Phonological activation of non-produced words. The dynamics of lexical access in speech production

Abstract

Speaking can be considered a goal-directed behavior because speakers have to retrieve the appropriate words and phonemes from their mental lexicon. However, observational and experimental evidence suggests that during the lexical and phonological retrieval processes other words than the intended ones are activated to some degree. Under this scenario, it is necessary to postulate selection mechanisms in charge of determining, among the activated representations, which ones will be prioritized and further processed in order to finally utter the speech signal. How does the control mechanism work that allows speakers to focus on the appropriate set of representations and reject the non-appropriate ones?

It is generally agreed that the most relevant parameter that guides word and phoneme selection is the level of activation of the corresponding representations, in the sense that the most activated representations at a specific moment will be the ones selected. In addition, theories of speech production agree that the selection mechanisms also take into account the activation level of other non-target representations, in the sense that the selection of one representation is more difficult the more activated other competing representations are. According to these two assumptions, the selection of a word would depend on two parameters: a) the amount of activation that this word receives from the conceptual system and b) the level of activation of other representations at the moment of selection. In order to have a clear understanding of the mechanisms that speakers employ to decide which representations to select, we first need to specify under which circumstances this selection mechanism takes place. In particular, this dissertation tries to describe the pattern of activation during lexical access. Specifically, which words and phonemes are activated during the lexicalization process of the intended concept? This is an important issue because the types of processes in charge of encoding/selecting information at each level of the system may differ depending on what other information is available at a particular moment. For instance, the selection of the word ‘car’ and its corresponding phonemes may depend on whether other words and phonemes are also activated or not.

The main purpose of this dissertation is to explore whether concepts outside of the communicative goal of the speaker are nevertheless activated in the process of language production. We assess whether there is lexical and phonological activation of these concepts. We take an experimental approach and measure speakers’ performance in different naming contexts. In particular, participants were instructed to name target stimuli while ignoring the presentation of distractor pictures. The semantic and phonological manipulations between target and distractor names allowed us to analyze whether participants have lexicalized the distractor picture and to what degree.

In the next chapter we introduce the functional architecture of the speech production system. In the first section we describe the architecture of the system and then we focus on describing how information is propagated between the different levels of the system. This is the main topic of the dissertation and in the rest of the chapter we introduce three theoretical proposals about the propagation of the information and also some experimental evidence. Chapter three contains the main aim and specific objectives of the thesis. Chapters four, five, six and seven contain the experimental part. Finally, in chapters eight and nine we discuss the theoretical implications that follow from our experiments.

Hablar es, sin duda alguna, una de las capacidades más asombrosas que los seres humanos adquieren. Una de las cuestiones que más interesa a los psicólogos que estudian la producción oral del lenguaje es la descripción de los procesos y mecanismos mediante los cuales el hablante recupera las palabras de su memoria. La presente tesis está relacionada con esta cuestión.

La producción del habla implica el acceso a representaciones léxicas y fonológicas muy concretas. Evidencia observacionale y experimental sugiere que durante el acceso léxico y fonológico otras palabras pueden estar activadas y llegar incluso a interferir. Por lo tanto, parece necesario postular un mecanismo que permita al hablante acceder a las palabras adecuadas y rechazar aquellas que, pese a no formar parte de la intención comunicativa, hayan podido ser activadas. Los modelos de producción coinciden en postular que el parámetro que guía la selección léxica y fonológica es el nivel de activación de las representaciones, en el sentido de que la representación más activada en un determinado momento es la que finalmente resulta seleccionada. Los modelos también consideran que esta selección depende del nivel de activación de otras representaciones, en el sentido de que resulta más difícil seleccionar una representación cuanto más activadas están otras representaciones ajenas a la intención comunicativa.

Esta tesis describe las circunstancias en las que se produce la selección léxica y la recuperación fonológica durante la producción del habla. Concretamente, ¿qué palabras y fonemas están activados durante el proceso de lexicalización del mensaje comunicativo? En la tesis analizamos si conceptos que no forman parte del mensaje preverbal del hablante llegan a activar sus correspondientes representaciones léxicas y fonológicas. En los experimentos de esta tesis, los participantes nombran un estímulo a la vez que ignoran la presencia de dibujos distractores. La manipulación de la relación semántica y fonológica entre el nombre del estímulo y el distractor permite analizar hasta qué punto se ha lexicalizado el dibujo distractor.