Implicit learning: Indirect, not unconscious

Dienes and Berry (1997) argue that there really are two kinds of knowledge, implicit and explicit, that can be characterized through a subjective threshold. We argue that the subjective threshold does not separate two forms of knowledge, but instead two uses of knowledge, for two different purposes. With Neal and Hesketh (1997), we suggest that an understanding of learning will be better served by investigating the processing that occurs under various circumstances than by attempting to isolate learning that occurs with awareness from that which occurs without it.     

Beyond Stewardship? Dietrich Bonhoeffer on Nature

This article questions whether the model of stewardship is helpful in considering Christian responsibility towards non‐human nature and proposes a different way of treating the issue of care of the environment. In an extended engagement with the theology of Dietrich Bonhoeffer, the article argues that human relations to non‐human nature are best understood by seeing humanity as historical, political and natural. In theological formulation, humanity must be understood asimago dei, imago civitatis andimago mundi. Therefore the place of humanity cannot properly be understood without reference to both God and nature. Humanity, nature and God thereby constitute a ‘common realm’. A new test of Christian responsibility towards non‐human nature is introduced: of primary interest is how historical, political and natural humanity acts in ways which either reveal or obscure the ‘common realm of God, nature and humanity’. At this point, theological self‐understanding moves beyond the model of stewardship.     

A human-centered approach for designing World-Wide Web browsers

Because the World-Wide Web has features that are not found in traditional information systems, it has some unique problems pertaining to human use, such as the difficulty of searching for specific information. This paper describes human cognitive limitations pertinent to the design of Web browsers and provides a conceptual model for human information processing on the Web. It also compares user strategies and use of browser functions for two tasks that differ in the specificity of the information that is to be retrieved. General principles and specific recommendations for the design of Web browsers are derived from these considerations.     

BasicBayes: A tutor system for simple Bayesian inference

To date, attempts to teach Bayesian inference to nonexperts have not met with much success. BasicBayes, the computerized tutor presented here, is an attempt to change this state of affairs. BasicBayes is based on a novel theoretical framework about Bayesian reasoning recently introduced by Gigerenzer and Hoffrage (1995). This framework focuses on the connection between “cognitive algorithms” and “information formats.” BasicBayes teaches people how to translate Bayesian text problems into frequency formats, which have been shown to entail computationally simpler cognitive algorithms than those entailed by probability formats. The components and mode of functioning of BasicBayes are described in detail. Empirical evidence demonstrates the effectiveness of BasicBayes in teaching people simple Bayesian inference. Because of its flexible system architecture, BasicBayes can also be used as a research tool.     

Spline smoothing with model-based penalties

Nonparametric regression techniques, which estimate functions directly from noisy data rather than relying on specific parametric models, now play a central role in statistical analysis. We can improve the efficiency and other aspects of a nonparametric curve estimate by using prior knowledge about general features of the curve in the smoothing process. Spline smoothing is extended in this paper to express this prior knowledge in the form of a linear differential operator that annihilates a specified parametric model for the data. Roughness in the fitted function is defined in terms of the integrated square of this operator applied to the fitted function. A fastO(n) algorithm is outlined for this smart smoothing process. Illustrations are provided of where this technique proves useful.     

Heading and path information from retinal flow in naturalistic environments

In four experiments, we explored the heading and path information available to observers as we simulated their locomotion through a cluttered environment while they fixated an object off to the side. Previously, we presented a theory about the information available and used in such situations. For such a theory to be valid, one must be sure of eye position, but we had been unable to monitor gaze systematically; in Experiment 1, we monitored eye position and found performance best when observers fixated the designated object at the center of the display. In Experiment 2, when we masked portions of the display, we found that performance generally matched the amount of display visible when scaled to retinal sensitivity. In Experiments 3 and 4, we then explored the metric of information about heading (nominal vs. absolute) available and found good nominal information but increasingly poor and biased absolute information as observers looked farther from the aimpoint. Part of the cause for this appears to be that some observers perceive that they have traversed a curved path even when taking a linear one. In all cases, we compared our results with those in the literature.     

Set- and Element-Level Stimulus-Response Compatibility Effects for Different Manual Response Sets

In a previous study of two-choice reactions, pairings of spatial stimuli with bimanual presses made on a keyboard and verbal stimuli with unimanual aimed movements made on a display screen showed higher set-level compatibility than the opposite pairings; element-level compatibility (i.e., mapping) effects were also larger for the conditions with high set-level compatibility than for those whose set-level compatibility was low. In the 4 experiments described here, the relevant factors were isolated, allowing the determinants of those compatibility differences to be evaluated in more detail. Forty-eight students participated in Experiment 1, and 24 each in Experiments 2, 3, and 4. The primary determinant of the set-level compatibility variation was whether the response alternatives involved 1 or 2 effectors, but the differences in element-level compatibility effects were determined primarily by the distinction between responding on the screen as opposed to on the keyboard. Implications for models of stimulus-response compatibility are examined.