Influence of dual-task load on redundant signal processes

In high demand contexts, uni-or multi-modal signals are used to convey redundant information and improve performance. This is especially the case with improving the detection of discrete peripheral signals. However, how one processes peripheral signals may change depending on the greater environmental context. The underlying cognitive processing of signals is important to determine how they may influence the degree to which each signal enhances, as opposed to slows down, detection. Until now, it was unclear if i) the introduction of, or increased difficulty of, a second task changes how people combine peripheral signals (that is, in a parallel, serial, or coactive fashion) and ii) if processing efficiency depends on the salience of the peripheral signals or the presence/difficulty of a centrally located and continuous tracking task. This manuscript describes an application of Systems Factorial Technology to investigate the cognitive processing mechanisms of redundant signals in the context of a multiple object tracking (MOT) task. The MOT task load (track 0, 1, or 4 dots) and the salience of peripheral signals (bright, dim) were manipulated. The data indicate peoples’ processing of peripheral signals changed depending on the MOT task load. Under a high MOT task load, most people processed redundant signals in a parallel fashion. Alternatively, nearly half of people processed the signals in a serial fashion when asked to simultaneously track 0 or 1 dot. Implications for the use and design of redundant signals in multi-task contexts that vary in task demands are discussed.