Counterfactual Reasoning: Sharpening Conceptual Distinctions in Developmental Studies

Counterfactual reasoning (CFR)—mentally representing what the world would be like now if things had been different in the past—is an important aspect of human cognition and the focus of research in areas such as philosophy, social psychology, and clinical psychology. More recently, it has also gained broad interest in cognitive developmental psychology, mainly focusing on the question of how this kind of reasoning can be characterized. Studies have been inconsistent in identifying when children can use CFR. In this article, we present theoretical positions that may account for this inconsistency and evaluate them in the light of research on counterfactual emotions

Spintronics: Fundamentals and applications

Spintronics, or spin electronics, involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. This article reviews the current status of this subject, including both recent advances and well-established results. The primary focus is on the basic physical principles underlying the generation of carrier spin polarization, spin dynamics, and spin-polarized transport in semiconductors and metals. Spin transport differs from charge transport in that spin is a nonconserved quantity in solids due to spin-orbit and hyperfine coupling. The authors discuss in detail spin decoherence mechanisms in metals and semiconductors. Various theories of spin injection and spin-polarized transport are applied to hybrid structures relevant to spin-based devices and fundamental studies of materials properties. Experimental work is reviewed with the emphasis on projected applications, in which external electric and magnetic fields and illumination by light will be used to control spin and charge dynamics to create new functionalities not feasible or ineffective with conventional electronics.Comment: invited review, 36 figures, 900+ references; minor stylistic changes from the published versio