Both of the datasets are from experiments where participants performed three different tasks on different trials within each block of trials. A cue word was shown on the screen to indicate which task should be performed on the current trial, then a target stimulus appeared that was a coloured outline of a shape, with two parallel straight lines extending between two opposite edges of the outline (e.g. from top to bottom, or from top-left to bottom-right). The index finger of the dominant hand rested on a central button between responses and moved to press the button to the left or right depending on which task had been cued and which target stimulus had been shown. The cue word "COLOUR" indicated that the colour of the shape should be responded to (blue and green with a leftward response; red and yellow for rightward response); the word "SHAPE" for the shape itself (square and triangle with a leftward response; circle and diamond with a rightward response); and the word "LINE" for the orientation of the line (slanted left and vertical with a leftward response; slanted right and horizontal with a rightward response). There were two types of trial. On "completed" trials, the task was performed as well as prepared: following cue-presentation, cue words were replaced by a target stimulus until a response was made. On "cue-only" trials, the trial could only be prepared but not performed: following cue-presentation, the cue simply disappeared with no target stimulus being shown. Following both types of trial there was then a 50ms blank screen until the next trial's cue was shown. Two experiments are included: fixed-CTI (cue-target interval) and varying-CTI. In the fixed-CTI experiment, cue words were presented for 1000ms; in the varying-CTI experiment, cue words were presented for either 300ms or 1000ms.This project investigates whether the so-called "n - 2 repetition cost" is evident following trials where the cued task was not performed. The n - 2 repetition cost has been proposed to index the effect of persisting inhibition of a recently switched-from task, or "backward inhibition". The experiments included here aimed to investigate whether there is evidence that backward inhibition can be generated by trials on which no target or response processing could occur.

The participants were primarily university students. They were tested in a laboratory, seated at a PC that displayed stimuli and collected response information. The duration of testing sessions was 45 minutes for the fixed-CTI experiment and 90 minutes for the varying-CTI experiment. In both experiments, cue-only and completed trials were intermixed, with around 28% trials being cue-only. Cue-only trials could not occur consecutively. In the fixed-CTI experiment, the practice blocks were as follows. The first three practice blocks constituted one 20-trial block for each of the three tasks; then there was a 20-trial block with all three tasks being randomly intermixed; and finally, there was a 50-trial block that also included cue-only trials. There were then 15 experimental blocks, with 50 trials in each, that were identical in nature to the final practice block. A break was given after each experimental block, during which the mean RT and total accuracy was shown for the preceding block. The varying-CTI experiment proceeded in a very similar way to the fixed-CTI block, except that there were 75 trials in each experimental block and 25 experimental blocks altogether.