Does Octopus vulgaris have preferred arms?

Previous behavioral studies in Octopus vulgaris revealed lateralization of eye use. In this study, the authors expanded the scope to investigate arm preferences. The octopus's generalist hunting lifestyle and the structure of their arms suggest that these animals have no need to designate specific arms for specific tasks. However, octopuses also show behaviors, like exploration, in which only single or small groups of arms are involved. Here the authors show that octopuses had a strong preference for anterior arm use to reach for and explore objects, which points toward a task division between anterior and posterior arms. Four out of 8 subjects also showed a lateral bias. In addition, octopuses had a preference for a specific arm to reach into a T maze to retrieve a food reward. These findings give evidence for limb-specialization in an animal whose 8 arms were believed to be equipotential.     

Feeding behavior of Aplysia: a model system for comparing cellular mechanisms of classical and operant conditioning

Feeding behavior of Aplysia provides an excellent model system for analyzing and comparing mechanisms underlying appetitive classical conditioning and reward operant conditioning. Behavioral protocols have been developed for both forms of associative learning, both of which increase the occurrence of biting following training. Because the neural circuitry that mediates the behavior is well characterized and amenable to detailed cellular analyses, substantial progress has been made toward a comparative analysis of the cellular mechanisms underlying these two forms of associative learning. Both forms of associative learning use the same reinforcement pathway (the esophageal nerve, En) and the same reinforcement transmitter (dopamine, DA). In addition, at least one cellular locus of plasticity (cell B51) is modified by both forms of associative learning. However, the two forms of associative learning have opposite effects on B51. Classical conditioning decreases the excitability of B51, whereas operant conditioning increases the excitability of B51. Thus, the approach of using two forms of associative learning to modify a single behavior, which is mediated by an analytically tractable neural circuit, is revealing similarities and differences in the mechanisms that underlie classical and operant conditioning.     

Measurement equivalence: a comparison of methods based on confirmatory factor analysis and item response theory

Current interest in the assessment of measurement equivalence emphasizes 2 major methods of analysis. The authors offer a comparison of a linear method (confirmatory factor analysis) and a nonlinear method (differential item and test functioning using item response theory) with an emphasis on their methodological similarities and differences. The 2 approaches test for the equality of true scores (or expected raw scores) across 2 populations when the latent (or factor) score is held constant. Both approaches can provide information about when measurement nonequivalence exists and the extent to which it is a problem. An empirical example is used to illustrate the 2 approaches.     

Validating the measurement and structure of self-concept: snapshots of past,present, and future research

Although the study of self-concept has been a topic of great interest and much study in the social sciences for many decades, it is really only in the past 30 years that any fruitful expansion in knowledge of both its theoretical structure and its related measurement has been forthcoming. From three perspectives--past, present, and future--the author presents abbreviated and selected highlights of important construct validity findings related to this research and postulates possible trends and areas of self-concept research yet to be explored.     

Counterfactual and semifactual conditionals prime alternative possibilities

The authors examined in 3 experiments the comprehension of counterfactuals, such as "If it had rained, the plants would have bloomed," and semifactuals, such as "Even if it had rained, the plants would have bloomed," compared with indicative conditionals, "If it rained, the plants bloomed." The first experiment showed that people read the negative conjunction, "not p and not q" faster when it was primed by a counterfactual than when it was primed by an indicative conditional. They read the affirmative conjunction, "p and q" equally quickly when it was primed by either conditional. The 2nd experiment showed that people read the negated-antecedent conjunction, "not p and q" faster when it was primed by a semifactual conditional. The 3rd experiment corroborated these results in a direct comparison of counterfactuals and semifactuals. The authors discuss the implications of the results for the mental representations of different conditionals.     

Cognitive capacities for behavioural flexibility in wild chimpanzees (Pan troglodytes): the effect of snare injury on complex manual food processing

In chimpanzees, it is only in the restricted context of tool use that manual and cognitive skills have been described, comparable to those that gorillas and orang-utans display in obtaining plant foods. We report the complex food preparation skills used to eat, without tools, the leaves of the tree Broussonettia papyrifera in the Sonso community of chimpanzees at Budongo Forest, Uganda. Able-bodied individuals used multi-stage techniques that required bimanual role differentiation at several stages, and were hierarchical in organisation. A total repertoire of 14 techniques was found, with strong preference in all individuals for either of two of these; 6 additional techniques were found when flowers and leaves were eaten together. However, in this community over 20% of individuals suffer from some form of upper- or lower-limb injury as a result of snares. We investigated the manner of compensation for upper-limb injury. Only the most severely injured showed reduced feeding efficiency. Injured individuals were found to use the same repertoire of techniques as able-bodied chimpanzees. We found no evidence to suggest that injured individuals were able to develop wholly novel techniques optimal for their specific injuries, although shifts in preference for particular techniques did occur. Rather, injured individuals used novel ways of achieving particular steps in the process; by "working around" their impairments; in this way, they managed to use the same techniques as the able-bodied. Since snare injuries generally befall young animals, these results suggest that chimpanzees learn techniques partly through observational learning (of, necessarily, able-bodied individuals). Accepted after revision: 8 February 2001 Electronic Publication     

Quantitation of contacts among sensory, motor, and serotonergic neurons in the pedal ganglion of aplysia

Present models of long-term sensitization in Aplysia californica indicate that the enhanced behavioral response is due, at least in part, to outgrowth of sensory neurons mediating defensive withdrawal reflexes. Presumably, this outgrowth strengthens pre-existing connections by formation of new synapses with follower neurons. However, the relationship between the number of sensorimotor contacts and the physiological strength of the connection has never been examined in intact ganglia. As a first step in addressing this issue, we used confocal microscopy to examine sites of contact between sensory and motor neurons in naive animals. Our results revealed relatively few contacts between physiologically connected cells. In addition, the number of contact sites was proportional to the amplitude of the EPSP elicited in the follower motor neuron by direct stimulation of the sensory neuron. This is the first time such a correlation has been observed in the central nervous system. Serotonin is the neurotransmitter most closely examined for its role in modulating synaptic strength at the sensorimotor synapse. However, the structural relationship of serotonergic processes and sensorimotor synapses has never been examined. Surprisingly, serotonergic processes usually made contact with sensory and motor neurons at sites located relatively distant from the sensorimotor synapse. This result implies that heterosynaptic regulation is due to nondirected release of serotonin into the neuropil.     

Student-teacher concordance on dimensions of student social competence: A multitrait-multimethod analysis

Teacher and self-ratings of social competence were obtained for 669 (341 males, 328 females) grades 3–6 students using the Social Behavior Assessment—Revised (SBA-R) and a self-report scale consisting of the identical items reworded in first person. Factor analysis and multitrait-multimethod matrix analysis were used to validate construct interpretations. The previous four-factor structure of the SBA-R was not replicated. However, the three-factor structure that did emerge was better defined. Although student-teacher concordance was moderate for the Self-Control/Social Convention and Academic Responsibility factors, it was minimal for the Social Participation factor. Evidence of discriminant validity was weak. As with other studies using rating scales, method bias was in evidence. Sex differences were found in terms of variance explained by each factor and convergent validity. Discussion focuses on problems associated with construct validation in general and validation of school-related social competence in particular.     

Ontario Child Health Study: reliability and validity of the general functioning subscale of the McMaster Family Assessment Device

The reliability and validity of the 12-item General Functioning (GF) subscale of the McMaster Family Assessment Device (FAD) is reported here. Psychometric properties of the FAD have been previously determined, but no independent assessment has been made of the GF subscale, which was used to measure family functioning in the Ontario Child Health Study (OCHS). Reliability was measured by Chronbach's alpha and split-half correlation. Validity was assessed by hypothesizing the relationships expected between the GF scores and other family variables included in the OCHS data set. The results indicate good reliability, and all hypotheses of validity were supported. The brevity and ease of administering the GF subscale recommend it for further use in survey research in which a global assessment of family functioning is required.     

Modal reasoning, models, and Manktelow and Over.

Manktelow and Over (1991) argue that their studies of Wason's selection task favor explanations of deontic reasoning based on mental models, but that such theories need to incorporate utilities. This theoretical note proposes a simpler explanation of the phenomena: subjects in the selection task consider only those cards that are explicitly represented in their models of the conditional, and so insight into the task depends on constructing fully explicit models. Such models for modal conditionals of the form, If p occurs then q may occur are: [formula: see text] Each line denotes a separate model, and the models represent either what is possible, or, in the deontic interpretation, what is permissible. A deontic rule is accordingly violated by the contingency: [symbol: see text] p and q, for example the rule, "If you spend more than 100 pounds, then you may take a free gift" is violated by taking the free gift (q) but not spending more than 100 pounds ([symbol: see text] p). If the rule is interpreted as a bi-conditional, then the second of the models, p and [symbol: see text] q, is also now a violation, for example spending more than 100 pounds (p) but not getting the free gift ([symbol: see text] q). Manktelow and Over's instructions lead subjects to focus on one or other of the two sorts of violations of the rule. There is accordingly no need to introduce utilities into models in order to explain the phenomena.