Topics are concrete and the organization of the text is very clear and simple 

Definition of simple text 

Text with a simple text structure would be easy to recall, so the signaling devices would present little effects in improving the free recall. 

University of Michigan - Ann Arbor

1. Meyer’s experiments tested the overall recall 
2. Text is too short and has a relatively simple structure 

Flaws of the experiments 

Lorch, R. F., Lorch, E. P., &amp; Inman, W. E. (1993). Effects of signaling topic structure on text recall. Journal of Educational Psychology, 85(2), 281–290. https://doi.org/10.1037/0022-0663.85.2.281 

Effects of Signaling Topic Structure on Text Recall

Signaling devices could undermine the recall of topics unrelated to the sigaling devices. So testing on the overall recall would not be accurate. 

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