Automatic semantic encoding in verbal short-term memory: Evidence from the concreteness effect

Abstract

The concreteness effect in verbal short-term memory (STM) tasks is assumed to be a consequence of semantic encoding in STM, with immediate recall of concrete words benefiting from richer semantic representations. We used the concreteness effect to test the hypothesis that semantic encoding in standard verbal STM tasks is a consequence of controlled, attention-demanding mechanisms of strategic semantic retrieval and encoding. Experiment 1 analysed the effect of presentation rate, with slow presentations being assumed to benefit strategic, time-dependent semantic encoding. Experiments 2 and 3 provided a more direct test of the strategic hypothesis by introducing three different concurrent attention-demanding tasks. Although Experiment 1 showed a larger concreteness effect with slow presentations, the following two experiments yielded strong evidence against the strategic hypothesis. Limiting available attention resources by concurrent tasks reduced global memory performance, but the concreteness effect was equivalent to that found in control conditions. We conclude that semantic effects in STM result from automatic semantic encoding and provide tentative explanations for the interaction between the concreteness effect and the presentation rate.

Keywords:

• Verbal short-term memory
• Concreteness effect
• Immediate serial recall
• Presentation rate
• Dual task paradigm

This study was supported by the Spanish Ministry of Science and Innovation [Projects PSI2009-07374 and CSD2008-00048].

Notes

1 In this and the following two experiments, we performed additional ANOVAs on the percentages of correct responses after including serial position as a within-subject factor. The standard serial position effect, consisting of better recall of the initial (primacy effect) and last (recency effect) items, was found in the three experiments. In Experiment 1, there was also a significant interaction between presentation rate and serial position, revealing that presentation rate had a greater effect on the recall of items presented in central positions. The three-way interaction between word type, presentation rate, and serial position was not significant. In Experiments 2 and 3, there was a significant interaction between concurrent task and serial position, which was a consequence of greater effect of the concurrent tasks for items presented in central serial positions. Importantly, however, the interaction between word type, concurrent task, and serial position was not significant in either experiment. For the sake of brevity, and given that these results do not contribute additional relevant information, they are not further discussed.