A category-order effect? Sub-categorical properties of stimuli determine a categorical effect
The category-order effect (COE) is observed when the categorical properties of items within the first half of a given list affect recall performance in an immediate serial-recall task. The present study examines whether this recall advantage is a consequence of categorical properties (e.g., semantic-relatedness and category set-size) or whether the advantage is due to sub-categorical properties (e.g., orthographic similarity and word frequency). Participants were presented with numeric stimuli and nouns from a variety of semantic categories while their orthography (Experiment 1) and frequency (Experiment 2) were systematically manipulated. The results suggest that a large portion of the COE can be attributed to a reduction of the detection threshold associated with the sub-categorical properties of the items.