Tension headache: Theoretical problems

The traditional view of tension (muscular contraction) headache is delineated in a set of seven assumptions. A review of recent psychophysiological studies gives little support for these assumptions. However the findings provide a basis for a preliminary hypothesis about tension cases, and some predictions concerning how they can be treated. A three-systems analysis of tension headache is recommended.     

The relationship between sighting dominance and the fading of a stabilized retinal image

The fading of a stabilized retinal image in the sighting and the nonsighting dominant eye was studied using the Haidinger’s brush target. Reaction time to the complete disappearance of the stabilized image was significantly longer when the target was input to the sighting eye. The greater persistence of stabilized targets in the sighting eye suggests possible differences in the neural channels from the two eyes or processing differences in the two monocular channels that are related behaviorally to eye dominance.     

Monocular asymmetries in recognition after an eye movement: Sighting dominance and dextrality

Although monocular recognition scores for targets presented immediately after an eye movement do not differ, the two eyes show marked recognition asymmetries when both eyes are receiving inputs but a specific target is only presented to one. In general, the right eye performs better than the left, although there are interactions with sighting dominance and the direction of eye movement.     

Physical Distance and Helping: Some Unexpected Benefits of “Crowding In” on Others1

One hundred and sixty undergraduates (80 males, 80 females) participated in a field experiment designed to examine the influence of invasions of personal space and sex of requester upon subsequent helping. On the basis of previous research, it was predicted that helping would be markedly inhibited by invasions of personal space, and that the magnitude of these effects would be mediated by the sex of the individuals who perpetrated such intrusions. Surprisingly, however, results indicated that subsequent helping was actually facilitated by such invasions. A follow-up investigation replicated these results and suggested that they stemmed from a tendency on the part of subjects to perceive close physical approach by the requester as indicative of a high need for assistance.     

Interaction of Combat Exposure and Unit Cohesion in Predicting Suicide‐Related Ideation Among Post‐Deployment Soldiers

Suicide is one of the leading causes of death among U.S. Army soldiers. Suicide‐related ideation, which is associated with suicide attempts and suicide, can cause considerable distress. In a sample of 1,663 recently redeployed soldiers, we used factor analysis and structural equation modeling to test the associations between combat exposure, unit cohesion, and their interaction in predicting suicide‐related ideation. We found that combat exposure was a significant risk factor for suicide‐related ideation, while unit cohesion was a significant protective factor. The significant interaction between the two factors indicated that soldiers who experienced greater combat exposure but also had higher levels of unit cohesion had relatively lower levels of suicide‐related ideation. In addition, those who had higher levels of combat exposure and lower unit cohesion were most at risk for suicide‐related ideation. Our findings indicate the importance of unit cohesion in protecting soldiers from suicide‐related ideation and suggest a higher risk group of soldiers who should be targeted for interventions.     

Participant recruitment methods and statistical reasoning performance

Optimal Bayesian reasoning performance has reportedly been elusive, and a variety of explanations have been suggested for this situation. In a series of experiments, it is demonstrated that these difficulties with replication can be accounted for by differences in participant-sampling methodologies. Specifically, the best performances are obtained with students from top-tier, national universities who were paid for their participation. Performance drops significantly as these conditions are altered regarding inducements (e.g., using unpaid participants) or participant source (e.g., using participants from a second-tier, regional university). Honours-programme undergraduates do better than regular undergraduates within the same university, paid participation creates superior performance, and top-tier university students do better than students from lower ranked universities. Pictorial representations (supplementing problem text) usually have a slight facilitative effect across these participant manipulations. These results indicate that studies should take account of these methodological details and focus more on relative levels of performance rather than absolute performance.     

Preference and resistance to change in concurrent variable-interval schedules

Pigeons were trained on a multiple schedule in which separate concurrent schedules were presented in the two components of the schedule. During one component, concurrent variable-interval 40-sec variable-interval 80-sec schedules operated. In the second component, concurrent variable-interval 40-sec variable-interval 20-sec schedules operated. After stable baseline performance was obtained in both components, extinction probe choice tests were presented to assess preference between the variable-interval 40-sec schedules from the two components. The variable-interval 40-sec schedule paired with the variable-interval 80-sec schedule was preferred over the variable-interval 40-sec schedule paired with the variable-interval 20-sec schedule. The subjects were also exposed to several resistance-to-change manipulations: (1) prefeeding prior to the experimental session, (2) a free-food schedule added to timeout periods separating components, and (3) extinction. The results indicated that preference and resistance to change do not necessarily covary.     

GROUP FORAGING SENSITIVITY TO PREDICTABLE AND UNPREDICTABLE CHANGES IN FOOD DISTRIBUTION: PAST EXPERIENCE OR PRESENT CIRCUMSTANCES?

The ideal free distribution theory (Fretwell & Lucas, 1970) predicts that the ratio of foragers at two patches will equal the ratio of food resources obtained at the two patches. The theory assumes that foragers have "perfect knowledge" of patch profitability and that patch choice maximizes fitness. How foragers assess patch profitability has been debated extensively. One assessment strategy may be the use of past experience with a patch. Under stable environmental conditions, this strategy enhances fitness. However, in a highly unpredictable environment, past experience may provide inaccurate information about current conditions. Thus, in a nonstable environment, a strategy that allows rapid adjustment to present circumstances may be more beneficial. Evidence for this type of strategy has been found in individual choice. In the present experiments, a flock of pigeons foraged at two patches for food items and demonstrated results similar to those found in individual choice. Experiment 1 utilized predictable and unpredictable sequences of resource ratios presented across days or within a single session. Current foraging decisions depended on past experience, but that dependence diminished when the current foraging environment became more unpredictable. Experiment 2 repeated Experiment I with a different flock of pigeons under more controlled circumstances in an indoor coop and produced similar results.     

Semantic priming in Alzheimer's dementia: evidence for dissociation of automatic and attentional processes

The nature of the semantic memory deficit in dementia of the Alzheimer's type (DAT) was investigated in a semantic priming task which was designed to assess both automatic and attention-induced priming effects. Ten DAT patients and 10 age-matched control subjects completed a word naming semantic priming task in which both relatedness proportion (RP) and stimulus-onset asynchrony (SOA) were varied. A clear dissociation between automatic and attentional priming effects in both groups was demonstrated; however, the DAT subjects' pattern of priming deviated significantly from that of the normal controls. The DAT patients failed to produce any priming under conditions which encouraged automatic semantic processing and produced facilitation only when the RP was high. In addition, the DAT group produced hyperpriming, with significantly larger facilitation effects than the control group. These results suggest an impairment of automatic spreading activation in DAT and have implications for theories of semantic memory impairment in DAT as well as models of normal priming.