The Cognitive Load (Performance) Decreases With Distractions or Events Requiring Multi-Tasking Increase
Cognitive Load Theory (CLT) was developed by John Sweller in the 1980s. CTL refers to the effort of the working memory. This theory does not imply that there is a limit to our capacity of cognition, but there is a limit to how many new elements we can hold in our working memory. In 2010, Sweller along with Van Merriènboer outlined three types of cognitive load, intrinsic, extraneous, and germane.
By comparing how long it takes for people to get everything done, the psychologists can measure the cost in time for switching tasks. They also assess how different aspects of the tasks, such as complexity or familiarity, affect any extra time cost of switching. In the mid-1990s, Robert Rogers, PhD, and Stephen Monsell, D.Phil, found that even when people had to switch completely predictably between two tasks every two or four trials, they were still slower on task-switch than on task-repeat trials. Moreover, increasing the time available between trials for preparation reduced but did not eliminate the cost of switching. There thus appear to be two parts to the switch cost -- one attributable to the time taken to adjust the mental control settings (which can be done in advance it there is time), and another part due to competition due to carry-over of the control settings from the previous trial (apparently immune to preparation).
This is at the center of the Cognitive Load theory fronted by Chandler and Sweller (1991). The third assumption is based on generative-learning theory and selecting-organizing-integrating theory of active learning fronted by Wittrock (1989) and Mayer (1999), respectively (Mayer and Moreno, 2003, p.44). The integration of Twitter into learning has the influence as illustrated below.
Mayer, R. E. and Moreno, R. (2003). Nine Ways to Reduce Cognitive Load in Multimedia Learning. Educational Psychologist 38(1), 43–52.
Cobb, T. (1997). Cognitive Efficiency: Toward a Revised Theory of Media. ETR&D 45, 21-35.
Dawley, L. (2009). Social network knowledge construction: emerging virtual world pedagogy. Emerald Group Publishing Limited 17(2), 109-121.