Task switching without knowledge of the tasks

Task switching without knowledge of the tasks. C.L. Forrest (clf206@exeter.ac.uk) H. Elchlepp (H.Elchlepp@exeter.ac.uk) S. Monsell (S.Monsell@exeter.ac.uk) I.P.L. McLaren (I.P.L.McLaren@exeter.ac.uk) School of Psychology, College of Life and Environmental Sciences, University of Exeter, UK. Abstract CSR Task-cuing paradigms are typically taken to explore control of task-set. However, they can be construed as requiring not selection of a task-set, just retrieval of a cue+stimulus-->response (CSR) mapping. In this paper we considered performance in a task-cuing paradigm in which participants saw a color cue that indicated whether they should classify a digit as odd/even or high/low using one of two responses. Half the participants were instructed in terms of tasks (Task group) whilst the others were required to learn the CSR mappings without mention of tasks (CSR group). Predicted performance under CSR conditions was modeled using an APECS connectionist network. Both the model and CSR group produced small switch costs, mostly due to incongruent stimuli, and large congruency effects that reduced with practice. In contrast, the Task group produced a larger switch-cost and a smaller, stable congruency effect. Figure 1 on the left shows the way in which the experiment was presented in the CSR condition and on the right in the Task condition. Keywords: task-switching, connectionist modeling, conditional discriminations, associative learning Introduction We often think of our behaviour as being governed by both higher-level cognitive control processes and lower- level associative processes (McLaren, Green & Mackintosh, 1994). Typically these processes are thought to operate simultaneously but with a degree of independence. This paper takes a task-cuing paradigm, typically taken as measuring the higher level cognitive control processes involved in changing between tasks (Monsell, 2003), and asks if the performance typically seen could instead be accounted for by lower level associative processes. This paradigm has been used widely to measure control processes in areas as diverse as aging (Mayr, 2001) and schizophrenia (Meiran, 2000) It is also commonly included in brain training packages as a way to improve your ability to multitask and pay attention. Given such widespread use, it is important to assess if the paradigm actually measures control processes at all; it has been argued that it does not (Logan and Bundesen, 2003; Schneider and Logan, 2005). The response contingencies in many task-cuing experiments can be construed without any reference to tasks. This paper examines what happens when participants approach such an experiment without knowledge of the task-sets. Data and simulation suggest that they can learn the statistical structure of the experiment through the use of Task associative learning mechanisms, but their performance differs from that of participants construing the situation as one requiring task-selection and switching. To clarify this, let us consider the task-cuing paradigm that we used. Under standard instructions in this paradigm participants are told, for example, that if the background circle is blue or green then they should classify the digit they then see as odd/even, where odd requires a response with the left key and even with the right. However, if the background circle is red or yellow they should classify the digit as higher/lower than 5, with a right response for high, and a left response for low. This is the task-set construal of what is required, as illustrated on the right of Figure 1. Yet participants do not need knowledge of these tasks to know how to respond, as the color and the number combination is completely predictive of the required response, e.g. a 4 on yellow will always require a left response. Hence, especially with small stimulus set, it is entirely possible for participants in a task cuing experiment not to use the task-sets at all, in which case the experiment is not measuring task-based control processes. In the experiment reported here we compare a group who are explicitly instructed to use the task-sets with one that has no knowledge of the underlying task-set structure. In order to examine whether, and in what ways, performance differs