Frequency of use by age (in year;month) among children reported to have used touch screens in the past.

<p>Data is grouped in deciles to even the number of infants in each category. As in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0128338#pone.0128338.g001" target="_blank">Fig 1</a>, “<1×” stands for “less than once a”; “wk” stands for “week” and “mth” for “month”.</p

Gestures displayed during interaction with a touch screen by age decile.

<p>Caregivers’ report of whether their child displayed an interactive gesture (red) or not (white), grouping children in ten equally-sized age groups. The limits of some of the age groups (in year;month) are given in the x-axis (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0128338#pone.0128338.g002" target="_blank">Fig 2</a> for full list).</p

Activity reportedly liked by age decile.

<p>Caregivers’ report of whether their child enjoyed an activity (red) or not (white), grouping children in ten equally-sized age groups. The limits of some of the age groups (in year;month) are given in the x-axis (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0128338#pone.0128338.g002" target="_blank">Fig 2</a> for full list).</p

Effects of age on activity reportedly liked.

<p>Results from logistic regressions attempting to predict whether parents report that their child likes an activity (1) or not (0) from the child’s age (Type II Analysis of Deviance).</p><p>* indicates significant given our pre-established alpha level.</p><p>Effects of age on activity reportedly liked.</p

Frequency of use by age.

<p>Data is grouped in deciles to even the number of infants in each frequency of use category; “<1×” stands for “less than once a”; “wk” stands for “week” and “mth” for “month”.</p

Average time course of the hemoglobin changes following auditory stimulation in individual channels revealed by a general linear model.

<p>The trace in red represents oxyHb, in blue deoxyHb; the error bars indicate standard error (over participants). The zero level or baseline is defined as the intercept of the linear model. The black dotted lines show the standard HRF model convolved with the average duration of stimulation, scaled to the maximum average concentration. The scale as well as the timing of stimulation (green box) are shown in the reference axes.</p

Discriminability of sound contrasts in the face of speaker variation quantified

How does a naive language learner deal with speaker variation irrelevant to distinguishing word meanings? Experimental data is contradictory, and incompatible models have been proposed. Here, we examine basic assumptions regarding the acoustic signal the learner deals with: Is speaker variability a hurdle in discriminating sounds or can it easily be ignored? To this end, we summarize existing infant data. We then present machine-based discriminability scores of sound pairs obtained without any language knowledge. Our results show that speaker variability decreases sound contrast discriminability, and that some contrasts are affected more than others. However, chance performance is rare; most contrasts remain discriminable in the face of speaker variation. We take our results to mean that speaker variation is not a uniform hurdle to discriminating sound contrasts, and careful examination is necessary when planning and interpreting studies testing whether and to what extent infants (and adults) are sensitive to speaker differences

Channels activated in the sound versus silence contrast.

<p>Ch  =  channel (channels with a number followed by a subscript are deep); <i>β</i> =  beta recovered from the GLM in mM.mm; SE <i>β</i>  =  standard error of the <i>β</i>, N  =  number of children contributing data for that channel and condition, t value, p unc(orrected), and p cor(rected through resampling). Only channels whose <i>β</i> value was significantly different from zero at p ≤ 0.05 uncorrected, for the relevant condition, are shown. Channels with significant <i>β</i> after correction through resampling are marked with *.</p><p>Channels activated in the sound versus silence contrast.</p

Channels activated in the five conditions.

<p>Ch  =  channel (channels with a number followed by a subscript are deep); <i>β</i>  =  beta recovered from the GLM in mM.mm; SE <i>β</i>  =  standard error of the <i>β</i>, N  =  number of children contributing data for that channel and condition, t value, p unc(orrected), and p cor(rected through resampling). Only channels whose <i>β</i> value was significantly different from zero at p ≤ 0.05 uncorrected, for the relevant condition, are shown.</p><p>Channels activated in the five conditions.</p

Comparison of amount of data between the newborn results reported here, and previous comparable infant work.

<p>Min/Max trial N stands for the minimum and maximum number of stimulation blocks or trials. Max Tot is calculated by multiplying the sample size by the maximum number of trials. White cells indicate unavailable information. Except for Shultz*, all studies focused on newborns and used fNIRS (see main text for details).</p><p>Comparison of amount of data between the newborn results reported here, and previous comparable infant work.</p