## 5 Results
### Cluster Analysis
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Variable** & **Factors** & **Interaction** & **Post hoc (Clusters)** & \(p\) & **Notes** \\ \hline \multirow{4}{*}{**MO\_VV**} & Stimulus & & Colours: ns & & \\  & Presentation & & Letters: & & \\  & Distractors & & 1 vs. 2 & 0.001 & Differences only for letters, \\  & Suppression & & 1 vs. 3 & 0.002 & TD vs. all SLD \\  & Suppression & & 1 vs. 4 & 0.013 & \\ \hline \multirow{4}{*}{**MO\_VV**} & Stimulus & & Colours: ns & & \\  & Presentation & & Letters: & & \\  & & & 1 vs. 2 & \textless{}0.001 & \\  & & & 1 vs. 3 & 0.004 & Differences only for letters, \\  & & & 1 vs. 4 & 0.024 & TD vs. all SLD \\  & & & Sequential: & & \\  & & & 1 vs. 2 & 0.001 & \\  & & & 1 vs. 3 & 0.014 & Cluster 3 (MD) \textless TD only with \\  & Stimulus & Stim \(\times\) cluster & Simultaneous: & & sequential presentation; \\  & Presentation & Pres \(\times\) cluster & 1 vs. 2 & 0.002 & Cluster 2 (RD) \textless TD for both \\  & Suppression & Stim \(\times\) sup \(\times\) cluster & 1 vs. 4 & 0.006 & presentation modalities \\  & & Letters no AS: & & With letters and without AS, all \\  & & & 1 vs. 2 & 0.015 & \\  & & & 1 vs. 3 & 0.005 & Cluster 2 (RD) \textless TD only with \\  & & & 1 vs.4 & 0.012 & AS (and different from all other \\  & & & Letters with AS: & & clusters) \\  & & & 1 vs. 2 & \textless{}0.001 & \\  & & & 2 vs. 3 & 0.028 & \\  & & & 2 vs. 4 & 0.012 & \\ \hline \multirow{4}{*}{**MO\_AV**} & Stimulus & & Colours: ns & & \\  & Distractors & Stim \(\times\) cluster & 1 vs. 2 & 0.002 & Differences only for letters, \\  & Distractors & Distr \(\times\) cluster & noDistr: ns & & TD vs. all SLD \\  & Suppression & & with distractors: & & \\  & & & 1 vs. 2 & 0.003 & \\  & & & 1 vs. 3 & 0.007 & \\  & & & 1 vs. 4 & 0.003 & \\ \hline \multirow{4}{*}{**MI\_VV**} & Stimulus & & Colours: ns & & \\  & Presentation & & Letters: & & \\  & Presentation & Stim \(\times\) cluster & 1 vs. 2 & \textless{}0.001 & \\  & Distractors & Distr \(\times\) cluster & noDistr: ns & & only with distractors, TD vs. all \\  & Suppression & & with distractors: & & SLD \\  & & & 1 vs. 2 & 0.003 & \\  & & & 1 vs. 3 & 0.007 & \\  & & & 1 vs. 4 & 0.003 & \\ \hline \multirow{4}{*}{**MI\_VO**} & Stimulus & & Colours: ns & & \\  & Presentation & & Letters: & & \\  & & & 1 vs. 2 & \textless{}0.001 & \\  & & & 1 vs. 3 & \textless{}0.001 & Differences only for letters (TD \\  & & & 1 vs. 4 & 0.002 & vs. all SLD) and more evident \\  & Stimulus & Stim \(\times\) cluster & Sequential: & & for sequential than for \\  & Presentation & Pres \(\times\) cluster & 1 vs. 2 & 0.001 & simultaneous presentation \\  & Suppression & & 1 vs. 3 & 0.001 & Cluster 3 (MD) \textless TD only for \\  & & & 1 vs. 4 & 0.024 & sequential presentation \\  & & & Simultaneous: & & \\  & & & 1 vs. 2 & 0.005 & \\  & & & 1 vs. 4 & 0.005 & \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Results of the ANOVA assessing the interactions between all involved factors and clusters for each of the overall STM variables. Significant differences between colours and letters involved in interactions with cluster differences for the various overall STM variables are illustrated in Figure 8.  
In general, it can be seen that letters are processed and retrieved more easily than colours, and this is especially true for children in the TD cluster. For all children with SLD, indeed, the advantage of letters over colours is actually reversed for MO_AV STM scores. In order to check for stimulus-based differences within each cluster, a series of \(t\)-tests for dependent groups (paired \(t\)-tests) was conducted comparing letters and colours. The tests showed a significant advantage for colours over letters in the MD group only (t(16) = 2.878,  
Figure 8: Mean scores (Logit-transformed, see Figure 6 and Appendix A) obtained for colours (light-coloured bars) and letters (dark-coloured bars) for the five overall STM variables that showed significant interactions between stimulus and cluster.