Understanding cooperation in the Prisoner’s Dilemma game

In the standard one-shot Prisoner’s Dilemma game, participants often choose to cooperate, when the optimal strategy is to defect. This puzzling finding has attracted considerable interest both in terms of possible computational frameworks for modeling human judgment, but also regarding the more general debate of human altruism. In this research, we ask how much of human behavior in this task can be explained by a putative bias for cooperative behavior and whether this, in turn, is influenced by personality. We compared performance on the standard task with performance on a matched neutral one; we manipulated the optimal strategy (defect or cooperate); and we manipulated the amount of payoff for responding optimally. Results revealed little evidence for a bias for cooperative behavior, but significant associations with the personality factors of Behavioural Activation System (BAS) Reward Responsivity and Agreeableness were found. These findings are discussed in terms of the attempt to explain judgment in one-shot, Prisoner’s Dilemma tasks with statistical or probabilistic models.     

Maternal sensitivity and overt aggression in young children with Down syndrome

Children with genetic syndromes offer a unique opportunity to combine genetic and environmental approaches to the study of aggression. Children with genetic syndromes associated with developmental delay are at increased risk for behavior problems, but little is known about risk and resilience factors. In this study, we examined maternal sensitivity of mothers of children with Down syndrome using home observations when their children were 2, 3, and 5 years old, and relations with maternal reports and observations of overt aggression at school at age 5. Maternal sensitivity at ages 2 and 3 years did not significantly predict child aggression at age 5, but low maternal sensitivity at age 5 was significantly related to overt aggression at both home and school. By replicating and extending earlier work, this study informs developmental theory and identifies an important maternal variable related to aggression in children with Down syndrome.     

The high costs of low agreeableness: Low agreeableness exacerbates interpersonal consequences of rejection sensitivity in U.S. and Chinese adolescents

Although personality is a powerful predictor of adjustment, its potential moderating effects have been less studied in youth. This investigation examined why some youth are more susceptible to the negative consequences of rejection sensitivity than others. Two separate studies tested the hypothesis that agreeableness moderates the links between rejection sensitivity and interpersonal outcomes. Study 1 included 198 boys and 264 girls from the U.S.A. (M = 14.24 years old). Study 2 included 86 boys and 115 girls from China (M = 14.21 years old). Across studies, low agreeableness and high rejection sensitivity were uniquely associated with withdrawal, friendship dissatisfaction, and adverse conflict consequences. Cross-cultural replication underscores the universality of the risk confronting low agreeable youth with elevated rejection sensitivity.     

Learning to allocate limited time to decisions with different expected outcomes

The goal of this article is to investigate how human participants allocate their limited time to decisions with different properties. We report the results of two behavioral experiments. In each trial of the experiments, the participant must accumulate noisy information to make a decision. The participants received positive and negative rewards for their correct and incorrect decisions, respectively. The stimulus was designed such that decisions based on more accumulated information were more accurate but took longer. Therefore, the total outcome that a participant could achieve during the limited experiments’ time depended on her “decision threshold”, the amount of information she needed to make a decision. In the first experiment, two types of trials were intermixed randomly: hard and easy. Crucially, the hard trials were associated with smaller positive and negative rewards than the easy trials. A cue presented at the beginning of each trial would indicate the type of the upcoming trial. The optimal strategy was to adopt a small decision threshold for hard trials. The results showed that several of the participants did not learn this simple strategy. We then investigated how the participants adjusted their decision threshold based on the feedback they received in each trial. To this end, we developed and compared 10 computational models for adjusting the decision threshold. The models differ in their assumptions on the shape of the decision thresholds and the way the feedback is used to adjust the decision thresholds. The results of Bayesian model comparison showed that a model with time-varying thresholds whose parameters are updated by a reinforcement learning algorithm is the most likely model. In the second experiment, the cues were not presented. We showed that the optimal strategy is to use a single time-decreasing decision threshold for all trials. The results of the computational modeling showed that the participants did not use this optimal strategy. Instead, they attempted to detect the difficulty of the trial first and then set their decision threshold accordingly.     

Social rejection and self- versus other-awareness

Recent research (Twenge, Catanese, & Baumeister, 2003) demonstrated decreased self-awareness among socially-rejected individuals as a defensive strategy designed to buffer the self from the acute distress of rejection. In the present study, we sought to demonstrate that this decreased self-awareness among socially-rejected individuals is: (a) primarily evident in social domains, as opposed to non-social domains and (b) accompanied by increased awareness of others’ behavior. Using a social memory paradigm, we found that rejected participants exhibited better memory for other-related social behaviors, but poorer memory for self-related social behaviors in comparison to accepted participants. These data provide evidence for a two-pronged response to social rejection characterized by both self-protective strategies and strategies aimed at regaining and maintaining social relationships.     

Maternal sensitivity and behaviour problems in young children with developmental delay

Children with developmental delay are at increased risk for behaviour problems, but little is known about risk and resilience factors. Previous research has established links between maternal sensitivity and behaviour problems in typically developing children, but no studies have examined maternal sensitivity in the development of behaviour problems in children with developmental delay. In this study, we coded videotaped interactions of 30 2‐year‐olds with developmental delay and their mothers using the maternal behaviour Q‐sort and a child behaviour coding system. Mothers completed the child behaviour checklist when their children were 2 and 3 years old. Results revealed significant inverse relations between maternal sensitivity and concurrent and later externalizing problems, and significant positive relations between maternal sensitivity and concurrent observed appropriate behaviour (compliance and social engagement). This study informs developmental theory and identifies an important maternal variable that may reduce the risk of behaviour problems in children with developmental delay. Copyright © 2006 John Wiley & Sons, Ltd.     

An improved learning algorithm for random neural networks based on particle swarm optimization and input-to-output sensitivity

Extreme learning machine (ELM) for random single-hidden-layer feedforward neural networks (RSLFN) has been widely applied in many fields in the past ten years because of its fast learning speed and good generalization performance. But because traditional ELM randomly selects the input weights and hidden biases, it typically requires high number of hidden neurons and thus decreases its convergence performance. It is necessary to select optimal input weights and hidden biases to improve the convergence performance of the traditional ELM. Generally, the single-hidden-layer feedforward neural networks (SLFN) with low input-to-output sensitivity will cause good robustness of the network, which may further lead into good generalization performance. Moreover, particle swarm optimization (PSO) has no complicated evolutionary operators and fewer parameters need to adjust, and is easy to implement. In this study, an improved ELM based on PSO and input-to-output sensitivity information is proposed to improve RSLFN’s convergence performance. In the improved ELM, PSO encoding the input to output sensitivity information of the SLFN is used to optimize the input weights and hidden biases. The improved ELM could obtain better generalization performance as well as improve the conditioning of the SLFN by decreasing the input-to-output sensitivity of the network. Finally, experiment results on the regression and classification problems verify the improved performance the proposed ELM.     

Infant frontal EEG asymmetry moderates the association between maternal behavior and toddler negative affectivity

Relatively little work has examined potential interactions between child intrinsic factors and extrinsic environmental factors in the development of negative affect in early life. This work is important because high levels of early negative affectivity have been associated with difficulties in later childhood adjustment. We examined associations between infant frontal electroencephalogram (EEG), maternal parenting behaviors, and children’s negative affect across the first two years of life. Infant baseline frontal EEG asymmetry was measured at 5 months; maternal sensitivity and intrusiveness were observed during mother-child interaction at 5 and 24 months; and mothers provided reports of toddler negative affect at 24 months. Results indicated that maternal sensitive behaviors at 5 months were associated with less negative affect at 24 months, but only for infants with left frontal EEG asymmetry. Similarly, maternal sensitive behaviors at 24 months were associated with less toddler negative affect at 24 months, but only for infants with left frontal EEG asymmetry. In contrast, maternal intrusive behaviors at 5- and 24-months were associated with greater toddler negative affect, but only for infants with right frontal EEG asymmetry at 5-months. Findings suggest that levels of negative affect in toddlers may be at least partially a result of interactions between children’s own early neurophysiological functioning and maternal behavior during everyday interactions with children in the first two years of life.     

Parent mind-mindedness,sensitivity, and infant affect: Implications for attachment with mothers and fathers

Previous research examining links between parenting and attachment has focused on behavioral aspects of parenting such as sensitivity. However, by assessing how parents reflect on infants’ mental states (mind-mindedness) we gain a broader understanding of parenting and how it impacts attachment. Mothers, fathers, and their infants (N = 135) participated in the Still Face Paradigm (SFP) at 3-, 5-, and 7- months of age, and the Strange Situation with mothers at 12 months and fathers at 14 months. Parent sensitivity and infant affect were coded from the SFP and all videos were transcribed and later coded for parents’ use of appropriate and non-attuned mind-mindedness toward their infants. Attachment with each parent was coded from the Strange Situation. Mixed effects models examined trajectories of parents’ mind-mindedness in relation to parent sensitivity and infant affect across attachment groups. Significant differences between parent gender and attachment category were detected. Specifically, parents who were less sensitive were also less mind-minded toward insecure-avoidant infants; parents used more non-attuned mind-mindedness when infants had higher negative affect. Findings suggest that, in addition to parent sensitivity, parents’ use of appropriate and non-attuned mind-mindedness during a parent-infant interaction provides insight into the developing attachment relationship for mothers and fathers.