On the dimensionality of the System Usability Scale: a test of alternative measurement models

The System Usability Scale (SUS), developed by Brooke (Usability evaluation in industry, Taylor & Francis, London, pp 189–194, 1996), had a great success among usability practitioners since it is a quick and easy to use measure for collecting users’ usability evaluation of a system. Recently, Lewis and Sauro (Proceedings of the human computer interaction international conference (HCII 2009), San Diego CA, USA, 2009) have proposed a two-factor structure—Usability (8 items) and Learnability (2 items)—suggesting that practitioners might take advantage of these new factors to extract additional information from SUS data. In order to verify the dimensionality in the SUS’ two-component structure, we estimated the parameters and tested with a structural equation model the SUS structure on a sample of 196 university users. Our data indicated that both the unidimensional model and the two-factor model with uncorrelated factors proposed by Lewis and Sauro (Proceedings of the human computer interaction international conference (HCII 2009), San Diego CA, USA, 2009) had a not satisfactory fit to the data. We thus released the hypothesis that Usability and Learnability are independent components of SUS ratings and tested a less restrictive model with correlated factors. This model not only yielded a good fit to the data, but it was also significantly more appropriate to represent the structure of SUS ratings.

Plant neurobiology: from sensory biology, via plant communication, to social plant behavior

In plants, numerous parameters of both biotic and abiotic environments are continuously monitored. Specialized cells are evolutionary-optimized for effective translation of sensory input into developmental and motoric output. Importantly, diverse physical forces, influences, and insults induce immediate electric responses in plants. Recent advances in plant cell biology, molecular biology, and sensory ecology will be discussed in the framework of recently initiated new discipline of plant sciences, namely plant neurobiology.     

Male–male combats in a polymorphic lizard: residency and size,but not color,affect fighting rules and contest outcome

Theoretical models predict that the outcome of dyadic agonistic encounters between males is influenced by resource‐holding potential, resource value, and intrinsic aggressiveness of contestants. Moreover, in territorial disputes residents enjoy a further obvious competitive advantage from the residency itself, owing to the intimate familiarity with their territory. Costs of physical combats are, however, dramatically high in many instances. Thus, signals reliably reflecting fighting ability of the opponents could easily evolve in order to reduce these costs. For example, variation in color morph in polymorphic species has been associated with dominance in several case studies. In this study, we staged asymmetric resident‐intruder encounters in males of the common wall lizard Podarcis muralis, a species showing three discrete morphs (white, yellow, and red) to investigate the effects of asymmetries in color morph, residency, and size between contestants on the outcome of territorial contests. We collected aggression data by presenting each resident male with three intruders of different color morph, in three consecutive tests conducted in different days, and videotaping their interactions. The results showed that simple rules such as residency and body size differences could determine the outcome of agonistic interactions: residents were more aggressive than intruders, and larger males were competitively superior to smaller males. However, we did not find any effect of color on male aggression or fighting success, suggesting that color polymorphism in this species is not a signal of status or fighting ability in intermale conflicts. Aggr. Behav. 35:274–283, 2009. © 2009 Wiley‐Liss, Inc.     

Personality traits and endocrine response as possible asymmetry factors of agonistic outcome in karate athletes

Individual variations of plasma levels of hormones testosterone (T) and cortisol (C), before (pre) and after (post) Kumite (real fight) and Kata (ritualized fight) were measured in male karate athletes and analyzed in relation with the agonistic outcome (i.e. winning or losing the fight) and personality trait measures. T and C increased only during Kumite contest and pre‐ and post‐competition C levels were higher in losers than winners. Losers showed higher levels of harm avoidance and anxiety as well as lower level of novelty seeking than winners. Importantly, novelty seeking negatively correlates with pre C and the higher the level of risk assessment, emotionality and insecurity indexes the higher the pre C level. In conclusion, personality traits might be an important factor asymmetry between athletes influencing both the probability of winning or losing an agonistic interaction and the different anticipatory endocrine response to the incipient fight. Aggr. Behav. 35:324–333, 2009. © 2009 Wiley‐Liss, Inc.     

Ethical recommendations for workers on aggression and predation in animals

The recommendations of a recent workshop (Leiden, Netherlands, November 17–18, 1990) concerning the use of animals in research on aggression and predation are listed. Major considerations included the grade of organisation/level of development of the organism, the duration and intensity of the interaction, post-treatment factors, the number of animals and reuse of animals. It is hoped that the recommendations will help scientists working in these areas to consider the increasingly important ethical dimension.     

Preference for the sites of fighting in two teleost species

Males of two species of freshwater fish (convict cichlids and Italian freshwater gobies) fought with conspecifics and subsequently remained near the visual and spatial cues that had been paired with those social encounters. These data show that postfight preference for combat sites is a phenomenon of some generality among teleosts. The likely role of learning in establishing postfight preferences for the locales of aggression is discussed.     

Play behaviors of handicapped preschool children in the presence and absence of nonhandicapped peers

Sixteen minimally handicapped children and 18 nonhandicapped children were observed playing as separate classes and as a combined group on their preschool playground. Play behaviors directed toward self, toys, teachers, and peers were recorded using a time sampling procedure. Repeated measures analyses revealed that: (1) handicapped children engaged in less peer-directed and more teacher-directed behaviors than the similar chronological age but developmentally more advanced normal children; (2) a comparison between a subsample of normal and handicapped children who were approximately equivalent on developmental age suggested that the normal children only vocalized more often; (3) when integrated with the normal children, handicapped children engaged in more peer-directed and less teacher-directed behaviors than when playing in the non-integrated situation; (4) during the combined group play situation, normal children directed more behaviors to their own classmates while handicapped children directed approximately equal amounts of behavior to their own classmates and to their normal peers. These results suggest that the normal children were not negatively affected and the handicapped children were positively affected by the integrated play situation.     

Dominance interactions in young adult paper wasp (Polistes dominulus) foundresses: a playlike behavior?

The idea that insects play has often aroused skepticism. Nevertheless, the authors investigated the occurrence of a playlike behavior in young individuals of a paper wasp. Polistes dominulus foundresses hibernate in aggregations and found associative nests in the spring. In aggregations, wasps exhibit most of the rank-dependent behaviors that they will use in the nest 6 months later. In aggregations, precocious dominance interactions are performed with exaggerated frequencies, whereas aggression and trophallaxis are rare. Dominance behavior in aggregations is apparently useless, but it probably allows wasps to assess their dominance potential without any apparent reproductive competition. Surprisingly, these interactions may be best interpreted as play because dominance behavior in aggregations shares several features with mammalian play fighting.     

Retrospective revaluation as simple associative learning

Backward blocking, unovershadowing, and backward conditioned inhibition are examples of retrospective revaluation phenomena that have been suggested to involve more than simple associative learning. Models of these phenomena have thus used additional concepts, for example, appealing to attentional effects or more elaborate learning mechanisms. The author shows that a suitable representation of stimuli, paired with a careful analysis of the discriminations faced by animals, leads to an account of these and other phenomena in terms of a simple elemental model of associative learning, with essentially the same learning mechanism as the R. A. Rescorla and A. R. Wagner (1972) model. The author concludes with a discussion of some implications for theories of learning.