Fig 1.
(a) Demonstration of experimental set-up; (b) illustration of visual coding that was applied to the data; (c) illustration of raw data. EEG data were decomposed using a Fourier decomposition, and power within continuous bins was calculated, epoched to 4 Hz; (d) cross-correlation showing the relationship between infant object looks and parent object looks [see 25]. The underlying data for this figure can be found in S1 Text. EEG, electroencephalography.
Fig 2.
Brain–behaviour associations: Solo play.
(a and b) Mean time-lagged cross-correlations between EEG power and visual attention for (a) infant solo play and (b) parent solo play. Time lag between EEG power and visual attention is shown on the x-axis, and the EEG frequency on the y-axis. (c) Cross-correlation plots just for those frequency bands identified from the cluster-based permutation test as showing the most marked differences from chance (infant: 3 Hz–7 Hz; adult: 6 Hz–12 Hz). x-axis shows time; y-axis, cross-correlation between EEG power and attention. Shaded areas show the standard error of the means. (d and e) Results of the cluster-based permutation statistic. Yellow squares indicate time × frequency points of significant cross-correlations. The underlying data for this figure can be found in S1 Text and S1 Data.
Fig 3.
Brain–behaviour associations: Infant solo play and joint play.
(a and b) Mean time-lagged cross-correlations between EEG power and visual attention for (a) infant solo play and (b) infant joint play. (Fig 3A is identical to Fig 2A but included to allow for comparison with Fig 3B). (c) Line plot showing cross-correlation between EEG power and visual attention for just the frequency ranges identified from the cluster-based permutation test as showing marked effects in both conditions (3 Hz–6 Hz). Red shows the joint play condition, and blue the solo play condition. Shaded areas show interparticipant variance (standard errors). Dots above the plots indicate the results of the significance calculations to assess whether the correlations observed differed significantly between the two conditions. (d) Results of the cluster-based permutation statistic for infant joint play. Yellow squares indicate time × frequency points of significant cross-correlations. The underlying data for this figure can be found in S1 Text and S1 Data.
Fig 4.
Brain–behaviour associations: Adult solo play and joint Play.
(a and b) Mean time-lagged cross-correlations examining the relationship between EEG power and attention for parent solo play and parent joint play. (Fig 4A is identical to Fig 2B but scaled to be equivalent to Fig 4B to allow for comparison.) (c) Bar chart comparing the frequency of the peak association between EEG power and looking behaviour for parents in the solo play and joint play conditions. * indicates the results of the significance calculations, conducted as described in the main text. (d) Line plot showing cross-correlation between EEG power and visual attention for just the frequency ranges identified from the cluster-based permutation test as showing marked effects in both conditions (parent solo play: 6 Hz–12 Hz; parent joint play: 2 Hz–8 Hz). Red shows the joint play condition, and blue the solo play condition. Shaded areas show interparticipant variance (standard errors). (e) Results of the cluster-based permutation statistic for parent joint play. Yellow squares indicate time × frequency points of significant cross-correlations. The underlying data for this figure can be found in S1 Text and S1 Data.
Fig 5.
Brain–behaviour associations: Adult brain and infant behaviour.
(a and b) Mean time-lagged cross-correlations between parent EEG power and infant attention for (a) solo play and (b) joint play. Time lag between brain activity and visual attention is shown on the x-axis, and the EEG frequency on the y-axis. (c) Line plot showing cross-correlation between EEG power and visual attention for just the frequency ranges identified from the cluster-based permutation test as showing marked differences in the joint play condition (4 Hz–6 Hz). Red shows the joint play condition, and blue the solo play condition. Shaded areas show interparticipant variance (standard errors). (d and e) Results of the cluster-based permutation statistic. Yellow squares indicate time × frequency points of significant cross-correlations. The underlying data for this figure can be found in S1 Text and S1 Data.
Fig 6.
Results of linear mixed effects models conducted to examine whether individual looks accompanied by higher theta power are longer lasting. For each look, the theta power for three time windows prior to look onset (3,000–2,000, 2,000–1,000, and 1,000–0 ms pre-look) and for three time windows post look onset (0–1,000, 1,000–2,000, and 2,000–3,000 ms post-look) was excerpted. We then calculated separate linear mixed effects models for each of the six windows to examine the relationship between EEG power within that time window and look duration. y-axis shows the t value. * indicates the p values (*p < 0.05, **p < 0.01). Full results are shown in S1 Table. The underlying data for this figure can be found in S1 Text and S1 Data.