Methods available here:
https://www.biorxiv.org/content/10.1101/2023.06.19.545295v3.full.pdf

Description of the data and file structure

This data set contains time series data, quantifying continuous fluctuations in behaviour and brain activity of caregivers and infants interacting with each other during table-top play. Caregivers and infants were video recorded with cameras recording at 50Hz during the play session. The auditory environment was recorded with microphones attached to caregivers and infants, recording at 44100Hz, and infant brain activity was recorded using electroencephalogram (EEG), recorded at 512Hz. Caregivers and infants engaged in two play sessions, each lasting five minutes – play section 1 (‘nat1’) and play section 2 (‘nat2’).

Five folders are included within the main data folder. All files within these folders, bar the ‘Participant sheets’ folder, are .mat files that can be opened in MATLAB2019a. A detailed description of the data sets contained in each folder is given below. In brief:

The first folder ‘Caregiver variables’ contains 2 sub-folders, that correspond to two continuous variables, quantifying fluctuations in caregiver behaviour during the shared play interaction – ‘caregiver continuous attention durations’ and ‘caregiver rate of change in f0’.

The second folder, ‘Infant looks’ contains two sub-folders, corresponding to the looks infants made towards objects – ‘object looks’, and looks infants made towards objects, their partner and elsewhere – ‘all looks’.

The third folder, ‘Infant variables’ contains 2 sub-folders, that correspond to two continuous variables, quantifying fluctuations in infant behaviour and brain activity during the shared play interaction – ‘infant continuous attention durations’ and ‘infant theta activity’.

The fourth folder, ‘Participant sheets’ contains .xlsx files that include the identification code of each participant included in each set of analyses.

The fifth folder, ‘synchronised look timeseries’ contains a .mat file for each participant, including synchronised, binary codes for caregiver and infant looking behaviour during the shared play interaction.

Caregiver variables

This folder contains two sub-folders. A description of each is given below.

caregiver continuous attention durations
This folder contains .m files for each participant (labelled with their identification number). Each file contains 2 columns, sampled at 50Hz that run for the length of the caregiver-infant interaction.
Column 1 – Camera frames (of camera directed towards the infant)
Column 2 – Caregiver continuous attention durations (in seconds). This column contains the continuous attention durations of the caregiver towards objects, their infant and elsewhere (see Methods, section ‘Computation of continuous variables’ in https://www.biorxiv.org/content/10.1101/2023.06.19.545295v3.full.pdf for a detailed description of how this continuous variable was computed for each camera frame).

caregiver rate of change in f0
This folder contains .m files for each participant (labelled with their identification number). Each file contains 2 columns, sampled at 50Hz that run for the length of the caregiver-infant interaction.
Column 1 – Camera frames (of camera directed towards the infant)
Column 2 – Caregiver rate of change in f0 (Hz/Seconds). This column contains the rate of change in caregiver f0, extracted from the caregiver’s microphone data (see Methods, section ‘Computation of continuous variables’ in https://www.biorxiv.org/content/10.1101/2023.06.19.545295v3.full.pdf for a detailed description of how this continuous variable was computed for each camera frame).

Infant looks

This folder contains 2 sub-folders. A description of each is given below.

object looks
This folder contains .m files for each participant (labelled with their identification number). Each file contains 3 columns, with each row corresponding to an individual look made by the infant towards an object.
Column 1 = camera frame number of the infant’s look onset towards an object.
Column 2 = camera frame number of the infant’s look offset towards an object.
Column 3 = look duration in camera frames (i.e. column 2 – column 1).

all looks
This folder contains .m files for each participant (labelled with their identification number). Each file contains 3 columns, with each row corresponding to an individual look made by the infant towards an object, their caregiver, or elsewhere.
Column 1 = camera frame number of the infant’s look onset towards an object, their caregiver, or elsewhere.
Column 2 = camera frame number of the infant’s look offset.
Column 3 = look duration in camera frames (i.e. column 2 – column 1).

Infant variables

This folder contains two sub-folders. A description of each is given below.

infant continuous attention durations
This folder contains .m files for each participant (labelled with their identification number). Each file contains 2 columns, sampled at 50Hz that run for the length of the caregiver-infant interaction.
Column 1 – Camera frames (of camera directed towards the infant).
Column 2 – Infant continuous attention durations (in seconds). This column contains the continuous attention durations of the infant towards objects, their caregiver and elsewhere (see Methods, section ‘Computation of continuous variables’ in https://www.biorxiv.org/content/10.1101/2023.06.19.545295v3.full.pdf for a detailed description of how this continuous variable was computed for each camera frame).

infant theta activity
This folder contains .m files for each participant (labelled with their identification number). Each file contains 2 columns, sampled at 50Hz that run for the length of the caregiver-infant interaction.
Column 1 – Camera frames (for camera directed towards the infant).
Column 2 – Infant relative theta activity. This column contains a continuous measure of infant theta activity, extracted from the EEG recordings, and averaged over fronto-central electrodes (see Methods, section ‘Computation of continuous variables’ in https://www.biorxiv.org/content/10.1101/2023.06.19.545295v3.full.pdf for a detailed description of how this continuous variable was computed for each camera frame).

Participant sheets

This folder contains .xlsx files for each analysis conducted, for play section 1 (‘nat1’) and play section 2 (‘nat2’). Each file lists the participant identification numbers included in each analysis. 0s correspond to where participants have data for play section 1 (‘nat1’) but not play section 2 (‘nat2’), or vice versa.
Each file contains the participant identification numbers used in different sets of analyses:
‘_voc_eeg’ – list of participant identification numbers included in all analyses involving gaze data, caregiver microphone data and infant eeg data.*
‘_eeg’ – list of participant identification numbers included in all analyses involving gaze data and infant eeg data.
‘.’ – list of participant identification numbers included in all analyses involving gaze data only.

Synchronised look time series

This folder contains .m files for each participant dyad, for each interaction – play section 1 (‘nat1’) and play section 2 (‘nat2’), labelled with their identification number. Each file contains 14 columns, where each row corresponds to 1 camera frame recorded in the caregiver and infant cameras. Columns 1-6 and 8-13 are binary variables that correspond to looks towards objects, the partner and elsewhere for each frame of the interaction (0=look away, 1=look towards). Columns 7 and 14 correspond to the camera frames of the infant and the caregiver, respectively. Caregiver and infant cameras have been synchronised using an LED light that went off in both cameras.
Columns 1-6: infant gaze data
1 - look to partner (0=look away, 1=look towards)
2 - look to object1 (0=look away, 1=look towards)
3 - look to object2 (0=look away, 1=look towards)
4 - look to object3 (0=look away, 1=look towards)
5 – looks elsewhere (0=look away, 1=look towards)
6 – uncodable (periods where researcher is in view of one of the cameras or infant gaze is blocked from view of the cameras; 1=uncodable, 0=codable).
Column 7: infant camera frames
Columns 8-13: caregiver gaze data
8 - look to partner (0=look away, 1=look towards)
9 - look to object1 (0=look away, 1=look towards)
10 - look to object2 (0=look away, 1=look towards)
11 - look to object3 (0=look away, 1=look towards)
12- looks elsewhere (0=look away, 1=look towards)
13 – uncodable (periods where researcher is in view of one of the cameras or caregiver gaze is blocked from view of the camera; 1=uncodable, 0=codable)
Column 14: caregiver camera frames