Up, down, and all around? Deciphering the boundary conditions for training-induced transfer effects within a set of hierarchically nested tasks.

Convergent evidence suggests that the transfer effects engendered by training studies are tied to specific task features. The present study examined transfer in a set of three hierarchically nested change-detection tasks (CDTs) using a tightly controlled adaptive training paradigm. These CDT paradigms all required participants to remember arrays of stimuli, and then report the change (in colour, orientation or both) of a probed item. The three tasks were identical except for the response judgement requirements: colour, orientation or dual (both colour and orientation). We also included a retro-cue - a spatial cue within the retention period - allowing us to test whether training impacts the allocation of attention during maintenance. Each training group made significantly greater on-task gains relative to the active control group (digit-span training). Between-task transfer patterns were present but limited and largely feature-specific. Training gains on the orientation task did not transfer to the colour variant and vice versa; in fact, there was some evidence of negative transfer. However, those trained on the colour variant did show benefits to both variants within the dual-task context. The dual-CDT trainees also showed transfer to the simple orientation and colour variants. Finally, we found no compelling evidence to distinguish whether training gains and transfer effects are due to improved capacity or the improved precision with which representations are held. In short, participants learn to better represent and report specific features, but it is not clear if this is driven by changes in capacity or precision.