retrieval activates related words more than presentation retrieving information enhances learning more than restudying one explanation of this effect is based on the role of mediators eg sandcastle can be mediated by beach retrieval is hypothesised to activate mediators more than restudying but existing tests of this hypothesis have had mixed results carpenter s k 2011 semantic information activated during retrieval contributes to later retention support for the mediator effectiveness hypothesis of the testing effect journal of experimental psychology learning memory and cognition 376 15471552 doi 101037a0024140 lehman m karpicke j d 2016 elaborative retrieval do semantic mediators improve memory journal of experimental psychology learning memory and cognition 4210 15731591 doi 101037xlm0000267 the present experiments explored an explanation of the conflicting results testing whether mediator activation during a retrieval attempt depends on the accessibility of the target information a target was considered less versus more accessible when fewer versus more cues were given during retrieval practice experiments 1 and 2 when the target had been studied once versus three times initially experiment 3 or when the target could not be recalled versus could be recalled during retrieval practice experiments 13 a mini metaanalysis of all three experiments revealed a small effect such that retrieval activated mediators more than presentation but mediator activation was not reliably related to target accessibility thus retrieval may enhance learning by activating mediators in part but these results suggest the role of other processes too