Predictable Task Switching: Manipulations of Preparation Interval and Preparation-interval Variability, 2018-2020

When more than one task has to be performed within a block of trials, a cost of switching relative to repeating tasks (a “switch cost”) is usually seen following completed trials (i.e., trials where the task was executed). In studies where completed trials involve making a response such as a button press, and where tasks are sequenced predictably (in alternating runs), that switch cost has tended to be overcome with just one instance of task-execution. In Experiment 1, we wished to see whether a switch cost that was overcome after just one trial of a new task-run would also be present following other types of trial: i) completed trials involving a nogo response (i.e., where not pressing the button is the appropriate response, such as where the task rule requires that the button not be pressed for even numbers); ii) cue-only trials, where a task cue but no target is presented, such that the prepared task cannot be performed. This experiment involved a single cue-type (colour cues), a fixed preparation (cue-target) interval and a fixed trial length. Because there was no way of knowing that participants had prepared the cued task before target onset in that first experiment, we explored in Experiment 2 whether we could observe pre-target task preparation by manipulating the preparation interval. This experiment included only completed trials, and it manipulated cue-type (between blocks; verbal or image), preparation interval (within participants) and whether preparation interval was varied between blocks or between trials (between participants). In Experiment 3, we used the between-trials method of varying preparation interval and image cues from Experiment 2, and we re-introduced cue-only trials.

当在一组试次（trials）区块内需完成多项任务时，通常在已完成试次（即执行过任务的试次）后会观察到相较于重复执行任务，任务切换所带来的成本，即“切换成本（switch cost）”。在那些已完成试次需做出按键反应等动作响应、且任务以可预测的方式排序（以交替区块形式呈现）的研究中，仅需一次任务执行实例即可克服该切换成本。在实验1中，我们旨在探究：仅在新任务区块完成一次试次后便被克服的切换成本，是否也会出现在其他类型的试次之后：i) 包含禁律反应（nogo response）的已完成试次——即按键不按压为恰当响应的情况，例如当任务规则要求对偶数不按压按键时；ii) 仅线索试次（cue-only trials）：仅呈现任务线索但无目标刺激，此时已准备好的任务无法执行。本实验采用单一线索类型（颜色线索）、固定的准备（cue-target，线索-目标）间隔以及固定的试次时长。由于无法确认被试在首个实验的目标刺激呈现前是否已准备好线索提示的任务，我们在实验2中探索：通过操纵准备间隔，是否能够观测到目标前任务准备（pre-target task preparation）。该实验仅包含已完成试次，并操纵了三类变量：线索类型（区块间变量，言语线索或图像线索）、准备间隔（被试内（within participants）变量），以及准备间隔是在区块间变化还是试次间变化（被试间（between participants）变量）。在实验3中，我们沿用了实验2中试次间变化准备间隔与图像线索的方法，并重新引入了仅线索试次。