Not All Isolation Effects are Created Equally: Evidence for Greater Processing Requirements for Semantic vs. Physical Isolation Effects

Abstract

The finding that memory is better for an item that differs from the surrounding items is known as the von Restorff effect or isolation effect (von Restorff, 1933). Isolated items can differ physically (e.g., a different font) or semantically (e.g., a different category). Most theories argue that the effect requires effortful processing (e.g., Hunt & Lamb, 2001). However, there is evidence that some isolation effects can occur more automatically (e.g., Bireta & Mazzei, 2016). The current study examined the processing requirements for physical and semantic isolation effects by manipulating the processing at encoding (Exp. 1), presentation rate (Exp. 2), and presence of divided attention during recall (Exp. 3). Participants viewed lists of items with all similar items (control), one item from a different category (semantic), or one item in a different font color (physical) for immediate recall. Semantic isolation effects were eliminated with certain types of processing, speeded presentation, and divided attention. None of the manipulations eliminated the physical isolation effect. These results suggest that physical isolation effects occur relatively automatically, whereas semantic isolation effects require more effortful processing.