112 research outputs found
Neural computations underlying social risk sensitivity
Under standard models of expected utility, preferences over stochastic events are assumed to be independent of the source of uncertainty. Thus, in decision-making, an agent should exhibit consistent preferences, regardless of whether the uncertainty derives from the unpredictability of a random process or the unpredictability of a social partner. However, when a social partner is the source of uncertainty, social preferences can influence decisions over and above pure risk attitudes (RA). Here, we compared risk-related hemodynamic activity and individual preferences for two sets of options that differ only in the social or non-social nature of the risk. Risk preferences in social and non-social contexts were systematically related to neural activity during decision and outcome phases of each choice. Individuals who were more risk averse in the social context exhibited decreased risk-related activity in the amygdala during non-social decisions, while individuals who were more risk averse in the non-social context exhibited the opposite pattern. Differential risk preferences were similarly associated with hemodynamic activity in ventral striatum at the outcome of these decisions. These findings suggest that social preferences, including aversion to betrayal or exploitation by social partners, may be associated with variability in the response of these subcortical regions to social risk
Bayesian Model of Behaviour in Economic Games
Classical game theoretic approaches that make strong rationality assumptions have difficulty modeling human behaviour in economic games. We investigate the role
of finite levels of iterated reasoning and non-selfish utility functions in a Partially Observable Markov Decision Process model that incorporates game theoretic notions
of interactivity. Our generative model captures a broad class of characteristic behaviours in a multi-round Investor-Trustee game. We invert the generative process
for a recognition model that is used to classify 200 subjects playing this game against randomly matched opponents
Recommended from our members
A 4-Year Longitudinal Neuroimaging Study of Cognitive Control Using Latent Growth Modeling: Developmental Changes and Brain-Behavior Associations
Despite theoretical models suggesting developmental changes in neural substrates of cognitive control in adolescence, empirical research has rarely examined intraindividual changes in cognitive control-related brain activation using multi-wave multivariate longitudinal data. We used longitudinal repeated measures of brain activation and behavioral performance during the multi-source interference task (MSIT) from 167 adolescents (53% male) who were assessed annually over four years from ages 13 to 17 years. We applied latent growth modeling to delineate the pattern of brain activation changes over time and to examine longitudinal associations between brain activation and behavioral performance. We identified brain regions that showed differential change patterns: (1) the fronto-parietal regions that involved bilateral insula, bilateral middle frontal gyrus, left pre-supplementary motor area, left inferior parietal lobule, and right precuneus; and (2) the rostral anterior cingulate cortex (rACC) region. Longitudinal confirmatory factor analyses of the fronto-parietal regions revealed strong measurement invariance across time implying that multivariate functional magnetic resonance imaging data during cognitive control can be measured reliably over time. Latent basis growth models indicated that fronto-parietal activation decreased over time, whereas rACC activation increased over time. In addition, behavioral performance data, age-related improvement was indicated by a decreasing trajectory of intraindividual variability in response time across four years. Testing longitudinal brain-behavior associations using multivariate growth models revealed that better behavioral cognitive control was associated with lower fronto-parietal activation, but the change in behavioral performance was not related to the change in brain activation. The current findings suggest that reduced effects of cognitive interference indicated by fronto-parietal recruitment may be a marker of a maturing brain that underlies better cognitive control performance during adolescence
Large Solar Angle and Seesaw Mechanism: a Bottom-up Perspective
In addition to the well established large atmospheric angle, a large solar
angle is probably present in the leptonic sector. In the context of the see-saw
and by means of a bottom-up approach, we explore which patterns for the Dirac
and Majorana right-handed mass matrices provide two large mixings in a robust
way and with the minimal amount of tuning. Three favourite patterns emerge,
which have a suggestive physical interpretation in terms of the role played by
right-handed neutrinos: in both solar and atmospheric sectors, either a single
or a pseudo-Dirac pair of right-handed neutrinos dominates. Each pattern gives
rise to specific relations among the neutrino mixing angles and mass
differences, which lead to testable constraints on U_{e3}. The connection with
the rate of LFV charged lepton decays is also addressed.Comment: 31 pages, 7 figures; published versio
Symmetries and fermion masses
We discuss whether quark, charged lepton and neutrino masses and mixing
angles may be related by an extended flavour and family symmetry group. We show
that current measurements of all fermion masses and mixing angles are
consistent with a combination of an underlying SU(3) family symmetry together
with a GUT symmetry such as SO(10). In this the near bi-maximal mixing observed
in the neutrino sector is directly related to the small mixing observed in the
quark sector, the difference between quark and lepton mixing angles being due
to the see-saw mechanism. Using this connection we make a detailed prediction
for the lepton mixing angles determining neutrino oscillation phenomena.Comment: 24 pages, 1 figure. To be submitted to Nucl. Phys.
Seesaw and Lepton Flavour Violation in SUSY SO(10)
That and are sensitive probes of
SUSY models with a see-saw mechanism is a well accepted fact. Here we propose a
`top-down' approach in a general SUSY SO(10) scheme. In this framework, we show
that at least one of the neutrino Yukawa couplings is as large as the top
Yukawa coupling. This leads to a strong enhancement of these leptonic flavour
changing decay rates. We examine two `extreme' cases, where the lepton mixing
angles in the neutrino Yukawa couplings are either small (CKM-like) or large
(PMNS-like). In these two cases, we quantify the sensitivity of leptonic
radiative decays to the SUSY mass spectrum. In the PMNS case, we find that the
ongoing experiments at the B-factories can completely probe the spectrum up to
gaugino masses of 500 GeV (any tan ). Even in the case of CKM-like
mixings, large regions of the parameter space will be probed in the near
future, making these two processes leading candidates for indirect SUSY
searches.Comment: 22 pages with 2 figures. Figures for \tau -> \mu \gamma decay
corrected after typo found in the program. Decay \mu -> e gamma completely
unchanged and conclusions basicaly unchange
The mediating role of attachment and mentalising in the relationship between childhood maltreatment, self-harm and suicidality
Background
Although the relationship between childhood maltreatment, self-harm and suicidality is well-established, less is known about the mediating mechanisms explaining it. Based on a developmental mentalisation-based theoretical framework, childhood adversity compromises mentalising ability and attachment security, which in turn increase vulnerability to later stressors in adulthood.
Objective
This study aimed to investigate the role of attachment and mentalising as potential mechanisms in the relationship between childhood maltreatment, self-harm and suicidality.
Participants and setting
We recruited 907 adults from clinical and community settings in Greater London.
Methods
The study design was cross-sectional. Participants completed self-report questionnaires on retrospectively rated childhood trauma, and current attachment to the romantic partner, mentalising, self-harm, suicidal ideation and attempt. We used structural equation modelling to examine the data and conceptualized childhood maltreatment as a general factor in a confirmatory bifactor model.
Results
The results showed that childhood maltreatment was both directly associated with self-harm and suicidality and indirectly via the pathways of attachment and mentalising.
Conclusions
These findings indicate that insecure attachment and impaired mentalising partially explain the association between childhood maltreatment, self-harm and suicidality. Clinically, they provide support for the potential of mentalisation-based therapy or other psychosocial interventions that aim to mitigate the risk of self-harm and suicidality among individuals who have experienced childhood maltreatment via increasing understanding of self and other mental states
SUSY GUT Models of Neutrino Mass and mu to e gamma
It is explained why excessive mu to e gamma can be a problem in SUSY GUT
see-saw models of neutrino mass, and ways that this problem might be avoided
are discussed.Comment: 13 pages, LaTeX, references adde
SUSY Seesaw and FCNC
After a quarter of century of intense search for new physics beyond the
Standard Model (SM), two ideas stand out to naturally cope with (i) small
neutrino masses and (ii) a light higgs boson : Seesaw and SUSY. The combination
of these two ideas, i.e. SUSY seesaw exhibits a potentially striking signature:
a strong (or even very strong) enhancement of lepton flavour violation (LFV),
which on the contrary remains unobservable in the SM seesaw. Indeed, even when
supersymmetry breaking is completely flavour blind, Renormalisation Group
running effects are expected to generate large lepton flavour violating entries
at the weak scale. In Grand Unified theories, these effects can be felt even in
hadronic physics. We explicitly show that in a class of SUSY SO(10) GUTs there
exist cases where LFV and CP violation in B-physics can constitute a major road
in simultaneously confirming the ideas of Seesaw and low-energy SUSY.Comment: Invited Talk at Seesaw (1979-2004), Fujihara Seminar, Neutrino mass
and Seesaw mechanism, Feb 23-25, 2004, KEK, Japan. To appear in the
proceedings. 13 pages and four figure
- âŠ