What Phonological Facilitation Tells about Semantic Interference: A Dual-Task Study

Abstract

Despite increasing interest in the topic, the extent to which linguistic processing demands attentional resources remains poorly understood. We report an empirical re-examination of claims about lexical processing made on the basis of the picture-word interference task when merged in a dual-task psychological refractory period (PRP) paradigm. Two experiments were conducted in which participants were presented with a tone followed, at varying stimulus onset asynchronies (SOAs), by a picture-word stimulus. In Experiment 1, the phonological relatedness between pictures and words was manipulated. Begin- and end-related words decreased picture naming latencies relative to unrelated words. This effect was additive with SOA effects. In Experiment 2, both the semantic and the phonological relatedness between pictures and words were manipulated. Replicating Experiment 1, effects arising from the phonological manipulation were additive with SOA effects on picture naming latencies. In contrast, effects arising from the semantic manipulation were under additive with SOA effects on picture naming latencies, that is, semantic interference decreased as SOA was decreased. Such contrastive pattern suggests that semantic and phonological effects on picture naming latencies are characterized by distinguishable sources, the former prior to the PRP bottleneck and the latter at the PRP bottleneck or after. The present findings are discussed in relation to current models of language production.

Keywords: dual-task; language production; phonological facilitation; picture–word interference; semantic interference.

Figure 1

(A) Gant diagrams illustrating the account of the under additivity between SOA and semantic effects (shaded box labeled S) proposed by Dell'Acqua et al. (2007a). (B) Gant diagrams illustrating the account of the additivity between SOA and phonological effects (shaded box labeled P) and the under additivity between SOA and semantic effects (shaded box labeled S) proposed in the present study. In the boxes, PE, perceptual encoding; RE, response execution. Numbers in the boxes are mapped to task order (1: Task1, S1 = tone, R1 = manual; 2: Task2, S2 = picture and word superimposed, R2 = vocal response).

Figure 2

Left panel: Results of the semantically related manipulation reported in Dell'Acqua et al. (2007a). Center Panel: Results for the begin-related phonological manipulation in Experiment 1. Mean reaction times, plotted separately for tone discrimination (RT1) and picture naming latencies (RT2), as a function of phonological relatedness, and SOA. PR = picture and word phonologically related; PU = picture and word phonologically unrelated. Right panel: Results for the end-related phonological manipulation in Experiment 1. Numerical values indicate the magnitudes of the semantic interference effect obtained in Dell'Acqua et al. (; left panel) and of the phonological facilitation effects obtained in Experiment 1 (center and right panels).

Figure 3

Mean reaction times in Experiment 2, plotted separately for tone discrimination (RT1) and picture naming latencies (RT2), as a function of distractor relatedness, and SOA. PR = picture and word phonologically related; SR = picture and word semantically unrelated; P-SU = picture and word phonologically and semantically unrelated. Numerical values indicate the magnitude of the semantic interference effect (positive values) and of the phonological facilitation effect (negative values).