The present research project adopted physiological measures to investigate the rela- tionship between anxiety and working memory (WM). The importance of WM for maths processing and the sensitivity of physiological measures to both anxious responses and executive processes make these measures appealing for advancing our understanding of maths anxiety (MA). The overarching research question asked whether anxiety affects the accuracy of the representations in WM, process that is thought to be central in performing maths task and that may explain the relationship between maths performance and MA. In this thesis the construct of anxiety was considered under two aspects. First, as source of noise causing a decrease in performance to tasks relying on WM. Second, as evolutionary determined physiological reaction to stressors. The former conceptualization of anxiety informed the parts of this thesis investigating the effects of anxiety over WM. The latter provided the starting point to investigate how physiological measures may provide insights on the relationship between the effects of MA on WM processes and maths performance. The first two studies in the thesis aimed at addressing the question of whether anxiety affects WM. WM was conceptualized as a limited capacity system where information is temporarily maintained and manipulated in order to perform a task. It is necessary for performing complex cognitive tasks as well as for later encoding of information in long term memory (Baddeley, 1992). The efficiency of such system can be compromised by events external or internal to the individual. One factor that may impact WM efficiency is anxiety. Anxiety is a state of tension in the face of threat and it is characterised by worry and increased physiological arousal. Task-irrelevant self-directed thoughts might reduce WM resources otherwise needed for performing cognitive tasks (Eysenck et al., 2007). Moreover, the effect that anxiety has on maths performance, as in the case of maths anxiety (MA), might be explained by the effect of anxiety on WM processing (Ashcraft and Kirk, 2001). The present thesis investigates the interplay between these three constructs with the aid of physiological measures. Attentional control has been found to be a central function of WM processing (Baddeley, 1992; Eysenck, 2007). In the first experiment I look at the involvement of attentional processes in memory encoding by investigating whether ERP prestimulus-memory effects (pSMEs) are of attentive nature (Otten et al., 2006). If that was the case, investigating how anxiety affected attentional processed prior memory encoding would have provided a starting point to address how MA may exert its influence on the performance of maths tasks. Contrary to my prediction, the pSME seemed to be better explained by semantic processing, rather than recruitment of attentional processes. In the second experiment, I investigated how anxiety affects maintenance in WM. To this aim I used experimentally induced by threat-of-shock might impact WM as conceptualized by resource models. Resource models of WM give a central role to attentional resources (Ma et al, 2014). To do so I implemented a modified NPU-threat test protocol (Shmitz & Grillon, 2012) combined with task in which WM was assessed through precision of recall (Bays et al., 2009) and anxiety was assessed by means of the startle reflex. In the different conditions, the probability of receiving a shock was manipulated and the estimates of the distributions fitted to the data were compared to assess whether anxiety decreased precision of recall. In a third experiment I looked at the specific case of MA. It is thought that MA impairs maths performance by depleting WM resources (Ashcraft and Kirk, 2001). While MA impacts on implicit processes such as WM, very few studies have attempted to investigate implicit measures of MA with varying success. In the experiment I attempt to replicate the behavioural findings of Rubinsten et al. (2010 and 2012) in which they use an affective priming task combined with a verification task. Furthermore, I investigate the startle reflex and heart rate variability as implicit physiological measures, which have never been studied in the context of MA.