Response-stimulus interval in choice serial reaction time: Interaction with sleep deprivation, choice, and practice

In choice serial reaction time (RT), Response-to-next-Stimulus Interval (RSI) was varied from 0 to 600 msec in 40-msec steps. In three experiments, RT fell and errors rose as RSI was increased to 480 msec; they remained unchanged thereafter. The effect of RSI on RT was not linear, was reduced by 6- as compared with 4- or 3-choice responding, and was unaffected by sleep deprivation, despite loss of sleep reducing RT overall. The effect of penultimate RSI on RT was similar to that current RSI, but smaller. Two explanations of RSI—response-generated kinaesthetic feedback blocking a “central processor” and a preparatory interval as in warned simple RT—are rejected. Instead, the idea of “relative refractory state” is revived but now, because of the RSI/error finding, biased more towards responding than stimulus reception and encoding. In all three experiments the influence of RSI on RT was reduced with practice. If practice encourages automatic rather than controlled processing (Shiffrin & Schneider, 1977), the prediction is that the former will show less refractoriness.     

How do we understand empathy systemically?

This paper considers what a systemic understanding of empathy might be in the context of recent developments in systemic approaches. Clinical work is the basis for an exploration of which systemic ideas might be useful in thinking about 'systemic empathy'. The question of whether empathy is inherent in the systemic approach is considered.     

Assessments of changes in the effective salience of stimulus elements as a result of stimulus preexposure

Rats received exposure to 3 flavor compounds, AX and BX, presented in alternation, and CX, presented on a separate block of trials. The hypothesis that this treatment would leave B effectively more salient than C was tested in 3 ways. Experiment 1 showed that the unconditioned response evoked by B was stronger than that evoked by C. Experiment 2 showed that B was more effective than C when used as a reinforcer in a sensory preconditioning procedure. Experiment 3 showed that B was learned about more readily than C as a conditioned stimulus in flavor aversion conditioning. Alternating preexposure to 2 similar stimuli may protect their distinctive features from the loss of salience normally produced by nonreinforced exposure to a stimulus.     

Clark’s nutcrackers (<Emphasis Type="Italic">Nucifraga columbiana</Emphasis>) use gestures to identify the location of hidden food

Heterospecific cues, such as gaze direction and body position, may be an important source of information that an animal can use to infer the location of resources like food. The use of heterospecific cues has been largely investigated using primates, dogs, and other mammals; less is known about whether birds can also use heterospecific gestures. We tested six Clark’s nutcrackers in a two-way object-choice task using touch, point, and gaze cues to investigate whether these birds can use human gestures to find food. Most of the birds were able to use a touch gesture during the first trial of testing and were able to learn to use point and gaze (eyes and head alternation) cues after a limited number of trials. This study is the first to test a non-social corvid on the object-choice task. The performance of non-social nutcrackers is similar to that of more social and related corvids, suggesting that species with different evolutionary histories can utilize gestural information.     

Radial-arm-maze behavior of the red-footed tortoise (Geochelone carbonaria)

The radial-arm maze is an established method for testing an animal's spatial win-shift behavior. Research on mammals, birds, and fish has shown that the mastery of this task is commonly mediated, to different degrees, by two types of strategy: those based on external cues and those based on response stereotypy. In the present study we trained four red-footed tortoises (Geochelone carbonaria) to navigate an eight-arm radial maze while providing different levels of access to visual room cues. The results indicate that response stereotypy is the more prevalent mechanism in these tortoises, although navigation based on landmarks can also occur if learned initially. The findings suggest that tortoise spatial navigation may be more similar to that observed in mammals and birds than previously thought.     

A reproductive threat-based model of evolved sex differences in jealousy

Although heterosexual women and men consistently demonstrate sex differences in jealousy, these differences disappear among lesbians and gay men as well as among heterosexual women and men contemplating same-sex infidelities (infidelities in which the partner and rival are the same sex). Synthesizing these past findings, the present paper offers a reproductive threat-based model of evolved sex differences in jealousy that predicts that the sexes will differ only when the jealous perceivers' reproductive outcomes are differentially at risk. This model is supported by data from a web-based study in which lesbians, gay men, bisexual women and men, and heterosexual women and men responded to a hypothetical infidelity scenario with the sex of the rival randomly determined. After reading the scenario, participants indicated which type of infidelity (sexual versus emotional) would cause greater distress. Consistent with predictions, heterosexual women and men showed a sex difference when contemplating opposite-sex infidelities but not when contemplating same-sex infidelities, whereas lesbians and gay men showed no sex difference regardless of whether the infidelity was opposite-sex or same-sex.     

Predicting Safer Sex Practices: The Interactive Role of Partner Cooperation and Cognitive Factors

This study integrates aspects of cognitive and social contextual approaches to understanding the practice of safer sex. Study participants were 398 unmarried college students attending one of two institutions of higher education in Texas. As predicted, individuals who perceived more cooperation from their sexual partner to practice safer sex were significantly more likely to do so than those who saw their partners as uncooperative. Especially important, as predicted, partner cooperation also moderated the relationship between cognitive and behavioral predictors and safer sex. These moderation findings demonstrate that partner cooperation limits the range of operation of psychological factors that have been shown in previous research to play a significant role in deciding to practice safer sex.     

Micro-mechanical measurements of fracture toughness of bismuth embrittled copper grain boundaries

Measuring the fracture properties of single grain boundaries has until now required macroscopic bi-crystals which are expensive and not always available. We describe a method for fracture testing using micro-cantilevers, manufactured using focussed ion beam machining and tested using a nanoindenter. We have used the method to measure the fracture toughness of selected grain boundaries in bismuth-embrittled copper. This technique is applicable to grain boundaries in other brittle polycrystalline samples for which large bi-crystals cannot be produced for conventional testing.