The visible kinematic pattern that occurs when objects collide contains information about the relative mass of the objects. Recently, Gilden and Proffitt (1989) have claimed that perceivers are limited to the use of simultaneous elemental cues and that therefore mass discrimination judgments are independent of whether the precollision epoch is visible or not. The present paper argues that their experimental results are irrelevant because crucial parameters were held constant, and that false conclusions were drawn because their data were not treated for what they are: threshold measurements obtained with the method of constant stimuli. Three experiments are reported, showing that a high level of performance is attainable only when the whole event is visible, and thus that the effective information is extended over time. In addition, modified PROBIT analysis was used to determine what information observers use when the precollision epoch is occluded. Analytically complex invariants, based on vector components in the abstract collision-axis system, proved to have the best fit to the data. Thus the elementaristic premises in Gilden and Proffitt's cue-heuristic model for relative mass perception are defeated.

Drawing on philosophy, the history of psychology and the natural sciences, this book proposes a new theoretical foundation for the psychology of the life course. It features the study of unique individual life courses in their social and cultural environment, combining the perspectives of developmental and sociocultural psychology, psychotherapy, learning sciences and geronto-psychology. In particular, the book highlights semiotic processes, specific to human development, that allow us to draw upon past experiences, to choose among alternatives and to plan our futures. Imagination is an important outcome of semiotic processes and enables us to deal with daily constraints and transitions, and promotes the transformation of social representation and symbolic systemsgiving each person a unique style, or 'melody', of living. The book concludes by questioning the methodology and epistemology of current life course studies.

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It is argued that a definition of intentionality in terms of object directedness is more adequate than the traditional definition in terms of goal directedness. Inconsistencies in the use of "intentionality" among infant researchers are pointed out. A method of observation is explored, based on the definition in terms of behavioral object directedness, that takes into account precursors to fully-fledged intentional actions by approaching intentionality as a matter of degree rather than as an all or none issue. The method, when used on longitudinal video recordings of parent-infant interaction, produced results that substantiated Trevarthen's observations of infant intentionality before the age of six months. Furthermore, the results suggest that the parent's attribution of intentions to the infant is based on the perception of the infant's intentionality, whether in social interaction or in interaction with "physical" objects.

The issue is discussed whether or not parental attribution of intentions to infants is a pretense. This issue cannot be investigated if it is meant to be a question whether or not the infant has the specific intentions attributed to it. Problems connected with the usual description of intentionality in terms of goal-directedness are discussed. It is proposed that instead the intentionality of behavior be described in terms of object-directedness, a concept central to the philosophical concept of intentionality. The object-directedness of an infant’s behavior is hypothesized to elicit the parent’s perception of infant intentionality. Parental attribution of infant intentions is proposed to be considered a pretense only in the absence of object-directedness in the behavior of the infant.

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