Improved Algorithms for Decremental Single-Source Reachability on Directed Graphs

Recently we presented the first algorithm for maintaining the set of nodes reachable from a source node in a directed graph that is modified by edge deletions with $o(mn)$ total update time, where $m$ is the number of edges and $n$ is the number of nodes in the graph [Henzinger et al. STOC 2014]. The algorithm is a combination of several different algorithms, each for a different $m$ vs. $n$ trade-off. For the case of $m = \Theta(n^{1.5})$ the running time is $O(n^{2.47})$, just barely below $mn = \Theta(n^{2.5})$. In this paper we simplify the previous algorithm using new algorithmic ideas and achieve an improved running time of $\tilde O(\min(m^{7/6} n^{2/3}, m^{3/4} n^{5/4 + o(1)}, m^{2/3} n^{4/3+o(1)} + m^{3/7} n^{12/7+o(1)}))$. This gives, e.g., $O(n^{2.36})$ for the notorious case $m = \Theta(n^{1.5})$. We obtain the same upper bounds for the problem of maintaining the strongly connected components of a directed graph undergoing edge deletions. Our algorithms are correct with high probabililty against an oblivious adversary.Comment: This paper was presented at the International Colloquium on Automata, Languages and Programming (ICALP) 2015. A full version combining the findings of this paper and its predecessor [Henzinger et al. STOC 2014] is available at arXiv:1504.0795

On the Regular Behaviour of Orthogonal Polynomials

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135623/1/plms0119.pd

Building Machines That Learn and Think Like People

Recent progress in artificial intelligence (AI) has renewed interest in building systems that learn and think like people. Many advances have come from using deep neural networks trained end-to-end in tasks such as object recognition, video games, and board games, achieving performance that equals or even beats humans in some respects. Despite their biological inspiration and performance achievements, these systems differ from human intelligence in crucial ways. We review progress in cognitive science suggesting that truly human-like learning and thinking machines will have to reach beyond current engineering trends in both what they learn, and how they learn it. Specifically, we argue that these machines should (a) build causal models of the world that support explanation and understanding, rather than merely solving pattern recognition problems; (b) ground learning in intuitive theories of physics and psychology, to support and enrich the knowledge that is learned; and (c) harness compositionality and learning-to-learn to rapidly acquire and generalize knowledge to new tasks and situations. We suggest concrete challenges and promising routes towards these goals that can combine the strengths of recent neural network advances with more structured cognitive models.Comment: In press at Behavioral and Brain Sciences. Open call for commentary proposals (until Nov. 22, 2016). https://www.cambridge.org/core/journals/behavioral-and-brain-sciences/information/calls-for-commentary/open-calls-for-commentar

TSD Symptoms and Self-Rated Recovery Among Adult Sexual Assault Survivors: The Effects of Traumatic Life Events and Psychosocial Variables

Prior research has demonstrated that self-blame is predictive of more PTSD symptoms and poorer recovery (Frazier, 2003; Koss, Figueredo, & Prince, 2002), and perceived control over recovery is associated with less distress (Frazier, 2003) in adult sexual assault (ASA) survivors. A structural equation model was tested to examine the role of traumatic events, self-blame, perceived control over recovery, and coping strategies on PTSD symptoms and self-rated recovery in women ASA survivors. Adaptive coping partially mediated the effects of other traumas, self-blame, and perceived control over recovery on PTSD symptoms, and showed a small positive association with increased PTSD symptoms. As hypothesized, maladaptive coping partially mediated the effects of other traumas, self-blame, and perceived control over recovery on both PTSD symptoms and self-rated recovery; greater maladaptive coping was associated with increased PTSD symptoms and lower self-rated recovery. Implications and directions for future research are discussed

Understanding Alcohol-Related Sexual Assaults: Characteristics and Consequences

Sexual assaults commonly involve alcohol use, but little is known about alcohol’s effects on many aspects of assaults and their aftermath. We investigated characteristics of victims, perpetrators, and assaults as a function of whether alcohol was involved in the assault, as well as differences in women’s post-assault experiences. Assaults prior to which only perpetrators were drinking differed not only from non-alcohol-related assaults, but also from those prior to which both perpetrators and victims were drinking. Understanding the effects of alcohol-related assaults is important for identifying victims who should be targeted for mental health and substance use interventions

Correlates of Serious Suicidal Ideation and Attempts in Female Adult Sexual Assault Survivors

Relations between (a) serious suicidal ideation and attempts and (b) demographics, trauma history, assault characteristics, post-assault outcomes, and psychosocial variables were examined among female adult sexual assault survivors. Younger, minority, and bisexual survivors reported greater ideation. More traumas, drug use, and assault disclosure related to greater attempts, whereas perceived control over recovery was related to fewer attempts. Child sexual abuse and some assault characteristics predicted suicidal behavior. Depression was related to suicidal behavior until psychosocial variables were accounted for. Specifically, using substances to cope and self-blame predicted greater ideation, whereas receiving aid/information support was related to less ideation. Implications for research and treatment are discussed. (PsycINFO Database Record (c) 2016 APA, all rights reserved

Vulnerability and Protective Factors for Sexual Assault

Approximately 1 in 5 women experience sexual assaults in adulthood during their lives (see Post, this volume, for review), including experiences of unwanted sexual contact, sexual coercion, attempted rape, and completed rape that result from threat, force, or incapacitation from alcohol or drugs (either willingly or unwillingly consumed)

Prospective Effects of Sexual Victimization on PTSD and Problem Drinking

Posttraumatic stress disorder (PTSD) and problem drinking are common and often co-occurring sequelae experienced by women survivors of adult sexual assault, yet it remains unclear whether survivors drink to cope with PTSD symptoms or whether PTSD symptoms are exacerbated by drinking. Thus, we used a cross-lagged panel design with a large (N = 555), ethnically diverse sample of women assault survivors to determine whether PTSD prospectively led to problem drinking or vice versa. We also examined whether cumulative sexual victimization experiences related to greater PTSD and problem drinking. Structural equation modeling revealed that child sexual abuse was associated with greater symptoms of PTSD and problem drinking and intervening sexual victimization was associated with greater symptoms of PTSD and problem drinking 1 year later. We found no evidence, however, that PTSD directly influenced problem drinking over the long term, or vice versa. Rather, experiencing revictimization during the study predicted survivors’ prospective PTSD and problem drinking symptoms. Implications and recommendations for future research are discussed

Prospective Changes In Attributions Of Self-Blame And Social Reactions To Women’s Disclosures Of Adult Sexual Assault

The present longitudinal study examined relations between self-blame attributions and social reactions to disclosure in a community sample of adult sexual assault victims (N = 555). Cross-lagged panel analyses showed that neither characterological self-blame nor behavioral self-blame related to negative social reactions over the 1-year follow-up period. In contrast, characterological but not behavioral self-blame predicted fewer positive reactions over time. Although positive reactions did not reduce self-blame, negative reactions led to greater characterological, but not behavioral, self-blame during the course of the study. Thus, relations between self-blame and social reactions were not reciprocal but rather quite complex. The effects of victims’ coping strategies and sexual revictimization were also assessed. Implications for research, treatment, and intervention are discussed