Marius usher
Tel Aviv University, School of Psychological Sciences, Faculty Member
- I am Professor of Psychology at the Tel-Aviv University (School of Psychology and Sagol School of Neuroscience) and ... moreI am Professor of Psychology at the Tel-Aviv University (School of Psychology and Sagol School of Neuroscience) and a researcher in the field of cognitive neuroscience. My research interests are: decision-making and numerical processing (the algorithm the mind/brain uses to generate preferences and make decisionsedit
Research Interests: Psychology, Cognitive Science, Philosophy, Metaphysics, Philosophy of Mind, and 15 moreEpistemology, Philosophy of Science, Consciousness, Physicalism, Functionalism, Recurrent Neural Network, Phenomenal Consciousness, Theories of Consciousness, Behaviorism, Recurrence, Philosophy of mind Free will and Consciousness, Philsophy of Science, Integrated Information Theory, Artificial Consciousness, and Electromagnetic theories of consciousness
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We show that our item-based model, competitive guided search, accounts for the empirical patterns that Hulleman & Olivers (H&O) invoke against item-based models, and we highlight recently reported diagnostic data that challenge their... more
We show that our item-based model, competitive guided search, accounts for the empirical patterns that Hulleman & Olivers (H&O) invoke against item-based models, and we highlight recently reported diagnostic data that challenge their approach. We advise against “forsaking the item” unless and until a full fixation-based model is shown to be superior to extant item-based models.
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ABSTRACTDecisions do not occur in isolation, but are embedded in sequences of other decisions, often pertaining to the same source of evidence. Here, we characterized the impact of intermittent choices on the accumulation of a protracted... more
ABSTRACTDecisions do not occur in isolation, but are embedded in sequences of other decisions, often pertaining to the same source of evidence. Here, we characterized the impact of intermittent choices on the accumulation of a protracted stream of decision-relevant evidence towards a final decision. Human participants performed two versions, based on perceptual or numerical evidence, of a decision task that required two successive judgments at different times during the evidence stream: an intermittent response consisting of a binary choice, and a continuous estimation at the end of the evidence stream. In a control condition, subjects executed a choice-independent motor response instead of binary choice as the intermittent response. In both, perceptual and numerical tasks, the intermittent choice reduced the sensitivity of subsequent evidence, and flipped the relative temporal weighting of early and late evidence in the final estimation judgment. The individual extent of the choice...
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Although ageing is known to affect memory, the precise nature of its effect on retrieval and encoding processes is not well understood. Here, we examine the effect of ageing on the free recall of word lists, in which the semantic... more
Although ageing is known to affect memory, the precise nature of its effect on retrieval and encoding processes is not well understood. Here, we examine the effect of ageing on the free recall of word lists, in which the semantic structure of word sequences was manipulated from unrelated words to pairs of associated words with various separations (between pair members) within the sequence. We find that ageing is associated with reduced total recall, especially for sequences with associated words. Furthermore, we find that the degree of semantic clustering (controlled for chance clustering) shows an age effect and that it interacts with the distance between the words within a pair. The results are consistent with the view that age effects in memory are mediated both by retrieval and by encoding processes associated with frontal control and working memory.
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Research Interests: Rationality and Axiom
Recent research has established that humans can extract the average perceptual feature over briefly presented arrays of visual elements or the average of a rapid temporal sequence of numbers. Here we compared the extraction of the average... more
Recent research has established that humans can extract the average perceptual feature over briefly presented arrays of visual elements or the average of a rapid temporal sequence of numbers. Here we compared the extraction of the average over briefly presented arrays, for a perceptual feature (orientations) and for numerical values (1–9 digits), using an identical experimental design for the two tasks. We hypothesized that the averaging of numbers, more than of orientations, would be constrained by capacity limitations. Arrays of Gabor elements or digits were simultaneously presented for 300 ms and observers were required to estimate the average on a continuous response scale. In each trial the elements were sampled from normal distributions (of various means) and we varied the set size (4–12). We found that while for orientation the averaging precision remained constant with set size, for numbers it decreased with set size. Using computational modeling we also extracted capacity parameters (the number of elements that are pooled in the average extraction). Despite marked heterogeneity between observers, the capacity for orientations (around eight items) was much larger than for numbers (around four items). The orientation task also had a larger fraction of participants relying on distributed attention to all elements. Our study thus supports the idea that numbers more than perceptual features are subject to capacity or attentional limitations when observers need to evaluate the average over an ensemble of stimuli.
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Research Interests: Compromise and Preference
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We study an Attractor Neural Network that stores natural concepts, organized in semantic classes. The concepts are related by both semantic and episodic associations. When neurons characterized by large synaptic connectivity are deleted,... more
We study an Attractor Neural Network that stores natural concepts, organized in semantic classes. The concepts are related by both semantic and episodic associations. When neurons characterized by large synaptic connectivity are deleted, semantic transitions among concepts decay before the episodic ones, in accordance with the findings in patients with Alzheimer’s disease.
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1. Excel Files "experiment*.xlsx" files contain raw data. In 'Notes' an explanation of the relevant variables is offered "Parameters.xlsx" file contains the best-fitting parameters of the selective integration... more
1. Excel Files "experiment*.xlsx" files contain raw data. In 'Notes' an explanation of the relevant variables is offered "Parameters.xlsx" file contains the best-fitting parameters of the selective integration model (the version that omits early noise). Each tab corresponds to a different experiment. 2. Matlab files Matlab files in the 'code' file allow one to reproduce simulation results in fig1b, fig3b and fig3d. The 'selective_sim.m' file offers a basic simulation of the selective integration model. For questions and further requests please contact Konstantinos Tsetsos: k.tsetsos62@gmail.com
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Traditional models of decision making under uncertainty explain human behavior in simple situations with a minimal set of alternatives and attributes. Some of them, such as prospect theory, have been proven successful and robust in such... more
Traditional models of decision making under uncertainty explain human behavior in simple situations with a minimal set of alternatives and attributes. Some of them, such as prospect theory, have been proven successful and robust in such simple situations. Yet, less is known about the preference formation during decision making in more complex cases. Furthermore, it is generally accepted that attention plays a role in the decision process but most theories make simplifying assumptions about where attention is deployed. In this study, we replace these assumptions by measuring where humans deploy overt attention, i.e. where they fixate. To assess the influence of task complexity, participants perform two tasks. The simpler of the two requires participants to choose between two alternatives with two attributes each (four items to consider). The more complex one requires a choice between four alternatives with four attributes each (16 items to consider). We then compare a large set of mo...
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In this paper, we revisit the debate surrounding the Unfolding Argument (UA) against causal structure theories of consciousness (as well as the hard-criteria research program it prescribes), using it as a platform for discussing... more
In this paper, we revisit the debate surrounding the Unfolding Argument (UA)
against causal structure theories of consciousness (as well as the hard-criteria research program it prescribes), using it as a platform for discussing theoretical and methodological issues in consciousness research. Causal structure theories assert that consciousness depends on a particular causal structure of the brain. Our claim is that some of the assumptions fueling the UA are not warranted, and therefore we should reject the methodology for consciousness science that the UA prescribes. First, we briefly survey the most popular philosophical positions in consciousness science, namely physicalism and functionalism. We discuss the relations between these positions and the behaviorist methodology that the UA assumptions express, despite the contrary claim of its proponents. Second, we argue that the same reasoning that the UA applies against causal structure theories can be applied to functionalist approaches, thus proving too much and deeming as unscientific a whole range of (non-causal structure) theories. Since this is overly restrictive and fits poorly with common practice in cognitive neuroscience, we suggest that the reasoning of the UA must be flawed. Third, we assess its philosophical assumptions, which express a restrictive methodology, and conclude that there are reasons to reject them. Finally, we propose a more inclusive methodology for consciousness science, that includes neural, behavioral, and phenomenological evidence (provided by the first-person perspective) without which consciousness science could not even start. Then, we extend this discussion to the scope of consciousness science, and conclude that theories of consciousness should be tested and evaluated on humans, and not on systems considerably different from us. Rather than restricting the methodology of consciousness science, we should, at this point, restrict the range of systems upon which it is supposed to be built.
against causal structure theories of consciousness (as well as the hard-criteria research program it prescribes), using it as a platform for discussing theoretical and methodological issues in consciousness research. Causal structure theories assert that consciousness depends on a particular causal structure of the brain. Our claim is that some of the assumptions fueling the UA are not warranted, and therefore we should reject the methodology for consciousness science that the UA prescribes. First, we briefly survey the most popular philosophical positions in consciousness science, namely physicalism and functionalism. We discuss the relations between these positions and the behaviorist methodology that the UA assumptions express, despite the contrary claim of its proponents. Second, we argue that the same reasoning that the UA applies against causal structure theories can be applied to functionalist approaches, thus proving too much and deeming as unscientific a whole range of (non-causal structure) theories. Since this is overly restrictive and fits poorly with common practice in cognitive neuroscience, we suggest that the reasoning of the UA must be flawed. Third, we assess its philosophical assumptions, which express a restrictive methodology, and conclude that there are reasons to reject them. Finally, we propose a more inclusive methodology for consciousness science, that includes neural, behavioral, and phenomenological evidence (provided by the first-person perspective) without which consciousness science could not even start. Then, we extend this discussion to the scope of consciousness science, and conclude that theories of consciousness should be tested and evaluated on humans, and not on systems considerably different from us. Rather than restricting the methodology of consciousness science, we should, at this point, restrict the range of systems upon which it is supposed to be built.
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Evidence integration is a normative algorithm for choosing between alternatives with noisy evidence. It has been successful in accounting for vast amounts of behavioural and neural data. However, this mechanism has been challenged by... more
Evidence integration is a normative algorithm for choosing between alternatives with noisy evidence. It has been successful in accounting for vast amounts of behavioural and neural data. However, this mechanism has been challenged by non-integration heuristics, and tracking decision boundaries has proven elusive. Here we first show that the decision boundary can be monitored using a model-free behavioural method termed decision classification boundary, which extracts decision boundaries by optimizing choice classification based on the accumulated evidence. Using this method, we provide direct support for evidence integration over non-integration heuristics, show that the decision boundaries collapse across time and identify an integration bias whereby incoming evidence is modulated based on its consistency with preceding information. This consistency bias, which is a form of pre-decision confirmation bias, was supported in four cross-domain experiments, showing that choice accuracy and decision confidence are modulated by stimulus consistency. Strikingly, despite its seeming sub-optimality, the consistency bias fosters performance by enhancing robustness to integration noise.
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Page 1. Semantic Clustering in Free Recall: Evidence for a Semantic Buffer? Eddy J. Davelaar (e.davelaar@psychology.bbk.ac.uk) Marius Usher (m.usher@psychology.bbk.ac.uk) School of Psychology, Birkbeck College, Malet Street, WC1E 7HX,... more
Page 1. Semantic Clustering in Free Recall: Evidence for a Semantic Buffer? Eddy J. Davelaar (e.davelaar@psychology.bbk.ac.uk) Marius Usher (m.usher@psychology.bbk.ac.uk) School of Psychology, Birkbeck College, Malet Street, WC1E 7HX, London, UK ...
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Individual differences in cognitive processing have been the subject of intensive research. One important type of such individual differences is the tendency for global versus local processing, which was shown to correlate with a wide... more
Individual differences in cognitive processing have been the subject of intensive research. One important type of such individual differences is the tendency for global versus local processing, which was shown to correlate with a wide range of processing differences in fields such as decision making, social judgments and creativity. Yet, whether these global/local processing tendencies are correlated within a subject across different domains is still an open question. To address this question, we develop and test a novel method to quantify global/local processing tendencies, in which we directly set in opposition the local and global information instead of instructing subjects to specifically attend to one processing level. We apply our novel method to two different domains: (1) a numerical cognition task, and (2) a preference task. Using computational modeling, we accounted for classical effects in choice and numerical-cognition. Global/local tendencies in both tasks were quantifie...
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Individual differences in cognitive processing have been the subject of intensive research. An important type of such individual differences is the tendency for global vs. local processing, which was shown to correlate with a wide range... more
Individual differences in cognitive processing have been the subject of intensive research. An important type of such individual differences is the tendency for global vs. local processing, which was shown to correlate with a wide range of processing differences in fields such as decision making, social judgments and creativity. Yet, whether these global/local processing tendencies are correlated within a subject across different domains is still an open question. To address this question, we develop and test a novel method to quantify global/local processing tendencies, in which we directly set in opposition the local and global information instead of instructing subjects to specifically attend to one processing level. We apply our novel method to two different domains: i) a numerical cognition task, and ii) a preference task. Using computational models, we accounted for classical effects in choice and numerical-cognition. Global/local tendencies in both tasks were quantified using...
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A considerable body of evidence recently gathered testifies to the possible role of synaptic deletion and compensation in the pathogenesis of Alzheimer's desease. These processes are examined in the framework of a recurrent neural... more
A considerable body of evidence recently gathered testifies to the possible role of synaptic deletion and compensation in the pathogenesis of Alzheimer's desease. These processes are examined in the framework of a recurrent neural network. The model is solved analytically. By the implications of the model different compensation strategies occurring in AD patients are discussed.
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We investigate a model for neural activity in the primary visual cortex. Cells are organized in a two-dimensional layer with an embedded orientation preference map and are modeled as leaky integrate-and-fire neurons. The connectivity... more
We investigate a model for neural activity in the primary visual cortex. Cells are organized in a two-dimensional layer with an embedded orientation preference map and are modeled as leaky integrate-and-fire neurons. The connectivity consists of local excitation, surround inhibition and long-range clustered connections, where the latter are only between cells with similar orientation preference. Due to the center-surround connectivity, the system generates irregular spike trains with broad inter-spike interval distribution as found in cortical data [Softky and Koch, 1993]. Neighboring cells show a large amount of synchronization while more distant cells show stimulus-dependent synchronization similar to that observed experimentally [Gray and Singer, 1989] the cross-correlation peaks are larger for cells stimulated with the same orientation (vs. different orientation) even if they don’t have the same orientation preference.
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At the core of the many debates throughout cognitive science concerning how decisions are made are the processes governing the time course of preference formation and decision. From perceptual choices, such as whether the signal on a... more
At the core of the many debates throughout cognitive science concerning how decisions are made are the processes governing the time course of preference formation and decision. From perceptual choices, such as whether the signal on a radar screen indicates an enemy missile or a spot on a CT scan indicates a tumor, to cognitive value-based decisions, such as selecting an agreeable flatmate or deciding the guilt of a defendant, significant and everyday decisions are dynamic over time. Phenomena such as decoy effects, preference reversals and order effects are still puzzling researchers. For example, in a legal context, jurors receive discrete pieces of evidence in sequence, and must integrate these pieces together to reach a singular verdict. From a standard Bayesian viewpoint the order in which people receive the evidence should not influence their final decision, and yet order effects seem a robust empirical phenomena in many decision contexts. Current research on how decisions unfold, especially in a dynamic environment, is advancing our theoretical understanding of decision making. This Research Topic aims to review and further explore the time course of a decision - from how prior beliefs are formed to how those beliefs are used and updated over time, towards the formation of preferences and choices and post-decision processes and effects. Research literatures encompassing varied approaches to the time-scale of decisions will be brought into scope: a) Speeded decisions (and post-decision processes) that require the accumulation of noisy and possibly non-stationary perceptual evidence (e.g., randomly moving dots stimuli), within a few seconds, with or without temporal uncertainty. b) Temporally-extended, value-based decisions that integrate feedback values (e.g., gambling machines) and internally-generated decision criteria (e.g., when one switches attention, selectively, between the various aspects of several choice alternatives). c) Temporally extended, belief-based decisions that build on the integration of evidence, which interacts with the decision maker's belief system, towards the updating of the beliefs and the formation of judgments and preferences (as in the legal context). Research that emphasizes theoretical concerns (including optimality analysis) and mechanisms underlying the decision process, both neural and cognitive, is presented, as well as research that combines experimental and computational levels of analysis
Research Interests: Psychology, Decision Making, Problem Solving, Belief, Bf, and 4 moreRc, Preference, Music Information Dynamics, and Q
Humans possess a remarkable ability to rapidly form coarse estimations of numerical averages. This ability is important for making decisions that are based on streams of numerical or value-based information, as well as for preference... more
Humans possess a remarkable ability to rapidly form coarse estimations of numerical averages. This ability is important for making decisions that are based on streams of numerical or value-based information, as well as for preference formation. Nonetheless, the mechanism underlying rapid approximate numerical averaging remains unknown, and several competing mechanism may account for it. Here, we tested the hypothesis that approximate numerical averaging relies on perceptual-like processes, instantiated by population coding. Participants were presented with rapid sequences of numerical values (four items per second) and were asked to convey the sequence average. We manipulated the sequences' length, variance, and mean magnitude and found that similar to perceptual averaging, the precision of the estimations improves with the length and deteriorates with (higher) variance or (higher) magnitude. To account for the results, we developed a biologically plausible population-coding mod...
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A model calculation is presented simulating the coordinated interaction between the walking legs of a multi-legged animal. The neural network consists of separate modules with oscillatory capabilities. It has the ability to adjust the... more
A model calculation is presented simulating the coordinated interaction between the walking legs of a multi-legged animal. The neural network consists of separate modules with oscillatory capabilities. It has the ability to adjust the necessary parameters for producing a coordinated interaction between the modules in a self-organizing fashion. Some sort of reinforcement comparison learning is used to train the network. It starts oscillations in a completely uncoupled state. After about 100 learning steps, the generation of a stable alternating pattern is usually terminated. Then, the network is able to maintain synchronization, even when disturbances are applied to single agents or to the network as a whole.
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We examine the ability of observers to extract summary statistics (such as the mean and the relative-variance) from rapid numerical sequences of two digit numbers presented at a rate of 4/s. In four experiments (total N = 100), we find... more
We examine the ability of observers to extract summary statistics (such as the mean and the relative-variance) from rapid numerical sequences of two digit numbers presented at a rate of 4/s. In four experiments (total N = 100), we find that the participants show a remarkable ability to extract such summary statistics and that their precision in the estimation of the sequence-mean improves with the sequence-length (subject to individual differences). Using model selection for individual participants we find that, when only the sequence-average is estimated, most participants rely on a holistic process of frequency based estimation with a minority who rely on a (rule-based and capacity limited) mid-range strategy. When both the sequence-average and the relative variance are estimated, about half of the participants rely on these two strategies. Importantly, the holistic strategy appears more efficient in terms of its precision. We discuss implications for the domains of two pathways n...