ON LEARNING FROM AMBIGUOUS INFORMATION

We investigate a variant of Probably Almost Correct learning model where the learner has to learn from ambiguous information. The ambiguity is introduced by assuming that the learner does not receive single instances with their correct labels as training data, but that the learner receives tuples of instances where a tuple has a negative label if all instances of the tuple should be labeled as negative and a tuple has a positive label if at least one instance of the tuple should be labeled as positive. Thus, a positive tuple is ambiguous since it is not known which of its instances is a positive instance. Such ambiguous information is, for example, relevant in learning problems for drug design. We present an improved algorithm for learning axis-parallel rectangles in this model of ambiguous information. In the drug design domain such rectangles represent the shapes of molecules with certain properties

Learning Under Ambiguity

This paper considers learning when the distinction between risk and ambiguity (Knightian uncertainty) matters. Working within the framework of recursive multiple-priors utility, the paper formulates a counterpart of the Bayesian model of learning about an uncertain parameter from conditionally i.i.d. signals. Ambiguous signals capture responses to information that cannot be captured by noisy signals. They induce nonmonotonic changes in agent confidence and prevent ambiguity from vanishing in the limit. In a dynamic portfolio choice model, learning about ambiguous returns leads to endogenous stock market participation costs that depend on past market performance. Hedging of ambiguity provides a new reason why the investment horizon matters for portfolio choice.ambiguity, learning, noisy signals, ambiguous signals, quality information, portfolio choice, portfolio diversification, Ellsberg Paradox

Imperfect Central Bank Communication: Information versus Distraction

Much of the information communicated by central banks is noisy or imperfect. This paper considers the potential benefits and limitations of central bank communications in a model of imperfect knowledge and learning. It is shown that the value of communicating imperfect information is ambiguous. If the public is able to assess accurately the quality of the imperfect information communicated by a central bank, such communication can inform and improve the public’s decisions and expectations. But if not, communicating imperfect communication has the potential to mislead and distract. The risk that imperfect communication may detract from the public’s understanding should be considered in the context of a central bank’s communications strategy. The risk of distraction means the central bank may prefer to focus its communication policies on the information it knows most about. Indeed, conveying more certain information may improve the public’s understanding to the extent that it "crowds out" a role for communicating imperfect information.Transparency, forecasts, learning

Opposite Influence of Perceptual Memory on Initial and Prolonged Perception of Sensory Ambiguity

Observers continually make unconscious inferences about the state of the world based on ambiguous sensory information. This process of perceptual decision-making may be optimized by learning from experience. We investigated the influence of previous perceptual experience on the interpretation of ambiguous visual information. Observers were pre-exposed to a perceptually stabilized sequence of an ambiguous structure-from-motion stimulus by means of intermittent presentation. At the subsequent re-appearance of the same ambiguous stimulus perception was initially biased toward the previously stabilized perceptual interpretation. However, prolonged viewing revealed a bias toward the alternative perceptual interpretation. The prevalence of the alternative percept during ongoing viewing was largely due to increased durations of this percept, as there was no reliable decrease in the durations of the pre-exposed percept. Moreover, the duration of the alternative percept was modulated by the specific characteristics of the pre-exposure, whereas the durations of the pre-exposed percept were not. The increase in duration of the alternative percept was larger when the pre-exposure had lasted longer and was larger after ambiguous pre-exposure than after unambiguous pre-exposure. Using a binocular rivalry stimulus we found analogous perceptual biases, while pre-exposure did not affect eye-bias. We conclude that previously perceived interpretations dominate at the onset of ambiguous sensory information, whereas alternative interpretations dominate prolonged viewing. Thus, at first instance ambiguous information seems to be judged using familiar percepts, while re-evaluation later on allows for alternative interpretations

Multi-stage Multi-recursive-input Fully Convolutional Networks for Neuronal Boundary Detection

In the field of connectomics, neuroscientists seek to identify cortical connectivity comprehensively. Neuronal boundary detection from the Electron Microscopy (EM) images is often done to assist the automatic reconstruction of neuronal circuit. But the segmentation of EM images is a challenging problem, as it requires the detector to be able to detect both filament-like thin and blob-like thick membrane, while suppressing the ambiguous intracellular structure. In this paper, we propose multi-stage multi-recursive-input fully convolutional networks to address this problem. The multiple recursive inputs for one stage, i.e., the multiple side outputs with different receptive field sizes learned from the lower stage, provide multi-scale contextual boundary information for the consecutive learning. This design is biologically-plausible, as it likes a human visual system to compare different possible segmentation solutions to address the ambiguous boundary issue. Our multi-stage networks are trained end-to-end. It achieves promising results on two public available EM segmentation datasets, the mouse piriform cortex dataset and the ISBI 2012 EM dataset.Comment: Accepted by ICCV201

The kindergarten-path effect revisited: children’s use of context in processing structural ambiguities

Research with adults has shown that ambiguous spoken sentences are resolved efficiently, exploiting multiple cues—including referential context—to select the intended meaning. Paradoxically, children appear to be insensitive to referential cues when resolving ambiguous sentences, relying instead on statistical properties intrinsic to the language such as verb biases. The possibility that children’s insensitivity to referential context may be an artifact of the experimental design used in previous work was explored with 60 4- to 11-year-olds. An act-out task was designed to discourage children from making incorrect pragmatic inferences and to prevent premature and ballistic responses by enforcing delayed actions. Performance on this task was compared directly with the standard act-out task used in previous studies. The results suggest that young children (5 years) do not use contextual information, even under conditions designed to maximize their use of such cues, but that adult-like processing is evident by approximately 8 years of age. These results support and extend previous findings by Trueswell and colleagues (Cognition (1999), Vol. 73, pp. 89–134) and are consistent with a constraint-based learning account of children’s linguistic development.</p

Evaluation on knowledge extraction and machine learning in resolving Malay word ambiguity

The involvement of linguistic professionals in resolving the ambiguity of a word within a particular context will produce a concise meaning of the words that are found in the lexical knowledge based collection. Motivated from that issue, we employed lexical knowledge and machine learning approach which includes the integration of data or/and information from the lexical knowledge based, that is Malay collections which linked to the ambiguous words. We used the most open class word and removed the stop words from the targeted sentences. Experiments have been conducted with and without lexical knowledge on 50 ambiguous words. The Word Sense Disambiguation (WSD) method is determined by machine learning, corpus based approaches namely Malay-Malay corpus and English-Malay corpus. The results show that the proposed method has improved the precision in resolving ambiguity.Keywords: ambiguity; lexical knowledge; machine learning; Malay wor