The power law repealed: The case for an exponential law of practice

The power function is treated as the law relating response time to practice trials. However, the evidence for a power law is flawed, because it is based on averaged data. We report a survey that assessed the form of the practice function for individual learners and learning conditions in paradigms that have shaped theories of skill acquisition. We fit power and exponential functions to 40 sets of data representing 7,910 learning series from 475 subjects in 24 experiments. The exponential function fit better than the power function in all the unaveraged data sets. Averaging produced a bias in favor of the power function. A new practice function based on the exponential, the APEX function, fit better than a power function with an extra, preexperimental practice parameter. Clearly, the best candidate for the law of practice is the exponential or APEX function, not the generally accepted power function. The theoretical implications are discussed.     

Making the audience a key participant in the science communication process

The public communication of science and technology has become increasingly important over the last several decades. However, understanding the audience that receives this information remains the weak link in the science communication process. This essay provides a brief review of some of the issues involved, discusses results from an audience-based study, and suggests some strategies that both scientists and journalists can use to modify media coverage in ways that can help audiences better understand major public issues that involve science and technology. Carol L. Rogers is editor of the interdisciplinary journal Science Communication.     

Schizophrenia Epigenesis?

I begin by examining how genetics drivesschizophrenia research, and raise both familiar andrelatively novel criticisms of the evidence putativelysupporting the genetic basis of schizophrenia. Inparticular, I call attention to a set of concernsabout the effects of placentation on concordance ratesof schizophrenia in monozygotic twins, which furtherweakens the case for schizophrenia's so-called stronggenetic component. I then underscore two criticalpoints. First, I emphasize the importance of takingseriously considerations about the complexity of bothontogenesis and the development of hereditarydiseases. The recognition of developmentalconstraints and supports is crucial, for attention todevelopment exposes the naivete of too many models ofgene action in the aetiology of disease. Secondly, Iattend to those schizophreniologists who ignoremethodological criticisms and thus presume a geneticbasis for schizophrenia, and then seek the schizophrenic genotype lacking an adequatephenotype. In response I attempt to demonstrate thenecessity of a sustained effort at characterizing thephenotype of schizophrenia as an enabling conditionfor the whole enterprise of psychiatric genetics – andfor psychiatry itself. Without the organism-levelphenotype, research at the level of genes will remainunproductive – assuming of course that research at thegenetic level is appropriate at all.     

Synaesthesia: the prevalence of atypical cross-modal experiences

Sensory and cognitive mechanisms allow stimuli to be perceived with properties relating to sight, sound, touch, etc, and ensure, for example, that visual properties are perceived as visual experiences, rather than sounds, tastes, smells, etc. Theories of normal development can be informed by cases where this modularity breaks down, in a condition known as synaesthesia. Conventional wisdom has held that this occurs extremely rarely (0.05% of births) and affects women more than men. Here we present the first test of synaesthesia prevalence with sampling that does not rely on self-referral, and which uses objective tests to establish genuineness. We show that (a) the prevalence of synaesthesia is 88 times higher than previously assumed, (b) the most common variant is coloured days, (c) the most studied variant (grapheme-colour synaesthesia)--previously believed most common--is prevalent at 1%, and (d) there is no strong asymmetry in the distribution of synaesthesia across the sexes. Hence, we suggest that female biases reported earlier likely arose from (or were exaggerated by) sex differences in self-disclosure.     

The development of implicit attitudes. Evidence of race evaluations from ages 6 and 10 and adulthood

To understand the origin and development of implicit attitudes, we measured race attitudes in White American 6-year-olds, 10-year-olds, and adults by first developing a child-oriented version of the Implicit Association Test (Child IAT). Remarkably, implicit pro-White/anti-Black bias was evident even in the youngest group, with self-reported attitudes revealing bias in the same direction. In 10-year-olds and adults, the same magnitude of implicit race bias was observed, although self-reported race attitudes became substantially less biased in older children and vanished entirely in adults, who self-reported equally favorable attitudes toward Whites and Blacks. These data are the first to show an asymmetry in the development of implicit and explicit race attitudes, with explicit attitudes becoming more egalitarian and implicit attitudes remaining stable and favoring the in-group across development. We offer a tentative suggestion that mean levels of implicit and explicit attitudes diverge around age 10.     

Rethinking speed theories of cognitive development. Increasing the rate of recall without affecting accuracy

Researchers have suggested that developmental improvements in immediate recall stem from increases in the speed of mental processes. However, that inference has depended on evidence from correlation, regression, and structural equation modeling. We provide counter-examples in two experiments in which the speed of spoken recall was manipulated. In one experiment, second-grade children and adults recalled lists of digits more quickly than usual when the lists were presented at a rapid rate of two items per second. In a second experiment, children received lists at a rate of one item per second; half the children were trained (successfully) to speak their responses more quickly than usual, at a rate similar to adults' usual rate. Recall accuracy was completely unaffected by either of these response-speed manipulations. Thus, although response rate is a strong marker of an individual's maturational level, it does not appear to determine the accuracy of immediate recall. These results have important methodological and theoretical implications for human development.     

The effects of HIV-related thought suppression on risk behavior: cognitive escape in men who have sex with men.

This study investigated the relationship between suppressing thoughts about HIV risk and several outcomes related to HIV risk, including sexual risk behavior and HIV prevention service use, in men who have sex with men (MSM). Synthesizing the ironic processing theory (D. M. Wegner, 1994) with a cognitive escape paradigm (D. J. McKiman, D. G. Ostrow, & B. Hope, 1996), it was hypothesized that thought suppression might increase risk by leading MSM to "escape" from sexual safety norms and engage in risky sex behaviors and, via a paradoxical process, increase future use of community prevention services. Results from a sample of MSM (N = 709) indicated that thought suppression was positively related to concurrent sexual risk behavior and to future use of prevention services.     

Ethical issues in exercise psychology

Exercise psychology encompasses the disciplines of psychiatry, clinical and counseling psychology, health promotion, and the movement sciences. This emerging field involves diverse mental health issues, theories, and general information related to physical activity and exercise. Numerous research investigations across the past 20 years have shown both physical and psychological benefits from physical activity and exercise. Exercise psychology offers many opportunities for growth while positively influencing the mental and physical health of individuals, communities, and society. However, the exercise psychology literature has not addressed ethical issues or dilemmas faced by mental health professionals providing exercise psychology services. This initial discussion of ethical issues in exercise psychology is an important step in continuing to move the field forward. Specifically, this article will address the emergence of exercise psychology and current health behaviors and offer an overview of ethics and ethical issues, education/training and professional competency, cultural and ethnic diversity, multiple-role relationships and conflicts of interest, dependency issues, confidentiality and recording keeping, and advertisement and self-promotion.     

Cone excitation ratios correlate with color discrimination performance in the horse (Equus caballus)

Six horses (Equus caballus) were trained to discriminate color from grays in a counterbalanced sequence in which lightness cues were irrelevant. Subsequently, the pretrained colors were presented in a different sequence. Two sets of novel colors paired with novel grays were also tested. Performance was just as good in these transfer tests. Once the horse had learned to select the chromatic from the achromatic stimulus, regardless of the specific color, they were immediately able to apply this rule to novel stimuli. In terms of the underlying visual mechanisms, the present study showed for the first time that the spectral sensitivity of horse cone photopigments, measured as cone excitation ratios, was correlated with color discrimination performance, measured as accuracy, repeated errors, and latency of approach.