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Unless Reasoning

  • Juan A. García-Madruga (a1), Nuria Carriedo (a1), Sergio Moreno-Ríos (a2), Francisco Gutiérrez (a1) and Walter Schaeken (a3)...


We report the results of two experiments investigating conditional inferences from conditional unless assertions, such as Juan is not in León unless Nuria is in Madrid. Experiments 1 and 2 check Fillenbaum's hypothesis about the semantic similarity of unless with if not and only if assertions; both also examine inferential endorsements (Experiment 1) and endorsements and latencies (Experiment 2) of the four logically equivalent conditional formulations: if A then B, if not-B then not-A, A only if B and not-A unless B. The results of these experiments show the similarity of unless and only if, confirming that the representation of both conditionals from the outset probably include two possibilities directionally oriented from B to A; results also confirm the especial difficulty of unless assertions. The implications of the results are discussed in the context of recent psychological and linguistic theories of the meaning of unless.

Se presentan los resultados de dos experimentos que investigan las inferencias a partir de enunciados condicionales a menos que, tales como “Juan no está en León a menos que Nuria esté en Madrid”. Los experimentos 1 y 2 comprueban la hipótesis de Fillenbaum sobre la similaridad semántica de los enunciados a menos que con si no y sólo si; ambos experimentos examinan las respuestas inferenciales (Experimento 1) y las respuestas inferenciales y las latencias (Experimento 2) de las cuatro formulaciones condicionales lógicamente equivalentes: si A entonces B, si no-B entonces no-A, A sólo si B y no-A a menos que B. Los resultados muestran la similaridad de a menos que y sólo si, confirmando que la representación de ambos condicionales probablemente incluya desde el principio dos posibilidades orientadas direccionalmente desde B a A; los resultados también confirman la dificultad especial de las afirmaciones del tipo a menos que. Las implicaciones de los resultados se comentan en el contexto de las teorías psicológicas y lingüísticas sobre el significado de a menos que.


Corresponding author

Correspondence concerning this article should be addressed to Prof. Juan A. García-Madruga, Department of Developmental and Educational Psychology, UNED – 28040, Madrid, Spain. Phone: 913986259. FAX: 913987951. Email:


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Unless Reasoning

  • Juan A. García-Madruga (a1), Nuria Carriedo (a1), Sergio Moreno-Ríos (a2), Francisco Gutiérrez (a1) and Walter Schaeken (a3)...


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