Intensität und Qualität in der Geruchswahrnehmung

Zusammenfassung Vier unterschiedliche Geruchsstoffe in je 4 Konzentrationen wurden von 23 Versuchspersonen nach Intensität beurteilt und paarweise auf ihre relative Ähnlichkeit hin verglichen. Eine Systematik der Versuchspersonenvarianz konnte weder in den Intensitäts- noch in den Ähnlichkeitsurteilen mit dem Tucker-Messick-Verfahren nachgewiesen werden. Mit den Medianwerten der Ähnlichkeitsurteile wurde das Skalierungsverfahren von Kruskal durchgeführt. Unter 25 Lösungen wurde diejenige mit einem Exponenten (Minkowski-Metrik) von r=2,5 und 5 Dimensionen als optimal ausgewählt und zur Grundlage der Interpretation genommen. Als wichtigstes Ergebnis erhielten wir eine unabhängige Intensitätsdimension mit Ursprung außerhalb der Reizkonfiguration, die eine hohe Übereinstimmung zur Intensitätsskalierung aufwies. Weiter konnte ein Qualitätswechsel jeweils innerhalb eines Stoffes zwischen den Konzentrationen festgestellt werden. Dieser Qualitätswechsel ist bei den einzelnen Stoffen unterschiedlich stark ausgeprägt.

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Quality and intensity in olfactory perception

Summary In an experiment on olfaction 23 subjects judged 16 odors (four chemicals each in four concentrations) with respect to intensity and with respect to similarity for each pair of stimuli. Systematic interindividual variation can he found neither in the intensity nor in the similarity data. Multidimensional scaling according to Kruskal's procedure reveals a configuration in 5 dimensions, the exponent of the optimal Minkowski-metric (out of 25 alternative solutions) is r=2.5. This scaling is based on the medians of similarity judgments. One of the dimensions corresponds to a subjective scale of intensity, with a zero-point lying outside of the configuration. The quality of the stimuli depends on their concentrations. The perceived quality-changes differ in amount and directions for each of the chemicals.

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Von der Philosophischen Fakultät der Universität des Saarlandes auf Antrag von Prof. Dr. K. Eyferth angenommene Dissertation.     

Pupillary and heart rate reactivity in children with minimal brain dysfunction

This study attempted to replicate and extend previous findings on autonomic arousal and responsivity in children with diagnoses of minimal brain dysfunction (MBD). Pupil size, heart rate, skin conductance, and skin temperature were recorded from 32 MBD and 45 control children during a session that included presentation of visual stimuli, simple reaction time (RT), a cold pressor procedure, and rest periods. The MBD children were tested both off and on clinical dosages of stimulant drugs in a crossover design. Evidence of higher than normal arousal levels in the unmedicated MBD Ss was obtained from resting skin conductance and, more tenuously, from pupil size. Lower phasic responsivity in the MBD children was evidenced by slower RT, less cardiac deceleration to both light and RT stimuli, and smaller pupil dilation to the RT stimuli. Spontaneous pupillary constrictions during rest periods, presumably indicating drowsiness, were observed about equally in MBD and control children. Stimulant drugs raised arousal levels but did not reverse the responsivity deficits. The lower phasic reactivity in the MBD group and the effects of stimulant drugs on arousal indices confirm earlier reports. The finding of higher arousal in drug-free MBD children is incompatible with the low arousal hypothesis of MBD but is consistent with a previous report of the effects of a stimulating environment on these children.This work was supported in part by a grant from the Ittleson Family Foundation. The authors thank Frank Abate for technical assistance.     

Kontexteffekte und Routenwissen

Knowledge about how to go from one location to another one is called route knowledge. The paper presents two experiments that examine how memories of objects along a route are activated. We tested especially for a context effect regarding memory performance. In two further experiments, the hypothesis was put to test whether the combined influence of cues is over-additive.     

Subitizing and its subprocesses

 When people are presented with small sets of elements such as dots they can very easily determine their number. This ability has been called subitizing. The present paper reports results from four experiments. The discussion focuses on the question whether one or two psychological processes have to be assumed for this task of subitizing. Taken together our results support the two-process theories. In particular, a distinction between a process of separation and a process of enumeration is suggested. Experiments 3 and 4 support the canonical pattern hypothesis. Canonical patterns are processed substantially faster than noncanonical patterns. Furthermore, if a complex pattern can be broken down into small canonical patterns, then participants follow a partition and add strategy. Accepted: 22 December 1999     

Epileptic seizures in young patients with hypodense lesions in the CT image

Progress in neurodiagnostic medical technology, and in computer tomography in particular, has raised fresh problems in connection with epilepsy. Among our patients we have observed three case of epilepsy, in whom the CT image unexpectedly revealed hypodense lesions of various sizes in the cerebrum. The three are young patients aged 20 to 25 years with negative neurological findings. The above changes in the CT image are extremely difficult to interpret. It is not even know whether the lesions must be considered the cause or a consequence of the epileptic seizures or whether the pathomorphological processes are basically identical or completely different in all three patients.     

Der Einfluß der Darbietungsmodalität auf das kurzfristige Behalten

Zusammenfassung Ausgehend von der Zweikomponententheorie des menschlichen Gedächtnisses wird die bessere Behaltensleistung bei akustischer gegenüber optischer Darbietung diskutiert. Drei Erklärungsvorschläge dieses Modalitäts-effektes werden einander gegenübergestellt. Ein Experiment mit unimodaler und bimodaler Darbietungsweise bei freier Reproduktion unterstützt die Annahme zweier getrennter Speicher. Die Ergebnisse werden mit Markov-Modellen beschrieben. Abschließend wird vorgeschlagen, die Gedächtnistheorie flexibler zu gestalten.

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Effect of the mode of presentation on short-term memory

Summary The two-component theory of human memory is taken as the basis for a discussion on the effect of mode of presentation on recall probability. Three different explanations for this modality effect are compared. An experiment using auditory and visual and bimodal presentations with single-trial free recall supports the two-store hypothesis. The results are described with the aid of Markov models. It is suggested that the theory of human memory should be modified to allow for greater flexibility.

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Die Untersuchung wurde durch eine Sachmittelbeihilfe der Deutschen Forschungsgemeinschaft an A.F. unterstützt. Wir danken Frau C. Klein und Herrn W. D. Müller für ihre Hilfe bei der Durchführung der Experimente.