Evidential reasoning in the prisoner's dilemma

Classic game theory considers defection to be the rational choice in the Prisoner's Dilemma. Although defection maximizes a player's gain regardless of the opponent's choice, many players cooperate. We suggest that cooperation can be explained in part by expectations of reciprocal behavior, that is, by the belief that players facing the same situation probably will come to the same decision. In Experiment 1, expectations of reciprocity were experimentally manipulated. As predicted, cooperation increased monotonically with these expectations. In Experiment 2, experimentally manipulated expectations of opponent cooperation were not associated with higher rates of cooperation. These findings are interpreted in light of a general model of payoff maximization, and implications for other models (e.g., social value orientation) are discussed.     

Perceived depth of 3-D objects in 3-D scenes

Effects of information specifying the position of an object in a 3-D scene were investigated in two experiments with twelve observers. To separate the effects of the change in scene position from the changes in the projection that occur with increased distance from the observer, the same projections were produced by simulating (a) a constant object at different scene positions and (b) different objects at the same scene position. The simulated scene consisted of a ground plane, a ceiling plane, and a cylinder on a pole attached to both planes. Motion-parallax scenes were studied in one experiment; texture-gradient scenes were studied in the other. Observers adjusted a line to match the perceived internal depth of the cylinder. Judged depth for objects matched in simulated size decreased as simulated distance from the observer increased. Judged depth decreased at a faster rate for the same projections shown at a constant scene position. Adding object-centered depth information (object rotation) increased judged depth for the motion-parallax displays. These results demonstrate that the judged internal depth of an object is reduced by the change in projection that occurs with increased distance, but this effect is diminished if information for change in scene position accompanies the change in projection.     

Briefe Deutscher Philosophen An Ernst Mach

Ohne Zusammenfassung     

Factors Affecting the Use of Dimensional Prepositions in German and American English: Object Orientation, Social Context, and Prepositional Pattern

Spatial language and the use of spatial prepositions has recently been intensively investigated. We add two novel aspects to the question of which frame of reference, i.e., the deictic or the intrinsic frame, is used when communicating about dimensional relations between objects. We restrict ourselves to the use of prepositions that refer to the first horizontal axis, i.e., in front of and behind in English, and vor and hinter in German, respectively, and report on a series of 16 experiments on the connection between the use of these prepositions and the indication of particular subspaces adjacent to reference objects in a traffic environment. First, we will show that an interaction between the intrinsic orientation of the reference object, the type of social situation in which spatial communication occurs, and the used language's pattern of prepositional word forms for temporal and spatiodimensional relations contributes to the proper prediction of the use of spatial prepositions. Second, we systematically consider production as well as interpretation of prepositions in two different languages in the same experimental setting, which allows for the estimation of communicative success. Here, it turns out that in German as well as in American English there are conditions in which speakers and listeners either agree or disagree on the chosen frame of reference; however, these conditions are different in the two languages investigated.     

Dementia with Lewy bodies: a pure case

A pure case of autopsy-confirmed dementia with Lewy bodies (DLB) is described. The patient presented with distinctive verbal fluency deficits in the context of mild language impairment, intact recognition memory, and impaired paragraph recall. Neuroimaging (CT and SPECT) showed progressive medial temporal lobe atrophy. Neuropathology revealed Lewy bodies, degeneration in the substantia nigra, nucleus basalis of Meynert (Nakano & Hirano, 1984), and locus ceruleus, but no pathology characteristic of Alzheimer's disease. It is in this sense that the case is "pure" DLB. Early neuropsychological diagnosis of DLB is essential (Salmon et al., 1996) given the potentially fatal hazard of neuroleptics (McKeith et al., 1992) and the difficulties associated with clinical neurological diagnoses (Litvan et al., 1998).     

How personal standards perfectionism and evaluative concerns perfectionism affect the error positivity and post-error behavior with varying stimulus visibility

Error detection is required in order to correct or avoid imperfect behavior. Although error detection is beneficial for some people, for others it might be disturbing. We investigated Gaudreau and Thompson’s (Personality and Individual Differences, 48, 532?537, 2010) model, which combines personal standards perfectionism (PSP) and evaluative concerns perfectionism (ECP). In our electrophysiological study, 43 participants performed a combination of a modified Simon task, an error awareness paradigm, and a masking task with a variation of stimulus onset asynchrony (SOA; 33, 67, and 100 ms). Interestingly, relative to low-ECP participants, high-ECP participants showed a better post-error accuracy (despite a worse classification accuracy) in the high-visibility SOA 100 condition than in the two low-visibility conditions (SOA 33 and SOA 67). Regarding the electrophysiological results, first, we found a positive correlation between ECP and the amplitude of the error positivity (Pe) under conditions of low stimulus visibility. Second, under the condition of high stimulus visibility, we observed a higher Pe amplitude for high-ECP–low-PSP participants than for high-ECP–high-PSP participants. These findings are discussed within the framework of the error-processing avoidance hypothesis of perfectionism (Stahl, Acharki, Kresimon, Völler, & Gibbons, International Journal of Psychophysiology, 97, 153–162, 2015).     

A Bayesian approach to mitigation of publication bias

The reliability of published research findings in psychology has been a topic of rising concern. Publication bias, or treating positive findings differently from negative findings, is a contributing factor to this “crisis of confidence,” in that it likely inflates the number of false-positive effects in the literature. We demonstrate a Bayesian model averaging approach that takes into account the possibility of publication bias and allows for a better estimate of true underlying effect size. Accounting for the possibility of bias leads to a more conservative interpretation of published studies as well as meta-analyses. We provide mathematical details of the method and examples.