The 'when' pathway of the right parietal lobe

The order of events, whether two events are seen as simultaneous or successive, sets the stage for the moment-to-moment interpretation of the visual world. Evidence from patients who have lesions to the parietal lobes and transcranial magnetic stimulation studies in normal subjects suggest that the right inferior parietal lobe underlies this analysis of event timing. Judgment of temporal order, simultaneity and high-level motion are all compromised following right parietal lesions and degraded after transcranial magnetic stimulation over the right parietal but not elsewhere. The results suggest that the right parietal lobe serves as part of a when pathway for both visual fields. We propose that the disruption of this mechanism is the underlying cause of a wide range of seemingly unrelated tasks being impaired in right parietal patients.     

On the basis of belief in causal and diagnostic conditionals

According to the suppositional theory of conditionals, people assess their belief in a conditional statement of the form “if p then q” by conducting a mental simulation on the supposition of p in which they assess their degree of belief in q. This leads to them to the judge the probability of a conditional statement to be equal to the conditional probability, P(q|p). Evidence for this conditional probability hypothesis has been adduced in earlier studies for abstract, causal, and counterfactual conditionals. For the realistic conditionals, it is natural to assume that people perform such mental simulations by building causal mental models from prior causes to later effects. However, in the present study we show that the conditional probability hypothesis extends to diagnostic conditionals, which relate effects to causes. This new finding presents a major challenge for theoretical accounts of the mental processing of conditional statements.     

Nanotechnology Bound: Evaluating the Case for More Regulation

In continuing news, there is a growing debate on whether current laws and regulations, both in the US and abroad, need to be strengthened as they relate to nanotechnology. On one side, experts argue that nanomaterials, which are making their way into the marketplace today, are possibly harmful to consumers and the environment, so stronger and new laws are needed to ensure they are safe. On the other side, different experts argue that more regulation will slow down the pace of business and innovation in nanotechnology, or that self-regulation is the answer, or other opposing positions. This paper will draw out the core issues behind the debate and explain that there is more at stake than merely environmental, health and safety (EHS) worries or business interests, as it first appears. We will also suggest an alternative solution to stricter laws, since stricter laws would face formidable practical challenges, even if they are warranted.     

The role of child adrenocortical functioning in pathways between interparental conflict and child maladjustment

This study examined the interplay between interparental conflict and child cortisol reactivity to interparental conflict in predicting child maladjustment in a sample of 178 families and their kindergarten children. Consistent with the allostatic load hypothesis (McEwen & Stellar, 1993), results indicated that interparental conflict was indirectly related to child maladjustment through its association with individual differences in child cortisol reactivity. Analyses indicated that the multimethod assessment of interparental conflict was associated with lower levels of child cortisol reactivity to a simulated phone conflict between parents. Diminished cortisol reactivity, in turn, predicted increases in parental reports of child externalizing symptoms over a 2-year period. Associations between interparental conflict, child cortisol reactivity, and child externalizing symptoms remained robust even after demographic factors and other family processes were taken into account.     

Gender differences and developmental change in externalizing disorders from late adolescence to early adulthood: A longitudinal twin study

Using data from over 1,000 male and female twins participating in the Minnesota Twin Family Study, the authors examined developmental change, gender differences, and genetic and environmental contributions to the symptom levels of four externalizing disorders (adult antisocial behavior, alcohol dependence, nicotine dependence, and drug dependence) from ages 17 to 24. Both men and women increased in symptoms for each externalizing disorder, with men increasing at a greater rate than women, such that a modest gender gap at age 17 widened to a large one at age 24. Additionally, a mean-level gender difference on a latent Externalizing factor could account for the mean-level gender differences for the individual disorders. Biometric analyses revealed increasing genetic variation and heritability for men but a trend toward decreasing genetic variation and increasing environmental effects for women. Results illustrate the importance of gender and developmental context for symptom expression and the utility of structural models to integrate general trends and disorder-specific characteristics.     

Memory for sequences of tone bursts in the rat: Reliance on temporal cues and evidence for an instructional ambiguity explanation of the choose-few effect

Two groups of rats were trained in a symbolic delayed matching-to-sample task with a 0-s delay to discriminate sample stimuli that consisted of sequences of tone bursts. For one group, sequences varied in number with total sequence duration controlled. For the other group, total sequence duration, sum of the tone durations, and sum of the gap durations were all controlled. The former group of rats acquired the discrimination, but the latter group of rats were not able to learn the discrimination with the additional temporal cues controlled. Retention functions for the group that acquired the discrimination exhibited a choose-many bias at the 1-s delay and a choose-few bias at the 8-s delay regardless of the similarity in the intertrial interval and delay interval illumination condition. The asymmetrical retention functions appeared to be due to instructional ambiguity which resulted from the similarity of the delay interval to temporal features of the tone burst sequence, such as the gap between tone bursts and the total duration of tone. In Experiment 2, diagnostic tests provided evidence that rats discriminated the sequences of tone bursts by timing and summing the duration of individual tone bursts rather than using an event switch to count tones. Like pigeons, rats use multiple temporal features rather than number to discriminate sequences of successive events.     

Utilization of covariation knowledge in source monitoring: no evidence for implicit processes

In three experiments, a "hidden covariation" (Lewicki, in Journal of Experimental Psychology: Learning, Memory, and Cognition, 12, 135-146, 1986) of nonsalient stimulus attributes and the source of stimulus information was established to test whether implicit knowledge about this correlation influences source memory judgments. The source monitoring framework (Johnson, Hashtroudi, and Lindsay, in Psychological Bulletin, 114, 3-28, 1993) postulates heuristic and strategic judgment processes in source attributions. A multinomial model analysis disentangled memory and guessing processes. While there were large strategic guessing biases involving explicit knowledge in all experiments, there was no evidence for the use of implicit covariation knowledge. Only participants who were later able to verbalize the covariation had shown corresponding biases during the source memory test, suggesting that implicit covariation knowledge plays no prominent role in the reconstruction processes in source monitoring.     

Humans do not switch between path knowledge and landmarks when learning a new environment

Using a metric shortcut paradigm, we have found that like honeybees (Dyer in Animal Behaviour 41:239–246, 1991), humans do not seem to build a metric “cognitive map” from path integration. Instead, observers take novel shortcuts based on visual landmarks whenever they are available and reliable (Foo, Warren, Duchon, & Tarr in Journal of Experimental Psychology-Learning Memory and Cognition 31(2):195–215, 2005). In the present experiment we examine whether humans, like ants (Wolf & Wehner in Journal of Experimental Biology 203:857–868, 2000), first use survey-type path knowledge, built up from path integration, and then subsequently shift to reliance on landmarks. In our study participants walked in an immersive virtual environment while head position and orientation were recorded. During training, participants learned two legs of a triangle with feedback: paths from Home to Red and Home to Blue. A configuration of colored posts surrounded the Red location. To test reliance on landmarks, these posts were covertly translated, rotated, or left unchanged during six probe trials. These probe trials were interspersed during the training procedure to measure changes over learning. Dependence on visual landmarks was immediate and sustained during training, and no significant learning effects were observed other than a decrease in hesitation time. Our results suggest that while humans have at least two distinct navigational strategies available to them, unlike ants, a computationally-simpler landmark strategy dominates during novel shortcut navigation.