Addition versus deletion as a signal

An Inconvenient Truth: Some Neglected Issues in Invertebrate Learning

The burgeoning field of invertebrate behavior is moving into what was the realm of human psychology concepts. This invites comparative studies not only between invertebrate and vertebrate species but also among the diverse taxa within the invertebrates, diverse even when considering only the insects. In order to make lasting progress two issues must be addressed. The first is inconsistent use of fundamental terms defining learning. The second is a focus on similarities, giving little attention to dissimilarities. In addition, much work is needed on whether behavioral similarities are grounded in the same neuronal architecture when considering disparate phyla. These concerns identify are "inconvenient truths" that weaken comparative behavioral analysis.

On Doing the Decision: Effects of Active versus Passive Choice on Commitment and Self-Perception

Two studies demonstrate that making a volunteer decision by doing something results in more commitment to it than making the identical decision by doing nothing. Undergraduates were asked to volunteer for a university committee (Study l a) or a sex and AIDS awareness education project (Study 2) and indicated their choice either by affirming it on two items or by skippping two items that affirmed the opposite choice. Subjects who responded actively were more extreme in the degree of their decision than passive respondents. This effect persevered over 6 weeks (Study lb) and had behavioral consequences (Study 2). Attributional analyses in both studies suggest that active and passive choice may result in unique construals of oneself and of the decision: Active agreement results in citing more types of reasons for one's decision, and active refusal heightens one's perceived resistance to social influence.

Feature-positive and feature-negative learning in honey bees

Honey bees (Apis mellifera anatolica) were subjected to sequential trials where they were given the choice between a feature-positive and a feature-negative feeding plate. The 'feature' being manipulated is the presence of a single blue circle among three circles marking the location of a small sucrose reward. That is, a 'feature-negative' target had three white circles, while a 'feature-positive' target had two white circles and one blue one. Two experiments were performed. In both experiments, each bee was tested under two different reward scenarios (treatments). In the first experiment, during the feature-positive treatment bees received 4 μl of 2 mol l(-1) sucrose when choosing the feature-positive plate, but received 4 μl of saturated NaCl solution (saltwater) when choosing the feature-negative plate. During the feature-negative treatment, bees were rewarded when visiting the feature-negative plate, while visitation to the feature-positive plate only offered bees the saltwater. The second experiment was a repeat of the first except that pure water was offered instead of saltwater in the non-rewarding feeding plate. As an experimental control, a set of bees was offered sequential trials where both the feature-positive and feature-negative plates offered the sucrose reward. Bee feeding plate choice differed between the feature-positive and feature-negative treatments in both experiments. Bees favored the feeding plate type with the sucrose reward in each treatment, and never consumed the saltwater or pure water when encountered in either treatment. Further, behavior of bees during both the feature-positive and feature-negative treatments differed from that of control bees. However, neither feature-positive nor feature-negative learning reached high levels of success. Further, a feature-positive effect was seen when pure water was offered; bees learned to solve the feature-positive problem more rapidly. When we tested bees using simply the choice of blue versus white targets, where one color held the sucrose reward and the other the saltwater, a bee's fidelity to the color offering the sucrose reward quickly reached very high levels.

Missing the dog that failed to bark in the nighttime: on the overestimation of occurrences over non-occurrences in hypothesis testing

In three studies, we investigated whether and to what extent the evaluation of two mutually exclusive hypotheses is affected by a feature-positive effect, wherein present clues are weighted more than absent clues. Participants (N = 126) were presented with abstract problems concerning the most likely provenance of a card that was drawn from one of two decks. We factored the correct response (the hypothesis favored by the consideration of all clues) and the ratio of present-to-absent features in each set of observations. Furthermore, across the studies, we manipulated the presentation format of the features' probabilities by providing the probability distributions of occurrences (Study 1), non-occurrences (Study 3) or both (Study 2). In all studies, both participant preference and accuracy were mostly determined by an over-reliance on present features. Moreover, across participants, both confidence in the responses and the informativeness of the present clues correlated positively with the number of responses given in line with an exclusive consideration of present features. These results were mostly independent of both the rarity of the absent clues and the presentation format. We concluded that the feature-positive effect influences hypothesis evaluation, and we discussed the implications for confirmation bias.

Simplicity and generalization: Short-cutting abstraction in children's object categorizations

Development in any domain is often characterized by increasingly abstract representations. Recent evidence in the domain of shape recognition provides one example; between 18 and 24 months children appear to build increasingly abstract representations of object shape [Smith, L. B. (2003). Learning to recognize objects. Psychological Science, 14, 244-250]. Abstraction is in part simplification because it requires the removal of irrelevant information. At the same time, part of generalization is ignoring irrelevant differences. The resulting prediction is this: simplification may enable generalization. Four experiments asked whether simple training instances could shortcut the process of abstraction and directly promote appropriate generalization. Toddlers were taught novel object categories with either simple or complex training exemplars. We found that children who learned with simple objects were able to generalize according to shape similarity, typically relevant for early object categories, better than those who learned with complex objects. Abstraction is the product of learning; using simplified - already abstracted instances - can short-cut that learning, leading to robust generalization.

Negative information: both presence and absence of spatial pattern elements guide rats' spatial choices

Rats learn the spatial pattern in which hidden caches of food are located. Once the pattern is learned, finding one or more baited locations provides (positive) information about the remaining baited locations. In the present experiment, we examined whether negative information (the absence of food in a location) would also be used in locating the remaining baited locations. Rats were tested in an apparatus containing a matrix of vertical poles, on top of which food could be hidden. At the beginning of the trial, the location of the baited poles was unpredictable, but the poles were always arranged in a linear pattern. The rats learned the pattern and used both positive and negative information in locating baited poles.