Reference problems in stoichiometry

This paper was written under DFG project Ba 678/3-1. The English text was corrected by Marcus Brown.     

Free-Variable Tableaux for Propositional Modal Logics

Free-variable semantic tableaux are a well-established technique for first-order theorem proving where free variables act as a meta-linguistic device for tracking the eigenvariables used during proof search. We present the theoretical foundations to extend this technique to propositional modal logics, including non-trivial rigorous proofs of soundness and completeness, and also present various techniques that improve the efficiency of the basic naive method for such tableaux.     

Successive olfactory reversal learning in honeybees

Honeybees Apis mellifera can associate an originally neutral odor with a reinforcement of sucrose solution. Forward pairings of odor and reinforcement enable the odor to release the proboscis extension reflex in consecutive tests. Bees can also be conditioned differentially: They learn to respond to a reinforced odor and not to a nonreinforced one. They can also learn to reverse their choice. Here we ask whether honeybees can learn successive olfactory differential conditioning tasks involving different overlapping pairs of odors. The conditioning schedules were established in order to train the animals with 3, 2, 1, or 0 reversals previous to a last differential conditioning phase in which two additional reversals were present. We studied whether or not successive reversal learning is possible and whether or not learning olfactory discrimination reversals affects the solving of subsequent discrimination reversals. Therefore we compared the responses of bees that had experienced reversals with those of bees that had not experienced such reversals when both are confronted with a new reversal situation. In experiment 1 we showed that bees that had experienced three previous reversals were better in solving the final reversal task than bees with no previous reversal experience. In experiment 2, we showed that one reversal learning is enough for bees to perform better in the final reversal task. The successive different reversals trained in our experiments resemble the natural foraging situation in which a honeybee forager has to switch successively from an initial floral species to different ones. The fact that experiencing such changes seems to improve a bee's performance in dealing with further new exploited food sources has therefore an adaptive impact for the individual and for the colony as a whole.     

The structure of affective action representations: temporal binding of affective response codes

Two experiments examined the hypothesis that preparing an action with a specific affective connotation involves the binding of this action to an affective code reflecting this connotation. This integration into an action plan should lead to a temporary occupation of the affective code, which should impair the concurrent representation of affectively congruent events, such as the planning of another action with the same valence. This hypothesis was tested with a dual-task setup that required a speeded choice between approach- and avoidance-type lever movements after having planned and before having executed an evaluative button press. In line with the code-occupation hypothesis, slower lever movements were observed when the lever movement was affectively compatible with the prepared evaluative button press than when the two actions were affectively incompatible. Lever movements related to approach and avoidance and evaluative button presses thus seem to share a code that represents affective meaning. A model of affective action control that is based on the theory of event coding is discussed.     

List-method directed forgetting: Evidence for the reset-of-encoding hypothesis employing item-recognition testing

In list-method directed forgetting (LMDF), people are cued to forget a previously studied item list (List 1) and to learn a new list of items (List 2) instead. Such cuing typically enhances memory for the List 2 items, in both recall and (sometimes) item-recognition testing. It has recently been hypothesized that the enhancement effect for List 2 items (partly) reflects the result of a reset-of-encoding process. The proposal is that encoding efficacy decreases with an increase in study material, but the forget cue can reset the encoding process to make the encoding of early List 2 items as effective as the encoding of early List 1 items. An experiment is reported that examined the reset-of-encoding hypothesis with item-recognition testing, examining influences of items' serial learning position on the effects of the forget cue. Item-recognition tests were conducted separately for the two lists. Consistent with the reset-of-encoding hypothesis, the results showed strong enhancement effects for early List 2 items, but hardly any enhancement effects for middle and late List 2 items. Like in previous item-recognition studies, no cuing effects were found for List 1 items. The results support two-mechanism accounts of LMDF, which assume a critical role for a reset-of-encoding process for List 2 enhancement.     

Digit ratio (2D:4D) and aggregate personality scores across nations: Data from the BBC internet study

The purpose of this study was to consider relationships between digit ratio (2D:4D, a putative correlate of prenatal sex steroids) and aggregate personality scores across nations. Differences in national personality scores may be influenced by such factors as prevalence of the parasite Toxoplasma gondii, latitude and economics, and variation in 2D:4D has also been linked to prevalence of T. gondii and to latitude. Here we report associations of mean 2D:4D per country and latitude, gross domestic product (GDP), T. gondii prevalence and personality profiles in 23 nations of an internet study. 2D:4D was not related to latitude or to T. gondii, but was related to GDP (women only). With regard to national personality scores, 2D:4D was not related to masculinity but there were significant positive relationships of 2D:4D with uncertainty avoidance in men and women and with neuroticism in men. Male 2D:4D was significantly related to uncertainty avoidance and neuroticism independent of T. gondii, whereas female 2D:4D was not significantly related to uncertainty avoidance or neuroticism after controlling for the effect of T. gondii and GDP. We conclude that nations with high male 2D:4D (low prenatal testosterone, high prenatal oestrogen) have high scores for uncertainty avoidance and neuroticism.     

Unconscious activation of task sets

Using an explicit task cuing paradigm, we tested whether masked cues can trigger task-set activation, which would suggest that unconsciously presented stimuli can impact cognitive control processes. Based on a critical assessment of previous findings on the priming of task-set activation, we present two experiments with a new method to approach this subject. Instead of using a prime, we varied the visibility of the cue. These cues either directly signaled particular tasks in Experiment 1, or certain task transitions (i.e., task repetitions or switches) in Experiment 2. While both masked task and transition cues affected task choice, only task cues affected the speed of task performance. This observation suggests that task-specific stimulus–response rules can be activated only by masked cues that are uniquely associated with a particular task. Taken together, these results demonstrate that unconsciously presented stimuli have the power to activate corresponding task sets.     

Morality shifting in the context of intergroup violence

We propose morality shifting as a mechanism through which individuals can maintain a moral image of the ingroup. We argue that a shift from the moral principles of harm and fairness to those of loyalty and authority occurs when assessing a potentially threatening event, particularly among high ingroup glorifiers. Three studies confirmed this hypothesis using three different methodologies. Study 1 compared the use of language related to four moral foundations formulated in moral psychology in response to ingroup‐ and outgroup‐committed wrongdoings. Results showed that loyalty‐ and authority‐related words were used more, whereas harm‐ and fairness‐related words were used less in response to ingroup‐ compared with outgroup‐committed wrongdoings. Study 2 replicated this effect with regards to the cognitive accessibility of these moral principles. Study 3 confirmed that morality shifting is a motivated response to social identity threat, rather than a response to mere activation of social identity. Finally, as predicted, Study 3 demonstrated the effect of morality shifting to be moderated by ingroup glorification but not ingroup attachment. Implications and consequences for intergroup and individual wrongdoings, as well as for intergroup relations, are discussed. Copyright © 2011 John Wiley & Sons, Ltd.