Academic journal article Memory & Cognition

Accessing Causal Relations in Semantic Memory

Academic journal article Memory & Cognition

Accessing Causal Relations in Semantic Memory

Article excerpt

Most studies investigating semantic memory have focused on taxonomic or associative relations. Little is known about how other relations, such as causal relations, are represented and accessed. In three experiments, we presented participants with pairs of words one after another, describing events that referred to either a cause (e.g., spark) or an effect (e.g., fire). We manipulated the temporal order of word presentation and the question participants had to respond to. The results revealed that questions referring to the existence of a causal relation are answered faster when the first word refers to a cause and the second word refers to its effect than vice versa. However, no such asymmetry was observed with questions referring to the associative relation. People appear to distinguish the roles of cause and effect when queried specifically about a causal relation, but not when the same information is evaluated for the presence of an associative relation.

Semantic memory is regarded as the long-term repertoire of our world knowledge (Tulving, 1972). Without world knowledge, we would be incapable of understanding the world around us and hence unable to communicate or to act in the service of goals (Hodges & Patterson, 1997). Semantic memory contains knowledge about categories and features that we use to represent the world, as well as knowledge about relations between categories and features (see Murphy & Medin, 1985). The great majority of this work has focused on either taxonomic relations (e.g., verifying category statements, such as "A robin is a bird") or general associative relations (e.g., priming a lexical decision about doctor by first presenting an associate such as hospital). Yet although taxonomic and associative relations are certainly important for understanding cognition, other types such as temporal, functional, and causal relations are also highly relevant for planning, predicting, acting, and reasoning. Research on categorization has focused increased attention on causal relations (e.g., lien & Cheng, 2000; Murphy, 2002; Murphy & Medin, 1985; Rehder, 2003; Waldmann, 1996; Waldmann, Holyoak, & Fratianne, 1995); nonetheless, few studies have addressed the question of how causal and similar functional relations are stored and accessed in semantic memory (but see Krüger, Nuthmann, & van der Meer, 2001 ; Moss, Ostrin, Tyler, & Marslen-Wilson, 1995; Tyler & Moss, 1997; van der Meer, Beyer, Heinze, & Badel, 2002).

The existence of multiple relations within semantic memory raises a particularly interesting question that has been neglected by theories of semantic knowledge: Assuming that different types of relational knowledge are relevant in different contexts, how are specific relations accessed within a network that contains many different kind of relations? The main goal of our study was to address this question by focusing on a particularly important class of relations, those that are causal in nature.

Causal Relations

The nature of causality has long been a hotly debated topic in philosophy. However, one aspect of causal relations seems undisputed: They are asymmetric (Hausman, 1998; Pearl, 2000; Waldmann, 1996). Causes temporally precede and generate effects in the world. For example, smoking causes lung cancer but lung cancer does not cause smoking.

There has been sharp disagreement among psychologists as to whether this asymmetry is mirrored in human cognitive representations. Some researchers in the area of learning have claimed that causal asymmetry is not a feature that is represented when people learn about causal relations (Cobos, López, Cano, Almaraz, & Shanks, 2002; Shanks & López, 1996). According to this associative view, learning leads to knowledge about the associative strength between cues and outcomes. Although associative relations are also asymmetric, being directed from cues to outcomes, this asymmetry is dependent on the temporal assignment of learning events to the roles of cues and outcomes, and not on causal asymmetry. …

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