Development of visual center of mass localization for grasp point selection

Adults assess precisely the center of mass (CM) of single-bodied objects and choose grasping points that span an axis through or close to the center of mass when lifting them. The present study examined how children and adults assess the CM when lifting two-bodied objects (barbells) and how this ability develops. Four- to five-year olds, 6- to 7-year olds, 9- to 11-year olds and adults were required to grasp and lift symmetrically and asymmetrically proportioned miniature barbells and their grasping points were recorded. While the 4- to 5-year olds grasped near the center of the barbell, accuracy of assessing the correct CM improved linearly with age. Although adults grasped close to the CM, their CM determination follows only an approximation of the physical law.     

Right or wrong, familiar or novel in pictorial list discrimination learning

The interaction between nonassociative learning (presentation frequencies) and associative learning (reinforcement rates) in stimulus discrimination performance was investigated. Subjects were taught to discriminate lists of visual pattern pairs. When they chose the stimulus designated as right they were symbolically rewarded and when they chose the stimulus designated as wrong they were symbolically penalised. Subjects first learned one list and then another list. For a "right" group the pairs of the second list consisted of right stimuli from the first list and of novel wrong stimuli. For a "wrong" group it was the other way round. The right group transferred some discriminatory performance from the first to the second list while the control and wrong groups initially only performed near chance with the second list. When the first list involved wrong stimuli presented twice as frequently as right stimuli, the wrong group exhibited a better transfer than the right group. In a final experiment subjects learned lists which consisted of frequent right stimuli paired with scarce wrong stimuli and frequent wrong stimuli paired with scarce right stimuli. In later test trials these stimuli were shown in new combinations and additionally combined with novel stimuli. Subjects preferred to choose the most rewarded stimuli and to avoid the most penalised stimuli when the test pairs included at least one frequent stimulus. With scarce/scarce or scarce/novel stimulus combinations they performed less well or even chose randomly. A simple mathematical model that ascribes stimulus choices to a Cartesian combination of stimulus frequency and stimulus value succeeds in matching all these results with satisfactory precision.     

Whence the Happiness Revolution? A Book Review of Richard Easterlin’s An Economist’s Lessons on Happiness

Journal of Happiness Studies -     

Varimax solution for primary mental abilities

The varimax solution for Thurstone's classic Primary Mental Abilities study is presented. Comparisons between the factors of Thurstone's original subjectively rotated factor pattern, Zimmerman's subjectively revised solution, Wrigley, Saunders, and Neuhaus' quartimax results, and the present varimax factor matrix are made by finding correlations between factors defined by these four solutions. It is pointed out that any possible ultimate merit of the varimax solution should be based on its psychological meaningfulness and on the rationale of the varimax criterion—not on its relationship to the other studies.The computations for this paper were done on Illiac, an electronic computer of the Digital Computer Laboratory of the University of Illinois. Mr. S. M. Hunka assisted in these computations.