Helsinki Institute for Information Technology

About: Helsinki Institute for Information Technology is a facility organization based out in Espoo, Finland. It is known for research contribution in the topics: Population & Bayesian network. The organization has 630 authors who have published 1962 publications receiving 63426 citations.

Probabilistic archetypal analysis

Abstract: Archetypal analysis represents a set of observations as convex combinations of pure patterns, or archetypes. The original geometric formulation of finding archetypes by approximating the convex hull of the observations assumes them to be real---valued. This, unfortunately, is not compatible with many practical situations. In this paper we revisit archetypal analysis from the basic principles, and propose a probabilistic framework that accommodates other observation types such as integers, binary, and probability vectors. We corroborate the proposed methodology with convincing real-world applications on finding archetypal soccer players based on performance data, archetypal winter tourists based on binary survey data, archetypal disaster-affected countries based on disaster count data, and document archetypes based on term-frequency data. We also present an appropriate visualization tool to summarize archetypal analysis solution better.

Gender-dependent progression of systemic metabolic states in early childhood.

Abstract: Little is known about the human intra-individual metabolic profile changes over an extended period of time. Here, we introduce a novel concept suggesting that children even at a very young age can be categorized in terms of metabolic state as they advance in development. The hidden Markov models were used as a method for discovering the underlying progression in the metabolic state. We applied the methodology to study metabolic trajectories in children between birth and 4 years of age, based on a series of samples selected from a large birth cohort study. We found multiple previously unknown age- and gender-related metabolome changes of potential medical significance. Specifically, we found that the major developmental state differences between girls and boys are attributed to sphingolipids. In addition, we demonstrated the feasibility of state-based alignment of personal metabolic trajectories. We show that children have different development rates at the level of metabolome and thus the state-based approach may be advantageous when applying metabolome profiling in search of markers for subtle (patho)physiological changes.

Just watching the game ain't enough: striatal fMRI reward responses to successes and failures in a video game during active and vicarious playing

Abstract: Although the multimodal stimulation provided by modern audiovisual video games is pleasing by itself, the rewarding nature of video game playing depends critically also on the players' active engagement in the gameplay. The extent to which active engagement influences dopaminergic brain reward circuit responses remains unsettled. Here we show that striatal reward circuit responses elicited by successes (wins) and failures (losses) in a video game are stronger during active than vicarious gameplay. Eleven healthy males both played a competitive first-person tank shooter game (active playing) and watched a pre-recorded gameplay video (vicarious playing) while their hemodynamic brain activation was measured with 3-tesla functional magnetic resonance imaging (fMRI). Wins and losses were paired with symmetrical monetary rewards and punishments during active and vicarious playing so that the external reward context remained identical during both conditions. Brain activation was stronger in the orbitomedial prefrontal cortex (omPFC) during winning than losing, both during active and vicarious playing. In contrast, both wins and losses suppressed activations in the midbrain and striatum during active playing; however, the striatal suppression, particularly in the anterior putamen, was more pronounced during loss than win events. Sensorimotor confounds related to joystick movements did not account for the results. Self-ratings indicated losing to be more unpleasant during active than vicarious playing. Our findings demonstrate striatum to be selectively sensitive to self-acquired rewards, in contrast to frontal components of the reward circuit that process both self-acquired and passively received rewards. We propose that the striatal responses to repeated acquisition of rewards that are contingent on game related successes contribute to the motivational pull of video-game playing.

What does it mean to be good at using a mobile device? An investigation of three levels of experience and skill

Abstract: An increasing number of computer users lack formal training in operating their devices. These daily users cannot be described as novices or experts within the predominant view of expertise. In order to describe and better understand this type of self-taught intermediate level of skill, 10 casual users of a high-end smartphone series were compared to 10 novices and 4 professionals (help desk personnel) in their learning histories, task performance, and cognitive outcomes. Our study suggests that this type of self-taught intermediate level of skill is device-specific. Experienced users (casual users and experts) exhibited superior performance for representative tasks. This is mainly attributable to faster navigation and better knowledge of interface terminology, not to deeper conceptual representation of the problems. Interviews suggest that this skill is the consequence of routine use and three recurring learning events: familiarization, following of media, and ad hoc problem-solving situations. We conclude by discussing why intermediate levels of skill deserve more attention in HCI research.

Weak models of distributed computing, with connections to modal logic

Abstract: This work presents a classification of weak models of distributed computing. We focus on deterministic distributed algorithms, and study models of computing that are weaker versions of the widely-studied port-numbering model. In the port-numbering model, a node of degree $$d$$ d receives messages through $$d$$ d input ports and sends messages through $$d$$ d output ports, both numbered with $$1,2,\ldots ,d$$ 1 , 2 , ? , d . In this work, $${\mathsf{VV}}_\mathsf{c}$$ VV c is the class of all graph problems that can be solved in the standard port-numbering model. We study the following subclasses of $${\mathsf{VV}}_\mathsf{c}$$ VV c : Now we have many trivial containment relations, such as $$\mathsf{SB}\subseteq \mathsf{MB}\subseteq \mathsf{VB}\subseteq {\mathsf {VV}}\subseteq {\mathsf{VV}}_\mathsf{c}$$ SB ⊆ MB ⊆ VB ⊆ VV ⊆ VV c , but it is not obvious if, for example, either of $$\mathsf{VB}\subseteq \mathsf{SV}$$ VB ⊆ SV or $$\mathsf{SV}\subseteq \mathsf{VB}$$ SV ⊆ VB should hold. Nevertheless, it turns out that we can identify a linear order on these classes. We prove that $$\mathsf{SB}\subsetneq \mathsf{MB}= \mathsf{VB}\subsetneq \mathsf{SV}= \mathsf{MV}= {\mathsf {VV}}\subsetneq {\mathsf{VV}}_\mathsf{c}$$ SB ? MB = VB ? SV = MV = VV ? VV c . The same holds for the constant-time versions of these classes. We also show that the constant-time variants of these classes can be characterised by a corresponding modal logic. Hence the linear order identified in this work has direct implications in the study of the expressibility of modal logic. Conversely, one can use tools from modal logic to study these classes.