Fig. 1: Overview of stimuli and task.

a Design of the stimuli. The 64 pictures used in any given participant were orthogonally split into 32 drawings and 32 photographs, out of which 16 were animate and 16 inanimate objects, respectively. Each object could thus be classified along a perceptual (photo/drawing, blue) or conceptual (animate-inanimate, red) dimension. b One prototypical task block of the paradigm within the repeated retrieval/restudy group. Both groups performed eight blocks, each starting with the encoding of eight novel verb-object associations. After a 20 s distractor task, each of the eight associations was practiced twice in each of the three practice cycles, once with a conceptual, once with a perceptual question, and reaction times (RTs) were measured on each of the overall six practice trials. The maximum response time in each practice cycle of the restudy group was set to the average response time of the corresponding cycle in the retrieval group. After 48 h, participants returned to complete a final test, where again each association was tested once with each of the two question types, with RTs being recorded, as indicated by the button press symbols. Finally, a written cued recall test was performed. Stimuli depicted are chosen from the BOSS database (https://sites.google.com/site/bosstimuli/home⁵⁹, https://creativecommons.org/licenses/by-sa/3.0/) and customized with free and open source GNU image manipulation software (www.gimp.org; see Linde-Domingo et al.²⁵).