Evaluating the Role of Personality Trait Information in Social Dilemmas

We investigate whether cooperative behavior in social dilemmas is conditional on information about a partner\u27s personality traits. Using a repeated one-shot continuous strategy Prisoner\u27s Dilemma (two person Public Goods game), we test how information on personality traits of partners influences cooperative actions. Before each game we provide subjects with the rank-order of their partner (relative to all subjects in the session) on one of the personality traits of the Big Five Inventory. Using a within-subjects design we find that subjects are more cooperative when informed that their partner is more ‘Agreeable’ or ‘Open to Experience’. The primary reason for more cooperative behavior is the expectation that partners will give more to the public good

A Redshift Survey of the Strong Lensing Cluster Abell 383

Abell 383 is a famous rich cluster (z = 0.1887) imaged extensively as a basis for intensive strong and weak lensing studies. Nonetheless there are few spectroscopic observations. We enable dynamical analyses by measuring 2360 new redshifts for galaxies with r$_{petro} \leq 20.5$ and within 50$^\prime$ of the BCG (Brightest Cluster Galaxy: R.A.$_{2000} = 42.014125^\circ$, Decl$_{2000} = -03.529228^\circ$). We apply the caustic technique to identify 275 cluster members within 7$h^{-1}$ Mpc of the hierarchical cluster center. The BCG lies within $-11 \pm 110$ km s$^{-1}$ and 21 $\pm 56 h^{-1}$ kpc of the hierarchical cluster center; the velocity dispersion profile of the BCG appears to be an extension of the velocity dispersion profile based on cluster members. The distribution of cluster members on the sky corresponds impressively with the weak lensing contours of Okabe et al. (2010) especially when the impact of foreground and background structure is included. The values of R$_{200}$ = $1.22\pm 0.01 h^{-1}$ Mpc and M$_{200}$ = $(5.07 \pm 0.09)\times 10^{14} h^{-1}$ M$_\odot$ obtained by application of the caustic technique agree well with recent completely independent lensing measures. The caustic estimate extends direct measurement of the cluster mass profile to a radius of $\sim 5 h^{-1}$ Mpc.Comment: 29 pages, 9 figures, ApJ accepte

CAIRNS: The Cluster And Infall Region Nearby Survey III. Environmental Dependence of H-alpha Properties of Galaxies

We investigate the environmental dependence of star formation in cluster virial regions and infall regions as part of CAIRNS (Cluster And Infall Region Nearby Survey), a large spectroscopic survey of the infall regions surrounding nine nearby rich clusters of galaxies. Our long-slit spectroscopy yields estimates of star formation rates in environments from cluster cores to the general large-scale structure. The fraction of galaxies with current star formation in their inner disks as traced by H-alpha emission increases with distance from the cluster and converges to the ``field'' value only at 2-3 virial radii, in agreement with other investigations. However, among galaxies with significant current star formation (EW[Ha]geq2\AA), there is no difference in the distribution of EW[Ha] inside and outside the virial radius. This surprising result, first seen by Carter et al., suggests that (1) star formation is truncated on either very short timescales or only at moderate and high redshifts or (2) that projection effects contaminate the measurement. The number density profiles of star-forming and non-star-forming galaxies indicate that, among galaxies projected inside the virial radius, at least half of the former and 20% of the latter are ``infall interlopers,'' galaxies in the infall region but outside the virial region. The kinematics of star-forming galaxies in the infall region closely match those of absorption-dominated galaxies. This result shows that the star forming galaxies in the infall regions are not interlopers from the field and excludes one model of the backsplash scenario of galaxy transformation. Finally, we quantify systematic uncertainties in estimating the global star formation in galaxies from their inner disks.Comment: 25 pages, 21 figures, accepted for publication in A

Evaluating Case-based Decision Theory: Predicting Empirical Patterns of Human Classification Learning (Extensions)

We introduce a computer program which calculates an agent’s optimal behavior according to Case-based Decision Theory (Gilboa and Schmeidler, 1995) and use it to test CBDT against a benchmark set of problems from the psychological literature on human classification learning (Shepard et al., 1961). This allows us to evaluate the efficacy of CBDT as an account of human decision-making on this set of problems. We find: (1) The choice behavior of this program (and therefore Case-based Decision Theory) correctly predicts the empirically observed relative difficulty of problems and speed of learning in human data. (2) ‘Similarity’ (how CBDT decision makers extrapolate from memory) is decreasing in vector distance, consistent with evidence in psychology (Shepard, 1987). (3) The best-fitting parameters suggest humans aspire to an 80 − 85% success rate, and humans may increase their aspiration level during the experiment. (4) Average similarity is rejected in favor of additive similarity