Table 1.
Design of the study.
Fig 1.
Schematic of the four consecutive screens of a JaJ trial of length two.
Note: Jill always stays in the same position holding a blue ball in her right (from the participant’s perspective) hand (Panels 1–4), while Jack rotates around his axis on each stimulus presentation and can hold a ball in either his right or left hand (Panels 1–2). Jack’s ball also moves, randomly taking one of the 6 marked possible positions on the screen (orange dots). On each stimulus presentation, participants are required to perform two tasks: a) indicate whether Jack holds the ball in the same hand as Jill; and b) memorise the current ball position. At the end of each trial, participants are asked to recall the sequence of the ball positions by clicking on the marked positions in the correct order (Panels 3–4). Cursor locations represent correct answers.
Fig 2.
Regression lines representing the decrease in response accuracy with increasing sequence length.
Note: The black line represents proportion of correct responses by length of sequences to be remembered; Error bars represent 95% CI of the proportion based on the standard error. The blue regression line was fit to sequences from length 1 to 7. The red line was only fit to sequences of length 2 to 7. The red regression line fits the empirical average accuracies connected by the dashed line fairly closely, suggesting an approximate linear trend.
Table 2.
Logistic regression of item accuracy.
Table 3.
Descriptive statistics for all performance tasks in Study 2.
Table 4.
Pairwise correlations of all tasks.
Table 5.
Exploratory factor analysis results for the hypothesized VSWM factor.
Table 6.
Descriptive statistics for variables used for analysis in Study 3.
Table 7.
Pearson’s correlations between behaviour, achievement and VSWM measures.
Fig 3.
Jack and Jill task performance by educational track.
Note: Error bars represent the 95% CI around the mean.
Table 8.
Spatial ability tasks.
Table 9.
Descriptive statistics for study variables.
Table 10.
Pearson’s correlations between JaJ, general cognitive ability, spatial abilities and achievement measures.
Fig 4.
Indicators of correlational test validity, measurement error and reliability by task length.
A. Correlations with other cognitive performance tasks by length of the a-JaJ test. B. Standard measurement error by test length. C. Marginal reliability of test scores by test length.