Backward inhibition has been posited to aid our ability to switch between tasks by counteracting the tendency to repeat a recently performed task. Evidence suggests that backward inhibition might be triggered during task-preparation, prior to performance, yet so far it has not been detected following trials involving task-preparation but no task-performance (Schuch & Koch, 2003 and Philipp, Jolicoeur, Falkenstein & Koch, 2007). However, those previous studies deployed a nogo method that might have prevented preparation-driven effects from being detected, due to the nogo signal wiping the effects of task processing (Lenartowicz, Yeung, & Cohen, 2011). To avoid the need for a nogo signal, we truncated trial n – 1 following task-preparation and used the n – 2 repetition cost (ABA versus CBA trial sequences) to measure the effect of returning to a previous task. In the cue-only abstract cues experiment we used abstract cues in an attempt to increase the size of any potential n – 2 repetition cost triggered by preparation on the preceding trial. In the double-registration cue-only experiment, responses were required to cues as well as to targets, to enable us to know that participants did some form of preparation on the truncated trials. In both experiments, the existence of an n – 2 repetition cost following truncated trials would constitute evidence that backward inhibition can be triggered task-preparation.Below is the original grant abstract, which encompasses a variety of studies. Please refer to Data description (abstract) for details on the two studies uploaded in this collection. 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.

The sample was undergraduate and postgraduate students. Participants were instructed that they would be switching between three tasks: a colour-judgement task (blue and green for left response and red and yellow for right response), a shape-judgement task (square and triangle for left response circle and diamond for right response) and a line orientation task (slanted left and vertical for left response and slanted right and horizontal for right response). The targets for the experiments were trivalent, consisting of coloured shapes that contained two lines in one of the four orientations. This research includes two experiments. CueOnlyAbstractCuesExpt: This experiment took roughly 45mins. Participants were informed what task to do on every trial by a cue that was presented for 1000ms. On completed trials the cue was then replaced by the target. The target stayed on the screen until participants gave a response. After the response on completed trials a blank screen was displayed for 50ms, and then the next trial started. On cue-only trials (roughly 28% of all experimental trials) the cue was replaced by a blank screen for 50ms. After the blank screen the next trial was started. The cues were * for the colour task, @@@@@ for the line orientation task and &&&&& for the shape task. Participants responded to the target using a Cedrus button box and the reaction time and accuracy of responses were measured. DoubleRegistrationCueOnlyExpt: This experiment took roughly 60mins. This experiment was based on Arrington, Logan, and Schneider’s (2007, and see also Regev & Meiran, 2017) dual-registration paradigm. Participants were informed what task to do on every trial by a cue that was presented for 200ms; this was followed by a blank screen. Participants then had to press one of three buttons (with their left hand) to confirm what task they were to perform. On 70% of trials (the “completed” trials), 100ms after they responded to the cue participants were presented with a target (a coloured shape) for 200ms. This was followed with a blank screen until participants responded by pressing one of two buttons (with their right hand) to perform the cued task. There was then a 100ms blank screen until the next trial started. On the remaining 30% of trials (the “cue-only” trials), 100ms after participants responded to the cue the next trial started. The cues were COLOUR, SHAPE, or LINE. Participants responded to the cue and target using a MasterCooler keyboard and the reaction time and accuracy of responses were measured.