When groups are more competitive than individuals: the domain of the discontinuity effect

The related goals of the research were to delineate the domain of discontinuity, 1st by demonstrating its occurrence in a nonmatrix situation and, 2nd, by establishing the antecedent outcome conditions necessary for producing a discontinuity effect. The 1st goal was met by designing a mixed motive situation involving the production of origami products. Under these conditions, the magnitude of the discontinuity effect did not significantly differ from that in a matrix-only condition. The 2nd goal was met by a separate experiment that used H. H. Kelley and J. W. Thibaut's (1978) analysis of degree of noncorrespondence of outcomes. This experiment demonstrated that as noncorrespondence increased, so did the rate of competitive responding by groups but not by individuals. This pattern was qualified by an interaction with gender such that competitiveness was more markedly affected by noncorrespondence for groups of women than for groups of men.     

Age of acquisition effects on the functional organization of language in the adult brain

Using functional magnetic resonance imaging (fMRI), we neuroimaged deaf adults as they performed two linguistic tasks with sentences in American Sign Language, grammatical judgment and phonemic-hand judgment. Participants’ age-onset of sign language acquisition ranged from birth to 14 years; length of sign language experience was substantial and did not vary in relation to age of acquisition. For both tasks, a more left lateralized pattern of activation was observed, with activity for grammatical judgment being more anterior than that observed for phonemic-hand judgment, which was more posterior by comparison. Age of acquisition was linearly and negatively related to activation levels in anterior language regions and positively related to activation levels in posterior visual regions for both tasks.     

Verbal and Numerical Expressions of Probability: "It's a Fifty-Fifty Chance"

When estimating risks, people may use "50" as an expression of the verbal phrase "fifty-fifty chance," without intending the associated number of 50%. The result is an excess of 50s in the response distribution. The present study examined factors determining the magnitude of such a "50 blip," using a large sample of adolescents and adults. We found that phrasing probability questions in a distributional format (asking about risks as a percentage in a population) rather than in a singular format (asking about risks to an individual) reduced the use of "50." Less numerate respondents, children, and less educated adults were more likely to say "50." Finally, events that evoked feelings of less perceived control led to more 50s. The results are discussed in terms of what they reveal about how people express epistemic uncertainty. Copyright 2000 Academic Press.     

Encoding variability theory and the spacing effect in associate learning

Encoding variability theory accounts for the spacing effect by assuming that, as the lag between repetitions increases, the memorial representations approach independence. A method for testing this assumption in determining repetition effects in associative learning is suggested. In the independence hypothesis, we simply assume that each presentation of a word pair is represented independently, so that the expected proportion recalled is simple, P=P1+P2 - PIP2. Two studies are reported using a continuous paired-associate task representing a factorial combination of lag and retention interval as well as single-presentation control conditions. The results indicate that for moderately long retention intervals, as the lag between repetitions increases, the observed proportion recalled is first less, then eventually exceeds, and then returns to the level expected by an independence hypothesis.