Three Essays on the generalizability of experimental results in economics

Although few economists today dismiss the use of the laboratory experiments, it would be a mistake to think that experimental methodology no longer represents a controversial issue in economics. One of the major criticisms is represented by the external validity of experimental data and concerns the transferability of results obtained in laboratory to the real world. The aim of this thesis is to tackle the issue of external validity focusing in particular on one aspect: the possible lack of representativeness of standard subjects pools usually used in economic research. The first experimental study compares the choices of undergraduates and subjects representative of population in different treatments and with different reward dimensions by exploiting the experimental design used by Pelligra and Stanca (2013) to investigate social preferences in a field experiment. Our results show that two samples follow a common behavioral pattern with the only exception of a significant difference in choices where self-interest may play a prominent role. In the second study we use a between-subjects design to compare the behavior of experienced and inexperienced subjects. We investigate whether the laboratory experience, built through repeated participation in experimental sessions, biases subjects’ behavior in a set of representative simple games used to study social preferences. Our main finding shows how subjects having a high level of experience in lab experiments do not behave in a significantly different way from novices

Lab-sophistication: does repeated participation in laboratory experiments affect pro-social behaviour?

Experimental social scientists working at research-intensive institutions deal inevitably with subjects who have most likely participated in previous experiments. It is an important methodological question to know whether participants that have acquired a high level of lab-sophistication show altered pro-social behavioural patterns. In this paper, we focus both on the potential effect of the subjects’ lab-sophistication, and on the role of the knowledge about the level of lab-sophistication of the other participants. Our main findings show that while lab-sophistication per se does not significantly affect pro-social behaviour, for sophisticated subjects the knowledge about the counterpart’s level of (un)sophistication may systematically alter their choices. This result should induce caution among experimenters about whether, in their settings, information about lab-sophistication can be inferred by the participants, due to the characteristics of the recruitment mechanisms, the management of the experimental sessions or to other contextual clues

From the Field to the Lab. An Experiment on the Representativeness of Standard Laboratory Subjects

We replicate in the laboratory an artefactual field experiment originally designed to investigate the incidence of various forms of social preferences in a representative sample of the population. Results show that, on aggregate, the two groups display a similar directional pattern in a set of simple dictator games. However, in situations in which giving is costly (or rewarding) for the dictator, the proportion of laboratory subjects who follow their self-interest is relatively higher than that in the rest of the population. We note a higher sensitivity of students, both from the laboratory and the field, to the possibility of losing part of their own payoff. Furthermore, students from the lab (all economics majors) are more sensitive to gains than students from different backgrounds even when these gains go against equality

Informal we stand? The role of social progress around the world

none3noSocial progress has increased around the world. Can it be considered a strategic tool to shrink the informal sector? Using data for 156 countries over the last 30 years, we find that social progress - measured though the Human Development Index (HDI) - exerts a strong negative impact on informal economy (IE). However, this impact diminishes for higher levels of social progress, depicting a non-linear relationship, and it is mainly driven by the income and health components of HDI, whereas the education component does not play a significant role. Among the mechanisms possibly affecting the investigated relationship, we focus on political corruption and the spread of internet as opposite factors at work. While the ‘virtuous’ effect of social progress on IE holds even in presence of high political corruption, it vanishes when the internet diffusion increases.mixedMedda, Tiziana; Palmisano, Flaviana; Sacchi, AgneseMedda, Tiziana; Palmisano, Flaviana; Sacchi, Agnes

Impact of High Body Mass Index on Vascular and Bleeding Complications After Transcatheter Aortic Valve Implantation

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A multi-marker integrative analysis reveals benefits and risks of bariatric surgery

Bariatric surgery (BS) is an effective intervention for severe obesity and associated comorbidities. Although several studies have addressed the clinical and metabolic effects of BS, an integrative analysis of the complex body response to surgery is still lacking. We conducted a longitudinal data study with 36 patients with severe obesity who were tested before, 6 and 12 months after restrictive BS for more than one hundred blood biomarkers, including clinical, oxidative stress and metabolic markers, peptide mediators and red blood cell membrane lipids. By using a synthetic data-driven modeling based on principal component and correlation analyses, we provided evidence that, besides the early, well-known glucose metabolism- and weight loss-associated beneficial effects of BS, a tardive, weight-independent increase of the hepatic cholesterol metabolism occurs that is associated with potentially detrimental inflammatory and metabolic effects. Canonical correlation analysis indicated that oxidative stress is the most predictive feature of the BS-induced changes of both glucose and lipids metabolism. Our results show the power of multi-level correlation analysis to uncover the network of biological pathways affected by BS. This approach highlighted potential health risks of restrictive BS that are disregarded with the current practice to use weight loss as surrogate of BS success

Clinical and pathological factors influencing survival in a large cohort of triple-negative breast cancer patients

Abstract Background To provide further information on the clinical and pathological prognostic factors in triple-negative breast cancer (TNBC), for which limited and inconsistent data are available. Methods Pathological characteristics and clinical records of 841 TNBCs diagnosed between 1994 and 2015 in four major oncologic centers from Sardinia, Italy, were reviewed. Multivariate hazard ratios (HRs) for mortality and recurrence according to various clinicopathological factors were estimated using Cox proportional hazards models. Results After a mean follow-up of 4.3 years, 275 (33.3%) TNBC patients had a progression of the disease and 170 (20.2%) died. After allowance for study center, age at diagnosis, and various clinicopathological factors, all components of the TNM staging system were identified as significant independent prognostic factors for TNBC mortality. The HRs were 3.13, 9.65, and 29.0, for stage II, III and IV, respectively, vs stage I. Necrosis and Ki-67 > 16% were also associated with increased mortality (HR: 1.61 and 1.99, respectively). Patients with tumor histotypes other than ductal invasive/lobular carcinomas had a more favorable prognosis (HR: 0.40 vs ductal invasive carcinoma). No significant associations with mortality were found for histologic grade, tumor infiltrating lymphocytes, and lymphovascular invasion. Among lymph node positive TNBCs, lymph node ratio appeared to be a stronger predictor of mortality than pathological lymph nodes stage (HR: 0.80 for pN3 vs pN1, and 3.05 for >0.65 vs <0.21 lymph node ratio), respectively. Consistent results were observed for cancer recurrence, except for Ki-67 and necrosis that were not found to be significant predictors for recurrence. Conclusions This uniquely large study of TNBC patients provides further evidence that, besides tumor stage at diagnosis, lymph node ratio among lymph node positive tumors is an additional relevant predictor of survival and tumor recurrence, while Ki-67 seems to be predictive of mortality, but not of recurrence