Seeing I to I: a pathway to interpersonal connectedness

The authors introduce the construct of I-sharing--the belief that one shares an identical subjective experience with another person--and the role it plays in liking. In Studies 1-3, participants indicated their liking for an objectively similar and an objectively dissimilar person, one of whom I-shared with them and the other of whom did not. Participants preferred the objectively similar person but only when that person I-shared with them. Studies 4 and 5 highlight the role that feelings of existential isolation and the need for closeness play in people's attraction to I-sharers. In Study 4, people with high needs for interpersonal closeness responded to I-sharers and non-I-sharers with great intensity. In Study 5, priming participants with feelings of existential isolation increased their liking for I-sharers over objectively similar others. The results highlight the importance of shared subjective experience and have implications for interpersonal and intergroup processes.     

Memory drum theory: alternative tests and explanations for the complexity effects on simple reaction time

Two experiments investigated the memory drum theory's prediction (Henry & Rogers, 1960) that simple reaction time (SRT) increased with the complexity of the response to be initiated. Experiment 1 (N = 9) matched the Experiment 1, Group 1, SRT condition described by Henry and Rogers. Results of Experiment 1 replicated those of Henry and Rogers and indicated that the memory drum theory's prediction of increased SRT as a function of increased complexity of response was tenable. Experiment 2 (N = 11) tested the effects of anatomical unit, extent and target size on SRT, premotor time, and motor time. The results supported the contention that alternative explanations for SRT were possible. With complexity constant, increases in anatomical unit lead to increases in SRT, but only in the motor time component which indicated electromechanical rather than neuromotor program delays. It is proposed that the increased motor time could be explained by peripheral events such as the duration maximum torque must be applied by the agonist muscle(s) to generate the angular acceleration required to initiate rapid movement. SRT, premotor time, and motor time increased when target size was reduced from 6.35 cm to 79 cm. The increased premotor time could be a function of the determining of new equilibrium points for the elbow joint during response initiation. No effects on SRT were observed for extent.     

Illusory contours as the solution to a problem

The perception of certain figures with illusory contours entails a reversal of figure and ground. It is hypothesized that this process occurs in two stages. First, some factor must suggest or cue the reversal. Experiments are described that isolate three such factors, namely, alignment of physically present contours, recognized incompletion of parts of the stimulus array, and set. Once cued, however, other experiments indicate that in a further stage of processing the solution is examined with respect to its compatibility with the stimulus display or with other preceptual properties to which the display gives rise. Only if such compatibility is present will the perception of a figure with illusory contours be maintained.     

Within- and between-nervous-system inhibition of return: Observation is as good as performance

Inhibition of return (IOR) has been shown to occur when an individual returns to a target location (within-person IOR) and when an individual moves to a location just engaged by another individual (between-person IOR). Although within- and between-person IOR likely result from the same inhibitory mechanisms, different processes must activate these mechanisms following the performance and observation of action. Consistent with the suggestion that the mirror neuron system may be responsible for activating the inhibitory mechanisms behind IOR on observation trials, between-person IOR was only detected under restricted viewing conditions known to activate mirror neurons. These results indicate that mirror neuron system may be involved in both higher-order and automatic cognitive behavior.     

The Learning of Programmed- and Feedback-Based Processes Controlling the Production of a Positioning Response in Two Dimensions

Two experiments were conducted to investigate the learning of the programmed- and feedback-based processes controlling the production of a slow, self-paced positioning response in two dimensions (direction and extent) in the horizontal plane. Both experiments had two phases: an acquisition phase of 60 trials with KR, followed by a KR withdrawal phase of 20 trials. In Experiment 1, one group (N=15) had visual feedback about the ongoing movement and the other group (N=15) did not. In Experiment 2, one group (N=15) practiced initiating the response in the criterion direction and moving the criterion extent, whereas, the other group (N=15) practiced initiating the response in the criterion direction and moving randomly varied extents. The results of Experiment 1 indicated that the learning of a programmed-based process is a gradually acquired freedom from visual feedback. Experiment 2 revealed that a programmed-based process can be learned independent of a feedback-based process.     

Sensitivity to reward and punishment in major depressive disorder: Effects of rumination and of single versus multiple experiences

In the current study, we examined the postulation that rumination makes it difficult for depressed individuals to learn the exact probability that different stimuli will be associated with punishment. To do so, we induced rumination or distraction in depressed and never-depressed participants and then measured punishment and reward sensitivity with a probabilistic selection task. In this task, participants first learn the probability that different stimuli will be associated with reward and punishment. During a subsequent test phase in which novel combinations of stimuli are presented, participants’ sensitivity to reward is tested by measuring their tendency to select the stimuli that were most highly rewarded during training, and their sensitivity to punishment is tested by measuring their tendency to not select the stimuli that were most highly punished during training. Compared with distraction, rumination led depressed participants to be less sensitive to the probability that stimuli will be associated with punishment and relatively less sensitive to punishment than reward. Never-depressed participants and depressed participants who were distracted from rumination were as sensitive to reward as they were to punishment. The effects of rumination on sensitivity to punishment may be a mechanism by which rumination can lead to maladaptive consequences.     

Switching and backward inhibition in major depressive disorder: the role of rumination

Previous studies have demonstrated that individuals with major depressive disorder have difficulties switching attention from one task set to another. In the current study we examined whether ruminative thinking drives the switching deficits of depressed individuals. A secondary, more exploratory, goal of this study was to examine whether state rumination would impair depressed individuals' ability to activate a new task set, to inhibit a no longer relevant task set, or both. Participants underwent either a rumination induction or a distraction induction and then completed a backward inhibition task that measures general switching abilities and the ability to inhibit previous task sets. Although depression was not related to switching ability as a main effect, depressed individuals who were induced to ruminate exhibited poorer switching ability than did both depressed and control individuals who were distracted from ruminating and control participants who were induced to ruminate. These findings suggest that depressed individuals are characterized by switching deficits only if they are ruminating. Moreover, the finding that state rumination did not affect participants' ability to inhibit previous task sets suggests that state rumination primarily impairs noninhibitory task-switching processes. It is interesting that the opposite pattern of results was obtained for trait rumination, which was related to inhibitory deficits during switching, but not to generally poorer switching. Thus, state and trait rumination may be associated with dissociable cognitive deficits.     

Interaction between visually and kinesthetically triggered voluntary responses

A voluntary motor response that is prepared in advance of a stimulus may be triggered by any sensory input. This study investigated the combination of visual and kinesthetic inputs in triggering voluntary torque responses. When a visual stimulus was presented alone, subjects produced a fast and accurate increase in elbow flexion torque. When a kinesthetic stimulus was presented instead of the visual stimulus, subjects produced a similar response with a reduced response latency. When a visual stimulus was presented in combination with a kinesthetic stimulus, subjects initiated their responses after either a visual or a kinesthetic response latency, depending on the relative timing of the two stimuli. An analysis of response amplitude suggested that when visual and kinesthetic stimuli were combined, both stimuli triggered a response. The results are more consistent with a simple behavioral model of addition of visual and kinesthetic responses (which predicts that the response to combined stimuli should be the sum of individual responses) than with a model of exclusion of one response (which predicts that the response to combined stimuli should be identical to either the visual or the kinesthetic response). Because addition of visually and kinesthetically triggered responses produced a response with an erroneously large amplitude, it is suggested that visual and kinesthetic inputs are not always efficiently integrated.     

Cortical cell assemblies: a possible mechanism for motor programs

The concept of a motor program has been used to interpret a diverse range of empirical findings related to preparation and initiation of voluntary movement. In the absence of an underlying mechanism, its exploratory power has been limited to that of an analogy with running a stored computer program. We argue that the theory of cortical cell assemblies suggests a possible neural mechanism for motor programming. According to this view, a motor program may be conceptualized as a cell assembly, which is stored in the form of strengthened synaptic connections between cortical pyramidal neurons. These connections determine which combinations of corticospinal neurons are activated when the cell assembly is ignited. The dynamics of cell assembly ignition are considered in relation to the problem of serial order. These considerations lead to a plausible neural mechanism for the programming of movements and movement sequences that is compatible with the effects of precue information and sequence length on reaction times. Anatomical and physiological guidelines for future quantitative models of cortical cell assemblies are suggested. By taking into account the parallel re-entrant loops between the cerebral cortex and basal ganglia, the theory of cortical cell assemblies suggests a mechanism for motor plans that involve longer sequences. The suggested model is compared with other existing neural network models for motor programming.