How can reaction times be measured, and what affects it? I was playing pinball the other day, and I wasn't doing very well - my reactions were far too slow it seemed. 

My question is - Firstly - how can someone's reactivity measured/determined? I imagine there are some quite conclusive tests. 

Secondly - what affects people's reaction times? I imagine alcohol impairment and sleep deprivation affects them - are there other common factors? Is there anything that increases reactivity?
Reaction times can be measured by a variety of techniques in the lab. The simplest test is to present a stimulus to a test subject and instruct the subject to press a button as fast as possible after the stimulus is perceived. Responses can be measured by using a response box. Often-used stimuli are either visual (e.g., a colored dot that pops up at random times on a computer screen), auditory (e.g., an acoustic beep), or tactile (e.g., a vibratory buzz or tap on the finger). These tests measure the reaction time from stimulus presentation up to the moment the subject presses the button. Hence, obtained response latencies include peripheral sensory processes, central sensorimotor processing in the brain, and motor output.  

Age increases reaction time, mainly due to a slowed motor output (Woods et al., 2015). The stimulus modality also affects response latency. Visual stimuli result in long reaction times, tactile stimuli in shorter latencies, and auditory stimuli induce the shortest reaction time (Ng &amp; Chan, 2012). These differences reflect the slow sensory processing in the visual system and the fast response of the auditory system. Neuro-supressants, such as alcohol, tranquilizers, antiepileptics- and anesthetics all increase reaction times (e.g., Mitchell et al.,, 1993). 

References
- Mitchell et al., Pediatrics (1993);91(1):101-5
- Ng &amp; Chan, Proc IMECS II (2012)
- Woods et al., Frontiers Human Neurosci (2015); 9:131-12p