What Is the Mechanism Underlying the Interleaving Effect in Category Induction: An Eye-Tracking and Behavioral Study

Interleaved practice (i.e., exemplars from different categories are intermixed within blocks) has been shown to enhance induction performance compared to blocked practice (i.e., exemplars from the same category are presented sequentially). The main aim of the present study was to examine explanations of why interleaved practice produces this benefit in category induction (known as the interleaving effect). We also evaluated two hypotheses, the attention attenuation hypothesis and the discriminative-contrast hypothesis, by collecting data on participants’ fixation on exemplars, provided by eye-tracking data, and manipulating the degree of discriminative-contrast. In Experiments 1 and 2, participants were instructed to learn the style of 12 new artists in blocked and interleaved practice in fixed-paced and self-paced learning conditions, respectively. We examined fixation durations for six positions (temporal sequence of exemplars presented in each block) using eye-tracking. The results of the two experiments, based on eye-tracking data, suggested that attention attenuation may not be the primary mechanism underlying the interleaving effect in category induction. In Experiment 3, we manipulated the degree of discriminative-contrast to examine the impact on the interleaving effect in category induction. The results showed that the main effect of the degree of discriminative-contrast was significant, and performance in the high-contrast condition was significantly better than those in the medium-contrast and low-contrast conditions. Thus, the current results support the discriminative-contrast hypothesis rather than the attention attenuation hypothesis.

Design with Knowledge—Light in Learning Environments

A range of artificial lighting characteristics have been found to influence our visual and cognitive capabilities, mood, motivation and/or (social) behaviour—all affecting how we (academically) perform. One such influential characteristic is spatial contrast, or the way light is distributed in space causing a pattern of light and darkness. This study looks at if and how spatial contrast influences pupil behaviour, and specifically their ability to concentrate. We first explored whether variances in pupil noise, physical activity and mood, which have been found to affect concentration, occur when exposed to either a high or a low spatial contrast in their learning environment. Preliminary data from field experiments in a primary school indicates towards decreased noise levels and improved environmental satisfaction when a high spatial contrast condition is present. This implies improved environmental circumstances to concentrate. Further research to confirm this assumption will be undertaken.

Capuchin monkeys (Sapajus [Cebus] apella) are more susceptible to contrast than to decoy and social context effects

Theories of optimal decision-making typically assume that animals have consistent preferences among options. In reality, economic behaviour in humans and foraging behaviour in some animals is often susceptible to choice-irrelevant factors such as inferior options or conspecifics’ outcomes, but the evidence for primate decision-making is mixed. Unlike previous experiments, we assessed the relative magnitude of three context effects. Using a food preference paradigm, we varied the number of cereal pieces to determine how much a piece of food A was “worth” (50% choice) to each of 13 capuchins. We predicted that monkeys would devalue A in the contrast condition (when a higher-quality but unattainable food was present) and overvalue it in the decoy condition (when a smaller version of A was a third option) and social condition (when A, if unchosen, was given to a partner). Capuchins were 4 times less likely to choose A in the contrast condition, but 2 to 3 times more likely to choose it in the decoy and social conditions. When carefully accounting for initial preferences, we found that these primates, like humans, are sensitive to context effects. This suggests that these biases are evolved and impacts how we think about them in humans.

Temporal integration and attentional selection of color and contrast target pairs in rapid serial visual presentation

Performance in a dual target rapid serial visual presentation task was investigated, dependent on whether the color or the contrast of the targets was the same or different. Both identification accuracy on the second target, as a measure of temporal attention, and the frequency of temporal integration were measured. When targets had a different color (red or blue), overall identification accuracy of the second target and identification accuracy of the second target at Lag 1 were both higher than when targets had the same color. At the same time, increased temporal integration of the targets at Lag 1 was observed in the different color condition, even though actual (non-integrated) single targets never consisted of multiple colors. When the color pairs were made more similar, so that they all fell within the range of a single nominal hue (blue), these effects were not observed. Different findings were obtained when contrast was manipulated. Identification accuracy of the second target was higher in the same contrast condition than in the different contrast condition. Higher identification accuracy of both targets was furthermore observed when they were presented with high contrast, while target contrast did not influence temporal integration at all. Temporal attention and integration were thus influenced differently by target contrast pairing than by (categorical) color pairing. Categorically different color pairs, or more generally, categorical feature pairs, may thus afford a reduction in temporal competition between successive targets that eventually enhances attention and integration.

Ellipsis in tautologous conditionals: the contrast condition on ellipsis

I compare two theories to account for the novel observation that ellipsis is ungrammatical in tautologous conditionals, e.g. If John is wrong, then he is *(wrong). One theory attributes the ungrammaticality to a contrast failure in ellipsis parallelism (Rooth 1992a,b); the other to triviality at a more abstract, logical level (Gajewski 2009). The ellipsis parallelism theory prevails on further data, joining Griffiths (to appear) in arguing that contrast plays a role in ellipsis licensing. Contrast is further shown to be sensitive to intensionality.

Local root growth and death are mediated by contrasts in nutrient availability and root quantity between soil patches

Plants are thought to be able to regulate local root growth according to its overall nutrient status as well as nutrient contents in a local substrate patch. Therefore, root plastic responses to environmental changes are probably co-determined by local responses of root modules and systematic control of the whole plant. Recent studies showed that the contrast in nutrient availability between different patches could significantly influence the growth and death of local roots. In this study, we further explored, beside nutrient contrast, whether root growth and death in a local patch are also affected by relative root quantity in the patch. We conducted a split-root experiment with different splitting ratios of roots of Canada goldenrod ( Solidago canadensis ) individuals, as well as high- (5× Hoagland solution versus water) or low- (1× Hoagland solution versus water) contrast nutrient conditions for the split roots. The results showed that root growth decreased in nutrient-rich patches but increased in nutrient-poor patches when more roots co-occurred in the same patches, irrespective of nutrient contrast condition. Root mortality depended on contrasts in both root quantity and nutrients: in the high-nutrient-contrast condition, it increased in nutrient-rich patches but decreased in nutrient-poor patches with increasing root proportion; while in the low-nutrient-contrast condition, it showed the opposite trend. These results demonstrated that root growth and death dynamics were affected by the contrast in both nutrient availability and root quantity between patches. Our study provided ecological evidence that local root growth and death are mediated by both the responses of root modules to a nutrient patch and the whole-plant nutrient status, suggesting that future work investigating root production and turnover should take into account the degree of heterogeneity in nutrient and root distribution.