Developmental differentiation in human infant cry through dynamic interaction with caregivers

cote interne IRCAM: Nonaka13aNone / NoneNational audienceNo infants in any primate species cry as much, and with as much diversity, as humans do. Two hypotheses compete to explain the development of such acoustical complexity in early life (Soltis, 2004). For one, the cry is a graded signal that develops to reflect the amount of e.g. neediness or pain felt by the infant. For the other, the cry is a categorical signal used to convey discrete types of needs. The present research proposes that it is, in fact, a mixture of both. We collected acoustic recordings of the cries of 35 infants, as well as verbal reports by their caregivers, at frequent and regular intervals during the infants' first year of age. Regression analyses of verbal categories identified in the reports indicate that, with development, caregivers increasingly attribute the cause of the cry to the infant's social (loneliness, shyness, opposition, etc.), rather than physiological (pain, sleepiness, hunger, etc.) needs; and that the cues utilized to infer one or the other type of need also change with time: the vocal content of the cry is used less and less to identify the infant's physiological needs, and more and more for its social needs. In parallel, acoustical analyses of the cries reveal a progressive differentiation of the patterns of expiration rate and pitch, in which each infant develops to adopt distinct signatures for different social needs. Together, these findings suggest that the infant's physiological states influence a graded-signal portion of the cry which is relatively stable through development, while social interactions influence a categorical-signal portion of the cry, a developping code which is probably learned jointly by the caregiver and the infant(Okanoya, 2007)

Sense of Accomplishment Is Modulated by a Proper Level of Instruction and Represented in the Brain Reward System

<div><p>Problem-solving can be facilitated with instructions or hints, which provide information about given problems. The proper amount of instruction that should be provided for learners is controversial. Research shows that tasks with intermediate difficulty induce the largest sense of accomplishment (SA), leading to an intrinsic motivation for learning. To investigate the effect of instructions, we prepared three instruction levels (No hint, Indirect hint, and Direct hint) for the same insight-problem types. We hypothesized that indirect instructions impose intermediate difficulty for each individual, thereby inducing the greatest SA per person. Based on previous neuroimaging studies that showed involvement of the bilateral caudate in learning and motivation, we expected SA to be processed in this reward system. We recruited twenty-one participants, and investigated neural activations during problem solving by functional magnetic resonance imaging (fMRI). We confirmed that the Indirect hint, which imposed intermediate difficulty, induced the largest SA among the three instruction types. Using fMRI, we showed that activations in the bilateral caudate and anterior cingulate cortex (ACC) were significantly modulated by SA. In the bilateral caudate, the indirect hint induced the largest activation, while the ACC seemed to reflect the difference between correct and incorrect trials. Importantly, such activation pattern was independent of notations (number or letter). Our results indicate that SA is represented in the reward system, and that the Indirect instruction effectively induces such sensation.</p></div

Behavioural data for the four conditions.

<p>Accuracy (A), RT (B), and SA (C) are shown for the four conditions (two notations concatenated). (D) SA in the correct and incorrect trials, averaged across No hint, Indirect, and Direct conditions. *<i>P</i> < 0.05. **<i>P</i> < 0.01. ***<i>P</i> < 0.001. Error bars, SD.</p

Activation modulated by SA in the answer-feedback period.

<p>The cortical activation map was projected onto the sagittal plain (uncorrected <i>P</i> < 0.001). See Table B in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0168661#pone.0168661.s015" target="_blank">S1 File</a> for the stereotactic coordinates.</p

Effect of intrinsic problem difficulty.

<p>Accuracy (A) and RT (B) for three instruction levels are shown as a function of intrinsic problem difficulty (Difficulty). (C) SA for the three difficulty levels, divided according to the RT differences for each participant. (D) The average number of trials for each of three instructions included in each difficulty level. ***<i>P</i> < 0.001. Error bars, SD.</p

Activations in the correct and incorrect trials.

<p>Beta estimates of correct and incorrect trials were extracted from the anatomically defined ROIs (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0168661#pone.0168661.s007" target="_blank">S7 Fig</a>) of the left caudate (A, D), right caudate (B, E), and ACC (C, F), for both problem-solving period and answer-feedback period. *<i>P</i> < 0.05. **<i>P</i> < 0.01. ***<i>P</i> < 0.001. Error bars, SD.</p

Experimental design.

<p>One of the four types of instructions was presented for 1 s, followed by the problem stimulus. Participants performed Number/Letter completion or button-press control tasks during the 5 s interval. After 1 s of a blank screen, 3 s of correct-answer feedback stimulus was presented. After the feedback stimuli, the participants rated their sense of accomplishment (SA) during the 3 s interval. Here we have shown an example of a Number notation task (translated in English).</p

Activation modulated by SA only for the correct trials.

<p>Neural activations parametrically modulated by SA, only for the correct trials. The cortical activation map was projected onto the coronal (A) and sagittal (B) plains (uncorrected <i>P</i> < 0.001). See Table C in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0168661#pone.0168661.s015" target="_blank">S1 File</a> for the stereotactic coordinates.</p