Stimulus Control by Timing in Pigeons

Timing has been widely studied in humans and animals across a variety of different timescales. The concept of time as a stimulus dimension, and how it is processed relative to other stimulus dimensions, has only recently been scrutinized. In the current work I present a review of interval timing as it relates to stimulus control, and discuss the role of attention in timing in the context of three sets of studies in pigeons. In the first set of studies, I analyzed whether the presence of a non-reinforced timed stimulus would disrupt timing of a stimulus reinforced on a fixed-interval schedule. In Experiment 1, half of the pigeons were trained on a 60-s fixed interval schedule of reinforcement signaled by onset of a sidekey; the other half of the birds had those same reinforced trials interspersed among trials in which the onset of a different sidekey signaled 60-s followed by non-reinforcement. Groups were reversed in the second phase of experimentation. Obtained peak-time curves showed flattened responding to the reinforced stimulus for birds which also received non-reinforced trials, suggesting that control by interval timing was overshadowed by the presence of a food/no food cue. Experiment 2 ruled out the possibility that this effect was caused by differences in reinforcement. Pigeons’ responding on this task was not controlled by timing because the visual discrimination based on food vs. no food was more salient than the temporal discrimination. In the second set of studies, I examined the ability of pigeons to track the identity of multiple stimuli presented in order across a temporal interval terminating in reinforcement. In Experiment 1A, pigeons responded to the final stimulus in a three-item sequence regardless of the preceding order of stimuli, or even if previous stimuli had not been presented, suggesting that the birds attended only to the reinforced stimulus and not to the order of stimuli. In Experiment 1B, pigeons were presented with baseline non-reinforced trials in which the order of the first two stimuli was reversed, and results showed that they responded differently to the third stimulus based on the order of stimuli. Experiment 2 extended these results with a five-stimulus sequence. Though birds showed only a weak appreciation of order, they nonetheless responded differentially based on temporal order. In the final study, I observed the tendency of pigeons to anticipate or perseverate after a mid-session reversal of response contingencies. The birds tended to make errors around the reversal point when the discrimination was a visually-based (red vs. green) task, and these errors were conclusively shown to be due to interval timing from the start of the session. However, when presented with a visual-spatial version of the same task, pigeons no longer made timing-induced errors and instead used a reinforcement-maximizing approach. The dimension of discrimination affected the strength of memory for the response and outcome of the previous trial, and in turn affected the tendency of birds to base their responding on an error-prone interval timing strategy

The Dotted straightening algorithm

AbstractIf a homogeneous bracket polynomial is antisymmetric in certain subsets of its points, then it can be represented in an abbreviated form called a dotted bracket expression. These dotted bracket expressions lead to a more compact expression in terms of tableaux than the usual representation. Consequently, we can derive a much more efficient straightening algorithm than the ordinary one for bracket polynomials already given in dotted form. This dotted straightening algorithm gives precisely the same result as the ordinary one, and preserves the dotted property at every step

Tracing masculinities in twentieth-century Scottish men's fiction

Tracing Masculinities in Twentieth-Century Scottish Men's Fiction takes account of the representation of masculinities in a selected group of novels by twentieth-century Scottish male authors. Rather than attempt a chronological survey of fictions during this period, the argument proceeds by analysing groups of texts which are axiomatic in specific ways: the Glasgow realist novels of the 1930s and post-1970s, from the works of James Barke and George Blake to those of William McIlvanney and James Kelman, which offer particular perspectives on relationships between men of different class identifications; fictions reliant upon existentialism, which intersect with the masculinist values of the Glasgow tradition in the figure of Kelman, but are also produced by Alexander Trocchi and Irvine Welsh; and novels which employ the technique of 'cross-writing', or literary transvestism, from the Renaissance fictions of Lewis Grassic Gibbon to the postmodern works of Alan Warner and Christopher Whyte. In a critical field which has always been concerned with a tradition of largely male-produced texts privileging the actions of male characters, but has neglected fully to consider the production and reception of those texts in terms of their specific articulations of gender positions, this thesis employs theories of masculinities developed in the study of American and English literatures since the 1980s in order to provide new perspectives on Scottish novels. It also draws upon the materialist theory of Louis Althusser for a model of ideological identification, as well as utilising several psychoanalytic and deconstructive approaches to gender formation in Western culture, epitomised by the work of Judith Butler and Kaja Silverman. The various perspectives on masculine gender and sexual identities thus assembled are primarily directed towards considering the novels under discussion as 'men's texts' - texts not only by or about men, but often directed towards men as readers too

Structural transformations and disordering in zirconolite (CaZrTi2O7) at high pressure

There is interest in identifying novel materials for use in radioactive waste applications and studying their behavior under high pressure conditions. The mineral zirconolite (CaZrTi2O7) exists naturally in trace amounts in diamond-bearing deep-seated metamorphic/igneous environments, and it is also identified as a potential ceramic phase for radionuclide sequestration. However, it has been shown to undergo radiation-induced metamictization resulting in amorphous forms. In this study we probed the high pressure structural properties of this pyrochlore-like structure to study its phase transformations and possible amorphization behavior. Combined synchrotron X-ray diffraction and Raman spectroscopy studies reveal a series of high pressure phase transformations. Starting from the ambient pressure monoclinic structure, an intermediate phase with P21/m symmetry is produced above 15.6 GPa via a first order transformation resulting in a wide coexistence range. Upon compression to above 56 GPa a disordered metastable phase III with a cotunnite-related structure appears that is recoverable to ambient conditions. We examine the similarity between the zirconolite behavior and the structural evolution of analogous pyrochlore systems under pressure.<br/

Living near the edge: how extreme outcomes and their neighbours drive risky choice

Extreme stimuli are often more salient in perception and memory than moderate stimuli. In risky choice, when people learn the odds and outcomes from experience, the extreme outcomes (best and worst) also stand out. This additional salience leads to more risk-seeking for relative gains than for relative losses—the opposite of what people do when queried in terms of explicit probabilities. Previous research has suggested that this pattern arises because the most extreme experienced outcomes are more prominent in memory. An important open question, however, is what makes these extreme outcomes more prominent? Here we assess whether extreme outcomes stand out because they fall at the edges of the experienced outcome distributions or because they are distinct from other outcomes. Across four experiments, proximity to the edge determined what was treated as extreme: Outcomes at or near the edge of the outcome distribution were both better remembered and more heavily weighted in choice. This prominence did not depend on two metrics of distinctiveness: lower frequency or distance from other outcomes. This finding adds to evidence from other domains that the values at the edges of a distribution have a special role

Living near the edge : how extreme outcome and their neighbours drive risky choice

Extreme stimuli are often more salient in perception and memory than moderate stimuli. In risky choice, when people learn the odds and outcomes from experience, the extreme outcomes (best and worst) also stand out. This additional salience leads to more risk-seeking for relative gains than for relative losses—the opposite of what people do when queried in terms of explicit probabilities. Previous research has suggested that this pattern arises because the most extreme experienced outcomes are more prominent in memory. An important open question, however, is what makes these extreme outcomes more prominent? Here we assess whether extreme outcomes stand out because they fall at the edges of the experienced outcome distributions or because they are distinct from other outcomes. Across four experiments, proximity to the edge determined what was treated as extreme: Outcomes at or near the edge of the outcome distribution were both better remembered and more heavily weighted in choice. This prominence did not depend on two metrics of distinctiveness: lower frequency or distance from other outcomes. This finding adds to evidence from other domains that the values at the edges of a distribution have a special role

Experience affects immediate early gene expression in response to conspecific call notes in black-capped chickadees (Poecile atricapillus)

This research was supported by a Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant and Discovery Accelerator Supplement, an Alberta Ingenuity Fund (AIF) New Faculty Grant, a Canada Foundation for Innovation (CFI) New Opportunities Fund (NOF), and Infrastructure Operating Fund (IOF) grants along with start-up funding and CFI partner funding from the University of Alberta (UofA) to C.B.S. L.M.G. was supported by an Izaak Walton Killam Memorial Scholarship (IWKMS) at UofA and is currently supported by a Newton International Fellowship jointly run by the Royal Society and the British Academy.Black-capped chickadees (Poecile atricapillus) produce numerous vocalizations, including the acoustically complex chick-a-dee call that is composed of A, B, C, and D notes. D notes are longer in duration and lower in frequency than the other note types and contain information regarding flock and species identification. Adult wild-caught black-capped chickadees have been shown to have similar amounts of immediate early gene (IEG) expression following playback of vocalizations with harmonic-like acoustic structure, similar to D notes. Here we examined how different environmental experiences affect IEG response to conspecific D notes. We hand-reared black-capped chickadees under three conditions: (1) with adult conspecifics, (2) with adult heterospecific mountain chickadees, and (3) without adults. We presented all hand-reared birds and a control group of field-reared black-capped chickadees, with conspecific D notes and quantified IEG expression in the caudomedial mesopallium (CMM) and caudomedial nidopallium (NCM). We found that field-reared birds that heard normal D notes had a similar neural response as a group of field-reared birds that heard playback of reversed D notes. Field-reared birds that heard normal D notes also had a similar neural response as birds reared with adult conspecifics. Birds reared without adults had a significantly reduced IEG response, whereas the IEG expression in birds reared with heterospecifics was at intermediate levels between birds reared with conspecifics and birds reared without adults. Although acoustic characteristics have been shown to drive IEG expression, our results demonstrate that experience with adults or normal adult vocalizations is also an important factor.PostprintPeer reviewe

Cue integration in spatial search for jointly learned landmarks but not for separately learned landmarks.

The authors investigated how humans use multiple landmarks to locate a goal. Participants searched for a hidden goal location along a line between 2 distinct landmarks on a computer screen. On baseline trials, the location of the landmarks and goal varied, but the distance between each of the landmarks and the goal was held constant, with 1 landmark always closer to the goal. In Experiment 1, some baseline trials provided both landmarks, and some provided only 1 landmark. On probe trials, both landmarks were shifted apart relative to the previously learned goal location. Participants searched between the locations specified by the 2 landmarks and their search locations were shifted more toward the nearer landmark, suggesting a weighted integration of the conflicting landmarks. Moreover, the observed variance in search responses when both cues were presented in their normal locations was reduced compared to the variance on tests with single landmarks. However, the variance reduction and the weightings of the landmarks did not always show Bayesian optimality. In Experiment 2, some participants were trained only with each of the single landmarks. On subsequent tests with the 2 cues in conflict, searching did not shift toward the nearer landmark and the variance of search responses of these single-cue trained participants was larger than their variance on single-landmark tests, and even larger than the variance predicted by using the 2 landmarks alternatively on different trials. Taken together, these results indicate that cue combination occurs only when the landmarks are presented together during the initial learning experience