No two individuals are exactly alike. More than a simple platitude, this observation reflects the fundamentally stochastic nature of biological systems. The term ‘stochastic’ describes features that ...cannot be predicted a priori from readily measurable variables. In the dichotomous framework in which biological variation arises from genetic or environmental effects, stochastic effects are classified as environmental because they are not passed on to offspring — any non-heritable cause is, by definition, environmental. But non-heritable effects can be subdivided into those which can be predicted from measurable variables, and those that cannot. These latter effects are stochastic.
In this Primer, Kyle Honegger and Benjamin de Bivort examine how stochastic effects are made manifest in persistent behavioral differences between individuals, and why this variability may be evolutionarily advantageous.
The topic of working memory (WM) is ubiquitous in research on cognitive psychology and on individual differences. According to one definition, it is a small amount of information kept in a temporary ...state of heightened accessibility; it is used in most types of communication and problem solving. Short-term storage has been defined as the passive (i.e., non-attention-based, nonstrategic) component of WM or, alternatively, as a passive store separate from an attention-based WM. Here I note that much confusion has been created by the use by various investigators of many, subtly different definitions of WM and short-term storage. The definitions are sometimes made explicit and sometimes implied. As I explain, the different definitions may have stemmed from the use of a wide variety of techniques to explore WM, along with differences in theoretical orientation. By delineating nine previously used definitions of WM and explaining how additional ones may emerge from combinations of these nine, I hope to improve scientific discourse on WM. The potential advantages of clarity about definitions of WM and short-term storage are illustrated with respect to several ongoing research controversies.
•Eye blink rate (EBR) predicts resting-state dopamine (DA) activity.•Receptor subtypes D1 and D2 can both modulate EBR.•EBR predicts abnormal DA activity in clinical disorders.•EBR is a useful ...predictor of individual differences in DA-related performance.
An extensive body of research suggests the spontaneous eye blink rate (EBR) is a non-invasive indirect marker of central dopamine (DA) function, with higher EBR predicting higher DA function. In the present review we provide a comprehensive overview of this literature. We broadly divide the available research in studies that aim to disentangle the dopaminergic underpinnings of EBR, investigate its utility in diagnosis of DA-related disorders and responsivity to drug treatment, and, lastly, investigate EBR as predictor of individual differences in DA-related cognitive performance. We conclude (i) EBR can reflect both DA receptor subtype D1 and D2 activity, although baseline EBR might be most strongly related to the latter, (ii) EBR can predict hypo- and hyperdopaminergic activity as well as normalization of this activity following treatment, and (iii) EBR can reliably predict individual differences in performance on many cognitive tasks, in particular those related to reward-driven behavior and cognitive flexibility. In sum, this review establishes EBR as a useful predictor of DA in a wide variety of contexts.
This paper addresses the way in which the expansion zones of the metropolitan areas of Medellín and Rionegro are currently moving from the communal relations that marked their rural life to anonymous ...relations in which notions of neighborliness are gradually disappearing. Understanding the urban as a social condition and not only as a physical expression of the territory, but the urban is also no longer the opposite of the rural, nor is it synonymous with the city. The urban constitutes a phenomenon where anonymity and individuality are privileged in a space. This process takes place in a rural space where part of its heritage is the landscape and unneighborly relations. We assume the notion of the peri-urban limit as a space of undefinition that extends from the periphery of the Aburrá Valley to some of the rural hamlets of the Territorial Subsystem: Alto Grande - La Ramada, in the San Nicolas Valley; places where the communal is disappearing to give way to new urban dynamics. The article constitutes a theoretical contribution to the interpretation of the new realities observed in the peri-urban fringes of many contemporary metropolises, not only because of the debate it opens on the ways of understanding current urban-rural problems, but also because it suggests other perspectives for territorial planning based on the readings of the new social realities that are established there.
Research suggests that individuals differ in the degree to which they rely on lexical information to support speech perception. However, the locus of these differences is not yet known; nor is it ...known whether these individual differences reflect a context-dependent “state” or a stable listener “trait.” Here we test the hypothesis that individual differences in lexical reliance are a stable trait that is linked to individuals' relative weighting of lexical and acoustic-phonetic information for speech perception. At each of two sessions, listeners (n = 73) completed a Ganong task, a phonemic restoration task, and a locally time-reversed speech task – three tasks that have been used to demonstrate a lexical influence on speech perception. Robust lexical effects on speech perception were observed for each task in the aggregate. Individual differences in lexical reliance were stable across sessions; however, relationships among the three tasks in each session were weak. For the Ganong and locally time-reversed speech tasks, increased reliance on lexical information was associated with weaker reliance on acoustic-phonetic information. Collectively, these results (1) provide some evidence to suggest that individual differences in lexical reliance for a given task are a stable reflection of the relative weighting of acoustic-phonetic and lexical cues for speech perception in that task, and (2) highlight the need for a better understanding of the psychometric characteristics of tasks used in the psycholinguistic domain to build theories that can accommodate individual differences in mapping speech to meaning.
By adopting ideas like "development," members of a Papua New Guinean community find themselves continuously negotiating what can be expected of a relative or a community member. Nearly half the ...people born on the remote Mbuke Islands become teachers, businessmen, or bureaucrats in urban centers, while those who stay at home ask migrant relatives "What about me?" This detailed ethnography sheds light on remittance motivations and documents how terms like "community" can be useful in places otherwise permeated by kinship. As the state withdraws, Mbuke people explore what social ends might be reached through involvement with the cash economy.
Two ongoing movements in human cognitive neuroscience have researchers shifting focus from group-level inferences to characterizing single subjects, and complementing tightly controlled tasks with ...rich, dynamic paradigms such as movies and stories. Yet relatively little work combines these two, perhaps because traditional analysis approaches for naturalistic imaging data are geared toward detecting shared responses rather than between-subject variability. Here, we review recent work using naturalistic stimuli to study individual differences, and advance a framework for detecting structure in idiosyncratic patterns of brain activity, or “idiosynchrony”. Specifically, we outline the emerging technique of inter-subject representational similarity analysis (IS-RSA), including its theoretical motivation and an empirical demonstration of how it recovers brain-behavior relationships during movie watching using data from the Human Connectome Project. We also consider how stimulus choice may affect the individual signal and discuss areas for future research. We argue that naturalistic neuroimaging paradigms have the potential to reveal meaningful individual differences above and beyond those observed during traditional tasks or at rest.
•We review literature using naturalistic paradigms to study individual differences.•We discuss the phenomenon of idiosyncratic time-locked responses (“idiosynchrony”).•We outline inter-subject representational similarity analysis (IS-RSA).•We apply IS-RSA to reveal brain-behavior relationships during movie watching.•We consider the role of stimulus selection and other directions for future work.
Human functional MRI (fMRI) research primarily focuses on analyzing data averaged across groups, which limits the detail, specificity, and clinical utility of fMRI resting-state functional ...connectivity (RSFC) and task-activation maps. To push our understanding of functional brain organization to the level of individual humans, we assembled a novel MRI dataset containing 5 hr of RSFC data, 6 hr of task fMRI, multiple structural MRIs, and neuropsychological tests from each of ten adults. Using these data, we generated ten high-fidelity, individual-specific functional connectomes. This individual-connectome approach revealed several new types of spatial and organizational variability in brain networks, including unique network features and topologies that corresponded with structural and task-derived brain features. We are releasing this highly sampled, individual-focused dataset as a resource for neuroscientists, and we propose precision individual connectomics as a model for future work examining the organization of healthy and diseased individual human brains.
•Individual brain organization is qualitatively different from group-average estimates•Individualized measures of brain function become reliable with large amounts of data•Individuals exhibit distinct brain network topography and topology•We release highly sampled, multi-modal fMRI data on ten subjects as a NeuroResource
Gordon et al. demonstrate advantages of conducting whole-brain fMRI research in individual humans using large amounts of per-individual data, which greatly increases reliability and specificity. This work illustrates new approaches for fMRI-based neuroscience that allow detailed characterization of individual brain organization.
The present research investigated the developmental trajectory of infants' fairness expectations from 6 to 15 months of age (N = 150). Findings revealed a developmental transition in infants' ...fairness expectations between 6 and 12 months, as indicated by enhanced visual attention to unfair outcomes of resource distribution events (a 3:1 distribution) relative to fair outcomes (a 2:2 distribution). The onset of naturalistic sharing behavior predicted infants' fairness expectations at transitional ages. Beyond this period of developmental transition, the presence of siblings and infants' prompted giving behavior predicted individual differences in infants' fairness concerns. These results provide evidence for the role of experience in the acquisition of fairness expectations and reveal early individual differences in such expectations.
It has been suggested that individual differences in interoception (the perception of the body’s internal state) can be divided into three distinct dimensions: interoceptive accuracy (performance on ...objective tests of interoceptive accuracy), interoceptive sensibility (self-reported beliefs concerning one’s own interoception) and interoceptive awareness (a metacognitive measure indexed by the correspondence between interoceptive accuracy and interoceptive sensibility). Research conducted under this model underscores the importance of interoceptive awareness for a variety of disorder-specific and transdiagnostic symptoms. However, the clinical importance of interoceptive awareness means that this aspect of interoception warrants further scrutiny, and such scrutiny suggests that revision of the three-dimensional model of interoception is necessary. In this theoretical paper, we outline such a revision, highlighting a need to distinguish not only how interoception is measured (objective measures vs. self-report), but also what is measured (accuracy vs. attention). The model refines how individual differences in interoception are categorised, with important consequences for the measurement of interoceptive awareness. Such a revision may help researchers to identify the strengths and weaknesses in interoception observed across clinical conditions, and to isolate clinically relevant individual differences.
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