Table 1.

Cost measures derived from the reference-back task.

Measure	Derivation	Interpretation
Updating	Difference between no-switch/reference and no-switch/comparison trials	Cost of updating WM
Comparison	Difference between no-switch/same (probe-referent match) and no-switch/different (probe-referent mismatch) trials	Cost of a mismatch between the probe stimulus and the WM referent
Switching	Difference between switch and no-switch trials	Cost of switching between WM modes
Gate opening	Difference between reference/switch and reference/no-switch trials	Cost specific to opening the gate to WM
Gate closing	Difference between comparison/switch and comparison/no-switch trials	Cost specific to closing the gate to WM
Substitution	Interaction of updating and comparison factors; difference between the cost of updating a new/mismatching item into WM and the cost of responding to a mismatching item without updating; (reference/different − reference/same) − (comparison/different − comparison/same)	Cost of updating a new item into WM