Metabolic trade-offs in childhood: Exploring the relationship between language development and body growth

During human childhood, brain development and body growth compete for limited metabolic resources, resulting in a trade-off where energy allocated to brain development can decrease as body growth accelerates. This preregistered study explores the relationship between language skills, serving as a proxy for brain development, and body mass index at three distinct developmental stages, representing different phases of body growth. Longitudinal data from 2002 children in the EDEN mother-child cohort were analyzed using structural equation modeling. Our findings reveal a compelling pattern of associations: girls with a delayed adiposity rebound, signaling slower growth rate, demonstrated better language proficiency at ages 5-6. Importantly, this correlation appears to be specific to language skills and does not extend to nonverbal cognitive abilities. Exploratory analyses show that early environmental factors contributing to enhanced cognitive development, such as higher parental socio-economic status and increased cognitive stimulation, are positively associated with both language skills and the timing of adiposity rebound in girls. Overall, our findings lend support to the existence of an energy allocation trade-off mechanism that appears to prioritize language function over body growth investment in girls.

Associations Between Early Life Adversity, Reproduction-Oriented Life Strategy, and Borderline Personality Disorder

Importance

Borderline personality disorder (BPD) is often accompanied by a history of high-risk sexual behavior and somatic comorbidities. Yet, these features are most often considered in isolation and little is known about their underlying developmental pathways. Life history theory, a leading framework in evolutionary developmental biology, can help make sense of the wide range of behaviors and health issues found in BPD.

Objective

To examine whether the emergence of BPD is associated with the prioritization of immediate reproductive goals over longer-term somatic maintenance goals, a life strategy that can be viewed as a developmental response to adverse early life experiences, providing rapid reproductive benefits despite costs to health and well-being.

Design, Setting, and Participants

This study used cross-sectional data from the second wave of the National Epidemiologic Survey on Alcohol and Related Conditions in 2004-2005 (n = 34 653). Civilian, noninstitutionalized individuals in the US, 18 years or older, and those with and without a DSM-IV diagnosis of BPD were included. Analysis took place between August 2020 and June 2021.

Main Outcomes and Measures

Structural equation models were used to examine whether early life adversity was associated with the likelihood of a BPD diagnosis, either directly or indirectly through a life strategy whereby individuals trade somatic maintenance for immediate reproduction.

Results

Analyses were performed on a sample of 30 149 participants (females: 17 042 [52%]; mean [SE] age, 48.5 [0.09]; males: 12 747 [48%]; mean [SE] age, 47 [0.08]). Of these, 892 (2.7%) had a diagnosis of BPD and 29 257 (97.3%) did not have BPD. Mean early life adversity, metabolic disorder score, and body mass index were significantly higher among participants with a diagnosis of BPD. In an analysis adjusted for age, individuals with BPD reported having significantly more children than those without BPD (b =0.06; SE, 0.01; t = 4.09; P < .001). Having experienced greater levels of adversity in early life was significantly associated with a greater risk of being diagnosed with BPD later in life (direct relative risk = 0.268; SE, 0.067; P < .001). Importantly, this risk was further increased by 56.5% among respondents who prioritized short-term reproductive goals over somatic maintenance (indirect relative risk = 0.565; SE, 0.056; P < .001). Similar patterns of associations were found in male and female individuals.

Conclusions and Relevance

The hypothesis of a reproduction/maintenance life history trade-off mediating the association between early life adversity and BPD helps make sense of the high dimensionality that characterizes the physiological and behavioral correlates of BPD. Additional studies are needed to confirm these results using longitudinal data.

The ecological roots of human susceptibility to social influence: a pre-registered study investigating the impact of early-life adversity

There is considerable variability in the degree to which individuals rely on their peers to make decisions. Although theoretical models predict that environmental risks shift the cost-benefit trade-off associated with social information use, this idea has received little empirical support. Here we aim to test the effect of childhood environmental adversity on humans' susceptibility to follow others' opinion in the context of a standard face evaluation task. Results collected in a pilot study involving 121 adult participants tested online showed that susceptibility to social influence and childhood environmental adversity are positively associated. Computational analyses further confirmed that this effect is not explained by the fact that participants exposed to early adversity produce noisier decisions overall but that they are indeed more likely to follow the group's opinion. To test the robustness of these findings, a pre-registered direct replication using an optimal sample size was run. The results obtained from 262 participants in the pre-registered study did not reveal a significant association between childhood adversity and task performance but the meta-analysis ran on both the pilot and the pre-registered study replicated the initial finding. This work provides experimental evidence for an association between individuals' past ecology and their susceptibility to social influence.

Human susceptibility to social influence and its neural correlates are related to perceived vulnerability to extrinsic morbidity risks

Humans considerably vary in the degree to which they rely on their peers to make decisions. Why? Theoretical models predict that environmental risks shift the cost-benefit trade-off associated with the exploitation of others' behaviours (public information), yet this idea has received little empirical support. Using computational analyses of behaviour and multivariate decoding of electroencephalographic activity, we test the hypothesis that perceived vulnerability to extrinsic morbidity risks impacts susceptibility to social influence, and investigate whether and how this covariation is reflected in the brain. Data collected from 261 participants tested online revealed that perceived vulnerability to extrinsic morbidity risks is positively associated with susceptibility to follow peers' opinion in the context of a standard face evaluation task. We found similar results on 17 participants tested in the laboratory, and showed that the sensitivity of EEG signals to public information correlates with the participants' degree of vulnerability. We further demonstrated that the combination of perceived vulnerability to extrinsic morbidity with decoding sensitivities better predicted social influence scores than each variable taken in isolation. These findings suggest that susceptibility to social influence is partly calibrated by perceived environmental risks, possibly via a tuning of neural mechanisms involved in the processing of public information.

Changing ideas about others' intentions: updating prior expectations tunes activity in the human motor system

Predicting intentions from observing another agent's behaviours is often thought to depend on motor resonance - i.e., the motor system's response to a perceived movement by the activation of its stored motor counterpart, but observers might also rely on prior expectations, especially when actions take place in perceptually uncertain situations. Here we assessed motor resonance during an action prediction task using transcranial magnetic stimulation to probe corticospinal excitability (CSE) and report that experimentally-induced updates in observers' prior expectations modulate CSE when predictions are made under situations of perceptual uncertainty. We show that prior expectations are updated on the basis of both biomechanical and probabilistic prior information and that the magnitude of the CSE modulation observed across participants is explained by the magnitude of change in their prior expectations. These findings provide the first evidence that when observers predict others' intentions, motor resonance mechanisms adapt to changes in their prior expectations. We propose that this adaptive adjustment might reflect a regulatory control mechanism that shares some similarities with that observed during action selection. Such a mechanism could help arbitrate the competition between biomechanical and probabilistic prior information when appropriate for prediction.

Perturbing the action observation network during perception and categorization of actions' goals and grips: state-dependency and virtual lesion TMS effects

Watching others grasping and using objects activates an action observation network (AON), including inferior frontal (IFC), anterior intraparietal (AIP), and somatosensory cortices (S1). Yet, causal evidence of the differential involvement of such AON sensorimotor nodes in representing high- and low-level action components (i.e., end-goals and grip type) is meager. To address this issue, we used transcranial magnetic stimulation-adaptation (TMS-A) during 2 novel action perception tasks. Participants were shown adapting movies displaying a demonstrator performing goal-directed actions with a tool, using either power or precision grips. They were then asked to match the end-goal (Goal-recognition task) or the grip (Grip-recognition task) of actions shown in test pictures to the adapting movies. TMS was administered over IFC, AIP, or S1 during presentation of test pictures. Virtual lesion-like effects were found in the Grip-recognition task where IFC stimulation induced a general performance decrease, suggesting a critical role of IFC in perceiving grips. In the Goal-recognition task, IFC and S1 stimulation differently affected the processing of "adapted" and "nonadapted" goals. These "state-dependent" effects suggest that the overall goal of seen actions is encoded into functionally distinct and spatially overlapping neural populations in IFC-S1 and such encoding is critical for recognizing and understanding end-goals.

Abstract and concrete phrases processing differentially modulates cortico-spinal excitability

An important challenge of embodied theories is to explain the comprehension of abstract sentences. The aim of the present study was to scrutinize the role of the motor cortex in this process. We developed a new paradigm to study the abstract-concrete dimension by combining concrete (i.e., action-related) and abstract (i.e., non-action-related) verbs with nouns of graspable and non-graspable objects. Using these verb-noun combinations we performed a Transcranial Magnetic Stimulation (TMS) on the left primary motor cortex while participants performed a sentence sensibility task. Single-TMS pulses were delivered 250ms after verb or noun presentation in each of four combinations of abstract and concrete verbs and nouns. To evaluate cortico-spinal excitability we registered the electromyographic activity of the right first dorsal interosseous muscle. As to verb-noun integration, analysis of motor evoked potentials (MEPs) after TMS pulse during noun presentation revealed greater peak-to-peak amplitude in phrases containing abstract rather than concrete verbs. Response times were also collected and showed that compatible (Concrete-Concrete and Abstract-Abstract) combinations were processed faster than mixed ones; moreover in combinations containing concrete verbs, participants were faster when the pulse was delivered on the first word (verb) than on the second one (noun). Results support previous findings showing early activation of hand-related areas after concrete verbs processing. The prolonged or delayed activation of the same areas by abstract verbs will be discussed in the framework of recent embodied theories based on multiple types of representation, particularly theories emphasizing the role of different acquisition mechanisms for concrete and abstract words (Borghi and Cimatti, 2009,2012).

Object affordances tune observers' prior expectations about tool-use behaviors

Learning about the function and use of tools through observation requires the ability to exploit one's own knowledge derived from past experience. It also depends on the detection of low-level local cues that are rooted in the tool's perceptual properties. Best known as 'affordances', these cues generate biomechanical priors that constrain the number of possible motor acts that are likely to be performed on tools. The contribution of these biomechanical priors to the learning of tool-use behaviors is well supported. However, it is not yet clear if, and how, affordances interact with higher-order expectations that are generated from past experience--i.e. probabilistic exposure--to enable observational learning of tool use. To address this question we designed an action observation task in which participants were required to infer, under various conditions of visual uncertainty, the intentions of a demonstrator performing tool-use behaviors. Both the probability of observing the demonstrator achieving a particular tool function and the biomechanical optimality of the observed movement were varied. We demonstrate that biomechanical priors modulate the extent to which participants' predictions are influenced by probabilistically-induced prior expectations. Biomechanical and probabilistic priors have a cumulative effect when they 'converge' (in the case of a probabilistic bias assigned to optimal behaviors), or a mutually inhibitory effect when they actively 'diverge' (in the case of probabilistic bias assigned to suboptimal behaviors).