Associative strength and semantic activation in the mental lexicon: evidence from continued word associations

Associative strength and semantic activation in the mental lexicon: evidence from continued word associations Simon De Deyne (simon.dedeyne@ppw.kuleuven.be) a , b Daniel J. Navarro (daniel.navarro@adelaide.edu.au) b Gert Storms (gert.storms@ppw.kuleuven.be) a a University of Leuven, Department of Psychology, Tiensestraat 102, 3000 Leuven, Belgium b University of Adelaide, School of Psychology, 5005 Adelaide, Australia Abstract ity of recall in cued-recall tasks (Nelson, Zhang, & McK- inney, 2001), reaction times in lexical decision (De Deyne, Navarro, & Storms, 2012) and generation frequencies in flu- ency tasks (Griffiths, Steyvers, & Tenenbaum, 2007). More- over, the overlap of the distributions of these strengths for two words indicates how semantically related they are and this is the basis of the success of lexico-semantic models such as Latent Semantic Analysis (LSA, Landauer & Dumais, 1997) and topic models (Griffiths et al., 2007). In a word association task, the probability of producing a cer- tain response to a cue is considered to be a direct measure of associative strength between words in the mental lexicon. The common single word association procedure is limited, since the number of words connected to a cue might be underesti- mated when a single response is asked. The continued asso- ciation task overcomes this limitation by asking a person to generate multiple associative responses. To test whether con- tinued strengths allow a better approximation of our lexicon, an experiment was conducted in which participants judged the associative strength between words. Our results show that in contrast to other semantic tasks, con- tinued strength predicts weak to moderate judgments only. Two explanations based on the sampling of information and differential semantic activation of later responses in continued association are proposed. Theoretical implications for seman- tic activation and methodological implications for derivation of strength are discussed. Keywords: associative strength, semantic relatedness; word associations. The free word association task has been used extensively to investigate processes and structure in semantic and episodic memory. The task is attractive because it is unconstrained and straightforward, and no apriori restrictions are formulated about what types of relationships between words are deemed relevant. It leads to a rich and varied source of information. Compared to constrained tasks such as feature generation, it tends to provide more thematic relations like DOCTOR - NURSE . There is increasing agreement that this thematic in- formation determines much of how natural language concepts are used both in daily life and in language phenomena studied in the lab including semantic priming, metaphor comprehen- sion, categorization and induction (e.g. Lin & Murphy, 2001; Wisniewski & Bassok, 1999). An influential metaphor for the representation of this knowledge presents the mental lexicon as a weighted graph, where the structure of the links between the nodes (words) determines how words relate to each other and get their mean- ing. Obviously, the value of such a representation hinges on how the words are connected and on what determines the strength of these connections. The key assumption under- lying the word association task, is that the number of peo- ple that generate a specific response to a cue is an indica- tion of the strength between cue and response. Approximat- ing the relations in the lexicon through word associations ex- plains numerous phenomena: facilitation of word process- ing in associative priming (Hutchison, 2003), the probabil- Associative strength is central to how we process the mean- ing of words, but the traditional way of measuring it, through asking a participant a single word association, is not with- out limitations. The response frequencies from the single word association task are considered reliable only for the very strong associates, since weaker responses are often missing (Nelson, McEvoy, & Dennis, 2000). This lack of weak asso- ciations is seen as a general drawback of the word association procedure (Aitchison, 2003, p. 101) and has been responsi- ble for questioning the results of previous findings in numer- ous tasks such as mediated priming (e.g., Chwilla, Kolk, & Mulder, 2000). Presumably, this reflects dominance effects where for a cue like UMBRELLA a single strong associate such as RAIN accounts for almost all responses (Nelson & Bajo, 1985). While the exact causes of dominance effects are not well understood, it is obvious that they make the response distributions overly sparse, and bias all kinds of association derived strength measures. Recently, a large-scale continued word association database was completed involving over 70,000 participants and 3 million responses (De Deyne, Navarro, & Storms, 2012). In contrast to previous studies, a continued word asso- ciation task was used in which subjects were presented a short list of stimulus or cue words and asked to give three different responses to each of these cues. The goal of the present study is to investigate how word association frequencies in contin- ued tasks map onto associative strength. If single word as- sociations tend to underestimate or be unreliable for weaker responses, then we would expect that using information en- coded in later responses might alleviate this problem. This would support previous findings where semantic relatedness derived from continued association norms results in a bet- ter predictor of semantic tasks including pair-wise similarity judgments (De Deyne, Peirsman, & Storms, 2009), prototypi- cality judgments (De Deyne, Voorspoels, Verheyen, Navarro,