Principal component (PCA) and factor analysis (FA) are widely used in animal behaviour research. However, many authors automatically follow questionable practices implemented by default in general‐purpose statistical software. Worse still, the results of such analyses in research reports typically omit many crucial details which may hamper their evaluation. This article provides simple non‐technical guidelines for PCA and FA. A standard for reporting the results of these analyses is suggested. Studies using PCA and FA must report: (1) whether the correlation or covariance matrix was used; (2) sample size, preferably as a footnote to the table of factor loadings; (3) indices of sampling adequacy; (4) how the number of factors was assessed; (5) communalities when sample size is small; (6) details of factor rotation; (7) if factor scores are computed, present determinacy indices; (8) preferably they should publish the original correlation matrix.

Differences in the exploratory behavior and social tendencies of 29 guppies (Poecilia reticulata) in 2 domains of situations involving novelty and conspecincs were investigated. Consistent individual differences were found in most behavior patterns. Two behavioral dimensions (Activity Exploration and Fear Avoidance) were identified in the novelty situations. Likewise, 2 dimensions (Sociability and Locomotion) were found in the social situations. An analysis of relationships between these 2 test domains revealed the existence of even broader behavioral dimensions (Approach, governing exploration and social attraction, and Fear Avoidance, governing responses to aversive stimulation). Thus, it was shown that "personality" may represent an important behavioral category in the guppy provided it is defined precisely and objectively.Comparative psychologists and ethologists have always been interested in the study of animal temperament (e.g.,

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Reebs 2006), which has for a long time been considered the most homogeneous social structure in fishes (Radakov 1972). Even the classical example of many ethological textbooks, the stereotypic response of male three-spined sticklebacks (Gasterosteus aculeatus) to the red belly of an opponent is very pronounced in some individuals but absent in others: it is so variable that the classical concept of innate releasing mechanisms (sign stimuli) can be questioned (Rowland 1982;Baerends 1985;Bolyard & Rowland 1996).Niko Tinbergen, in his classical work 'On the aims and methods of ethology' (Tinbergen 1963), outlined four questions that are fundamental for our understanding of any behaviour:(1) Causation: What is the cause of the behaviour in question?(2) Function: What is its survival value? (3) Ontogeny: How does it develop? (4) Evolution: How did it evolve?

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Some aspects of lateralization are widespread. This is clear for the association between left-eye (LE) use and readiness to respond intensely to releasing stimuli presented by others, which has been found in representatives of all major groups of tetrapods and in fishes. In the chick, this behavioural asymmetry is linked developmentally to greater ability to sustain response against distracting stimuli with right-eye (RE) use, in that both reverse with the reversal of the normal RE exposure to light. In the zebrafish, the same two asymmetries (normally) have similar associations with the LE and the RE, and both also reverse together (owing to epithalamic reversal). Here, we show that light exposure early in development is needed in zebrafish to generate both asymmetries. Dark development largely abolishes both the enhanced abilities, confirming their linkage. Resemblance to the chick is increased by the survival in the chick, after dark development, of higher ability to assess familiarity of complex stimuli when using the LE. A somewhat similar ability survives in dark-developed zebrafish. Here, LE use causes lesser reliance on a single recent experience than on longer term past experience in the assessment of novelty. Such resemblances between a fish and a bird suggest that we should look not only for resemblances between different groups of vertebrates in the most common overall pattern of lateralization, but also for possible resemblances in the nature of inter-individual variation and in the way in which it is generated during development.