'EyeTunes - Infant perception of audio-visual temporal (a)synchrony'
(AsPredicted #29811)
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1) Have any data been collected for this study already?
No, no data have been collected for this study yet.

2) What's the main question being asked or hypothesis being tested in this study?
We hypothesize that 4-month-old infants will detect temporal asynchrony between rhythmic audio-visual stimuli when they are simple and socially meaningful (i.e., infant-directed singing, peer bouncing), but not when they are complex (i.e., complex music, adult dancing).

3) Describe the key dependent variable(s) specifying how they will be measured.
Cumulative looking times will be measured to synchronous and asynchronous stimuli presented simultaneously on the left and right side of a computer screen, respectively, resulting in a value each for the left and right area of interest (AOI).

Next, we will calculate relative looking times, i.e. cumulative looking times to the left and right AOI, respectively, relative to the overall looking to the screen.

Our main DV will be difference scores (DS): We will calculate DS by subtracting relative looking times to the asynchronous from relative looking times to the synchronous stimulus, and dividing the result by the sum of both values (Senju & Csibra, 2008). A DS > 0 indicates a preference for the synchronous stimulus, a DS < 0 indicates a preference for the asynchronous stimulus.

Looking times will be measured through EyeLink 1000 Plus (SR Research Ltd., 2013-2015), arm mount with remote mode, with a high-speed camera with a 16 mm/1:14 lens and a 940 nm Illuminator. The stimuli will be presented on a 1090x1850 pixel screen. A target will be placed on infants’ forehead, and they will sit on an experimenter’s lap at approximately 55 cm from the camera.

4) How many and which conditions will participants be assigned to?
Infants will be tested in a within-subjects design. In each trial, they will be presented with two side-by-side videos, one of which will be synchronous while the other one will be asynchronous with an auditory stimulus (i.e., Hungarian children’s song). We will manipulate the complexity of both the visual and auditory stimuli:
- Visual: a baby being bounced (simple) vs. a person dancing (complex)
- Auditory: song being sung by a female voice in an infant-directed way (simple) vs. song being sung as a duet with
instrumental accompaniment (complex)

Asynchrony between the auditory and visual stimuli will be achieved by manipulating the meter. Because the auditory stimulus is in 4/4 meter, in the synchronous trials the movements will be performed in 4/4 meter (with stress on the first beat), while in the asynchronous trials the movements will be performed in 3/4 meter (with stress on the first beat).

There will be two test conditions:
- complex video and audio
- simple video and audio

To control for the possibility that infants have an a priori preference for one of the two visual displays (i.e., the asynchronous visual stimulus is moving faster than the synchronous visual stimulus), infants will additionally see two control conditions (i.e., simple, complex), where they will be shown the video stimuli without sound.

The presentation of the stimuli will be preceded by a 3-point calibration with an animation target. Conditions will be organized into 4 blocks, with 4 trials of 23 sec in each block. The first block will contain the silent control conditions, while blocks 2-4 will contain the test conditions. Each trial will be preceded by an attention getter (spinning spiral) to direct infant attention to the centre of the screen. The presentation order of the conditions and the position of the synchronous video (left/right) will be pseudorandomized in 4 lists, to avoid order/position biases. The total duration of the experiment (excluding the time for initial calibration) will be 6 min and 56 sec.

5) Specify exactly which analyses you will conduct to examine the main question/hypothesis.
Through the software DataViewer (SR Research) the data from the eye-tracking system will be analysed and total looking time to each AOI as well as the whole screen for each condition for each trial will be extracted.

First, we will analyze infant looking during the control conditions. We will use a one-sample t-test to test whether infant DS are significantly different from 0 (i.e., chance level) for both simple and complex videos. If the results of this test are non-significant (i.e., indicating no systematic preference), then we will procede with further analyses without change. If the results are significant suggesting that infants systematically prefer one visual stimulus over the other, then infant looking pattern in the control conditions will be included as a control variable in all further analyses.

If infants detect a difference between synchronized and asynchronized stimuli, then we expect that the DS scores are significantly different from 0 (i.e., chance level). To test this hypothesis we will use t-tests to test DS (a) against 0 for both simple and complex conditions, and (b) against each other.

6) Describe exactly how outliers will be defined and handled, and your precise rule(s) for excluding observations.
Trials will be excluded when infants do not look for at least 200 ms at both AOIs.

An infant will be excluded from analyses when:
- he/she has less than 2 valid trials per condition
- he/she shows a position bias (looking to one direction for more than 90% of the time)
- he/she fails to be calibrated after 2 attempts

7) How many observations will be collected or what will determine sample size?
No need to justify decision, but be precise about exactly how the number will be determined.
A power analysis with medium to big effect size (f=0.4, 1- β=0.95), yielded an optimal sample size of 30 participants, excluding attrition. Participants will be 4-month-old infants (4 months 0 days – 4 months 30 days).

8) Anything else you would like to pre-register?
(e.g., secondary analyses, variables collected for exploratory purposes, unusual analyses planned?)
To examine whether infants preferred the synchronous or asynchronous stimuli, we will compute how many infants showed a preference for one or the other in both simple and complex conditions using binomial tests.

If our analyses show that infants systematically prefer one visual display over the other in the control conditions, then we will additionally examine potential changes in infant looking patterns between the control and test conditions.

Potential sub-AOIs within the two large AOIs will be explored in infants’ looking patterns.

We will control for musical background of both mother and infant.