Replacement—A Sheffer Stroke for Belief Change

By replacement is meant an operation that replaces one sentence by another in a belief set. Replacement can be used as a kind of Sheffer stroke for belief change, since contraction, revision, and expansion can all be defined in terms of it. Replacement can also be defined either in terms of contraction or in terms of revision. Close connections are shown to hold between axioms for replacement and axioms for contraction and revision. Partial meet replacement is axiomatically characterized. It is shown that this operation can have outcomes that are not obtainable through either partial meet contraction or partial meet revision.     

Knowing The World By Knowing One's Mind

This paper addresses the question whetherintrospection plus externalism about mental contentwarrant an a priori refutation of external-worldskepticism and ontological solipsism. The suggestionis that if thought content is partly determined byaffairs in the environment and if we can havenon-empirical knowledge of our current thoughtcontents, we can, just by reflection, know about theworld around us – we can know that our environment ispopulated with content-determining entities. Afterexamining this type of transcendental argument anddiscussing various objections found in the literature,I argue that the notion of privileged self-knowledgeunderlying this argument presupposes that we canlearn, via introspection, that our so-called thoughtsare propositional attitudes rather than contentlessstates. If, however, externalism is correct andthought content consists in the systematic dependencyof internal states on relational properties, we cannotknow non-empirically whether or not we havepropositional attitudes. Self-knowledge (apropositional attitude) is consistent with us lackingthe ability to rule out, via introspection, thepossibility that we don't have any propositionalattitudes. Self-knowledge provides us with knowledgeof what is in our minds, but not that we haveminds. Hence, the combination of externalism with thedoctrine of privileged self-knowledge does not allowfor an a priori refutation of skepticism and istherefore unproblematic.     

Gendered Morality and Backlash Effects in Online Discussions: An Experimental Study on How Users Respond to Hate Speech Comments Against Women and Sexual Minorities

Sex Roles - Hate speech in online users’ comments is often targeted toward underprivileged social groups such as immigrants, sexual minorities, and women. Besides the general severity of such...     

Phosphodiesterase type 5 (PDE5) inhibition improves object recognition memory: indications for central and peripheral mechanisms

A promising target for memory improvement is phosphodiesterase type 5 (PDE5), which selectively hydrolyzes cyclic guanosine monophosphate (cGMP). In rodents, PDE5 inhibitors (PDE5-Is) have been shown to improve memory performance in many behavioral paradigms. However, it is questioned whether the positive effects in animal studies result from PDE5 inhibition in the central nervous system or the periphery. Therefore, we studied the effects of PDE5 inhibition on memory and determined whether compound penetration of the blood-brain barrier (BBB) is required for this activity. Two selective PDE5-Is, vardenafil and UK-343,664, were tested in the object recognition task (ORT) in both a MK-801- and scopolamine-induced memory deficit model, and a time-delay model without pharmacological intervention. Compounds were dosed 30 min before the learning trial of the task. To determine if the PDE5-Is crossed the BBB, their concentrations were determined in plasma and brain tissue collected 30 min after oral administration. Vardenafil improved object recognition memory in all three variants of the ORT. UK-343,664 was ineffective at either preventing MK-801-induced memory disruption or time-dependent memory decay. However, UK-343,664 attenuated the memory impairment of scopolamine. Vardenafil crossed the BBB whereas UK-343,664 did not. Further, co-administration of UK-343,664 and scopolamine did not alter the brain partitioning of either molecule. This suggests that the positive effect of UK-343,664 on scopolamine-induced memory decay might arise from peripheral PDE5 inhibition. The results herein suggest that there may be multiple mechanisms that mediate the efficacy of PDE5 inhibition to improve memory performance in tasks such as the ORT and that these involve PDE5 located both within and outside of the brain. To further elucidate the underlying mechanisms, the cellular and subcellular localization of PDE5 needs to be determined.     

The language of landmarks: the role of background knowledge in indoor wayfinding

To effectively wayfind through unfamiliar buildings, humans infer their relative position to target locations not only by interpreting geometric layouts, especially length of line of sight, but also by using background knowledge to evaluate landmarks with respect to their probable spatial relation to a target. Questionnaire results revealed that participants have consistent background knowledge about the relative position of target locations. Landmarks were rated significantly differently with respect to their spatial relation to targets. In addition, results from a forced-choice task comparing snapshots of a virtual environment revealed that background knowledge influenced wayfinding decisions. We suggest that landmarks are interpreted semantically with respect to their function and spatial relation to the target location and thereby influence wayfinding decisions. This indicates that background knowledge plays a role in wayfinding.