The primary investigation of this thesis was the relationship between informationprocessing and the internal clock. Clicks trains have previously been found to increaseinternal clock rate and information processing (Jones, Allely & Wearden, 2010). Chapter 1 examines the existing literature on the internal clock and information processing. Chapter 2 reviews possible mechanisms underlying the effect of clicks and Chapter 3 outlines the research strategy and aims. Chapter 4 investigates the behavioural parallels between internal clock speed and information processing. Chapter 5 explores the parametrics of clicks using a 1, 2 and 4 choice reaction time (RT) task (Experiment 1a, b & c). Overall, RT was reduced on trials preceded by clicks compared to no-clicks and we found that this advantage of clicks can persist for up to 10s. Chapter 6 investigates whether any prestimulus event (in this case white noise) would have the same effect as clicks in tasks of verbal estimation (VE), RT and mental arithmetic (Experiment 2a, b & c). White noise was found to have no effect on either information processing or internal clock speed, which strengthens the idea that the clicks effect is mediated by its influence on the speed of the internal clock. Chapter 7 explores whether processing the clicks as opposed to passively experiencing them would change their effect on a 1, 2 and 4 choice RT and VE task (Experiment 3a & b). Both experiments included two experimental groups (Ask & Don't Ask). In the Ask group, participants had to actively process the clicks by reporting whether there had been a shift in pitch in the clicks. In the Don't Ask they were never asked this. Experiment 3a found longer RTs across all conditions in the Ask group compared to the Don't Ask group suggesting that this processing manipulation had an effect on information processing. Experiment 3b explores the same change to the stimuli in a VE task and found that the click processing manipulation had no detrimental effect on the typical effect produced clicks. Both click types increased verbal estimates of duration in both the Ask and Don't Ask groups. Greater overestimation was found with the clicks compared to the click-change condition. So the processing manipulation had an effect on information processing while leaving the internal clock spared, weakening the idea of a link between the two processes. Frequency and duration of the clicks were manipulated in Experiment 4a and b (Chapter 8) in tasks of RT and VE. Experiment 4a demonstrated no significant effect of frequency on RT. In Experiment 4b, the main findings highlighted the importance click duration not frequency. Experiment 5 (Chapter 9) addresses the question of whether participants have a simultaneous lengthening of subjective duration as well as an increase in information processing by investigating the effect of clicks on memory recall and time estimation of the same stimuli. Overall, clicks enabled participants to correctly recall more letters as well as increasing participants' verbal estimates. Experiment 6 (Chapter 10) used clicks to change the rate of memory decay using a 3, 5 and 8 s delay. Clicks increased the rate of memory decay for the 3 and 5 s delay duration only. In order to explore whether the effect of clicks is due to arousal, Chapter 11 replaced clicks with arousing visual (Experiment 7a) and auditory stimuli (Experiment 7b) in a VE task. There was no relationship between arousal and time estimation. Experiment 8 (Chapter 12) explores whether estimating the duration of emotionally arousing auditory stimuli themselves has an effect on the internal clock. No relationship between arousal and time estimation was evident. Experiment 9 (Chapter 13) explores electrophysiological arousal in a VE task. While there was a behavioural effect of clicks, they did not alter physiological arousal. These findings have major implications for the common notion that arousal mediates the effect of clicks.