There are four sets of experiments in this collection. The experiments in SET1 were designed to allow us to measure and compare the sizes of potential costs of a switch between tasks when on the preceding trial the task had not been completed in the standard way. The different experiments include different sets of non-completed trial types. The experiments in SET2 were designed to allow us to investigate the effects of explicitly indicating when a trial had finished, and of different types of task cue, upon the size of the switch cost measured on the subsequent trial. The experiments in SET3 were designed to enable us to assess whether there would be any difference between the sizes of switch costs measured on trials following different types of nogo trial. The experiments in SET4 were designed to enable us to assess whether the nature of switch costs would differ following cue-only trials versus following completed trials.In this project we will investigate whether what we “know” and what we “do” have different effects on our subsequent behaviour. We will do this by looking at our ability to switch between different tasks. Specifically, we will compare how difficult it is to switch away from a task that we have either: a) only prepared to perform (we “knew” what the relevant task was but we didn't “do” it), or ii) actually performed (we both “knew” it and “did” it). In our everyday lives we frequently need to switch between the different rules that guide our behaviour. For instance, when driving a car we might switch rapidly between the following “tasks”: visually assessing potential hazards at a junction; accelerating past a tractor; performing an emergency stop. From studies using laboratory tasks, we know that switching tasks usually leads to slowed responses, and that we occasionally even repeat the previous task in error. The existence of this “switch cost” reveals that some aspect of the previous task must persist in some way to affect the speed or accuracy of our subsequent behaviour, even though we know that it is no longer relevant. In this project, we wish to find out about what causes this cost of switching between tasks. Our main question concerns whether just preparing a task (“knowing”) will have different consequences from actually performing it (“doing”). There are various examples in psychology of situations where what we know has surprisingly little impact upon what we do. For instance, we can sometimes verbally repeat instructions given to us, and demonstrate that we understand and remember them, but then fail to implement them at all (a phenomenon known as “goal neglect”). A similar distinction has been drawn in task-switching research. It had been thought that doing a task would produce a subsequent switch cost, but that knowing which task should be performed without actually carrying it out would produce no subsequent cost. However, more recent evidence using a different method suggests that merely preparing a task can in fact produce a substantial switch cost, even if the prepared task was not performed. We will conduct a series of psychological experiments in which people perform two different tasks. For instance, we will show them coloured shapes (like a blue circle) and ask them to press a button to indicate either what the colour is or what the shape is. By intermixing the two tasks randomly, we will be able to assess people's ability to switch between tasks, relative to repeating tasks - that is, we can measure each person's switch cost. On most trials, people will prepare a task and then perform it: for instance, they may see the word “colour” and then a blue circle, at which point they press the appropriate button to indicate that the colour is blue. Crucially, however, on some trials we will require a task to be prepared but not performed: e.g., we may show the word “colour” but then no coloured shape, instead moving straight on to the next trial. Therefore, we will be able to measure the switch cost that follows preparation separately from the switch cost that follows performance. Across a series of experiments we aim to find out what causes these types of switch cost to be established and abolished, and in what ways the switch cost driven by preparation may differ from that driven by performance. The cost of switching tasks indicates a fundamental limitation in our cognitive system that is relevant to many situations (e.g., working in a busy office, driving in heavy traffic, preparing dinner while taking care of a baby). Understanding the mechanisms behind this limitation is of potential practical importance with respect to reducing risks associated with this cost. The present project will meet this challenge by illuminating the origin of this limitation.

Experiments that were run in-person (SET1 Expt 1; SET2; SET3 SGN) were run using the software E-Prime 2.0; participants were primarily undergraduate and postgraduate students. Experiments that were run online (SET1 Expts 2-4; SET3 DR-SGN; SET4) were run using the software PsychoPy/PsychoJS via the server Pavlovia, with recruitment via Prolific from the general population. In all cases, instructions were presented on-screen and all responses were made using a computer keyboard. More details about the experiments in all sets are given in the ExperimentDetails.pdf document for that set.