MA
Behavioural measures have been employed to investigate automatised processes (Hopko et al., 1998, 2002; Rubinsten et al., 2015; Rubinsten and Tannock, 2010; Suárez-Pellicioni et al., 2015). One task that has been implemented to study the emotional value that the subjects attribute to stimuli is the affective priming task. The idea behind the affective priming task is that participants respond quicker to stimuli that are emotionally congruent with the preceding prime (Fazio et al., 1986; Houwer et al., 2002). There are two mechanisms that have been suggested to underlie such effect. According to the spreading of activation account (Collins and Loftus, 1975), concepts are organized as nodes in semantic networks. Nodes that share similar valence are linked to each other. If a node is activated (for example by a priming word with a certain valence) the activation spreads to the neighbouring nodes. If response selection depends on node activation, the nodes that have been activated because linked to the prime will elicit a faster response compared to nodes that do not share strong links with the prime (Fazio, 2001). On the other hand the response activation account explains affective priming effects in terms of response selection, rather than target evaluation. According to this account, the prime stimuli activate responses on the basis of their valence (positive or negative). For example, if subjects are asked to judge if a target word is positive or negative (e.g. beautiful), response selection will be faster if the preceding prime had positive valence as well (e.g. a smiley face). Because the prime will have activated a positive response, the subject will be facilitated to select a response that is congruent with the valence of the prime (De Houwer et al., 2009).
Rubinsten and Tannock (2010) used an affective priming task paired with an arithmetic verification task to study MA in children with developmental dyscalculia (DD). Specifically, they looked at how priming words influence the processing of mental arithmetic in DD children. They used prime words that could either be positive, negative, neutral or related to maths (such as quantity). Words were followed by an arithmetic operation that the subject had to judge whether it was correct or incorrect. They found that DD children responded faster when the operation was preceded by negative prime words. On the other hand, controls responded faster when the operations were preceded by positive prime words. No difference was found between responses to trials with maths-related and neutral primes. Because affective prime words facilitate responses to targets that are emotionally congruent, the authors concluded that DD children attributed negative valence to maths. The same task was used in Rubinsten et al. (2012) to assess whether gender differences in the ability to solve arithmetic facts depend on differences in MA. An affective priming effect was found in both groups but with different directionality. Males had responded faster when the operations were preceded by positive prime words. On the other hand, females were faster when the operations were preceded by negative prime words. Hence, the authors concluded that males attribute positive valence to maths while females attributed negative valence. The authors suggested that the priming effect may be due to differences in MA. Therefore the affective priming task may be an implicit measure of MA.
4.1.4
The startle reflex and HRV as physiological implicit measures of
MA
Because of the automatised nature of physiological reactions to stress, several studies have attempted to investigate MA by means of physiological indices with varying success (as reported in the general introduction). The measure that seems to be the most effective in measuring MA is salivary cortisol (Mattarella-Micke et al., 2011; Pletzer et al., 2010; Sarkar et al., 2014). However, the fact that changes in cortisol levels reflect an hormonal response makes it difficult to pair it with computerised tasks that are usually employed to investigate cognitive processes. First, the time lag between psychological responses and endocrine responses (Hellhammer et al., 2009; Schlotz et al., 2008; Smyth et al., 1998) makes cortisol measurements suitable for paradigms that require a small number of measurements spaced in time (e.g. before and after a maths exam). However, it is less suitable to be used in conjunction with tasks that require fast online measurements. This is the case for computerised tasks with fast presentation of stimuli and within-participants design. Second,
salivary cortisol spontaneously varies throughout the day, making it difficult to compare levels across participants (Gröschl et al., 2003).
Physiological measures that have faster reactivity to stressors are the ocular startle reflex and HR measures. As mentioned in the general introduction, the ocular startle reflex has widely been used to assess the physiological arousal during anxious states (Davis, 2006; Grillon et al., 1991; Grillon and Davis, 1997). However, to the best of my knowledge it has never been employed to assess MA. Regarding HR measures, the literature investigating the sensitivity of HR (measured as beats-per-minute) to MA levels has produced inconsistent results (Dew et al., 1984; Hopko et al., 2005, 2003b). Whether heart rate increases or decreases in anticipation of threatening stimuli is still debated (Alm, 2004). Inconsistency in HR results might be due to the fact that during anxious responding the sympathetic and the parasympathetic branches of the autonomic nervous system coactivate exerting opposite effects on the heart rate. Therefore, measures of HRV may be more suitable for the assessment of anxiety (Chalmers et al., 2014; Shaffer et al., 2014). Similarly to the startle reflex, to the best of my knowledge HRV has not been used to assess MA.
4.1.5
Rationale of the study
The aim of the present study was to investigate implicit measures of MA. I adopted the same affective priming task paired with a verification task developed by Rubinsten and Tannock (2010) and replicated by Rubinsten et al. (2012), recording the startle reflex and HRV data. The priming task consisted in the presentation of emotionally charged words followed by an arithmetic verification task. The purpose of the task was to test the behavioural and physiological response to the association between the emotional valence of the prime words and the emotional valence attributed to performing maths. Furthermore, a two-back task with geometrical figures was administered. Participants had to judge whether the current stimulus was the same as the one presented two trials earlier. The aim of the two-back task was to assess how variations in HRV measures could be attributed to WM load regradless of emotional valence. Regarding HRV measures, the mean of the IBIs was selected as simple time-domain measure, the SDNN and the RMSSD as complex time-domain measures and the ratio LF/HF as frequency domain measure.
From the present experiment, I first expected to replicate the affective priming effects: participants with higher levels of MA were expected to respond faster to negative compared to positive prime trials. On the other hand, I did not expect prime effects on neutral and maths trials as in Rubinsten and Tannock (2010) and Rubinsten et al. (2012). Second, I expected to observe larger startle reflexes and reduced HRV in HMAs. Third, I aimed at assessing whether the effects of MA on the affective priming task showed a corresponding activation
in physiological measures. I expected that HMAs showed larger startle reflex and smaller HRV in trials preceded by negative words than in trials preceded by positive words. I did not have strong hypotheses regarding trials preceded by negative and maths primes. Finally, I wanted to assess whether implicit measures of MA predicted self-report ratings.
4.2
Materials and methods
4.2.1
Participants
60 participants were tested. 40 participants (11 M, 29 F, mean age 24.44, mean education was Master’s degree) were retained for the analysis (see sections 4.2.2 and 4.2.5 for details on inclusion criteria). Participants were over 18 years of age, English native speakers, did not have a history of psychiatric disorders or learning disabilities and had normal or corrected-to normal vision and hearing.
Participants were recruited via the University bulletin and paid £20 for their participation. The study was approved by the Psychology Research Ethics Committee of the University of Cambridge.