## 2 Materials and Methods
### Cognitive Tasks  
The cognitive task battery lasted 30 min and consisted of the following tasks presented in the order described below:  
Modified Attention Network Task (MANT) to measure selective attention under different levels of cognitive demand. Using the method described in [PERSON] et al. [30], participants were presented with either orienting or alerting cues followed by an array of congruent arrows--all arrows pointing in the same direction (i.e., <<<<s or >>>>>>), incongruent arrows--the center arrow pointing in the opposite direction to the surrounding 4 arrows (i.e., <<<<s or >>>>>>) or neutral--only one arrow (i.e., < or >).Trials could either be high load--an additional row of 5 arrows is presented immediately above or below giving 10 arrows in total, medium load--a single row of 5 arrows, or low load--only one arrow is presented. Additionally, trials were split into two blocks, one as a silent condition, and one as a noise condition where school playground noise was played through headphones. Participants were instructed to press the left or right arrow keys on the keyboard according to the direction of the center arrow. Incongruent, high load, noise trials are considered to be the most cognitively demanding with slower response time and decreased accuracy expected. Accuracy and response time for congruency and load were measured separately. Task Switch Task (TST) to measure mental flexibility. This employed a modified version of the task as described in [PERSON] et al. [18]. Participants viewed eight equally spaced radii of a circle displayed in such a way that there are four equally spaced segments above and below a bold line. A stimulus digit selected from between 1-9 (excluding 5) appeared in each segment in turn in a clockwise direction. Each digit was displayed for a duration of 3000 ms, or until the participant responded. The inter-stimulus \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & **Age** & \begin{tabular}{c} **Alcohol** \\ **Units/Week** \\ \end{tabular} & **Tea/Day** & \begin{tabular}{c} **Exercise** \\ **Hours/Week** \\ \end{tabular} & \
\begin{tabular}{c} **Letter** \\ **Fluency** \\ \end{tabular} &
\begin{tabular}{c} **Category** \\ **Fluency** \\ \end{tabular} \\ \hline Placebo & 22.8 (2.8) & 3.24 (3.44) & 0.88 (0.96) & 2.73 (2.26) & 16.55 (3.52) & 22.1 (4.35) \\ Berry & 22.8 (2.46) & 5.07 (5.74) & 1.25 (1.47) & 4.30 (3.24) & 15.25 (4.44) & 19.65 (4.74) \\ \(p\)-value & 1.00 & 0.229 & 0.347 & 0.083 & 0.311 & 0.097 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Demographic details by intervention group standard deviation in parenthesis. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & **Antho-Cyanidins** & \
\begin{tabular}{c} **Flavan-3-ol** \\ \end{tabular} & **Flavanone** & **Flavone** & **Flavonol** &
\begin{tabular}{c} **Proantho-** \\ **Cyanidin** \\ \end{tabular} & **Total** \\ \hline Raspberry & 36.45 & 4.35 & 0 & 0 & 0.9 & 26.9 & 68.6 \\ Blueberry & 122.4 & 5 & 0 & 0.15 & 8 & 136.5 & 272.05 \\ Blackberry & 75.5 & 32 & 0 & 0 & 3.45 & 14 & 124.95 \\ Strawberry & 20.3 & 3.37 & 0.23 & 0 & 1.2 & 79 & 104.1 \\ \hline Total & 254.65 & 44.72 & 0.23 & 0.15 & 13.55 & 256.4 & 569.7 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Average flavonoid content mg/75 g by flavonoid class and berry type [7]. interval was 500 ms. Dependent on whether the stimulus was above or below the bold line, participants performed different tasks. If the number was above the bold line, participants discerned whether the stimulus was odd or even by pressing the relevant response key, whereas if the number was below the bold line, participants discerned whether the number was higher or lower than 5 again by pressing the relevant key. The task therefore switches every 4 trials, with S0 denoting the initial trial following task switch and S1, S2, and S3 denoting the remaining 3 trials before the next task switch. The initial S0 trial following switch is considered to the most cognitively demanding with slower response time and increased errors expected.