Corvid Re-Caching without ‘Theory of Mind’: A Model

Scrub jays are thought to use many tactics to protect their caches. For instance, they predominantly bury food far away from conspecifics, and if they must cache while being watched, they often re-cache their worms later, once they are in private. Two explanations have been offered for such observations, and they are intensely debated. First, the birds may reason about their competitors' mental states, with a ‘theory of mind’; alternatively, they may apply behavioral rules learned in daily life. Although this second hypothesis is cognitively simpler, it does seem to require a different, ad-hoc behavioral rule for every caching and re-caching pattern exhibited by the birds. Our new theory avoids this drawback by explaining a large variety of patterns as side-effects of stress and the resulting memory errors. Inspired by experimental data, we assume that re-caching is not motivated by a deliberate effort to safeguard specific caches from theft, but by a general desire to cache more. This desire is brought on by stress, which is determined by the presence and dominance of onlookers, and by unsuccessful recovery attempts. We study this theory in two experiments similar to those done with real birds with a kind of ‘virtual bird’, whose behavior depends on a set of basic assumptions about corvid cognition, and a well-established model of human memory. Our results show that the ‘virtual bird’ acts as the real birds did; its re-caching reflects whether it has been watched, how dominant its onlooker was, and how close to that onlooker it has cached. This happens even though it cannot attribute mental states, and it has only a single behavioral rule assumed to be previously learned. Thus, our simulations indicate that corvid re-caching can be explained without sophisticated social cognition. Given our specific predictions, our theory can easily be tested empirically

Rufous hummingbirds' (Selasphorus rufus) memory for flowers: Patterns or actual spatial locations?

Two field experiments were performed to examine the use of absolute and relative spatial cues by foraging rufous hummingbirds (Selasphorus rufus). Presented with 5 flowers arranged in a cross, birds learned that only the center flower was rewarded. When the array was shifted, birds returned to the relative center of the array when flowers were closely spaced but to the absolute location of the reward when spacing was greater than 40 cm. In Experiment 2, a 16-flower array was used, spaced either at 10 or 80 cm. Flowers were either visually identical or different, and 8 were rewarded with sucrose. Birds learned the rewarded locations more quickly when flowers were visually different. When the arrays of flowers were moved, performance was independent of flower visual patterns. At 10-cm spacing, birds tended to use relative location to recall rewarded flowers but used absolute location at 80-cm spacing.</p

Cue learning by rufous hummingbirds (Selasphorus rufus)

The authors investigated the use by wild-living rufous hummingbirds (Selasphorus rufus) of flower color pattern and flower position for remembering rewarded flowers. Birds were presented with arrays of artificial flowers, a proportion of which was rewarded. Once the locations were learned by the birds, the array was moved 2 in, and flower color pattern and/or rewarded positions were manipulated. The birds' ability to learn which were the rewarded flowers in this 2nd array was much more strongly affected by whether the rewarded flowers occupied the same positions as in the 1st array than by their color patterns.</p

Cue learning by rufous hummingbirds (Selasphorus rufus)

The authors investigated the use by wild-living rufous hummingbirds (Selasphorus rufus) of flower color pattern and flower position for remembering rewarded flowers. Birds were presented with arrays of artificial flowers, a proportion of which was rewarded. Once the locations were learned by the birds, the array was moved 2 in, and flower color pattern and/or rewarded positions were manipulated. The birds' ability to learn which were the rewarded flowers in this 2nd array was much more strongly affected by whether the rewarded flowers occupied the same positions as in the 1st array than by their color patterns.</p

Spatial learning and memory in birds

Behavioral ecologists, well versed in addressing functional aspects of behavior, are acknowledging more and more the attention they need also to pay to mechanistic processes. One of these is the role of cognition. Song learning and imprinting are familiar examples of behaviors for which cognition plays an important role, but attention is now turning to other behaviors and a wider diversity of species. We focus here on work that investigates the nature of spatial learning and memory in the context of behaviors such as foraging and food storing. We also briefly explore the difficulties of studying cognition in the field. The common thread to all of this work is the value of using psychological techniques as tools for assessing learning and memory abilities in order to address questions of interest to behavioral ecologists. Copyright (C) 2004 S. Karger AG, Basel.</p

Spatial learning and memory in birds

Behavioral ecologists, well versed in addressing functional aspects of behavior, are acknowledging more and more the attention they need also to pay to mechanistic processes. One of these is the role of cognition. Song learning and imprinting are familiar examples of behaviors for which cognition plays an important role, but attention is now turning to other behaviors and a wider diversity of species. We focus here on work that investigates the nature of spatial learning and memory in the context of behaviors such as foraging and food storing. We also briefly explore the difficulties of studying cognition in the field. The common thread to all of this work is the value of using psychological techniques as tools for assessing learning and memory abilities in order to address questions of interest to behavioral ecologists. Copyright (C) 2004 S. Karger AG, Basel.</p

Rufous hummingbirds' (Selasphorus rufus) memory for flowers: Patterns or actual spatial locations?

Two field experiments were performed to examine the use of absolute and relative spatial cues by foraging rufous hummingbirds (Selasphorus rufus). Presented with 5 flowers arranged in a cross, birds learned that only the center flower was rewarded. When the array was shifted, birds returned to the relative center of the array when flowers were closely spaced but to the absolute location of the reward when spacing was greater than 40 cm. In Experiment 2, a 16-flower array was used, spaced either at 10 or 80 cm. Flowers were either visually identical or different, and 8 were rewarded with sucrose. Birds learned the rewarded locations more quickly when flowers were visually different. When the arrays of flowers were moved, performance was independent of flower visual patterns. At 10-cm spacing, birds tended to use relative location to recall rewarded flowers but used absolute location at 80-cm spacing.</p

Memory for flowers in rufous hummingbirds: Location or local visual cues?

Rufous hummingbirds, Selasphorus rufus, remember locations of flowers. They avoid flowers they have emptied recently and those they have found to be empty. In contrast, after one brief experience they return to flowers they have left with food remaining. To determine whether hummingbirds primarily use spatial or colour/pattern cues to return to previously visited flowers, two field experiments were performed. In the first, subjects fed from a reward flower and on their subsequent return had to choose between visual cues that were dissociated from spatial cues. The birds showed a marked preference for returning to the correct location of the previously visited flower and not to the flower bearing the appropriate colour/pattern. The second experiment involved a delayed-matching-to-location task in which the subjects fed from, but did not deplete, a focal flower and on return had to choose between the focal flower and a new distractive flower. The latter was presented at three different distances from the focal flower and was either the same or different in colour to the focal flower. Subjects most often chose the focal flower when the distractive flower was of a different colour, whereas performance was poor when it resembled the focal flower. However, a significant interaction between the colour and distance of the distractive flower suggests that the hummingbirds were able to discriminate between focal and distractive flowers under both conditions, but that they employed different foraging tactics according to the colour of the distractive flower in the choice phase. (C) 1996 The Association for the Study of Animal Behaviour.</p

Memory for flowers in rufous hummingbirds: Location or local visual cues?

Rufous hummingbirds, Selasphorus rufus, remember locations of flowers. They avoid flowers they have emptied recently and those they have found to be empty. In contrast, after one brief experience they return to flowers they have left with food remaining. To determine whether hummingbirds primarily use spatial or colour/pattern cues to return to previously visited flowers, two field experiments were performed. In the first, subjects fed from a reward flower and on their subsequent return had to choose between visual cues that were dissociated from spatial cues. The birds showed a marked preference for returning to the correct location of the previously visited flower and not to the flower bearing the appropriate colour/pattern. The second experiment involved a delayed-matching-to-location task in which the subjects fed from, but did not deplete, a focal flower and on return had to choose between the focal flower and a new distractive flower. The latter was presented at three different distances from the focal flower and was either the same or different in colour to the focal flower. Subjects most often chose the focal flower when the distractive flower was of a different colour, whereas performance was poor when it resembled the focal flower. However, a significant interaction between the colour and distance of the distractive flower suggests that the hummingbirds were able to discriminate between focal and distractive flowers under both conditions, but that they employed different foraging tactics according to the colour of the distractive flower in the choice phase. (C) 1996 The Association for the Study of Animal Behaviour.</p