Hierarchical structures induce long-range dynamical correlations in written texts.

Thoughts and ideas are multidimensional and often concurrent, yet they can be expressed surprisingly well sequentially by the translation into language. This reduction of dimensions occurs naturally but requires memory and necessitates the existence of correlations, e.g., in written text. However, correlations in word appearance decay quickly, while previous observations of long-range correlations using random walk approaches yield little insight on memory or on semantic context. Instead, we study combinations of words that a reader is exposed to within a "window of attention," spanning about 100 words. We define a vector space of such word combinations by looking at words that co-occur within the window of attention, and analyze its structure. Singular value decomposition of the co-occurrence matrix identifies a basis whose vectors correspond to specific topics, or "concepts" that are relevant to the text. As the reader follows a text, the "vector of attention" traces out a trajectory of directions in this "concept space." We find that memory of the direction is retained over long times, forming power-law correlations. The appearance of power laws hints at the existence of an underlying hierarchical network. Indeed, imposing a hierarchy similar to that defined by volumes, chapters, paragraphs, etc. succeeds in creating correlations in a surrogate random text that are identical to those of the original text. We conclude that hierarchical structures in text serve to create long-range correlations, and use the reader's memory in reenacting some of the multidimensionality of the thoughts being expressed.

The topological relationship between the large-scale attributes and local interaction patterns of complex networks.

Recent evidence indicates that the abundance of recurring elementary interaction patterns in complex networks, often called subgraphs or motifs, carry significant information about their function and overall organization. Yet, the underlying reasons for the variable quantity of different subgraph types, their propensity to form clusters, and their relationship with the networks' global organization remain poorly understood. Here we show that a network's large-scale topological organization and its local subgraph structure mutually define and predict each other, as confirmed by direct measurements in five well studied cellular networks. We also demonstrate the inherent existence of two distinct classes of subgraphs, and show that, in contrast to the low-density type II subgraphs, the highly abundant type I subgraphs cannot exist in isolation but must naturally aggregate into subgraph clusters. The identified topological framework may have important implications for our understanding of the origin and function of subgraphs in all complex networks.

[Differentiation of existential guilt and compassion in relation to responsibility induction: a film experiment]. / Zur Differenzierung von Existentieller Schuld und Mitleid über Verantwortlichkeitsinduktion: ein Filmexperiment.

Feelings of existential guilt are assumed to depend on the perception of a causal relationship between one's own behavior or (privileged) situation and the disadvantages of others. By contrast, pity should not depend on such perceptions. This hypothesis, which has been supported so far only by correlational studies, was tested experimentally. Eighty students were shown a film about a developing country. The film was provided with four different comments, each representing one experimental condition (between-subjects design). Experimental factors were "amount of misery of the people shown" and "subject's responsibility for these peoples' conditions of life". As expected, subjects in the condition "misery and responsibility" reported higher feelings of guilt, though no more pity than subjects in the remaining three treatment conditions (experiment 1, n = 40). This mean difference, however, was statistically significant for men only. Contrary to our theoretical expectations--and to finding from other experiments on vicarious reparation--the induction of guilt had no effect on willingness to help a third party (experiment 2, n = 40). Possible reasons for this unexpected finding are suggested.