Caffeine and Cognitive Performance - Caffeine: Chemistry, Analysis, Function and Effects - page 274

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Figure 15.1 A set of eight Visual Analogue-Scales (VAS) to measure subjective

activation and subjective affect. Size of the horizontal lines must be
exactly 100 mm long. Subjective activation was measured using the
adjectives alert, vigorous, weary, and sleepy. Subjective affect was
measured using the adjectives sad, tense, happy and calm. A score of
zero corresponds to the lowest rating in reference to positive scales (e.g.,
alertness) or the optimal response in reference to negative scales (e.g.,
sleepiness).

2008b; Brice and Smith 2001; Bruny´ et al 2010a; 2010b; Childs and de Witt
2006; Christopher et al 2005; Haskell et al 2005; Hewlett and Smith 2007;
Smith 2002; 2009). In general, there seems to be a dose-dependent effect, where
the most effective dose range goes from 100 to 400 mg.
More beneficial subjective effects were observed with administration of low
doses of caffeine in situations with a deficit in activation, such as in the case of
fatigued subjects (Hogervorst et al 2008; Smith et al 2005), and working at
night or during sleep deprivation (Killgore et al 2006; Kohler et al 2006;
Wesensten et al 2005; Wyatt et al 2004). Moreover, although the subjective
activation and affect-enhancing effects of caffeine occur both in habitual and
in non-habitual consumers, high-caffeine consumers are more likely to perceive
broadly positive effects (Attwood et al 2007; Hewlett and Smith 2006; Rogers
et al 2003).
On the negative side, there are some adverse effects of caffeine, particularly
its tendency to increase anxiety, tension, nervousness and dysphoria, as well as
producing tremor, which can negatively affect performance in tasks with a
motor component. This has been associated with the administration of high
doses of caffeine in subjects vulnerable to the adverse behavioral effects of this
substance (Attwood et al 2007; Childs and de Wit 2006; Smith 2002).
The research by Adan et al (2008) is of interest because it highlights the
existence of an early effect of caffeinated coffee (100 mg; 10-30 min post-
consumption) and decaffeinated coffee consumption in the subjective state of
healthy participants. The administration of a caffeinated espresso coffee
induced arousing effects (lesser somnolence and greater activation) in all post-