The metric and dimensional assumptions that underlie the geometric representation of similarity are questioned on both theoretical and empirical grounds. A new set-theoretical approach to similarity is developed in which objects are represented as collections of features, and similarity is described as a feature-matching process. Specifically, a set of qualitative assumptions is shown to imply the contrast model, which expresses the similarity between objects as a linear combination of the measures of their common and distinctive features. Several predictions of the contrast model are tested in studies of similarity with both semantic and perceptual stimuli. The model is used to uncover, analyze, and explain a variety of empirical phenomena such as the role of common and distinctive features, the relations between judgments of similarity and difference, the presence of asymmetric similarities, and the effects of context on judgments of similarity. The contrast model generalizes standard representations of similarity data in terms of clusters and trees. It is also used to analyze the relations of prototypicality and family resemblance

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Features of Similarity

This paper examines the effects of stress on sustained attention. With recognition of the task itself as the major source of cognitive stress, a dynamic model is presented that addresses the effects of stress on vigilance and, potentially, a wide variety of attention-demanding performance tasks.

/pdf/a-dynamic-model-of-stress-and-sustained-attention-2pj5ck9kp6.pdf

A dynamic model of stress, and sustained attention

Méthodes : Sur une série de 31 femmes présentant des varices périnéales d’origine extrasaphéniennes ayant bénéficié d’une exploration radiologique veineuse pelvienne et de l’embolisation des veines incontinentes nous avons étudié les résultats et les corrélations anatomo-clinique entre les varices et les signes cliniques de l’insuffisance veineuse pelvienne. Un sous-groupe B de 23 patientes présentant une insuffisance veineuse pelvienne et des signes cliniques a été comparé à un groupe A de 4 patientes qui ne présentaient pas d’insuffisance veineuse pelvienne à l’exploration. Nous avons choisi d’étudier 3 signes cliniques : la douleur pelvienne et la douleur des membres inférieurs survenant au début ou pendant les règles ainsi que la dyspareunie. La symptomatologie a été évaluée sur une échelle analogique de 0 à 10 et un score clinique (de 0 à 30) a été établi en ajoutant ces 3 chiffres.

http://link.springer.com/content/pdf/10.1007/BF02973687.pdf

Références bibliographiques: La fibroscopie bronchique

Similarity data can be represented by additive trees. In this model, objects are represented by the external nodes of a tree, and the dissimilarity between objects is the length of the path joining them. The additive tree is less restrictive than the ultrametric tree, commonly known as the hierarchical clustering scheme. The two representations are characterized and compared. A computer program, ADDTREE, for the construction of additive trees is described and applied to several sets of data. A comparison of these results to the results of multidimensional scaling illustrates some empirical and theoretical advantages of tree representations over spatial representations of proximity data.

Additive similarity trees

Judgments of linguistic acceptability constitute an important source of evidence for theoretical and applied linguistics, but are typically elicited and represented in ways which limit their utility. This paper describes how MAGNITUDE ESTIIMATION, a technique used in psychophysics, can be adapted for eliciting acceptability judgments. Magnitude estimation of linguistic acceptability is shown to solve the measurement scale problems which plague conventional techniques; to provide data which make fine distinctions robustly enough to yield statistically significant results of linguistic interest; to be usable in a consistent way by linguistically naive speaker-hearers, and to allow replication across groups of subjects. Methodological pitfalls are discussed and suggestions are offered for new approaches to the analysis and measurement of linguistic acceptability.*

Magnitude estimation of linguistic acceptability

Summary.-28 lower-case letters of the Swedish alphabet were studied by the method of multidimensional similarity analysis. 57 Ss participated in the experiment. 9 factors were found. Factor I is called 't' or 'Vertical linearity,' Factor 11: '0' or 'Roundness,' Factor 111: 'n' or 'Parallel vertical linearity,' Factor IV: 'i' or 'Vertical linearity with dot,' Factor V: 'p' or 'Roundness attached to vertical linearity,' Factor VI: 'k' or 'Vertical linearity with crossness,' Factor VII: 'a' or 'Roundness attached to a hook,' Factor VIII: 'v' or 'Angularity open upward' and Factor IX: '2' or 'Zigzaggedness.' 'Vertical linearity' and 'Roundness' are the most important of these factors and account for a considerable portion of the similarity among many letters. In previous experiments with nine capital letters (Kuennapas, 1966, 1967, 1968a) it was shown that multidimensional similarity analysis (Ekman, 1965, 1968) could be used successfully for the study of the perceived forms of these capitals. The factors revealed by the analyses could be interpreted easily and meaningfully as 'Rectangularity,' 'Roundness' and 'Vertical linearity.' The purposes of the present study were (a) to extend the multidimensional similarity analysis to the whole alphabet of lower-case letters, and (b) to reveal the main perceptual dimensions of visual forms of these letters.

Multidimensional Similarity of Letters

Two direct and one indirect scaling methods were used to construct scales of occupational preferences. The scales constructed by the direct methods of magnitude estimation and ratio estimation were linearly related. The pair comparison scale was found to be a logarithmic function of the magnitude estimation scale and of the ratio estimation scale. This was in line with the results obtained in several previous studies. It was suggested that the logarithmic relation between the pair comparison scale (R-scale) and the magnitude scale (ψ-scale) is due to the model of Case V. Application of Case VI, which is based on the lognormal distribution of subjective magnitudes and Weber's law for subjective continua and yields a logarithmic interval scale of subjective magnitude, would give a linear relation for prothetic continua. For metathetic continua Case V is probably applicable, yielding a linear relation between the indirect and direct scaling.

Measurement of occupational preferences: a comparison of scaling methods

In a recent investigation made at this laboratory, the aesthetic value of a set of handwriting specimens was srudied by means of one indirect method and one direct method. These two types of psychophysical methods have usually been applied to quite different kinds of problems, and very little work has been done in which scales obtained by the differenc methods could be compared. The need for research of this kind was discussed in some detail in the previous paper (Ekrnan & Kuennapas, 1961; cf. Ekrnan, 1961). In two previous investigations, covering only a narrow range, an approximately linear relation was found (Bjoerkman, 1959; Ekman & Kuennapas, 1960a). In the recent study over a considerably wider range, the relation berween a ratio scale and an interval scale from pair comparisons was logarithmic. The present paper reports a further experimenc with a similar purpose. Another aesthetic variable was measured by the indirect method of pair comparisons, and by the direct method of ratio estimation. W e consider it important to carry out several such experiments, in order to find out whether there is a relatively general relation between the differenc types of scales. In addition, the direct method of category estimation was used. One reason for including this method was that the category scale from some points of view may be expected to be rather closely related to the interval scale from pair comparisons.

Scales of Aesthetic Value

The similarity of 9 capital letters, as judged on the basis of visual memory, was studied by direct multidimensional ratio scaling and by the method of similarity analysis. Three factors were isola...

Visual memory of capital letters: multidimensional ratio scaling and multidimensional similarity.

: Several previous investigations have demonstrated a logarithmic relation between scales constructed by the method of pair comparisons on the assumption of Case V and scales constructed by the method of ratio estimation. In the present investigation the same problem was studied for continua of estimated conservatism. In this case, however, the relation between the two types of scales was linear. According to preliminary interpretation this result may be related to a qualitative character of the radicalism-conservatism continuum. (Author)

Teodor Kuennapas

Papers

Multidimensional Similarity of Letters

Measurement of occupational preferences: a comparison of scaling methods

Scales of Aesthetic Value

Visual memory of capital letters: multidimensional ratio scaling and multidimensional similarity.

Scales of Conservatism