This ReadMe file describes the datasets included in the paper entitled "Two weeks of mirror exposure enhances sensorimotor cortex activation but not facial mimicry in 4-month-old infants". The document provides an overview of the study’s data structure, descriptions of each data file, and definitions of all variables. All datasets use a shared participant identifier to enable merging across files.

Data structure notes:
* Throughout all files, each row corresponds to one participant.
* Missing data is left blank. 

EEG Data File Description
Filename: EEG Data.csv
This file contains baseline-corrected sensorimotor alpha suppression of infants in the mirror and control condition at pre-test and post-test. It also includes basic demographic information and a behavioural measure reflecting the average amount of time infants spent looking at their own reflection.

Variables included in the file:
* Participant: Unique numeric identifier for each infant participant.
* Sex: The sex of the infant (M/F).
* Age: Infant age in days at pre-test. 
* Condition: The experimental group assignment (0 = control group, 1 = mirror group). 
* Imputed: Whether the pre-test data was imputed (0 =no imputation, 1 = imputation). 
* Pre_Left: Baseline-corrected sensorimotor alpha suppression measured during the pretest over the left sensorimotor cortex. 
* Pre_Right: Baseline-corrected sensorimotor alpha suppression measured during the pretest over the right sensorimotor cortex.
* Pre_Occipital: Baseline-corrected sensorimotor alpha suppression measured during the pretest over the occipital region.
* Post_Left: Baseline-corrected sensorimotor alpha suppression measured during the posttest over the left sensorimotor cortex.
* Post_Right: Baseline-corrected sensorimotor alpha suppression measured during the posttest over the right sensorimotor cortex.
* Post_Occipital: Baseline-corrected sensorimotor alpha suppression measured during the posttest over the occipital region.
* Reflection_Min_Average: The average number of minutes per day an infant spent looking at their own reflection.
* Right_Diff: The difference between posttest and pretest sensorimotor alpha suppression values over the right sensorimotor cortex (post minus pre).
* Left_Diff: The difference between posttest and pretest values over the left sensorimotor cortex (post minus pre).


EMG Data Files Description
Filename: EMG Data.csv
This file contains electromyography (EMG) measures of infants’ facial mimicry responses during the observation of eyebrow and mouth trials at pre- and post-test
Variables included in the file:
* Participant: Unique numeric identifier for each infant participant.
* Sex: The sex of the infant (M/F).
* Condition: The experimental group assignment (0 = control group, 1 = mirror group). 
* Age: Infant age in days at pre-test. 
* Imputed: Whether the pre-test data was imputed (0 =no imputation, 1 = imputation). 
* V1_Mouth_Corrugator: Standardised EMG activity over the corrugator muscle during the observation of mouth actions at pre‑test.
* V1_Mouth_Zygomaticus: Standardised EMG activity over the zygomaticus muscle during the observation of mouth actions at pre‑test.
* V1_Eyebrow_Corrugator: Standardised EMG activity over the corrugator muscle during the observation of eyebrow actions at pre‑test.
* V1_Eyebrow_Zygomaticus: Standardised EMG activity over the zygomaticus muscle during the observation of eyebrow actions at pre‑test.
* V2_Mouth_Corrugator: Standardised EMG activity over the corrugator muscle during the observation of mouth actions at post‑test.
* V2_Mouth_Zygomaticus: Standardised EMG activity over the zygomaticus muscle during the observation of mouth actions at post‑test.
* V2_Eyebrow_Corrugator: Standardised EMG activity over the corrugator muscle during the observation of eyebrow actions at post‑test.
* V2_Eyebrow_Zygomaticus: Standardised EMG activity over the zygomaticus muscle during the observation of eyebrow actions at post‑test.
* V1_MouthMimicry: Mimicry score for Mouth actions at pre-test
* V1_EyebrowMimicry: Mimicry score for Eyebrow actions at pre-test
* V1_AverageMimicry: Average pre-test Mimicry score
* V2_MouthMimicry: Mimicry score for Mouth actions at post-test
* V2_EyebrowMimicry: Mimicry score for Eyebrow actions at post-test
* V2_AverageMimicry: Average post-test Mimicry score
* Toy_Times_Average: Average number of times per day the infant played with the toy. 
* Toy_Min_Average: Average number of minutes per day the infant played with the toy. 
* Reflection_Min_Average: The average number of minutes per day an infant spent looking at their own reflection.
* Mimicry_Difference: The difference in mimicry between pre-test and post-test (V2_AverageMimicry minus V1_AverageMimicry).

Filename: EMG Data Baseline Corrected.csv
This file contains baseline-corrected electromyography (EMG) measures of infants’ facial mimicry responses during the observation of eyebrow and mouth trials at pre- and post-test
Variables included in the file:
* Participant: Unique numeric identifier for each infant participant.
* Sex: The sex of the infant (M/F).
* Condition: The experimental group assignment (0 = control group, 1 = mirror group). 
* Age: Infant age in days at pre-test. 
* Imputed: Whether the pre-test data was imputed (0 =no imputation, 1 = imputation). 
* V1_Mouth_Corrugator: Standardised baseline-corrected EMG activity over the corrugator muscle during the observation of mouth actions at pre‑test.
* V1_Mouth_Zygomaticus: Standardised baseline-corrected EMG activity over the zygomaticus muscle during the observation of mouth actions at pre‑test.
* V1_Eyebrow_Corrugator: Standardised baseline-corrected EMG activity over the corrugator muscle during the observation of eyebrow actions at pre‑test.
* V1_Eyebrow_Zygomaticus: Standardised baseline-corrected EMG activity over the zygomaticus muscle during the observation of eyebrow actions at pre‑test.
* V2_Mouth_Corrugator: Standardised baseline-corrected EMG activity over the corrugator muscle during the observation of mouth actions at post‑test.
* V2_Mouth_Zygomaticus: Standardised baseline-corrected EMG activity over the zygomaticus muscle during the observation of mouth actions at post‑test.
* V2_Eyebrow_Corrugator: Standardised baseline-corrected EMG activity over the corrugator muscle during the observation of eyebrow actions at post‑test.
* V2_Eyebrow_Zygomaticus: Standardised baseline-corrected EMG activity over the zygomaticus muscle during the observation of eyebrow actions at post‑test.
* V1_MouthMimicry: Mimicry score for Mouth actions at pre-test
* V1_EyebrowMimicry: Mimicry score for Eyebrow actions at pre-test
* V1_AverageMimicry: Average pre-test Mimicry score
* V2_MouthMimicry: Mimicry score for Mouth actions at post-test
* V2_EyebrowMimicry: Mimicry score for Eyebrow actions at post-test
* V2_AverageMimicry: Average post-test Mimicry score
* Reflection_Min_Average: The average number of minutes per day an infant spent looking at their own reflection.
* Mimicry_Difference: The difference in mimicry between pre-test and post-test (V2_AverageMimicry minus V1_AverageMimicry).

Supplementary Analyses File Description
Filename: Supplementary Analyses Overt Actions and Mimicry.csv
This file contains variables used in supplementary analyses examining (a) the frequency of infants’ overt facial movements during the stimulus videos, and (b) baseline‑corrected overt facial mimicry at pre‑ and post‑test. These measures complement the EMG and EEG datasets by providing behavioural indices of infants’ observable facial actions.
Variables included in the file:
Participant: Unique numeric identifier for each infant participant.
Condition: The experimental group assignment (0 = control group, 1 = mirror group). 
* PercentOvertMove_Pre: Proportion of included EMG trials at pre‑test in which the infant showed any overt facial movement (e.g., visible smile, frown, eyebrow raise). Values represent the percentage of trials with any movement.
* PercentOvertMove_Post: Proportion of included EMG trials at post‑test in which the infant showed any overt facial movement (e.g., visible smile, frown, eyebrow raise). Values represent the percentage of trials with any movement.
* Pre_BaselineCorr_Mouth: Baseline‑corrected overt mimicry score for mouth actions at pre‑test. 
* Pre_BaselineCorr_Eyebrow: Baseline‑corrected overt mimicry score for eyebrow actions at pre‑test. 
* Pre_BaselineCorrectedMimicry: Overall baseline‑corrected mimicry score at pre‑test, averaged across mouth and eyebrow actions.
* Post_BaselineCorr_Mouth: Baseline‑corrected mimicry score for mouth actions at post‑test.
* Post_BaselineCorr_Eyebrow: Baseline‑corrected mimicry score for eyebrow actions at post‑test.
* Post_BaselineCorrectedMimicry: Overall baseline‑corrected mimicry score at post‑test, averaged across mouth and eyebrow actions.