http://hdl.handle.net/2123/6344 Wed, 19 Jun 2013 22:26:29 GMT 2013-06-19T22:26:29Z http://hdl.handle.net/2123/9069 Title: Magazine approach during a signal for food depends on Pavlovian, not instrumental, conditioning Authors: Harris, Justin; Andrew, Benjamin; Kwok, Dorothy Abstract: In the conditioned magazine approach paradigm, rats are exposed to a contingent relationship between a conditioned stimulus (CS) and the delivery of food (the unconditioned stimulus, US). As the rats learn the CS-US association, they make frequent anticipatory head entries into the food magazine (the conditioned response, CR) during the CS. Conventionally, this is considered to be a Pavlovian paradigm because food is contingent on the CS and not on the performance of CRs during the CS. However, because magazine entries during the CS are reliably followed by food, the increase in frequency of those responses may involve adventitious (“superstitious”) instrumental conditioning. The existing evidence, from experiments using an omission schedule to eliminate the possibility of instrumental conditioning (Farwell & Ayres, 1979; Holland, 1979), is ambiguous: rats acquire magazine CRs despite the omission schedule, demonstrating that the response does not depend on instrumental conditioning, but the response rate is greatly depressed compared with that of rats trained on a yoked schedule, consistent with a contribution from instrumental conditioning under normal (non-omission) schedules. Here we describe experiments in which rats were trained on feature-positive or feature-negative type discriminations between trials that were reinforced on an omission schedule versus trials reinforced on a yoked schedule. The experiments show that the difference in responding between omission and yoked schedules is due to suppression of responding under the omission schedule rather than an elevation of responding under the yoked schedule. We conclude that magazine responses during the CS are largely or entirely Pavlovian CRs. Mon, 01 Apr 2013 00:00:00 GMT http://hdl.handle.net/2123/9069 2013-04-01T00:00:00Z http://hdl.handle.net/2123/8973 Title: Vulnerability to Sea Level Rise Of 8 Beaches In Shoalhaven: A New Multi-Dimensional Assessment Methodology Authors: Tonmoy, Fahim; El-Zein, Abbas; Ghetti, Isabelle; Massie, Ray Abstract: Coastal councils around the world are likely to be affected by future climatic impacts such as sea level rise and extreme flooding. Shoalhaven City Council is responsible for the sustainable management of 165 kilometres of open coast, the longest of any local government area in New South Wales. In order to prepare a comprehensive coastal zone management plan, Council investigated present and expected future coastal risks on its beaches. Detailed studies identified eight beaches where coastal hazards would significantly impact private properties and public assets. In order to help decision-makers in prioritising management actions for the eight areas, an analytical tool is needed that would not only quantify the physical risks to infrastructure but would also be able to integrate social and environmental considerations towards a holistic assessment of the vulnerability of each beach area. Following the Intergovernmental Panel on Climate Change (IPCC) conceptualisation, the vulnerability of a community to a climate hazard can be seen as determined by the degree of physical exposure to the hazard, as well as the community’s sensitivity to its impacts and its ability to cope with, or adapt to, these impacts. Hence, vulnerability assessment presents a number of theoretical and methodological challenges, the most important of which are epitomized by the following questions: 1. how to determine, say whether a community with high exposure and high adaptive capacity is more vulnerable or less vulnerable than a community with lower exposure but lower adaptive capacity? (problem of compensation). 2. how to incorporate the imprecision and value-judgments inevitably present in multistakeholder vulnerability assessments while maintaining a consistent and robust scientific process? (problem of fuzziness). A new methodology has been developed at the University of Sydney that addresses these questions and offers a clear and consistent approach for conducting vulnerability assessments. The paper describes the application of this methodology to the ranking of vulnerabilities to sea level rise of eight beaches in Shoalhaven. Sun, 01 Jan 2012 00:00:00 GMT http://hdl.handle.net/2123/8973 2012-01-01T00:00:00Z http://hdl.handle.net/2123/8901 Title: ARC Open Access Policy Info Session Authors: Holcombe, Alex; Todd, Matt; Arndell, Michael; Christensen, Sten; Stanton, Kate Abstract: Presentations from the ARC Open Access Policy Info Session for the Faculty of Science at the University of Sydney Fri, 25 Jan 2013 00:00:00 GMT http://hdl.handle.net/2123/8901 2013-01-25T00:00:00Z http://hdl.handle.net/2123/8648 Title: Tactile Motion Adaptation Reduces Perceived Speed but Shows No Evidence of DIrection Sensitivity Authors: McIntyre, Sarah Abstract: Introduction: While the directionality of tactile motion processing has been studied extensively, tactile speed processing and its relationship to direction is little-researched and poorly understood. We investigated this relationship in humans using the ‘tactile speed aftereffect’ (tSAE), in which the speed of motion appears slower following prolonged exposure to a moving surface. Method: We used psychophysical methods to test whether the tSAE is direction sensitive. After adapting to a ridged moving surface with one hand, participants compared the speed of test stimuli on the adapted and unadapted hands. We varied the direction of the adapting stimulus relative to the test stimulus. Results: Perceived speed of the surface moving at 81mms-1 was reduced by about 30% regardless of the direction of the adapting stimulus (when adapted in the same direction, Mean reduction = 23mms-1, SD=11; with opposite direction, Mean reduction = 26mms-1, SD=9). In addition to a large reduction in perceived speed due to adaptation, we also report that this effect is not direction sensitive. Conclusions: Tactile motion is susceptible to speed adaptation. This result complements previous reports of reliable direction aftereffects when using a dynamic test stimulus as together they describe how perception of a moving stimulus in touch depends on the immediate history of stimulation. Given that the tSAE is not direction sensitive, we argue that peripheral adaptation does not explain it, because primary afferents are direction sensitive with friction-creating stimuli like ours (thus motion in their preferred direction should result in greater adaptation, and if perceived speed were critically dependent on these afferents’ response intensity, the tSAE should be direction sensitive). The adaptation that reduces perceived speed therefore seems to be of central origin. Sun, 01 Jan 2012 00:00:00 GMT http://hdl.handle.net/2123/8648 2012-01-01T00:00:00Z http://hdl.handle.net/2123/8422 Title: Okamoto's space for the first Painlevé equation in Boutroux coordinates Authors: Duistermaat, Johannes (Hans) J.; Joshi, Nalini Abstract: We study the completeness and connectedness of asymptotic behaviours of solutions of the first Painlev ́e equation d^2 y/ dx^2 = 6 y^2 + x, in the limit x → ∞, x ∈ C. This problem arises in various physical contexts including the critical behaviour near gradient catastrophe for the focusing nonlinear Schrodinger equation. We prove that the complex limit set of solutions is non-empty, compact and invariant under the flow of the limiting autonomous Hamiltonian system, that the infinity set of the vector field is a repellor for the dynamics and obtain new proofs for solutions near the equilibrium points of the autonomous flow. The results rely on a realization of Okamoto’s space, i.e., the space of initial values compactified and regularized by embedding in CP2 through an explicit construction of nine blow-ups. Sat, 01 Jan 2011 00:00:00 GMT http://hdl.handle.net/2123/8422 2011-01-01T00:00:00Z http://hdl.handle.net/2123/7877 Title: Constructivism for Philosophers (Be it a Remark on Realism) Authors: Gal, Ofer Abstract: Bereft of the illusion of an epistemic vantage point external to science, what should be our commitment towards the categories, concepts and terms of that very science? Should we, despaired of the possibility to found these concepts on rock bottom, adopt empiricist skepticism? Or perhaps the inexistence of external foundations implies, rather, immunity for scientific ontology from epistemological criticism? Philosophy’s “realism debate” died out without providing a satisfactory answer to the dilemma, which was taken over by the neighboring disciplines. The “symmetry principle” of the “Strong Programme” for the sociology of science-the requirement that truth and error receive the same kind of causal explanations-offered one bold metaphysical answer, under the guise of a methodological decree. Recently, however, it has been argued that this solution is not bold enough, that the social constructivists replaced the naïve presumption of an independent nature which adjudicates our beliefs with a mirror-image presumption of a sui generis society which furnishes these beliefs autonomously. The proper metaphysics for a foundationless epistemology,argues Bruno Latour, is one which grants nature and society, object and subject, equal roles in the success and failure of science and technology; one in which history of society merges with a history of things-in-themselves. The paper analyzes the philosophical and methodological motivations and ramifications of this extraordinary suggestion. Wed, 01 Jan 2003 00:00:00 GMT http://hdl.handle.net/2123/7877 2003-01-01T00:00:00Z http://hdl.handle.net/2123/7876 Title: The 'absolute existence' of phlogiston: the losing party's point of view. Authors: Gal, Ofer; Boantza, Victor Abstract: Long after its alleged demise, phlogiston was still presented, discussed and defended by leading chemists. Even some of the leading proponents of the new chemistry admitted its ‘absolute existence’. We demonstrate that what was defended under the title ‘phlogiston’ was no longer a particular hypothesis about combustion and respiration. Rather, it was a set of ontological and epistemological assumptions and the empirical practices associated with them. Lavoisier’s gravimetric reduction, in the eyes of the phlogistians, annihilated the autonomy of chemistry together with its peculiar concepts of chemical substance and quality, chemical process and chemical affinity. The defence of phlogiston was the defence of a distinctly chemical conception of matter and its appearances, a conception which rejected the chemist’s acquaintance with details and particularities of substances, properties and processes and his skills of adducing causal relations from the interplay between their complexity and uniformity. Sat, 01 Jan 2011 00:00:00 GMT http://hdl.handle.net/2123/7876 2011-01-01T00:00:00Z http://hdl.handle.net/2123/7875 Title: The Body as Object and Instrument of Knowledge:Embodied Empiricism in Early Modern Science Authors: Gal, Ofer; Wolfe, Charles T. Abstract: It was in 1660s England, according to the received view, in the Royal Society of London, that science acquired the form of empirical enquiry we recognize as our own: an open, collaborative experimental practice, mediated by specially-designed instruments, supported by civil discourse, stressing accuracy and replicability. Guided by the philosophy of Francis Bacon, by Protestant ideas of this worldly benevolence, by gentlemanly codes of decorum and by a dominant interest in mechanics and the mechanical structure of the universe, the members of the Royal Society created a novel experimental practice that superseded former modes of empirical inquiry, from Aristotelian observations to alchemical experimentation. Fri, 01 Jan 2010 00:00:00 GMT http://hdl.handle.net/2123/7875 2010-01-01T00:00:00Z http://hdl.handle.net/2123/7874 Title: Empiricism Without the Senses: How the Instrument Replaced the Eye Authors: Gal, Ofer; Chen-Morris, Raz Abstract: On receiving news of Galileo’s observations of the four satellites of Jupiter and the rugged face of the moon through his newly invented perspicillum, Kepler in great excitement exclaimed: Therefore let Galileo take his stand by Kepler’s side. Let the former observe the moon with his face turned skyward, while the latter studies the sun by looking down at a screen (lest the lens injure his eyes). Let each employ his own device, and from this partnership may there some day arise an absolutely perfect theory of the distances. This Hollywood-like scene of the two astronomers marching hand in hand toward the dawn of a new scientific era was no attempt by Kepler to appropriate Galileo’s success or to diminish the novelty of the telescope. On the contrary, Kepler repeatedly asserted how short sighted he was in misjudging the potential for astronomical observations inherent in lenses, and how radically Galileo’s instrument transformed the science of astronomy. It was a deep sense of recognition that beyond their different scientific temperaments and projects, they shared a common agenda of a new mode of empirical engagement with the phenomenal world: the instrument. For Kepler and Galileo, empirical investigation was no longer a direct engagement with nature, but an essentially mediated endeavor. The new instruments were not to assist the human senses, but to replace them. Fri, 01 Jan 2010 00:00:00 GMT http://hdl.handle.net/2123/7874 2010-01-01T00:00:00Z http://hdl.handle.net/2123/7873 Title: Baroque Optics and the Disappearance of the Observer: From Kepler’s Optics to Descartes’ Doubt Authors: Gal, Ofer; Chen Morris, Raz Abstract: In the seventeenth century the human observer gradually disappeared from optical treatises. It was a paradoxical process: the naturalization of the eye estranged the mind from its objects. Turned into a material optical instrument, the eye no longer furnished the observer with genuine representations of visible objects. It became a mere screen, on which rested a blurry array of light stains, accidental effects of a purely causal process. It thus befell the intellect to decipher one natural object—a flat image of no inherent epistemic value—as the vague, reversed reflection of another, wholly independent object. In reflecting on and trespassing the boundaries between natural and artificial, orderly and disorderly, this optical paradox was a Baroque intellectual phenomenon; and it was the origin of Descartes’ celebrated doubt— whether we know anything at all. Thu, 01 Apr 2010 00:00:00 GMT http://hdl.handle.net/2123/7873 2010-04-01T00:00:00Z http://hdl.handle.net/2123/7869 Title: Attentional Changes During Implicit Learning: Signal Validity Protects a Target Stimulus from the Attentional Blink Authors: Livesey, Evan J; Harris, Irina M; Harris, Justin A Abstract: Participants in two experiments performed two simultaneous tasks: one, a dual-target detection task within a rapid sequence of target and distractor letters; the other, a cued reaction time task requiring participants to make a cued left/right response immediately after each letter sequence. Under these rapid visual presentation conditions, it is usually difficult to identify the second target when it is presented in close temporal proximity of the first target, a phenomenon known as the attentional blink. However, here, participants showed an advantage for detecting a target presented during the attentional blink if that target predicted which response cue would appear at the end of the trial. Participants also showed faster reaction times on trials with a predictive target. Both of these effects were independent of conscious knowledge of the target-response contingencies assessed by post-experiment questionnaires. The results suggest that implicit learning of the association between a predictive target and its outcome can automatically facilitate target recognition during the attentional blink, and therefore shed new light on the relationship between associative learning and attentional mechanisms. Thu, 01 Jan 2009 00:00:00 GMT http://hdl.handle.net/2123/7869 2009-01-01T00:00:00Z http://hdl.handle.net/2123/7868 Title: Tracking a single fast-moving object exhausts attentional resources Authors: Holcombe, Alex; Chen, Wei-Ying Abstract: Driving on a busy road, eluding a group of predators, or playing a team sport involves keeping track of multiple moving objects. In typical laboratory tasks, the number of visual targets that humans can track is about four. Three types of theories have been advanced to explain this limit. The fixed-limit theory posits a set number of attentional pointers available to follow objects. Spatial interference theory proposes that when targets are near each other, their attentional spotlights mutually interfere. Resource theory asserts that a limited resource is divided among targets, and performance reflects the amount available per target. Utilising widely separated objects to avoid spatial interference, the present experiments validated the predictions of resource theory. The fastest target speed at which two targets could be tracked was much slower than the fastest speed at which one target could be tracked. This speed limit for tracking two targets was approximately that predicted if at high speeds, only a single target could be tracked. This result cannot be accommodated by the fixed-limit or interference theories. Evidently a fast target, if it moves fast enough, can exhaust attentional resources. Description: NOTICE: this is the author’s version of a work that was accepted for publication in Cognition. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Mon, 31 Oct 2011 00:00:00 GMT http://hdl.handle.net/2123/7868 2011-10-31T00:00:00Z http://hdl.handle.net/2123/7865 Title: Power and Responsibility: The Mekong River Commission and Lower Mekong mainstream dams Authors: Lee, Gary; Scurrah, Natalia Abstract: The revival of plans to build up to 11 hydropower dams on the Lower Mekong mainstream focuses attention on the Mekong River Commission (MRC), an international river basin organisation assigned with the task of ensuring the sustainable use and management of water and related resources of the Lower Mekong Basin. Although questions regarding MRC’s role have been posed since its inception, the proposed mainstream dams signal an especially critical time for MRC. How MRC addresses key concerns and balances different interests in the basin will have signifi cant bearing on MRC’s perceived relevance to its member states, donors and the people of the basin. This report focuses on two aspects of MRC’s structure and activities in relation to mainstream dams: its governance role and its role as a knowledge-based organisation. In regard to governance, MRC asserts that it is an intergovernmental organisation, not a supranational one and, as such, its role is primarily to serve its member states. This position calls for a better understanding of MRC power and responsibilities, and whose interests the MRC serves. MRC’s governance structure has implications for a river basin organisation that portrays itself as an independent producer of knowledge and science. There are many areas of knowledge in which MRC can use its science to help manage and develop the river more equitably and sustainably. This report reviews MRC’s fi sheries research and modelling of development scenarios and examines how MRC acts on its knowledge base to infl uence planning and decision making on mainstream dams. The final section examines the responsiveness of MRC to the wider basin community and the opportunities and challenges arising from its recent efforts to engage various stakeholders more actively. Drawing heavily on MRC’s own research and statements, this report seeks to inform and open discussions regarding MRC’s role in relation to the proposed lower mainstream dams. Thu, 01 Oct 2009 00:00:00 GMT http://hdl.handle.net/2123/7865 2009-10-01T00:00:00Z http://hdl.handle.net/2123/7859 Title: Comparing learned predictiveness effects within and across compound discriminations Authors: Livesey, Evan J; Thorwart, Anna; De Fina, Nicole L; Harris, Justin A Abstract: In four human learning experiments, we examined the extent to which learned predictiveness depends upon direct comparison between relatively good and poor predictors. Participants initially solved (1) linear compound discriminations in which one or both of the stimuli in each compound were predictive of the correct outcome, (2) biconditional discriminations where only the configurations of the stimuli were predictive of the correct outcome, or (3) pseudo-discriminations in which no stimulus features were predictive. In each experiment, subsequent learning and test stages were used to assay changes in the associability of each stimulus brought about by its role in the initial discriminations. Although learned predictiveness effects were observed in all experiments (i.e. previously predictive cues were more readily associated with a new outcome than previously non-predictive cues), the same changes in associability were observed regardless of whether the stimulus was initially learned about in the presence of an equally predictive, more predictive, or less predictive stimulus. The results suggest that learned associability is not controlled by competitive allocation of attention, but rather by the absolute predictiveness of each individual cue. Sat, 01 Oct 2011 00:00:00 GMT http://hdl.handle.net/2123/7859 2011-10-01T00:00:00Z http://hdl.handle.net/2123/7857 Title: Response Rate and Reinforcement Rate in Pavlovian Conditioning Authors: Harris, Justin A Abstract: Four experiments used delay conditioning of magazine approach in rats to investigate the relationship between the rate of responding, R, to a conditioned stimulus (CS) and the rate, r, at which the CS is reinforced with the unconditioned stimulus (US). Rats were concurrently trained with four variable-duration CSs with different rs, either as a result of differences in the mean CS-US interval or in the proportion of CS presentations that ended with the US. In each case, R was systematically related to r, and the relationship was very accurately characterized by a hyperbolic function, R = Ar/(r+c). Accordingly, the reciprocal of these two variables – response interval, I (=1/R), and CS-US interval, i (=1/r) – were related by a simple affine (straight line) transformation, I = mi+b. This latter relationship shows that each increment in the time that the rats had to wait for food produced a linear increment in the time they waited between magazine entries. We discuss the close agreement between our findings and the Matching Law (Herrnstein, 1970), and consider their implications for both associative theories (e.g., Rescorla & Wagner, 1972) and non-associative theories (Gallistel & Gibbon, 2000) of conditioning. Sat, 01 Oct 2011 00:00:00 GMT http://hdl.handle.net/2123/7857 2011-10-01T00:00:00Z http://hdl.handle.net/2123/7856 Title: Summation of reinforcement rates when conditioned stimuli are presented in compound Authors: Andrew, Benjamin J; Harris, Justin Abstract: Three experiments used delay conditioning of magazine approach in rats to examine the summation of responding when two conditioned stimuli (CSs) are presented together as a compound. The duration of each CS varied randomly from trial-to-trial around a mean that differed between the CSs. This meant that the rats’ response rate to each CS was systematically related to the reinforcement rate of that CS, but remained steady as time elapsed during the CS (Harris & Carpenter, in press; Harris, Gharaei, & Pincham, in press). When the rats were presented with a compound of two CSs that had been conditioned separately, they responded more during the compound than during either of the CSs individually. More significantly, however, in all three experiments, the rats responded to the compound at the same rate as they responded to a third CS that had been reinforced at a rate equal to the sum of the reinforcement rates of the two CSs in compound. We discuss the implications of this finding for associative models (e.g., Rescorla & Wagner, 1972) and rate-based models (Gallistel & Gibbon, 2000) of conditioning. Sat, 01 Oct 2011 00:00:00 GMT http://hdl.handle.net/2123/7856 2011-10-01T00:00:00Z http://hdl.handle.net/2123/7796 Title: Elemental Representations of Stimuli in Associative Learning Authors: Harris, Justin A Abstract: This paper reviews evidence and theories concerning the nature of stimulus representations in Pavlovian conditioning. It focuses on the elemental approach developed in Stimulus Sampling Theory (Atkinson & Estes, 1963; Bush & Mosteller, 1951b) and extended by McLaren and Mackintosh (2000; 2002), and contrasts this with models that that invoke notions of configural representations that uniquely code for different patterns of stimulus inputs (e.g., Pearce, 1987, 1994; Rescorla & Wagner, 1972; Wagner & Brandon, 2001). The paper then presents a new elemental model that emphasizes interactions between stimulus elements. This model is shown to explain a range of behavioral findings, including those (e.g., negative patterning and biconditional discriminations) traditionally thought beyond the explanatory capabilities of elemental models. Moreover, the model offers a ready explanation for recent findings reported by Rescorla (2000; 2001; 2002b) concerning the way that stimuli with different conditioning histories acquire associative strength when conditioned in compound Sun, 01 Jan 2006 00:00:00 GMT http://hdl.handle.net/2123/7796 2006-01-01T00:00:00Z http://hdl.handle.net/2123/7793 Title: The arguments of associations Authors: Harris, Justin A Abstract: This chapter considers associative solutions to “non‐linear” discrimination problems, such as negative patterning (A+ and B+ vs AB‐) and the biconditional discrimination (AB+ and CD+ vs AC‐ and BD‐). It is commonly assumed that the solution to these discriminations requires “configural” elements that are added to the compound of two stimuli. However, these discriminations can be solved by assuming that some elements of each stimulus are suppressed when two stimuli are presented in compound. Each of these approaches can solve patterning and biconditional discriminations because they allow some elements, as the arguments of associations, to have differential “presence” on reinforced versus nonreinforced trials, and thus differential associability and control over responding. The chapter then presents a more specific version of one of these models, describing how interactions between stimuli, particularly the competition for attention, provide a mechanism whereby some elements are more suppressed than others when stimuli are presented simultaneously as a compound. Fri, 01 Jan 2010 00:00:00 GMT http://hdl.handle.net/2123/7793 2010-01-01T00:00:00Z http://hdl.handle.net/2123/7792 Title: Increasing the frequency of breakfast consumption Authors: Kothe, Emily J; Mullan, Barbara A Abstract: Purpose – A number of interventions aimed at increasing breakfast consumption have been designed and implemented in recent years. This paper seeks to review the current research in this area with the aim of identifying common features of successful interventions and strengths and weaknesses in the current research methodology. Design/methodology/approach – A systematic review of interventions aimed at increasing breakfast-eating frequency in a non-clinical sample was conducted. Findings – A total of 11 interventions were identified and reviewed; of these, only three resulted in an increase in breakfast consumption at follow-up. The three studies that were successful in changing breakfast consumption all included a psychosocial component that was successful in increasing positive attitudes towards nutrition in the intervention protocol. Many of the breakfast-eating interventions included in this review have methodological weaknesses, including difficulties in implementing interventions, small sample sizes, and selection biases, which future researchers should consider when designing and evaluating their own interventions. Research limitations/implications – These findings highlight the importance of including psychosocial components in interventions designed to increase breakfast consumption, while also signalling issues that should be addressed when designing and reporting future interventions. Originality/value – This review was the first to investigate the efficacy of interventions aimed at increasing breakfast consumption. The identification of weaknesses in the current body of research, and of successful and unsuccessful intervention practices is an important step in developing successful interventions in the future. Sat, 01 Jan 2011 00:00:00 GMT http://hdl.handle.net/2123/7792 2011-01-01T00:00:00Z http://hdl.handle.net/2123/7791 Title: An attention modulated associative network. Authors: Harris, Justin A; Livesey, Evan J Abstract: We present an elemental model of associative learning that describes interactions between stimulus elements as a process of competitive normalization. Building on the assumptions laid out in Harris (2006), stimuli are represented as an array of elements that compete for attention according to the strength of their input. Elements form associations among each other according to temporal correlations in their activation but restricted by their connectivity. The model moves beyond its predecessor by specifying excitatory, inhibitory, and attention processes for each element in real time and describing their interaction as a form of suppressive gain control. Attention is formalized in this model as a network of mutually inhibitory units that moderate the activation of stimulus elements by controlling the level to which the elements are suppressed by their own inhibitory processes. The model is applied to a range of complex discriminations and related phenomena that have been taken as evidence for configural-learning processes. Fri, 01 Jan 2010 00:00:00 GMT http://hdl.handle.net/2123/7791 2010-01-01T00:00:00Z http://hdl.handle.net/2123/7782 Title: The acquisition of conditioned responding Authors: Harris, Justin A Abstract: This report analyzes the acquisition of conditioned responses in rats trained in a magazine approach paradigm. Following the suggestion by Gallistel, Fairhurst and Balsam (2004), Weibull functions were fitted to the trial-by-trial response rates of individual rats. These showed that the emergence of responding was often delayed, after which the response rate would increase relatively gradually across trials. The fit of the Weibull function to the behavioral data of each rat was equaled by that of a cumulative exponential function incorporating a response threshold. Thus the growth in conditioning strength on each trial can be modeled by the derivative of the exponential – a difference term of the form used in many models of associative learning (e.g., Rescorla & Wagner, 1972). Further analyses, comparing the acquisition of responding to a continuously reinforced stimulus (CRf) and a partially reinforced stimulus (PRf), provided further evidence in support of the difference term. In conclusion, the results are consistent with conventional models that describe learning as the growth of associative strength, incremented on each trial by an error-correction process. Sat, 01 Jan 2011 00:00:00 GMT http://hdl.handle.net/2123/7782 2011-01-01T00:00:00Z http://hdl.handle.net/2123/7781 Title: Response rates track the history of reinforcement times Authors: Harris, Justin A; Gharaei, Saba; Pincham, Hannah L Abstract: When conditioning involves a consistent temporal relationship between the conditioned stimulus (CS) and unconditioned stimulus (US), the expression of conditioned responses within a trial peaks at the usual time of the US relative to the CS. Here we examine the temporal profile of responses during conditioning with variable CS-US intervals. We conditioned stimuli with either uniformly distributed or exponentially distributed random CS-US intervals. In the former case, the frequency of each CS-US interval within a specified range is uniform but the momentary probability of the US (the hazard function) increases as time elapses during the trial; with the latter distribution, short CS-US intervals are more frequent than longer intervals, but the momentary probability of the US is constant across time within the trial. We report that, in a magazine approach paradigm, rats’ response rates remained stable as time elapses during the CS when the CS-US intervals were uniformly distributed, whereas their response rates declined when the CS-US intervals were exponentially distributed. In other words, the profile of responding during the CS matched the frequency distribution of the US times, not the momentary probability of the US during the CS. These results are inconsistent with real-time associative models, which predict that associative strength tracks the momentary probability of the US, but may provide support for timing models of conditioning in which conditioned responding is tied to remembered times of reinforcement. Sat, 01 Jan 2011 00:00:00 GMT http://hdl.handle.net/2123/7781 2011-01-01T00:00:00Z http://hdl.handle.net/2123/7721 Title: Seeing slow and seeing fast: Two limits on perception Authors: Holcombe, Alex Abstract: Video cameras have a single temporal limit set by the frame rate. The human visual system has multiple temporal limits set by its various constituent mechanisms. These limits appear to form two groups. A fast group comprises specialized mechanisms for extracting perceptual qualities such as motion direction, depth, and edges. The second group, with coarse temporal resolution, includes judgments of the pairing of color and motion, the joint identification of arbitrary spatially separated features, the recognition of words, and high-level motion. These temporally coarse percepts may all be mediated by high-level processes. Working at very different timescales, the two groups of mechanisms collaborate to create our unified visual experience. Thu, 01 Jan 2009 00:00:00 GMT http://hdl.handle.net/2123/7721 2009-01-01T00:00:00Z http://hdl.handle.net/2123/7281 Title: program code for "Perceiving spatial relations via attentional tracking and shifting" Authors: Holcombe, Alex; Linares, Daniel; Vaziri-Pashkam, Maryam Abstract: Program code for software associated with "Perceiving spatial relations via attentional tracking and shifting" article by Holcombe, Linares, & Vaziri-Pashkam Thu, 28 Apr 2011 00:00:00 GMT http://hdl.handle.net/2123/7281 2011-04-28T00:00:00Z http://hdl.handle.net/2123/7216 Title: The Return of Vitalism: Authors: Wolfe, Charles T. Abstract: The eminent French biologist and historian of biology, François Jacob, once notoriously declared "On n‘interroge plus la vie dans les laboratoires": laboratory research no longer inquires into the notion of Life‘. Nowadays, as David Hull puts it, "both scientists and philosophers take ontological reduction for granted… Organisms are ‗nothing but‘ atoms, and that is that." In the mid-twentieth century, from the immediate post-war period to the late 1960s, French philosophers of science such as Georges Canguilhem, Raymond Ruyer and Gilbert Simondon returned to Jacob‘s statement with an odd kind of pathos: they were determined to reverse course. Not by imposing a different kind of research program in laboratories, but by an unusual combination of historical and philosophical inquiry into the foundations of the life sciences (particularly medicine, physiology and the cluster of activities that were termed 'biology' in the early 1800s). Even in as straightforwardly scholarly a work as La formation du concept de réflexe aux XVIIe et XVIIIe siècles (1955), Canguilhem speaks oddly of "defending vitalist biology," and declares that Life cannot be grasped by logic (or at least, "la vie déconcerte la logique"). Was all this historical and philosophical work merely a reassertion of 'mysterian‘, magical vitalism? In order to answer this question we need to achieve some perspective on Canguilhem‘s 'vitalism‘, notably with respect to its philosophical influences such as Kurt Goldstein. Fri, 04 Mar 2011 00:00:00 GMT http://hdl.handle.net/2123/7216 2011-03-04T00:00:00Z