Conceptual Combination as Theory Formation

Conceptual Combination as Theory Formation Dietmar Janetzko dietmar@cognition.iig. uni-freiburg.de Institute of Computer Science and Social Research Center of Cognitive Science University of Freiburg i. Br. D-79098 Freiburg Abstract Conceptual combination is an instance of synthetic prob- lem solving comparable to design or planning. This work reviews evidence supporting the view that the result of such a synthesis has much in common with theory forma- tion. Similar to theory formation inference in conceptual combination can be modeled by using abduction as the principal mechanism to generate hypotheses. However, abduction in itself provides no answer to questions re- garding the explanation and selection of hypotheses. Re- sults of two experiments address these issues and provide converging evidence to the view that conceptual combi- nation is a form of theory formation. The results are interpreted within a framework of constraint satisfaction which is assumed to take place on a micro-level (com- pounding relations) and on a macro-level (principle of parsimony). Introduction What is the “glue” between words like house and boat that allows us to make sense out of the resulting concep- tual combination house boat ? There is a number of indi- cations suggesting that conceptual combination is an in- stance of synthetic problem solving (like design or plan- ning) that may be qualified as theory formation en minia- ture : First, most of the researchers in the field agree that conceptual combination can be best described in terms of knowledge structures, viz., two or more concepts that are reconstructed locally once they are involved in con- ceptual combination. Simple concepts in itself are often viewed as condensed theories (e.g., Murphy & Medin, 1985). Second, in many cases conceptual combinations can be paraphrased by a relative clause (e.g., a house boat is a boat that . ). In this way it becomes evident that conceptual combinations may add a more fine-grained conceptual schema to the conceptual classification sys- tem we already have. This is an example of taxonomy revision that is often related to theory formation (e.g., Shrager & Langley, 1990). Third, conceptual combi- nations provide support in description, explanation and prediction of phenomena, all of which are often taken to be the defining functions of theories (e.g., Brown & Ghiselli, 1955). The descriptive function is perhaps the most obvious one since conceptual combination is one of the major linguistic mechanisms for word formation (Olsen, 2000). The explanatory function is actually at the heart of conceptual combination: whenever we are con- fronted with a combination of concepts, we cannot but start searching for a coherent explanation that integrates the concepts usually by relation linking or carry over of an attribute. Finally, the predictive function is sup- ported by the fact that selective inheritance of attributes is made possible in conceptual combination (Hampton, 1987). Hence, new phenomena or artifacts are often la- beled by making use of it (Costello & Keane, 2000). While work in theory formation has traditionally focused on respectable scientific theories that have become hall- marks in the history of science, theory formation in con- ceptual combination is of a more mundane type. Usually, its basic function is to set up micro theories that help ex- plaining simple compounds like, e.g., turpentine jar and the phenomena they are referring to. However, there are striking parallels between both types of theory formation. Though most of the work on conceptual combination relies on comparable schemas of knowledge represen- tation, the procedural assumptions may differ consider- ably. Upon closer inspection it becomes evident that some of the variance in the field is due to the fact that dif- ferent problems of conceptual combination are focused. These aspects can be sorted by recasting them in terms of a model of theory formation. In so doing, constraint sat- isfaction needs to be recognized as a major aspect of pro- cessing in synthetic problem solving (Smith & Brown, 1993). As in many instances of synthetic problem solv- ing, in conceptual combination there is a huge number of possibilities to integrate entities (e.g., nouns). This is ev- idenced by the high number of interpretations obtained especially from novel compounds (Costello & Keane, However, many of the investigations of conceptual combination rely exclusively on interpretation and rat- ing tasks. These methods can only tap time-consuming processes. Clearly, we all know that conceptual com- bination can proceed both slowly and controlled. But there is also evidence from the few reaction time studies on conceptual combination that this process can also be very fast and and carried out automatically (e.g., Gagn´e & Shoben, 1997). The fact that processing of concep- tual combinations may be accomplished either very fast or slowly needs to be accounted for. For this reason, I will suggest a schema that addresses the issue of con- straint satisfaction in conceptual combination on two lev-