Influence of world knowledge and context on the comprehension of natural language translation of logical formulas

In this paper we present an approach to conditional reasoning tasks based on two main ideas. The first idea is that, in contrast with what is usually assumed, an ‘if… then…’ sentence is not an adequate translation in natural language of a logical formula containing a material implication as its principal operator. The second idea is that when subjects are required to check the validity of a sentence in a task, their inferences are not driven uniquely by the content of the sentence, but also by other information embedded in the task scenario and, eventually, by their knowledge about the topic (i.e. information stored in memory). Data from 30 subjects tested on six different tasks are reported as evidence for our approach. The results show that conditional tasks are significantly more complex only when they are presented with ‘if… then…’ sentences and when the subject cannot rely on any extra information, such as contextual information or knowledge about the topic.