Development of a contact call in black-capped chickadees (Poecile atricapillus) hand-reared in different acoustic environments.

The tseet contact call, common to black-capped (Poecile atricapillus) and mountain chickadees (P. gambeli), is the most frequently produced vocalization of each species. Previous work has characterized the tseet call of black-capped and mountain chickadees from different geographic locations in terms of nine acoustic features. In the current study, using similar methods, the tseet call of black-capped chickadees that were hand reared with either conspecifics, heterospecifics (mountain chickadees), or in isolation from adult chickadees are described. Analysis of call features examined which acoustic features were most affected by rearing environment, and revealed that starting frequency and the slope of the descending portion of the tseet call differed between black-capped chickadees reared with either conspecific or heterospecific adults. Birds reared in isolation from adults differed from the other hand-reared groups on almost every acoustic feature. Chickadee tseet calls are more individualized when they are reared with adult conspecifics or heterospecifics compared to chickadees that are reared in isolation from adults. The current results suggest a role of learning in this commonly used contact call.

Proximity to an edge affects search strategy in adults and children.

When searching for a hidden goal, search patterns are often defined according to one of two main search strategies: an absolute strategy, which usually involves searching at a fixed learned distance and direction from a particular reference point, or a relational strategy, which involves searching at a point that maintains the relationship between two or more other points. Past research has shown that humans tend to prefer a relational strategy whereas most non-humans prefer an absolute strategy. However, recent research (Hartley et al., 2004) used a simulated 3D environment to demonstrate that proximity to a boundary affects strategy. In particular, when searching close to an edge, human participants were more likely to use an absolute strategy whereas when searching at a central location, participants were more likely to use a relational strategy. The current studies extend the findings of Hartley et al. Experiment 1 showed that adult humans use different strategies based on the goal's proximity to the edge of a search space, and that strategies differed between males and females. Experiment 2 suggested that children also use different strategies based on the goal's proximity to a boundary, and that some goal locations may be harder to learn than others. Taken together, our results show that search strategies are flexible and context-specific.

Black-capped (Poecile atricapillus) and mountain chickadee (Poecile gambeli) contact call contains species, sex, and individual identity features.

The tseet contact call, common to both black-capped and mountain chickadees, is among the most frequently produced call of each species, but has remained little studied until now. In the current study, the authors characterized the tseet call of adult allopatric and sympatric black-capped and mountain chickadees in terms of nine acoustic features in a fashion similar to descriptive accounts of both species' chick-a-dee calls. Summary statistics, the potential for individual coding, and classification by linear discriminant analysis were used to describe the tseet call. The authors were able to correctly classify tseet calls in terms of which group or individual produced it with high accuracy. Furthermore, several acoustic features are highly individualized, indicating that the chickadees may use these features to identify signalers as individuals or members of a particular group.

Rats' use of geometric, featural and orientation cues to locate a hidden goal.

Over the past 20 years, a great deal of research has examined how different animals can use the geometric properties of the environment to determine their heading. Less well studied is how rats use the geometric properties of an environment to navigate, or determine the location, when it is not necessary to establish heading. Specifically, it is unclear to what extent rats still rely on geometric cues when they are not disoriented. In the current study, rats were trained to find food in one corner of a rectangular environment under either oriented or disoriented conditions. Probe tests placed geometric, featural and orientation cues in conflict. Results showed that featural cues exerted little control over the rats' search preferences. All rats, whether trained while oriented or trained while disoriented, used geometric cues when these were the only cues available. Rats trained in the disoriented condition preferred geometric cues to orientation cues, whereas rats trained in the oriented condition showed more equal preference for orientation and geometric cues.

Comparing black-capped (Poecile atricapillus) and mountain chickadees (Poecile gambeli): use of geometric and featural information in a spatial orientation task.

Since Cheng (Cognition 23:149-178, 1986) first proposed the "geometric module" in rats, a great deal of research has focused on how other species use geometric information and how geometric encoding may differ across species. Here, hand-reared and wild-caught black-capped chickadees and wild-caught mountain chickadees searched for food hidden in one corner in a rectangular environment. Previous research has shown that mountain chickadees do not spontaneously encode geometric information when a salient feature is present near the goal location. Using a slightly different training and testing procedure, we found that both hand-reared and wild-caught black-capped chickadees encoded geometric information, even in the presence of a salient landmark. Some, but not all, mountain chickadees also encoded geometric information. Overall, our results suggest that use of geometric information may be a less preferred strategy for mountain chickadees than for either wild-caught or hand-reared black-capped chickadees. To our knowledge, this is the first direct interspecies comparison of use of geometric information in a spatial orientation task.

Pigeons' (Columba livia) hierarchical organization of local and global cues in touch screen tasks.

Redundant encoding of local and global spatial cues is a common occurrence in many species. However, preferential use of the each type of cue seems to vary across species and tasks. In the current study, pigeons (Columba livia) were trained in three experiments on a touch screen task which included redundant local positional cues and global spatial cues. Specifically, pigeons were required to choose the middle out of three choice squares, such that the position within the array provided local information and the location on the screen provided global information. In Experiment 1, pigeons were trained and tested on vertically aligned arrays. In Experiment 2, pigeons were trained and tested on horizontally aligned arrays, and in Experiment 3, pigeons were trained and tested with vertical, horizontal and diagonally aligned arrays. The results indicate that preference for cue type depends upon the type of spatial information being encoded. Specifically, on vertical and diagonally aligned arrays, pigeons preferred global cues, whereas on horizontally aligned arrays, pigeons preferred local cues.