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Profile: Niki Pfeifer (Ludwig Maximilians Universität, München)
  1. Niki Pfeifer & Katrin Pfeifer, Severe Storm Reports of the 17th Century: Examples From the UK and France.
    In this work we survey reports on selected severe storms of the 17th century. Specifically, we investigate a severe storm which was accompanied by a ball lightning phenomenon in Cornwall (UK) in 1640. The “fiery Ball”, which reportedly made a “ter[r]ible sound”, entered the church, broke stones and smashed windows. It made holes in stone walls and injured about 14 people. Furthermore, we report on a 1672 storm in Bedford (UK) that tore down houses, blew down stone walls and uprooted (...)
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  2. Niki Pfeifer & Gernot D. Kleiter, Syllogistic Reasoning with Intermediate Quantifiers.
    n S are P ”) is proposed for evaluating the rationality of human syllogistic reasoning. Some relations between intermediate quantifiers and probabilistic interpretations are discussed. The paper concludes by the generalization of the atmosphere, matching and conversion hypothesis to syllogisms with intermediate quanti- fiers. Since our experiments are currently still running, most of the paper is theoretical and intended to stimulate psychological studies.
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  3. Niki Pfeifer (2013). Reasoning About Uncertain Conditionals. Studia Logica:1-18.
    There is a long tradition in formal epistemology and in the psychology of reasoning to investigate indicative conditionals. In psychology, the propositional calculus was taken for granted to be the normative standard of reference. Experimental tasks, evaluation of the participants’ responses and psychological model building, were inspired by the semantics of the material conditional. Recent empirical work on indicative conditionals focuses on uncertainty. Consequently, the normative standard of reference has changed. I argue why neither logic nor standard probability theory provide (...)
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  4. Niki Pfeifer (2013). The New Psychology of Reasoning: A Mental Probability Logical Perspective. Thinking and Reasoning 19 (3-4):329-345.
  5. Niki Pfeifer & Igor Douven (2013). Formal Epistemology and the New Paradigm Psychology of Reasoning. Review of Philosophy and Psychology:1-23.
    This position paper advocates combining formal epistemology and the new paradigm psychology of reasoning in the studies of conditionals and reasoning with uncertainty. The new paradigm psychology of reasoning is characterized by the use of probability theory as a rationality framework instead of classical logic, used by more traditional approaches to the psychology of reasoning. This paper presents a new interdisciplinary research program which involves both formal and experimental work. To illustrate the program, the paper discusses recent work on the (...)
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  6. Niki Pfeifer (2012). Experiments on Aristotle's Thesis: Towards an Experimental Philosophy of Conditionals. The Monist 95 (2):223-240.
    Two experiments (N1 = 141, N2 = 40) investigate two versions of Aristotle’s Thesis for the first time. Aristotle’s Thesis is a negated conditional, which consists of one propositional variable with a negation either in the antecedent (version 1) or in the consequent (version 2). This task allows to infer if people interpret indicative conditionals as material conditionals or as conditional events. In the first experiment I investigate between-participants the two versions of Aristotle’s Thesis crossed with abstract versus concrete task (...)
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  7. A. J. B. Fugard, Niki Pfeifer & B. Mayerhofer (2011). Probabilistic Theories of Reasoning Need Pragmatics Too: Modulating Relevance in Uncertain Conditionals. Journal of Pragmatics 43:2034–2042.
    According to probabilistic theories of reasoning in psychology, people's degree of belief in an indicative conditional `if A, then B' is given by the conditional probability, P(B|A). The role of language pragmatics is relatively unexplored in the new probabilistic paradigm. We investigated how consequent relevance a ects participants' degrees of belief in conditionals about a randomly chosen card. The set of events referred to by the consequent was either a strict superset or a strict subset of the set of events referred (...)
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  8. A. J. B. Fugard, Niki Pfeifer, B. Mayerhofer & G. D. Kleiter (2011). How People Interpret Conditionals: Shifts Towards the Conditional Event. Journal of Experimental Psychology 37 (3):635-648.
    We investigated how people interpret conditionals and how stable their interpretation is over a long series of trials. Participants were shown the colored patterns on each side of a six-sided die, and were asked how sure they were that a conditional holds of the side landing upwards when the die is randomly thrown. Participants were presented with 71 trials consisting of all combinations of binary dimensions of shape (e.g., circles and squares) and color (e.g., blue and red) painted onto the (...)
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  9. A. J. B. Fugard, Niki Pfeifer, B. Mayerhofer & Gernot D. Kleiter (2011). How People Interpret Conditionals: Shifts Towards the Conditional Event. Journal of Experimental Psychology 37 (3):635-648.
    We investigated how people interpret conditionals and how stable their interpretation is over a long series of trials. Participants were shown the colored patterns on each side of a six-sided die, and were asked how sure they were that a conditional holds of the side landing upwards when the die is randomly thrown. Participants were presented with 71 trials consisting of all combinations of binary dimensions of shape (e.g., circles and squares) and color (e.g., blue and red) painted onto the (...)
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  10. Niki Pfeifer (2011). Systematic Rationality Norms Provide Research Roadmaps and Clarity. Behavioral and Brain Sciences 34 (5):263-264.
    Normative theories like probability logic provide roadmaps for psychological investigations. They make theorizing precise. Therefore, normative considerations should not be subtracted from psychological research. I explain why conditional elimination inferences involve at least two norm paradigms; why reporting agreement with rationality norms is informative; why alleged asymmetric relations between formal and psychological theories are symmetric; and I discuss the arbitration problem.
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  11. Niki Pfeifer & G. D. Kleiter (2011). Uncertain Deductive Reasoning. In K. Manktelow, D. E. Over & S. Elqayam (eds.), The Science of Reason: A Festschrift for Jonathan St B.T. Evans. Psychology Press. 145--166.
    Probabilistic models have started to replace classical logic as the standard reference paradigm in human deductive reasoning. Mental probability logic emphasizes general principles where human reasoning deviates from classical logic, but agrees with a probabilistic approach (like nonmonotonicity or the conditional event interpretation of conditionals). -/- This contribution consists of two parts. In the first part we discuss general features of reasoning systems including consequence relations, how uncertainty may enter argument forms, probability intervals, and probabilistic informativeness. These concepts are of (...)
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  12. Niki Pfeifer & G. D. Kleiter (2010). The Conditional in Mental Probability Logic. In M. Oaksford & N. Chater (eds.), Cognition and Conditionals: Probability and Logic in Human Thought. Oxford University Press. 153--173.
    The present chapter describes a probabilistic framework of human reasoning. It is based on probability logic. While there are several approaches to probability logic, we adopt the coherence based approach.
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  13. A. J. B. Fugard, Niki Pfeifer, B. Mayerhofer & G. D. Kleiter (2009). How People Interpret an Uncertain If. In T. Kroupa & J. Vejnarova (eds.), Proceedings of the 8th Workshop on Uncertainty Processing. 80-91.
    Conditionals are central to inference. Before people can draw inferences about a natural language conditional, they must interpret its meaning. We investigated interpretation of uncertain conditionals using a probabilistic truth table task, focussing on (i) conditional event, (ii) material conditional, and (iii) conjunction interpretations. The order of object (shape) and feature (color) in each conditional's antecedent and consequent was varied between participants. The conditional event was the dominant interpretation, followed by conjunction, and took longer to process than conjunction (mean di erence (...)
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  14. Andrew Jb Fugard, Niki Pfeifer, Bastian Mayerhofer & Gernot D. Kleiter (2009). How People Interpret an Uncertain If. In T. Kroupa & J. Vejnarova (eds.), Proceedings of the 8th Workshop on Uncertainty Processing.
  15. Niki Pfeifer & G. D. Kleiter (2009). Framing Human Inference by Coherence Based Probability Logic. Journal of Applied Logic 7 (2):206--217.
  16. Niki Pfeifer & Gernot D. Kleiter (2009). Mental Probability Logic. Behavioral and Brain Sciences 32 (1):98-99.
    We discuss O&C's probabilistic approach from a probability logical point of view. Specifically, we comment on subjective probability, the indispensability of logic, the Ramsey test, the consequence relation, human nonmonotonic reasoning, intervals, generalized quantifiers, and rational analysis.
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  17. Niki Pfeifer (2008). A Probability Logical Interpretation of Fallacies. In G. Kreuzbauer, N. Gratzl & E. Hiebl (eds.), Rhetorische Wissenschaft: Rede Und Argumentation in Theorie Und Praxis. Lit. 225--244.
    This chapter presents a probability logical approach to fallacies. A special interpretation of (subjective) probability is used, which is based on coherence. Coherence provides not only a foundation of probability theory, but also a normative standard of reference for distinguishing fallacious from non-fallacious arguments. The violation of coherence is sufficient for an argument to be fallacious. The inherent uncertainty of everyday life argumentation is captured by attaching degrees of belief to the premises. Probability logic analyzes the structure of the argument (...)
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  18. Niki Pfeifer (2007). Rational Argumentation Under Uncertainty. In G. Kreuzbauer, N. Gratzl & E. Hiebl (eds.), Persuasion Und Wissenschaft: Aktuelle Fragestellungen von Rhetorik Und Argumentationstheorie. Lit. 181--191.
    Common sense arguments are practically always about incomplete and uncertain information. We distinguish two aspects or kinds of uncertainty. The one is defined as a persons’ uncertainty about the truth of a sentence. The other uncertainty is defined as a persons’ uncertainty of his assessment of the truth of a sentence. In everyday life argumentation we are often faced with both kinds of uncertainty which should be distinguished to avoid misunderstandings among discussants. The paper presents a probabilistic account of both (...)
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  19. Niki Pfeifer & G. D. Kleiter (2007). Human Reasoning with Imprecise Probabilities: Modus Ponens and Denying the Antecedent. In Proceedings of the 5 T H International Symposium on Imprecise Probability: Theories and Applications. 347--356.
    The modus ponens (A -> B, A :. B) is, along with modus tollens and the two logically not valid counterparts denying the antecedent (A -> B, ¬A :. ¬B) and affirming the consequent, the argument form that was most often investigated in the psychology of human reasoning. The present contribution reports the results of three experiments on the probabilistic versions of modus ponens and denying the antecedent. In probability logic these arguments lead to conclusions with imprecise probabilities. In the (...)
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  20. Niki Pfeifer (2006). Contemporary Syllogistics: Comparative and Quantitative Syllogisms. In G. Kreuzbauer & G. J. W. Dorn (eds.), Argumentation in Theorie Und Praxis: Philosophie Und Didaktik des Argumentierens. Lit. 57--71.
    Traditionally, syllogisms are arguments with two premises and one conclusion which are constructed by propositions of the form “All… are…” and “At least one… is…” and their respective negated versions. Unfortunately, the practical use of traditional syllogisms is quite restricted. On the one hand, the “All…” propositions are too strict, since a single counterexample suffices for falsification. On the other hand, the “At least one …” propositions are too weak, since a single example suffices for verification. The present contribution studies (...)
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  21. Niki Pfeifer (2006). On Mental Probability Logic. Dissertation, Department of Psychology
    Mental probability logic is a psychological competence theory about how humans interpret and reason about common-sense conditionals. Probability logic is proposed as an appropriate standard of reference for evaluating the rationality of human inferences. Common-sense conditionals are interpreted as “high” conditional probabilities, P(B|A) > .5. Probability logical accounts of nonmonotonic reasoning and inference rules like the modus ponens are explored. Categorical syllogisms with comparative and quantitative quantifiers are investigated. A series of eight experiments on human probabilistic reasoning in the framework (...)
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  22. Niki Pfeifer & G. D. Kleiter (2006). Is Human Reasoning About Nonmonotonic Conditionals Probabilistically Coherent? In Proceedings of the 7 T H Workshop on Uncertainty Processing. 138--150.
    Nonmonotonic conditionals (A |∼ B) are formalizations of common sense expressions of the form “if A, normally B”. The nonmonotonic conditional is interpreted by a “high” coherent conditional probability, P(B|A) > .5. Two important properties are closely related to the nonmonotonic conditional: First, A |∼ B allows for exceptions. Second, the rules of the nonmonotonic system p guiding A |∼ B allow for withdrawing conclusions in the light of new premises. This study reports a series of three experiments on reasoning (...)
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  23. Niki Pfeifer & G. D. Kleiter (2006). Inference in Conditional Probability Logic. Kybernetika 42 (2):391--404.
    An important field of probability logic is the investigation of inference rules that propagate point probabilities or, more generally, interval probabilities from premises to conclusions. Conditional probability logic (CPL) interprets the common sense expressions of the form “if . . . , then . . . ” by conditional probabilities and not by the probability of the material implication. An inference rule is probabilistically informative if the coherent probability interval of its conclusion is not necessarily equal to the unit interval (...)
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  24. Niki Pfeifer & G. D. Kleiter (2006). Towards a Probability Logic Based on Statistical Reasoning. In Proceedings of the 11th IPMU Conference (Information Processing and Management of Uncertainty in Knowledge-Based Systems. 9.
    Logical argument forms are investigated by second order probability density functions. When the premises are expressed by beta distributions, the conclusions usually are mixtures of beta distributions. If the shape parameters of the distributions are assumed to be additive (natural sampling), then the lower and upper bounds of the mixing distributions (Polya-Eggenberger distributions) are parallel to the corresponding lower and upper probabilities in conditional probability logic.
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  25. Niki Pfeifer & G. D. Kleiter (2006). Proceedings of the 7 T H Workshop on Uncertainty Processing.
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  26. Niki Pfeifer & G. D. Kleiter (2005). Towards a Mental Probability Logic. Psychologica Belgica 45 (1):71--99.
    We propose probability logic as an appropriate standard of reference for evaluating human inferences. Probability logical accounts of nonmonotonic reasoning with system p, and conditional syllogisms (modus ponens, etc.) are explored. Furthermore, we present categorical syllogisms with intermediate quantifiers, like the “most . . . ” quantifier. While most of the paper is theoretical and intended to stimulate psychological studies, we summarize our empirical studies on human nonmonotonic reasoning.
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  27. Niki Pfeifer & Gernot D. Kleiter (2005). Coherence and Nonmonotonicity in Human Reasoning. Synthese 146 (1-2):93 - 109.
    Nonmonotonic reasoning is often claimed to mimic human common sense reasoning. Only a few studies, though, have investigated this claim empirically. We report four experiments which investigate three rules of SYSTEMP, namely the AND, the LEFT LOGICAL EQUIVALENCE, and the OR rule. The actual inferences of the subjects are compared with the coherent normative upper and lower probability bounds derived from a non-infinitesimal probability semantics of SYSTEM P. We found a relatively good agreement of human reasoning and principles of nonmonotonic (...)
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  28. Niki Pfeifer & G. D. Kleiter (2003). Nonmonotonicity and Human Probabilistic Reasoning. In Proceedings of the 6 T H Workshop on Uncertainty Processing. 221--234.
    Nonmonotonic logics allow—contrary to classical (monotone) logics— for withdrawing conclusions in the light of new evidence. Nonmonotonic reasoning is often claimed to mimic human common sense reasoning. Only a few studies, though, have investigated this claim empirically. system p is a central, broadly accepted nonmonotonic reasoning system that proposes basic rationality postulates. We previously investigated empirically a probabilistic interpretation of three selected rules of system p. We found a relatively good agreement of human reasoning and principles of nonmonotonic reasoning according (...)
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  29. Niki Pfeifer & G. D. Kleiter (2003). Proceedings of the 6 T H Workshop on Uncertainty Processing.
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  30. Niki Pfeifer & G. D. Kleiter (2002). Experiments on Nonmonotonic Reasoning. The Coherence of Human Probability Judgments. In H. Leitgeb & G. Schurz (eds.), Pre-Proceedings of the 1 s T Salzburg Workshop on Paradigms of Cognition.
    Nonmonotonic reasoning is often claimed to mimic human common sense reasoning. Only a few studies, though, investigated this claim empirically. In the present paper four psychological experiments are reported, that investigate three rules of system p, namely the and, the left logical equivalence, and the or rule. The actual inferences of the subjects are compared with the coherent normative upper and lower probability bounds derived from a non-infinitesimal probability semantics of system p. We found a relatively good agreement of human (...)
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