systematically between searching and hiding. Specifically, participants moved farther from origin and dispersed their choices more when hiding objects than when searching for hidden objects. In addition, in both virtual and real-space rooms, prior experience in the hiding task increased the distance participants traveled from origin and the dispersion of their choices during searching. Furthermore, gender differences appeared in the virtual room but not in the real-space room. Specifically, during hiding females travelled farther from origin than males and during searching they dispersed their choices more than males. Overall, the results suggest that strategies used by adult humans for searching and caching are consistent with those seen in non-human animals and children.
Animal Cognition, Jan 1, 2010
Many ant species travel large distances to find food, sometimes covering distances that are up to... more Many ant species travel large distances to find food, sometimes covering distances that are up to one million times their body length. Even when these foraging trips follow convoluted paths, the ants usually find their way back to their nest with precision (Wehner et al. in J Exp Biol 199:129–140, 1996). Ants have been shown to use both compass cues in the sky (pattern of polarised light) and landmarks on Earth to return to their nest. We present two experiments conducted on a solitary foraging ant: Melophorus bagoti in their natural habitat in the central Australian desert. Ants were trained and tested in situ. We tested foragers’ ability to exit a circular arena which provided an undifferentiated panorama. Artificial visual landmarks were located near a small exit. On tests in which path integration information was not available, foragers did not use artificial landmarks as beacons. Instead, they oriented in the learned exit direction, whether or not it pointed to the nest. We suggest that M. bagoti foragers learned a context-specific local vector when cued by the context of the circular arena. Our findings present the first evidence that M. bagoti foragers learn context-specific compass directions to chart their initial path home.
Behavioural Processes, Jan 1, 2009
Redundant encoding of local and global spatial cues is a common occurrence in many species. Howev... more Redundant encoding of local and global spatial cues is a common occurrence in many species. However, preferential use of the each type of cue seems to vary across species and tasks. In the current study, pigeons (Columba livia) were trained in three experiments on a touch screen task which included redundant local positional cues and global spatial cues. Specifically, pigeons were required to choose the middle out of three choice squares, such that the position within the array provided local information and the location on the screen provided global information. In Experiment 1, pigeons were trained and tested on vertically aligned arrays. In Experiment 2, pigeons were trained and tested on horizontally aligned arrays, and in Experiment 3, pigeons were trained and tested with vertical, horizontal and diagonally aligned arrays. The results indicate that preference for cue type depends upon the type of spatial information being encoded. Specifically, on vertical and diagonally aligned arrays, pigeons preferred global cues, whereas on horizontally aligned arrays, pigeons preferred local cues.
Learning and Motivation, Jan 1, 2009
We investigated whether search accuracy of adult humans could be enhanced using differential rewa... more We investigated whether search accuracy of adult humans could be enhanced using differential reward contingencies in landmark-based spatial tasks conducted on a computer screen. We found that search accuracy was significantly enhanced by differential outcomes in a conditional spatial search task, in which the landmark-to-goal relationship depended on a previously presented sample object (Experiment 4). In contrast, no significant differential outcomes effect (DOE) was seen in several other variations of spatial search tasks. We interpret the pattern of significant and non-significant results in terms of the information value of outcome expectancies. To our knowledge this is the first report of a DOE in a landmark-based spatial localization task and is one of only a few demonstrations that differential outcomes can enhance memory performance in normal functioning adults.