Schumacher Eric H, Cookson Savannah L, Smith Derek M, Nguyen Tiffany V N, Sultan Zain, Reuben Katherine E, Hazeltine Eliot
School of Psychology, Georgia Institute of Technology, Atlanta, GA, United States.
Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA, United States.
Front Psychol. 2018 Jun 25;9:1031. doi: 10.3389/fpsyg.2018.01031. eCollection 2018.
Limitations in our ability to produce two responses at the same time - that is, dual-task interference - are typically measured by comparing performance when two stimuli are presented and two responses are made in close temporal proximity to when a single stimulus is presented and a single response is made. While straightforward, this approach leaves open multiple possible sources for observed differences. For example, on dual-task trials, it is typically necessary to identify two stimuli nearly simultaneously, whereas on typical single-task trials, only one stimulus is presented at a time. These processes are different from selecting and producing two distinct responses and complicate the interpretation of dual- and single-task performance differences. Ideally, performance when two tasks are executed should be compared to conditions in which only a single task is executed, while holding constant all other stimuli, response, and control processing. We introduce an alternative dual-task procedure designed to approach this ideal. It holds stimulus processing constant while manipulating the number of "tasks." Participants produced unimanual or bimanual responses to pairs of stimuli. For one set of stimuli (two-task set), the mappings were organized so an image of a face and a building were mapped to particular responses (including no response) on the left or right hands. For the other set of stimuli (one-task set), the stimuli indicated the same set of responses, but there was not a one-to-one mapping between the individual stimuli and responses. Instead, each stimulus pair had to be considered together to determine the appropriate unimanual or bimanual response. While the stimulus pairs were highly similar and the responses identical across the two conditions, performance was strikingly different. For the two-task set condition, bimanual responses were made more slowly than unimanual responses, reflecting typical dual-task interference, whereas for the one-task set, unimanual responses were made more slowly than bimanual. These findings indicate that dual-task costs occur, at least in part, because of the interfering effects of task representation rather than simply the additional stimulus, response, or other processing typically required on dual-task trials.
我们同时做出两种反应的能力存在局限——即双重任务干扰——通常是通过比较在呈现两个刺激并在时间上紧密接近时做出两种反应的表现，与呈现单个刺激并做出单个反应时的表现来衡量的。虽然这种方法很直接，但它为观察到的差异留下了多种可能的来源。例如，在双重任务试验中，通常需要几乎同时识别两个刺激，而在典型的单任务试验中，一次只呈现一个刺激。这些过程与选择和产生两种不同的反应不同，并且使对双重任务和单任务表现差异的解释变得复杂。理想情况下，执行两项任务时的表现应该与只执行一项任务的条件进行比较，同时保持所有其他刺激、反应和控制处理不变。我们引入了一种替代的双重任务程序，旨在接近这一理想状态。它在操纵“任务”数量的同时保持刺激处理不变。参与者对成对的刺激做出单手或双手反应。对于一组刺激（双任务组），映射被组织成一张脸和一座建筑物的图像被映射到左手或右手的特定反应（包括无反应）。对于另一组刺激（单任务组），刺激指示相同的一组反应，但单个刺激和反应之间没有一对一的映射。相反，每个刺激对必须一起考虑以确定适当的单手或双手反应。虽然在两种条件下刺激对非常相似且反应相同，但表现却显著不同。在双任务组条件下，双手反应比单手反应慢，这反映了典型的双重任务干扰，而在单任务组中，单手反应比双手反应慢。这些发现表明，双重任务成本至少部分是由于任务表征的干扰效应，而不是简单地由于双重任务试验通常需要的额外刺激、反应或其他处理。
