Biased extensive measurement: The general case

We develop a theory of biased extensive measurement which allows us to prove the existence of a ratio-scale without transitivity of indifference and with a property of homothetic invariance weaker than independence. These representations, which cover the cases of interval orders and of semiorders, reveal a unique biasing function smaller or equal to 1 that distorts extensive measurement and explains departures from its standard axioms. We interpret this biasing function as characterizing the qualitative influence of the underlying measurement process and we show that it induces a proportional indifference threshold.     

Titrating-delay matching-to-sample in the pigeon

The titrating-delay matching-to-sample (TDMTS) procedure offers researchers an additional behavioral task thought to capture some important features of remembering. In this procedure, the delay between sample offset and comparison onset adjusts as a function of the subject's performance. Specifically, correct matches increase the delay and incorrect matches decrease the delay, and steady-state titrated delays serve as the primary dependent measure. The present series of experiments investigated the effects of several procedural variables on performance in TDMTS procedures in an effort to elucidate better its features to allow for more precision in future use. Experiment 1 reports results from a parametric analysis of fixed-ratio response requirements on the sample key that indicated improved remembering in the form of higher daily titrated delay values as the requirement was increased. Experiment 2 investigated the extent to which the initial delay value in each session affected session-wide delay values. Results indicated that regardless of value of the initial delay, the subjects' performances adjusted the delay values in the direction of the known baseline delay-value levels. Experiment 3 manipulated the step size by which delay values were adjusted and the results indicated that larger step sizes increased both session-to-session variability and within-session range of titrated delay values, although the average values remained approximately the same. These results suggest that the TDMTS task serves as a promising procedure to study what many refer to as memory.     

Darwin’s solution to the species problem

Biologists and philosophers that debate the existence of the species category fall into two camps. Some believe that the species category does not exist and the term ‘species’ should be eliminated from biology. Others believe that with new biological insights or the application of philosophical ideas, we can be confident that the species category exists. This paper offers a different approach to the species problem. We should be skeptical of the species category, but not skeptical of the existence of those taxa biologists call ‘species.’ And despite skepticism over the species category, there are pragmatic reasons for keeping the word ‘species.’ This approach to the species problem is not new. Darwin employed a similar strategy to the species problem 150 years ago.     

When groups are wrong and deviants are right

How do group members respond when their group wrongfully punishes a group member? In two experiments, participants were presented with an ingroup member who argued for group change on moral (Experiment 1, N = 73) or scientific grounds (Experiment 2, N = 94). Despite being right, the member was treated as deviant by the group. We manipulated whether the group retained its former opinion or adopted the deviant's position, and whether the deviant's punishment was ongoing or whether the deviant was reinstated. We tested opposing predictions about how these group actions would affect group members' negativity towards the deviant. Both studies showed that negativity towards the deviant was highest when the group opinion was unchanged and the deviant was not reinstated. Further, opinion change or reintegration defused negativity towards the deviant. Implications of groups rejecting or embracing change, and their effects on the evaluation of wrongfully accused deviants are discussed. Copyright © 2010 John Wiley & Sons, Ltd.     

Risk factors associated with eating disorders in Mexican preadolescents with normal weight

This study aimed to identify the differences in body self-esteem, general self-esteem and eating attitudes in a representative sample of children, aged 9-12 years, attending school in México DF. The logistic regression model incorporated the variables of sex, general self-esteem, BMI, age and discrepancy between the perceived image and the ideal image. Participants with an increased risk of eating disorders were girls: a) with less general self-esteem; b) BMI at the upper range of normal weight; c) greater negative discrepancy between perceived and ideal image; d) aged 11-12 years. Higher general self-esteem would act as a protector for eating disorders, while the desire for a thinner ideal body would be a risk factor.     

In hindsight, life flows from left to right

Three experiments investigated the mental representation of meaningful event sequences. Experiment 1 used extended (5 min long) naturalistic scenes excerpted from commercial movies. Experiments 2 and 3 presented everyday activities by means of sequences of six photographs. All experiments found both left–right and distance effects in an order decision task, suggesting that when contemplated in hindsight, experienced events unfold along a left-to-right analogical mental line. Present results are discussed in the context of the mental representation of other kinds of ordinal sequences, and other left–right effects reported in non-ordinal domains.     

Abolishing the effect of reinforcement delay on human causal learning

Associative learning theory postulates two main determinants for human causal learning: contingency and contiguity. In line with such an account, participants in Shanks, Pearson, and Dickinson (1989) failed to discover causal relations involving delays of more than two seconds. More recent research has shown that the impact of contiguity and delay is mediated by prior knowledge about the timeframe of the causal relation in question. Buehner and May (2002, 2003) demonstrated that the detrimental effect of delay can be significantly reduced if reasoners are aware of potential delays. Here we demonstrate for the first time that the negative influence of delay can be abolished completely by a subtle change in the experimental instructions. Temporal contiguity is thus not essential for human causal learning.