Motivation enhancement is an increased desire to perform tasks and accomplish goals in a productive manner.    This includes tasks and goals that would normally be considered too monotonous or overwhelming to fully commit oneself to.
A number of factors (which often, but not always, co-occur) reflect or contribute to task motivation: namely, wanting to complete a task, enjoying it or being interested in it.  Motivation may also be supported by closely related factors, such as positive mood, alertness, energy, and the absence of anxiety. Although motivation is a state, there are trait-like differences in the motivational states that people typically bring to tasks, just as there are differences in cognitive ability. 
Motivation enhancement is often accompanied by other coinciding effects such as stimulation and thought acceleration in a manner which further increases one's productivity. It is most commonly induced under the influence of moderate dosages of stimulant and nootropic compounds, such as amphetamine   , methylphenidate  , nicotine  , and modafinil  . However, it may also occur to a much lesser extent under the influence of certain opioids   , and GABAergic depressants  .
- Kjærsgaard, T. (2015). Enhancing motivation by use of prescription stimulants: The ethics of motivation enhancement. AJOB Neuroscience, 6(1), 4-10. | https://doi.org/10.1080/21507740.2014.990543
- Terbeck, S. (2013). Why students bother taking Adderall: Measurement validity of self-reports. AJOB Neuroscience, 4(1), 21-22. | https://doi.org/10.1080/21507740.2012.762064
- Sagara, H., Kitamura, Y., Esumi, S., Sendo, T., Araki, H., & Gomita, Y. (2008). Motivational effects of nicotine as measured by the runway method using priming stimulation of intracranial self-stimulation behavior. Acta Med Okayama, 62, 227-233. | https://doi.org/10.18926/AMO/30940
- Young, J. W., & Geyer, M. A. (2010). Action of modafinil—increased motivation via the dopamine transporter inhibition and D1 receptors?. Biological psychiatry, 67(8), 784-787. | https://dx.doi.org/10.1016%2Fj.biopsych.2009.12.015
- Riters, L. V. (2010). Evidence for opioid involvement in the motivation to sing. Journal of chemical neuroanatomy, 39(2), 141-150. | https://dx.doi.org/10.1016%2Fj.jchemneu.2009.03.008