Is it good to take playful breaks at work? I read this Washingon Post article about groups that are trying to encourage play in "workaholic" adults. I'm curious if anything is known on the psychological effects of taking playful breaks at work.

From personal experience, taking playful breaks seems to improve my productivity and resistance to distractions. On the other hand, maybe taking playful breaks makes work seem even more drab by comparison, lessening motivation?
Building on @caseyr547's answer, and especially the second link in the first reply to your comment, yes!

From Cook's (2009) abstract (emphasis added):


  Over the past decade, there have been numerous claims in the popular media relating to having fun at work, touting a plethora of benefits for both individuals and organisations that have to date not been empirically investigated. Thus far, any research related to fun in the workplace has often been indiscriminate with its use of terms, interspersing fun with humour and play, thus adding confusion to an already inadequately defined construct. The aim of this research is two fold: to develop a more comprehensive understanding of the construct to differentiate and define fun in a work context, and to measure the perceived impact of having fun in the workplace. In order to locate fun as a unique construct, literature related to fun, humour and play/playfulness was reviewed and positioned in a nomological net utilising a three phase framework consisting of presage, process and product (3P). Four studies in this research program investigated the domain of fun activities in the workplace, the underlying structure of the construct, the process of having fun and the perceived impact of fun specifically in relation to job satisfaction, stress reduction, effectiveness and workplace relationships. Results identified a domain of 15 distinct fun activities. Using multidimensional scaling, an underlying structure of four neighbourhood clusters (humour and play, informal socialising, formal socialising and organisational activities) and two dimensions (contextual connections with others and activity structure and intensity) were identified. The investigation of the process of fun was conducted by examining case vignettes using the 3P framework. Results suggest the experience of fun at work is activity based, with an emotionally qualitative dimension that is highly socially interactive and engaging. The organisational context for fun appears to be embodied in supportive management and colleagues, positive team dynamics and a non stressed environment. The participant experiencing the fun is usually in the role of contributor rather than observer, is highly engaged, experiencing amusement, laughter, flow, social connection and as an outcome, an increase in positive mood. While humour and play contribute to the process of fun, fun appears to be a uniquely distinct construct. Finally, the present results suggest the perceived impact of having fun at work, while positive, was not reported globally to the extent suggested in the popular press. The most significant outcome of having fun was the reporting of improved positive mood after the fun event, with the related cascading organisational effects discussed. Complimentary to this, having fun at work was perceived to positively influence workplace relationships to a moderate-high degree, contribute to managing stress to a moderate degree, improved job satisfaction to moderate degree and was reported to have a little more than neutral, direct impact on workplace effectiveness. These outcomes must however be examined in the context of results, suggesting not only are different types of fun activities enjoyed more, but different types of activities are highly salient in relation to the particular organisational variable measured. Results of this series of studies have provided a revised nomological net that can be used in further research to define the construct of fun in a workplace context. Supplementary to this, outcomes suggest having fun at work has positive impacts for both individuals and workplaces and therefore further
  investigation, at multiple organisational levels is required, ranging from individual
  disposition in relation to fun, to the effects of fun on workplace culture.


In summary, @what is right to be concerned about the definition of "playful break". The particular kind of fun activity in question seems to moderate the effects quite a bit. Popular media seems to have over-hyped the effects somewhat. Still, overall, fun is indeed fun – i.e., the behavior affects affect and cognition. It may also improve coworker relations, reduce stress, and make people happier with and better at their jobs...but these results may be too subjective to trust on their own, and deserve replication and reexamination.

Reference

Cook, K. (2009). Fun at Work: Construct Definition and Perceived Impact in the Workplace. (Doctoral dissertation.) Griffith University. Retrieved from https://www120.secure.griffith.edu.au/rch/file/16034620-6834-02f5-2d07-79df62b21e6c/1/02Whole.pdf.