Three problems regarding medical triage

This paper presents preliminary solutions to three conceptual problems posed by the use of triage to sort candidates for scarce medical resources: (1) By what criteria are the candidates grouped? (2) To what extent can triage be justified? (3) Under what conditions are different versions of triage equivalent? Four explicit methods of applying triage are described and compared, with the aid of examples. The extent to which they either maximize expected utility or show cost-benefit dominance is discussed. And cases in which one triage method reduces to another are contrasted with others where no such reduction occurs.     

Conditional mechanisms of decision making

Decision making is an important link in the central part of a reflex—the “mental element” according to Sechenov. The reflex nature of this mental process is revealed in experiments where a voluntary motor reaction is chosen unconsciously as a response to subliminal conditional visual stimuli. Thus, learning which is reflected by “advance” or prior decision making can be performed unconsciously through a conditional reflex. But, once elaborated, temporary connections are preserved only in shortterm memory. They are not transferred to long-term memory, as in the case of recognition of signals. Decision making, being the central mental part of the reflex, like any activity of the brain, is performed in time by a certain cortical structure. Analysis of P₃₀₀ amplitudes shows that decision making is related to local activation of the frontal parts of the cerebral hemispheres. We suggest that the local activation of these areas is induced by conditional excitation of the neuronal mechanisms of focused attention. It provides a “command” to perform a voluntary motor reaction adequate to the conditions at hand. A large part of latency of voluntary motor response of man is spent on decision making, especially in discrimination of signals and in choice of reactions.     

Spatial frequency content of visual imagery

Three experiments employing the McCollough paradigm were conducted to determine the spatial-frequency content of visual imagery. In Experiment 1, large and reliable pattern-contingent color aftereffects were obtained after adaptation to visual imagery. The direction of the aftereffects indicated that subjects were adapting to higher spatial frequencies in their imagery. These results contrast with the data of Experiment 2, which demonstrate that color aftereffects obtained with adaptation to physically present stimuli are mediated by the fundamental spatial frequency components. The magnitude of the imagery-induced aftereffects in Experiment 1 equaled the magnitude of the externally induced aftereffects obtained in Experiment 2 with the same subjects. By blurring the to-be-imaged patterns (Experiment 3), the fundamental Fourier components became the salient perceptual features of the stimuli, and the direction of the imagery-induced aftereffects was reversed from that of Experiment 1, indicating that the spatial frequency content of the imagery had changed from higher to lower frequencies. Under normal viewing conditions, subjects use the higher spatial frequencies associated with the perceptually salient edges of stimuli to construct their images. The results of Experiments 1 and 3 are discussed in light of a current controversy over the nature of information representation in imagery, and it is concluded that support has been obtained for the analog model of visual imagery.     

Picture perception: An analysis of visual compensation

Although geometric information is altered when a picture’s viewing point is changed, such changes often do not affect perception. Two experiments assessed pictorial perception relative to the distortions introduced by viewing point dislocation. Results provide a psychophysical demonstration of pictorial compensation and suggest that it is based on the discrepancy between the actual and an assumed-correct viewing position. An explanation of pictorial compensation is offered that could be applied to direct picture perception and to picture-in-a-picture perception.     

Flow thresholds of nonodorous air through the human naris as a function of temperature and humidity

The process of olfactory sensation is probably a Gestalt consisting of motor, physical, and chemical components formed during the transport of the odor-bearing airstream past the olfactory epithelium. In studying a sensory process, it is often necessary to examine the components independently. Apart from its contribution to the olfactory Gestalt, in dynamic olfactometry airflow may distract from, compete with, or mask chemical sensation. Four nonsmoking male subjects were employed to obtain flow thresholds of nonodorous air at eight temperature/ humidity combinations. The stimulus-generating apparatus was housed in a temperature-regulated oven. All materials in contact with the airstream were thoroughly cleaned and were constructed of nonreactive materials to avoid olfactory cues. An evaluation of the quality of the output demonstrated purity. A Béésy technique was used to deliver stimuli via a nasal catheter to the subject. Thresholds were found to be nearly identical for the lowest humidity levels regardless of the temperature. In general, the closer the temperature/humidity was to physiological normal, the higher the threshold. Since the thresholds were so strongly functions of temperature and humidity, it is likely that transduction was by trigeminal thermoreceptive afferents. The utilization of subthreshold flows in olfactory research may reduce the trigeminal component in olfaction, thus permitting better assessment of the contribution of the olfactory nerve to olfactory sensation.     

The relationship of extraversion,neuroticism, and sensation-seeking to questionnaire-derived measures of nervous system properties

Five obliquely rotated factor analyses were performed on items from Eysenck and Eysenck’s (1975) EPQ, Zuckerman’s (1975) Sensation-Seeking Scale, and Strelau’s (1972) temperament inventory (STI), administered to 277 subjects (Ss). The analyses were used to examine the relationships between the personality dimensions E, N, L, P and Sensation-Seeking, which pertain mainly to social situations, attitudes and feelings, and questionnaire-derived measures of nervous system properties, which, while validated on experimental indices of nervous system properties derived from Nebylitsyn’s (1972) model, are expressed as characteristic features of social behavior, work style and activity. Four factors were identified—extraversion/strength of excitation/mobility; self-control of affect/stability/caution; strength of inhibition/verbal control/motor expressiveness/ nonmanipulativeness; and sensation-seeking/nervousness. The results offer support for Eysenck’s claim of some identity between excitatory strength and E, for the reported relationship between E and mobility, and for Eysenck’s conditioning postulate. They also suggest that similar temperamental variables underlie individual differences in both social and occupational/motor activity. Since Strelau’s STI items are validated on experimental indices of nervous system properties, it follows that typological characteristics may be inferred from questionnaire data derived from both behavioral categories.     

A simple special-purpose interval-duration timer for acoustic research

A special-purpose interval-duration timer is described. The device is designed to interface with commercially available psychophysical packages, to be used in time interval calibration. The extremely low cost of materials justifies the construction of this essentially single-purpose device.     

Free classification: Element-level and subgroup-level similarity

Subjects classified sets of multidimensional stimuli into two groups in any way they wished. The sets were composed of 6 or 12 stimuli: 2 or 4 instances of 3 different stimuli (e.g., 2 blue circles, 2 green circles, 2 red circles). There were striking individual differences in the preferred classification. Some subjects maximized the similarity between subgroups by matching the composition of the subgroups--one instance of each stimulus was placed in each group. The other subjects maximized the similarity among stimuli within each subgroup by placing similar stimuli in each group (the blues and greens in one group, the reds in the other). The nature of the stimuli as well as the relationships among the three stimuli had little effect on classification. In this case, cognitive styles specific to individuals but general across diverse dimensions and stimulus sets determined classification.     

Contextual effects in vowel perception II: Evidence for two processing mechanisms

Recent experiments have indicated that contrast effects can be obtained with vowels by anchoring a test series with one of the endpoint vowels. These contextual effects cannot be attributed to feature detector fatigue or to the induction of an overt response bias. In the present studies, anchored ABX discrimination functions and signal detection analyses of identification data (before and after anchoring) for an [i]-[I] vowel series were used to demonstrate that [i] and [I] anchoring produce contrast effects by affecting different perceptual mechanisms. The effects of [i] anchoring were to increase within-[i] category sensitivity, while [I] anchoring shifted criterion placements. When vowels were placed in CVC syllables to reduce available auditory memory, there was a significant decrease in the size of the [I]-anchor contrast effects. The magnitude of the [i]-anchor effect was unaffected by the reduction in vowel information available in auditory memory. These results suggest that [i] and [I] anchors affect mechanisms at different levels of processing. The [i] anchoring results may reflect normalization processes in speech perception that operate at an early level of perceptual processing, while the [I] anchoring results represent changes in response criterion mediated by auditory memory for vowel information.     

Target-size influences on reaction time with movement time controlled

The variable that affect motor programming time may be studied by changing the nature of the response and measuring the subsequent changes in reaction time (RT). One notion of motor programming suggests that aiming responses with reduced target size and/or increased target amplitude require more "complex" motor programs that require longer RTs. In a series of five experiments which movement time (MT) was experimentally varied target size neither influences RT when the movement amplitude was 2 or 30 cm nor when the target sizes differed by as much as a factor of 16:1. Increasing the movement amplitude from 15 to 30 cm also had no influence on RT. Movement time, however, did affect RT, with 200-msec movements having longer RTs than 120-msec movements. Target size and movement amplitude did not appear to be factors that influence programming time or program complexity.