Pre-delinquent peers in Achievement Place (a community based family style rehabilitation program based on a token economy) were given points (token reinforcement) to modify the articulation errors of two boys. In Experiment I, using a multiple baseline experimental design, error words involving the /l/, /r/, /th/, and /ting/ sounds were successfully treated by both a group of peers and by individual peers. Also, generalization occurred to words that were not trained. The speech correction procedure used by the peers involved a number of variables including modelling, peer approval, contingent points, and feedback. The individual role of each of these variables was not experimentally analyzed, but it was demonstrated that peers could function as speech therapists without instructions, feedback, or the presence of an adult. It was also found that payment of points to peers for detecting correct articulations produced closer agreement with the experimenter than when they were paid points for finding incorrect articulations. The results were replicated in a second experiment with another subject who had similar articulation errors. In addition, the second experiment showed that peer speech correction procedures resulted in some generalization to the correct use of target words in sentences and significant improvements on standard tests of articulation.
In this paper we introduce Armadillo v1.1, a novel workflow platform dedicated to designing and conducting phylogenetic studies, including comprehensive simulations. A number of important phylogenetic and general bioinformatics tools have been included in the first software release. As Armadillo is an open-source project, it allows scientists to develop their own modules as well as to integrate existing computer applications. Using our workflow platform, different complex phylogenetic tasks can be modeled and presented in a single workflow without any prior knowledge of programming techniques. The first version of Armadillo was successfully used by professors of bioinformatics at Université du Quebec à Montreal during graduate computational biology courses taught in 2010–11. The program and its source code are freely available at: .
This study examined the nature and correlates of Mexican American mothers’ and fathers’ involvement in adolescents’ peer relationships along four dimensions: support, restriction, knowledge, and time spent with adolescents and peers. Mexican American adolescents and their parents in 220 families described their family relationships, cultural orientations/values, and experiences with adolescents’ peers in home interviews. In addition, time-use data were collected during a series of seven phone calls to measure parents’ time spent with adolescents and peers and parents’ knowledge of adolescents’ daily experiences with peers. Multi-level models revealed connections between parents’ involvement in adolescents’ peer relationships and both parents’ Mexican and Anglo orientations and familism values and adolescents’ peer experiences (e.g., deviant peer affiliations, friends’ ethnic orientation). Findings further revealed some evidence that parent and adolescent gender moderated the patterns, with mothers’ (but not fathers’) restrictions on peer relationships being associated with adolescents’ deviant peer affiliations and parents placing greater restrictions on daughters’ than on sons’ peer relationships when they had more frequent deviant peer affiliations.
Mentoring in academic medicine has been shown to contribute to the success of junior faculty, resulting in increased productivity, career satisfaction, and opportunities for networking. Although traditional dyadic mentoring, involving one senior faculty member and one junior protégé, is the dominant model for mentoring in the academic environment, there is increasing recognition that the sharing of knowledge, skills, and experiences among peers may also contribute to the career development of junior faculty. The authors describe the structure, activities, and outcomes of the Junior Faculty Laboratory (JFL), a self-organized, flexible, and dynamic peer mentoring model within the Duke University Center for the Study of Aging and Human Development. As an innovative mentoring model, JFL is entirely peer-driven and its activities are determined by the real-time needs of members. In contrast to some other peer mentoring models, JFL lacks senior faculty input or a structured curriculum, members are multidisciplinary, meeting times are project-driven rather than preset, and participation in collaborative projects is optional based on the interests and needs of group members. Additionally, JFL was not formed as a substitute for, but as a complement to the dyadic mentoring relationships enjoyed by its members. The model, now in its fifth year, has demonstrated success and sustainability. The authors present the JFL as an innovative, mentoring model that can be reproduced by other junior faculty seeking to foster collegial relationships with peers while simultaneously enhancing their career development.
A substantial amount of research has suggested that adolescents’ attitudes and behaviors are influenced by peers; however, little is known regarding adolescents’ individual variability, or susceptibility, to peer influence. In this study, a performance-based index from an experimental paradigm was used to directly measure adolescents’ susceptibility to peers. A total of 36 adolescent boys participated in a “chat room” experiment in which they ostensibly were exposed to deviant or risky social norms communicated either by high-peer-status (i.e., popular, well-liked) or low-peer-status (i.e., unpopular, disliked) grade mates who actually were electronic confederates. Changes in adolescents’ responses before and after exposure to peer norms were used as a measure of peer influence susceptibility. These same adolescents completed a questionnaire assessment at the study outset and again 18 months later to assess their actual engagement in deviant behavior and their perceptions of their best friend’s engagement in deviant behavior. Only among adolescents with high levels of susceptibility to high-status peers was a significant longitudinal association revealed between their best friend’s baseline deviant behavior and adolescents’ own deviant behavior 18 months later. Findings support the predictive validity of a performance-based susceptibility measure and suggest that adolescents’ peer influence susceptibility may generalize across peer contexts.
peer influence; deviant/delinquent behavior; susceptibility; adolescents
Congratulations to the publisher, members of the editorial board of the journal, all the authors and readers for launching the World Journal of Transplantation (WJT) as a new member of the World series journal family. Transplantations are rapidly evolving and share knowledge with a number of basic and clinical sciences: molecular biology, stem cell investigators, immune system, pharmacology, biotechnology, surgery and physicians of different organs such as the kidneys, liver, heart, lung, bone marrow and so on. The WJT is a peer reviewed open access journal centered on the different fields involved in transplant activity. If you want to share your experiences and new findings in the field of transplantation with your peers you will find the WJT a good media to publish your papers.
Transplantation; Peer reviewed; Open access journal; Transplant related sciences
The emergence of the Internet has triggered tremendous changes in the publication of scientific peer-reviewed journals. Today, journals are usually available in parallel electronic versions, but the way the peer-review process works, the look of articles and journals, and the rigid and slow publication schedules have remained largely unchanged, at least for the vast majority of subscription-based journals. Those publishing firms and scholarly publishers who have chosen the more radical option of open access (OA), in which the content of journals is freely accessible to anybody with Internet connectivity, have had a much bigger degree of freedom to experiment with innovations.
The objective was to study how open access journals have experimented with innovations concerning ways of organizing the peer review, the format of journals and articles, new interactive and media formats, and novel publishing revenue models.
The features of 24 open access journals were studied. The journals were chosen in a nonrandom manner from the approximately 7000 existing OA journals based on available information about interesting journals and include both representative cases and highly innovative outlier cases.
Most early OA journals in the 1990s were founded by individual scholars and used a business model based on voluntary work close in spirit to open-source development of software. In the next wave, many long-established journals, in particular society journals and journals from regions such as Latin America, made their articles OA when they started publishing parallel electronic versions. From about 2002 on, newly founded professional OA publishing firms using article-processing charges to fund their operations have emerged. Over the years, there have been several experiments with new forms of peer review, media enhancements, and the inclusion of structured data sets with articles. In recent years, the growth of OA publishing has also been facilitated by the availability of open-source software for journal publishing.
The case studies illustrate how a new technology and a business model enabled by new technology can be harnessed to find new innovative ways for the organization and content of scholarly publishing. Several recent launches of OA journals by major subscription publishers demonstrate that OA is rapidly gaining acceptance as a sustainable alternative to subscription-based scholarly publishing.
Scholarly publishing; open access; Internet; peer review
Introduction The development of professional behaviour is an important objective for students in Health Sciences, with reflective skills being a basic condition for this development. Literature describes a variety of methods giving students opportunities and encouragement for reflection. Although the literature states that learning and working together in peer meetings fosters reflection, these findings are based on experienced professionals. We do not know whether participation in peer meetings also makes a positive contribution to the learning experiences of undergraduate students in terms of reflection. Aim The aim of this study is to gain an understanding of the role of peer meetings in students’ learning experiences regarding reflection. Method A phenomenographic qualitative study was undertaken. Students’ learning experiences in peer meetings were analyzed by investigating the learning reports in students’ portfolios. Data were coded using open coding. Results The results indicate that peer meetings created an interactive learning environment in which students learned about themselves, their skills and their abilities as novice professionals. Students also mentioned conditions for a well-functioning group. Conclusion The findings indicate that peer meetings foster the development of reflection skills as part of professional behaviour.
Reflection; Peer meetings; Professional behaviour; Teaching; Collaborative learning
Associating with substance using peers is generally considered as one of the most important predictors of adolescent substance use. However, peer association does not affect all adolescents in the same way. To better understand when and under what conditions peer association is most linked with adolescent substance use (SU), this review focuses on the factors that may operate as moderators of this association. The review highlighted several potential moderators reflecting adolescents’ individual characteristics (e.g., pubertal status, genes and personality), peer and parental factors (e.g., nature of relationships and parental monitoring), and contextual factors (e.g., peer, school and neighborhood context). As peer association is a broad concept, important methodological aspects were also addressed in order to illustrate how they can potentially bias interpretation. Taking these into account, we suggest that, while the effects of some moderators are clear (e.g., parental monitoring and sensation seeking), others are less straightforward (e.g., neighborhood) and need to be further examined. This review also provides recommendations for addressing different methodological concerns in the study of moderators, including: the use of longitudinal and experimental studies and the use of mediated moderation. These will be key for developing theory and effective prevention.
PMID: 24183303 CAMSID: cams3491
Peers; substance use; alcohol use; adolescence; moderation effect
The Taverna workflow tool suite (http://www.taverna.org.uk) is designed to combine distributed Web Services and/or local tools into complex analysis pipelines. These pipelines can be executed on local desktop machines or through larger infrastructure (such as supercomputers, Grids or cloud environments), using the Taverna Server. In bioinformatics, Taverna workflows are typically used in the areas of high-throughput omics analyses (for example, proteomics or transcriptomics), or for evidence gathering methods involving text mining or data mining. Through Taverna, scientists have access to several thousand different tools and resources that are freely available from a large range of life science institutions. Once constructed, the workflows are reusable, executable bioinformatics protocols that can be shared, reused and repurposed. A repository of public workflows is available at http://www.myexperiment.org. This article provides an update to the Taverna tool suite, highlighting new features and developments in the workbench and the Taverna Server.
Early stressful events can increase vulnerability for psychopathology, although knowledge on the effectors is still limited. In this report we describe the characterization of a single nucleotide polymorphism (SNP) in rhesus macaques, which results in a Val to Met transition in the pro-BDNF domain, similar to a well described variant in the human gene. Further, we tested the hypothesis that peripheral levels of BDNF, which is involved in the response to stress and in the pathophysiology of anxiety and depression, might be differentially affected in a non-human primate model of early adverse rearing in a genotype-dependent manner. Males and females rhesus macaques reared either with their mothers (MR), in peer-only groups (PR), or in a “surrogate/peer-reared” (SPR) condition with limited peer interactions, were used as experimental subjects. BDNF levels were determined at baseline on postnatal days (PND) 14, 30 and 60 by means of specific ELISA procedure. Data indicate that BDNF levels were increased as a result of peer-rearing and that this increase was moderated by the presence of the SNP. Overall these data indicate that a SNP, which results in a Val to Met transition in the pro-BDNF domain, is present in rhesus macaques and is able to affect BDNF peripheral levels, thus making this primate model a fundamental tool to study gene by environment interactions involving the BDNF gene.
Brain-derived neurotrophic factor (BDNF); polymorphism; stress; depression; non-human primates
Peer review is the major method used by biomedical journals for making the decision of publishing an article. This cross-sectional survey assesses views concerning the review system of biomedical journals among academics globally.
A total of 28,009 biomedical academics from high-ranking universities listed by the 2009 Times Higher Education Quacquarelli Symonds (THE-QS) World University Rankings were contacted by email between March 2010 and August 2010. 1,340 completed an online survey which focused on their academic background, negative experiences and views on biomedical journal peer review and the results were compared among basic scientists, clinicians and clinician scientists.
Fewer than half of the respondents agreed that the peer review systems of biomedical journals were fair (48.4%), scientific (47.5%), or transparent (25.1%). Nevertheless, 58.2% of the respondents agreed that authors should remain anonymous and 64.4% agreed that reviewers should not be disclosed. Most, (67.7%) agreed to the establishment of an appeal system. The proportion of native English-speaking respondents who agreed that the “peer review system is fair” was significantly higher than for non-native respondents (p = 0.02). Similarly, the proportion of clinicians stating that the “peer review system is fair” was significantly higher than that for basic scientists and clinician-scientists (p = 0.004). For females, (β = −0.1, p = 0.03), the frequency of encountering personal attacks in reviewers’ comments (β = −0.1, p = 0.002) and the frequency of imposition of unnecessary references by reviewers (β = −0.06, p = 0.04) were independently and inversely associated with agreement that “the peer review system is fair”.
Academics are divided on the issue of whether the biomedical journal peer review system is fair, scientific and transparent. A majority of academics agreed with the double-blind peer review and to the establishment of an appeal system. Female academics, experience of personal attacks and imposition of unnecessary references by reviewers were related to disagreement about fairness of the peer review system of biomedical journals.
Academics; Peer review; Biomedical journal; Online survey
There has been considerable examination and critique of traditional (academic) peer review processes in quality assessment of grant applications. At the same time, the use of traditional research processes in Indigenous research has been questioned. Many grant funding organisations have changed the composition of their peer review panels to reflect these concerns but the question remains do these reforms go far enough? In this project we asked people working in areas associated with Aboriginal health research in a number of capacities, their views on the use of peer review in assessing Indigenous research proposals.
In semi-structured interviews we asked 18 individuals associated with an Australian Indigenous research funding organisation to reflect on their experience with peer review in quality assessment of grant applications. We also invited input from a steering group drawn from a variety of organisations involved in Aboriginal research throughout Australia and directly consulted with three Aboriginal-controlled health organisations.
There was consensus amongst all participants that traditional academic peer review is inappropriate for quality assessment in Indigenous research. Many expressed the view that using a competitive grant review system in Aboriginal health was counterintuitive, since good research transfer is based on effective collaboration. The consensus within the group favoured a system which built research in a collaborative manner incorporating a variety of different stakeholders in the process. In this system, one-off peer review was still seen as valuable in the form of a "critical friend" who provided advice as to how to improve the research proposal.
Peer review in the traditional mould should be recognised as inappropriate in Aboriginal research. Building research projects relevant to policy and practice in Indigenous health may require a shift to a new way of selecting, funding and conducting research.
In order to tackle the important and challenging problem in proteomics of identifying known and new protein sequences using high-throughput methods, we propose a data-sharing platform that uses fully distributed P2P technologies to share specifications of peer-interaction protocols and service components. By using such a platform, information to be searched is no longer centralised in a few repositories but gathered from experiments in peer proteomics laboratories, which can subsequently be searched by fellow researchers.
The system distributively runs a data-sharing protocol specified in the Lightweight Communication Calculus underlying the system through which researchers interact via message passing. For this, researchers interact with the system through particular components that link to database querying systems based on BLAST and/or OMSSA and GUI-based visualisation environments. We have tested the proposed platform with data drawn from preexisting MS/MS data reservoirs from the 2006 ABRF (Association of Biomolecular Resource Facilities) test sample, which was extensively tested during the ABRF Proteomics Standards Research Group 2006 worldwide survey. In particular we have taken the data available from a subset of proteomics laboratories of Spain's National Institute for Proteomics, ProteoRed, a network for the coordination, integration and development of the Spanish proteomics facilities.
Results and Discussion
We performed queries against nine databases including seven ProteoRed proteomics laboratories, the NCBI Swiss-Prot database and the local database of the CSIC/UAB Proteomics Laboratory. A detailed analysis of the results indicated the presence of a protein that was supported by other NCBI matches and highly scored matches in several proteomics labs. The analysis clearly indicated that the protein was a relatively high concentrated contaminant that could be present in the ABRF sample. This fact is evident from the information that could be derived from the proposed P2P proteomics system, however it is not straightforward to arrive to the same conclusion by conventional means as it is difficult to discard organic contamination of samples. The actual presence of this contaminant was only stated after the ABRF study of all the identifications reported by the laboratories.
Single-item global ratings are commonly used at the end of undergraduate clerkships and residency rotations to measure specific competencies and/or to compare the performances of individuals against their peers. We hypothesized that an Internet-based instrument would be feasible to adequately distinguish high- and low-ability residents.
Materials and Methods
After receiving Institutional Review Board approval, we developed an Internet-based global ranking instrument to rank 42 third-year residents (21 in 2008 and 21 in 2009) in a major university teaching hospital's department of anesthesiology. Evaluators were anesthesia attendings and nonphysicians in 3 tertiary-referral hospitals. Evaluators were asked this ranking question: “When it comes to overall clinical ability, how does this individual compare to all their peers?”
For 2008, 111 evaluators completed the ranking exercise; for 2009, 79 completed it. Residents were rank-ordered using the median of evaluator categorizations and the frequency of ratings per assigned relative performance quintile. Across evaluator groups and study years, the summary evaluation data consistently distinguished the top and bottom resident cohorts.
An Internet-based instrument, using a single-item global ranking, demonstrated feasibility and can be used to differentiate top- and bottom-performing cohorts. Although ranking individuals yields norm-referenced measures of ability, successfully identifying poorly performing residents using online technologies is efficient and will be useful in developing and administering targeted evaluation and remediation programs.
Open peer review has been proposed for a number of reasons, in particular, for increasing the transparency of the article selection process for a journal, and for obtaining a broader basis for feedback to the authors and for the acceptance decision. The review discussion may also in itself have a value for the research community. These goals rely on the existence of a lively review discussion, but several experiments with open-process peer review in recent years have encountered the problem of faltering review discussions. The present article addresses the question of how lively review discussion may be fostered by relating the experience of the journal Electronic Transactions on Artificial Intelligence (ETAI) which was an early experiment with open peer review. Factors influencing the discussion activity are identified. It is observed that it is more difficult to obtain lively discussion when the number of contributed articles increases, which implies difficulties for scaling up the open peer review model. Suggestions are made for how this difficulty may be overcome.
open peer review; community peer review; two-stage peer review; live discussion
Peer review is fundamentally a cooperative process between scientists in a community who agree to review each other's work in an unbiased fashion. Peer review is the foundation for decisions concerning publication in journals, awarding of grants, and academic promotion. Here we perform a laboratory study of open and closed peer review based on an online game. We show that when reviewer behavior was made public under open review, reviewers were rewarded for refereeing and formed significantly more cooperative interactions (13% increase in cooperation, P = 0.018). We also show that referees and authors who participated in cooperative interactions had an 11% higher reviewing accuracy rate (P = 0.016). Our results suggest that increasing cooperation in the peer review process can lead to a decreased risk of reviewing errors.
We conducted a comprehensive narrative review and used a systematic search strategy to identify studies related to peer support among adults with mental health difficulties. The purposes of this review were to describe the principles, effects and benefits of peer support documented in the published literature, to discuss challenging aspects of peer support and to investigate lessons from peer support. Fifty-one studies, including 8 review articles and 19 qualitative studies, met the inclusion criteria for this review. Most of the challenges for peer support were related to “role” and “relationship” issues; that is, how peer support providers relate to people who receive peer support and how peer support providers are treated in the system. The knowledge gained from peer support relationships, such as mutual responsibility and interdependence, might be a clue toward redefining the helper-helper relationship as well as the concepts of help and support.
Benefit; Effect; Mental Health; Mutuality; Peer Support; Principle; Reciprocity; Relationship.
Research on adolescent development suggests that peer influence may play a key role in explaining adolescents’ willingness to drink, an important predictor of drinking initiation. However, experiments that thoroughly examine these peer influence effects are scarce. This study experimentally examined whether adolescents adapted their willingness to drink when confronted with the pro-alcohol and anti-alcohol norms of peers in a chat room session and whether these effects were moderated by the social status of peers.
We collected survey data on drinking behavior, social status, and willingness to drink among five hundred thirty-two 14- to 15-year-olds. Of this sample, 74 boys participated in a simulated Internet chat room session in which participants were confronted with preprogrammed pro-alcohol or anti-alcohol norms of “grade-mates” which were in fact preprogrammed e-confederates. Accordingly, we tested whether participants adapted their willingness to drink to the norms of these grade-mates. To test whether adaptations in participants’ willingness to drink would depend on grade-mates’ social status, we manipulated their level of popularity.
The results indicated that adolescents adapted their willingness to drink substantially to the pro-alcohol (i.e., more willing to drink) as well as anti-alcohol (i.e., less willing to drink) norms of these peers. Adolescents were more influenced by high-status than low-status peers. Interestingly, the anti-alcohol norms of the popular peers seemed most influential in that adolescents were less willing to drink when they were confronted with the anti-alcohol norms of popular peers. Additionally, the adolescents internalized these anti-alcohol norms.
This study gives more insight into peer influence processes that encourage or discourage alcohol use. These results could be fundamental for the development of prevention and intervention programs to reduce alcohol use among the adolescents.
Peer Influence; Drinking Norms; Adolescents; Popularity
A longitudinal, prospective design was used to examine the roles of peer rejection in middle childhood and antisocial peer involvement in early adolescence in the development of adolescent externalizing behavior problems. Both early starter and late starter pathways were considered. Classroom sociometric interviews from ages 6 through 9 years, adolescent reports of peers' behavior at age 13 years, and parent, teacher, and adolescent self-reports of externalizing behavior problems from age 5 through 14 years were available for 400 adolescents. Results indicate that experiencing peer rejection in elementary school and greater involvement with antisocial peers in early adolescence are correlated but that these peer relationship experiences may represent two different pathways to adolescent externalizing behavior problems. Peer rejection experiences, but not involvement with antisocial peers, predict later externalizing behavior problems when controlling for stability in externalizing behavior. Externalizing problems were most common when rejection was experienced repeatedly. Early externalizing problems did not appear to moderate the relation between peer rejection and later problem behavior. Discussion highlights multiple pathways connecting externalizing behavior problems from early childhood through adolescence with peer relationship experiences in middle childhood and early adolescence.
When the human genome project was conceived, its leaders wanted all researchers to have equal access to the data and associated research tools. Their vision of equal access provides an unprecedented teaching opportunity. Teachers and students have free access to the same databases that researchers are using. Furthermore, the recent movement to deliver scientific publications freely has presented a second source of current information for teaching. I have developed a genomics course that incorporates many of the public-domain databases, research tools, and peer-reviewed journals. These online resources provide students with exciting entree into the new fields of genomics, proteomics, and bioinformatics. In this essay, I outline how these fields are especially well suited for inclusion in the undergraduate curriculum. Assessment data indicate that my students were able to utilize online information to achieve the educational goals of the course and that the experience positively influenced their perceptions of how they might contribute to biology.
genomic; proteomics; bioinformatics; teaching; research; undergraduate; model organisms; online databases; public domain
Many protein structures determined in high-throughput structural genomics centers, despite their significant novelty and importance, are available only as PDB depositions and are not accompanied by a peer-reviewed manuscript. Because of this they are not accessible by the standard tools of literature searches, remaining underutilized by the broad biological community.
To address this issue we have developed TOPSAN, The Open Protein Structure Annotation Network, a web-based platform that combines the openness of the wiki model with the quality control of scientific communication. TOPSAN enables research collaborations and scientific dialogue among globally distributed participants, the results of which are reviewed by experts and eventually validated by peer review. The immediate goal of TOPSAN is to harness the combined experience, knowledge, and data from such collaborations in order to enhance the impact of the astonishing number and diversity of structures being determined by structural genomics centers and high-throughput structural biology.
TOPSAN combines features of automated annotation databases and formal, peer-reviewed scientific research literature, providing an ideal vehicle to bridge a gap between rapidly accumulating data from high-throughput technologies and a much slower pace for its analysis and integration with other, relevant research.
This paper uses random assignment in professional golf tournaments to test for peer effects in the workplace. We find no evidence that playing partners’ ability affects performance, contrary to recent evidence on peer effects in the workplace from laboratory experiments, grocery scanners, and soft-fruit pickers. In our preferred specification we can rule out peer effects larger than 0.043 strokes for a one stroke increase in playing partners’ ability. Our results complement existing studies on workplace peer effects and are useful in explaining how social effects vary across labor markets, across individuals, and with the form of incentives faced.
The influence of deviant peers on youth behavior is of growing concern, both in naturally occurring peer interactions and in interventions that might inadvertently exacerbate deviant development. The focus of this special issue is on understanding the moderating and mediating variables that account for peer contagion effects in interventions for youth. This set of nine innovative papers moves the field forward on three fronts: (1) Broadening the empirical basis for understanding the conditions under which peer contagion is more or less likely (that is, moderators of effects); (2) Identifying mechanisms that might account for peer contagion effects (mediators); and (3) Forging the methodological rigor that is needed to study peer contagion effects within the context of intervention trials. We propose an ecological framework for disentangling the effects of individuals, group interactions, and program contexts in understanding peer contagion effects. Finally, we suggest methodological enhancements to study peer contagion in intervention trials.
peer contagion; peer influences; deviant peers
Social influence is the process by which individuals adapt their opinion, revise their beliefs, or change their behavior as a result of social interactions with other people. In our strongly interconnected society, social influence plays a prominent role in many self-organized phenomena such as herding in cultural markets, the spread of ideas and innovations, and the amplification of fears during epidemics. Yet, the mechanisms of opinion formation remain poorly understood, and existing physics-based models lack systematic empirical validation. Here, we report two controlled experiments showing how participants answering factual questions revise their initial judgments after being exposed to the opinion and confidence level of others. Based on the observation of 59 experimental subjects exposed to peer-opinion for 15 different items, we draw an influence map that describes the strength of peer influence during interactions. A simple process model derived from our observations demonstrates how opinions in a group of interacting people can converge or split over repeated interactions. In particular, we identify two major attractors of opinion: (i) the expert effect, induced by the presence of a highly confident individual in the group, and (ii) the majority effect, caused by the presence of a critical mass of laypeople sharing similar opinions. Additional simulations reveal the existence of a tipping point at which one attractor will dominate over the other, driving collective opinion in a given direction. These findings have implications for understanding the mechanisms of public opinion formation and managing conflicting situations in which self-confident and better informed minorities challenge the views of a large uninformed majority.