One-trial spatial learning: wild hummingbirds relocate a reward after a single visit

Beaconing to rewarded locations is typically achieved by visual recognition of the actual goal. Spatial recognition, on the other hand, can occur in the absence of the goal itself, relying instead on the landmarks surrounding the goal location. Although the duration or frequency of experiences that an animal needs to learn the landmarks surrounding a goal have been extensively studied with a variety of laboratory tasks, little is known about the way in which wild vertebrates use them in their natural environment. Here, we allowed hummingbirds to feed once only from a rewarding flower (goal) before it was removed. When we presented a similar flower at a different height in another location, birds frequently returned to the location the flower had previously occupied (spatial recognition) before flying to the flower itself (beaconing). After experiencing three rewarded flowers, each in a different location, they were more likely to beacon to the current visible flower than they were to return to previously rewarded locations (without a visible flower). These data show that hummingbirds can encode a rewarded location on the basis of the surrounding landmarks after a single visit. After multiple goal location manipulations, however, the birds changed their strategy to beaconing presumably because they had learned that the flower itself reliably signalled reward.     

Transposition of flower height by bumble bee foragers (Bombus impatiens)

Honeybees learn visual characteristics of reinforced and non-reinforced flowers in differential conditioning experiments (i.e., experiments that require subjects to choose between a reinforced and non-reinforced flower). In this study bumble bee foragers (Bombus impatiens) were trained in a transposition paradigm to determine if the relational properties of flowers also influence choice behavior. Subjects in one group (group A) were trained with repeated choices between a medium-height flower replete with sucrose solution and an empty tall flower until the medium-height flower was sampled preferentially in five consecutive trials. A second group (group B) was trained on the medium height flower alone for five trials. In a single test trial subjects were given a choice between the medium-height flower and a short flower, each filled with water. A control group showed no preference in this test. Group B subjects showed a significant preference for the medium-height flower and group A subjects that exhibited flower constancy (i.e., sampled only the medium-height flower in training trials) showed an identical pattern of choice. Subjects in group A that sampled both flowers during training, in contrast, transposed flower height and preferred the short flower. These results suggest that the choice behavior of bumble bee foragers is influenced by relational and absolute properties of flowers. The flower characteristics learned by foragers appear to depend on the difficulty of the discrimination problem and the context in which flowers are sampled. Patches of flowers limited in phenotypic variability may produce simple associative learning and flower constancy by foragers. Received: 17 September 1999 / Accepted after revision: 22 June 2000     

Spatial encoding by bumblebees (Bombus impatiens) of a reward within an artificial flower array

We presented bumblebees a spatial memory task similar to that used with other species (e.g., cats, dogs, and pigeons). In some conditions we allowed for presence of scent marks in addition to placing local and global spatial cues in conflict. Bumblebees (Bombus impatiens) were presented an array of artificial flowers within a flight cage, one flower offering reward (S+), while the others were empty (S−). Bees were tested with empty flowers. In Experiment 1, flowers were either moved at the time of testing or not. Bees returned to the flower in the same absolute position of the S+ (the flower-array-independent (FAI) position), even if it was in the wrong position relative to the S− and even when new flower covers prevented the use of possible scent marks. New flower covers (i.e., without possible scent marks) had the effect of lowering the frequency of probing behavior. In Experiment 2, the colony was moved between training and testing. Again, bees chose the flower in the FAI position of the S+, and not the flower that would be chosen using strictly memory for a flight vector. Together, these experiments show that to locate the S+ bees did not rely on scent marks nor the positions of the S−, though the S− were prominent objects close to the goal. Also, bees selected environmental features to remember the position of the S+ instead of relying upon a purely egocentric point of view. Similarities with honeybees and vertebrates are discussed, as well as possible encoding mechanisms.     

Do rufous hummingbirds (<Emphasis Type="Italic">Selasphorus rufus</Emphasis>) use visual beacons?

Animals are often assumed to use highly conspicuous features of a goal to head directly to that goal (‘beaconing’). In the field it is generally assumed that flowers serve as beacons to guide pollinators. Artificial hummingbird feeders are coloured red to serve a similar function. However, anecdotal reports suggest that hummingbirds return to feeder locations in the absence of the feeder (and thus the beacon). Here we test these reports for the first time in the field, using the natural territories of hummingbirds and manipulating flowers on a scale that is ecologically relevant to the birds. We compared the predictions from two distinct hypotheses as to how hummingbirds might use the visual features of rewards: the distant beacon hypothesis and the local cue hypothesis. In two field experiments, we found no evidence that rufous hummingbirds used a distant visual beacon to guide them to a rewarded location. In no case did birds abandon their approach to the goal location from a distance; rather they demonstrated remarkable accuracy of navigation by approaching to within about 70 cm of a rewarded flower’s original location. Proximity varied depending on the size of the training flower: birds flew closer to a previously rewarded location if it had been previously signalled with a small beacon. Additionally, when provided with a beacon at a new location, birds did not fly directly to the new beacon. Taken together, we believe these data demonstrate that these hummingbirds depend little on visual characteristics to beacon to rewarded locations, but rather that they encode surrounding landmarks in order to reach the goal and then use the visual features of the goal as confirmation that they have arrived at the correct location.     

特征和位置信息在价值驱动注意捕获中的作用

本研究采用训练−测试范式考察颜色和位置信息在价值驱动注意捕获中的作用。实验1考察是否存在基于具体位置的价值驱动的注意捕获效应。在训练阶段, 被试对8个位置中两个位置出现的红色目标反应伴随着高奖励反馈, 而对另外两个位置出现的红色目标反应伴随着低奖励反馈, 其它4个位置为中性位置, 没有目标出现。在测试阶段, 一半试次中红色刺激作为分心物出现。结果发现, 只有当分心刺激出现在高奖励位置和两个高奖励位置之间的中性位置时才能够捕获注意; 实验2考察颜色和位置信息在价值驱动注意捕获中的交互作用。在训练阶段, 将颜色特征和位置信息联合起来进行学习。在测试阶段, 和高、低奖励相联结的颜色刺激各在1/3试次中作为分心物出现。结果发现, 只有当高奖励颜色出现在高奖励位置或出现在高奖励位置之间的中性位置时才能够捕获注意。研究结果表明：(1)位置联结的价值驱动的注意捕获效应能够泛化到特定邻近位置上; (2)个体在训练阶段将颜色和位置的联合特征与奖励建立联结, 训练阶段建立的联结不能泛化到部分特征上。价值驱动注意捕获效应的泛化具有选择性。     

Spatial relational learning in rufous hummingbirds (Selasphorus rufus)

There is increasing evidence that animals can learn abstract spatial relationships, and successfully transfer this knowledge to novel situations. In this study, rufous hummingbirds (Selasphorus rufus) were trained to feed from either the lower or the higher of two flowers. When presented with a test pair of flowers, one of which was at a novel height, they chose the flower in the appropriate spatial position rather than the flower at the correct height. This response may also have been influenced by a preference for taller flowers as acquisition of the task during experimental training occurred more readily when the reward flower was the taller of the pair. Thus, it appears that although learning abstract relationships may be a general phenomenon across contexts, and perhaps across species, the ease with which they are learned and the context in which they are subsequently used may not be the same.     

Buildup and release from proactive interference in a rhesus monkey

The potential of the buildup and release from proactive interference (PI) technique in the study of animal categorization was demonstrated with a rhesus monkey. A serial probe recognition task was used with a list of 4 consecutive slide pictures (upper screen) followed by a single probe picture (lower screen). The monkey moved a lever to indicate whether or not the probe was contained in the list. PI built over 40 consecutive trials tested with either flowers or primate faces. PI was released on category change and then built during 40 trials with the second category. The first 2 serial positions showed somewhat greater PI buildup and release, supporting conclusions from human studies that the effects occur primarily in secondary memory. A second experiment provided 2 replications of the main effect and showed through color border changes and elimination of color differences that color was not a critical feature.     

How images may or may not represent flowers: picture–object correspondence in bumblebees (Bombus impatiens)?

Studies of bee cognition frequently use two-dimensional stimuli referred to as floral patterns, and yet how bees perceive pictorial representations is not known. An investigation of bumblebee (Bombus impatiens) picture–object correspondence was undertaken according to the theory of Fagot et al. (Picture perception in animals. Psychology Press Ltd, East Sussex, pp 295–320, 2000) that pictures and objects may be confused, perceived as independent or equivalent. In three experiments, bumblebees were given discrimination training and unrewarded testing in a radial maze. In the first experiment, preferences between artificial flowers and photographs of those flowers revealed a significant learned preference for the stimulus rewarded during training: no confusion following training. In the second experiment, bees did transfer learning from artificial flowers to photographs: some commonality between an object and photograph was perceived. In the third experiment, bees spontaneously generalized a learned preference for one artificial flower to its silhouette, but only for one of two flowers used in training. No generalization was obtained to drawn images. Some transfer between image and object is exhibited, likely by low-level feature matching, but transfer is poor with degraded images, cautioning against extrapolation of picture-based responding to natural correspondents. Despite evidence that bees exhibit some transfer while retaining discrimination, it is likely that the observed response is due to generalization more akin to confusion than true equivalence. Furthermore, although 2D patterning cues (line, edge and shade) provide discriminable cues for bees between 2D stimuli, it is not here supported that such features are perceived as equivalent to the intended floral structures.     

Visual search with biological threat stimuli: accuracy, reaction times, and heart rate changes

Twenty-four participants were given a visual search task of deciding whether all the pictures in 3 x 3 search arrays contained a target picture from a deviant category, and heart rate was measured. The categories were snakes, spiders, flowers, and mushrooms. Shorter reaction times (RTs) were observed for fear-relevant (snake and spider) targets rather than for fear-irrelevant/neutral (flower and mushroom) targets. This difference was most pronounced for the participants presented with a gray-scale version of the search arrays. The 1st interbeat interval (IBI), after the search array onset, showed an effect of the target, whereas the 2nd IBI also showed an effect of the distractors. The results suggest that controlled processing of the task operates together with automatic processing.     

"Say it...near the flower shop": further evidence of the effect of flowers on mating

For millennia, flowers have been used to convey romance. In this study, 18-25-year-old women (N = 600) walking alone in a shopping mall were approached by an attractive 20-year-old male-confederate who solicited them for their phone number. The women were solicited as they were walking in the area of a flower shop, a cake shop, or a women's shoes shop. It was found that women agreed more favorably to the confederate's courtship solicitation when solicited in the area of the flower shop. Positive mood induced by exposure to flowers was used to explain these results.     

Control of instrumental behavior by deprivation stimuli

In Experiment 1, rats were given one trial per day in a straight alley under food deprivation on half of the trials and under water deprivation on the other half. Wet mash was available in the goal box under food deprivation for Group H and under water deprivation for Group T, the other deprivation being nonrewarded for each group. After 15--18 trials both groups ran significantly faster on their rewarded than on their nonrewarded deprivation days. A third group showed that random variation of alley color retarded formation of the discrimination. A fourth group was run in a conditional discrimination in which under food deprivation wet mash was available in a black alley, nonreward in a white alley, and vice versa under water deprivation. This group took 114 trials to begin running significantly faster in their rewarded than in their nonrewarded alley under each deprivation. In Experiment 2, it was shown that prior learning about deprivation cues "blocks" learning about alley color when alley color is subsequently presented in compound with the deprivation cue but that when both alley color and deprivation cues are relevant from the start of training, the rat learns about both cues. It is suggested that previous studies have underestimated the importance of deprivation cues by using conditional discrimination designs, choice measures rather than speeds, and parameters that are not optimal for discrimination learning.     

Perspective-taking ability in bilingual children: Extending advantages in executive control to spatial reasoning

Monolingual and bilingual 8-year-olds performed a computerized spatial perspective-taking task. Children were asked to decide how an observer saw a four-block array from one of three different positions (90°, 180°, and 270° counter-clockwise from the child's position) by selecting one of four responses – the correct response, the egocentric error, an incorrect choice in which the array was correct but in the wrong orientation for the viewer, and an incorrect choice in which the array included an internal spatial error. All children performed similarly on background measures, including fluid intelligence, but bilingual children were more accurate than monolingual children in calculating the observer's view across all three positions, with no differences in the pattern of errors committed by the two language groups. The results are discussed in terms of the effect of bilingualism on modifying performance in a complex spatial task that has implications for academic achievement.     

Two bases of the compatibility effect in the Implicit Association Test (IAT)

Four experiments are reported, investigating the mechanisms underlying the compatibility effect in the Implicit Association Test (IAT; Greenwald, McGhee, & Schwartz, 1998). All experiments involved two IATs: flower IAT, in which the target categories were flowers and insects, and number IAT, involving even and odd numbers as target categories. In Experiment 1, using the standard IAT procedure, the two IATs produced equal IAT effects, despite large differences in rated valence contrast between flowers and insects and between even and odd numbers. Experiment 2 used a procedure developed by Klauer and Mierke (2005) and produced results consistent with the view that valence plays a role in the flower IAT but not in the number IAT. Experiments 3 and 4 used manipulations similar to those developed by Rothermund and Wentura (2004) and showed that these manipulations affected the flower IAT and number IAT differently. The results provide converging evidence that the two types of IAT effects-one based on valence and one based on familiarity-are empirically dissociable.Experiments 1and 2 reported in this paper were conducted as an honours project by Marie Peek-O'Leary under the supervision of Sachiko Kinoshita. Parts of this paper were presented at the 44th Annual Meeting of the Psychonomic Society held in Vancouver, Canada, in November, 2003.     

Children's reasoning about spatial relational similarity: the effect of alignment and relational complexity

We investigated 4- and 5-year-old children's mapping strategies in a spatial task. Children were required to find a picture in an array of three identical cups after observing another picture being hidden in another array of three cups. The arrays were either aligned one behind the other in two rows or placed side by side forming one line. Moreover, children were rewarded for two different mapping strategies. Half of the children needed to choose a cup that held the same relative position as the rewarded cup in the other array; they needed to map left-left, middle-middle, and right-right cups together (aligned mapping), which required encoding and mapping of two relations (e.g., the cup left of the middle cup and left of the right cup). The other half needed to map together the cups that held the same relation to the table's spatial features-the cups at the edges, the middle cups, and the cups in the middle of the table (landmark mapping)-which required encoding and mapping of one relation (e.g., the cup at the table's edge). Results showed that children's success was constellation dependent; performance was higher when the arrays were aligned one behind the other in two rows than when they were placed side by side. Furthermore, children showed a preference for landmark mapping over aligned mapping.     

Sensitivity to reward frequency in boys with attention deficit hyperactivity disorder.

Compared the sensitivity of boys with and without attention deficit hyperactivity disorder (ADHD) to differences in reward frequency. Fifteen boys with ADHD as diagnosed in the Diagnostic and Statistical Manual of Mental Disorders (3rd ed., rev.; American Psychiatric Association, 1987) and a matched control group completed a signal-detection task in which correct identification of 1 stimulus was rewarded 3 times as often as correct identification of the other. Boys in the ADHD group completed the task twice, on and off medication. Group differences emerged in response bias toward the more frequently rewarded alternative. Boys in the control group showed a stable pattern of response bias, irrespective of which alternative they were last rewarded on. Boys in the ADHD group showed different patterns of response bias following rewards on the 2 alternatives. These results suggest children with ADHD were more sensitive to individual instances of reward compared with controls, whose response bias is governed more by their reinforcement history. Methylphenidate improved discriminability and reduced sensitivity to individual instances of reward in the boys with ADHD.     

The control of food-caching behavior by Western scrub-jays (Aphelocoma californica)

Western scrub-jays (Aphelocoma californica) did not show extinction when caching behavior was never rewarded and they had no choice of where to cache the food. However, when the jays had the choice of caching items in 2 different locations or during 2 successive episodes, and only 1 of each was always rewarded at recovery, they rapidly learned to cache in the rewarded location or episode. When the jays had learned during training trials that their caches were always moved to 1 of 2 locations they did not cache in, then on the test trial they cached in the location that had been previously rewarded. To test whether these jays avoided the location in which their caches had been pilfered or chose the rewarded location, the procedure was repeated to include a 3rd location that was never rewarded. The jays avoided the pilfered location but cached equally in the rewarded and nonrewarded locations.     

Ambiguous-cue learning in preschool children: A test of the dimensional characteristics of task stimuli

Sixteen preschool children were administered a two-choice discrimination problem consisting of three stimulus compounds: the consistently rewarded stimulus, the consistently nonrewarded stimulus, and the ambiguous stimulus which was nonrewarded when paired with the positive, but rewarded when paired with the negative. When both pair of stimuli, positive-ambiguous and negative-ambiguous, were presented together the subject was required either to choose or to avoid the ambiguous stimulus depending upon the stimulus with which it was paired. In Experiment 1, when each of three stimuli (positive, negative, ambiguous) varied along one nonspatial cue dimension (color), performance was better on negative-ambiguous trials than positive-ambiguous trials. In Experiment 2, when the positive and negative stimuli varied along three nonspatial cue dimensions (colors and form) and the ambiguous stimulus varied along one of these dimensions (color), superior positive-ambiguous over negative-ambiguous performance was obtained. These findings complement those reported for other subjects and confirm Berch's (D. B. Berch, Learning and Motivation, 1974, 5, 135–148) predictions regarding use of differential numbers of cue dimensions.     

Two bases of the compatibility effect in the Implicit Association Test (IAT)

Four experiments are reported, investigating the mechanisms underlying the compatibility effect in the Implicit Association Test (IAT; Greenwald, McGhee, & Schwartz, 1998). All experiments involved two IATs: flower IAT, in which the target categories were flowers and insects, and number IAT, involving even and odd numbers as target categories. In Experiment 1, using the standard IAT procedure, the two IATs produced equal IAT effects, despite large differences in rated valence contrast between flowers and insects and between even and odd numbers. Experiment 2 used a procedure developed by Klauer and Mierke (2005) and produced results consistent with the view that valence plays a role in the flower IAT but not in the number IAT. Experiments 3 and 4 used manipulations similar to those developed by Rothermund and Wentura (2004) and showed that these manipulations affected the flower IAT and number IAT differently. The results provide converging evidence that the two types of IAT effects—one based on valence and one based on familiarity—are empirically dissociable.     

What do children know about the universal quantifiers all and each?

Children's comprehension of the universal quantifiers all and each was explored in a series of experiments using a picture selection task. The first experiment examined children's ability to restrict a quantifier to the noun phrase it modifies. The second and third experiments examined children's ability to associate collective, distributive, and exhaustive representations with sentences containing universal quantifiers. The collective representation corresponds to the “group” meaning (for All the flowers are in a vase all of the flowers are in the same vase). The distributive representation implies a pairing (e.g., each flower paired with a vase for Each flower is in a vase). The exhaustive representation exhausts both sets (e.g., for The flowers are in the vases all the flowers are in vases and all the vases have flowers in them). Four- to 10-year-old children had little difficulty restricting the quantifier all to the noun it modified in a task which required them to attend to the group feature of all. In contrast, only 9- and 10-year-olds were able to solve the task when the quantifier was each and the pictures showed entities in partial one-to-one correspondence. Children showed a preference for associating collective pictures with sentences containing all and distributive pictures with sentences containing each. The results suggest that between the ages of 5 and 10 years, children's semantic representations undergo less radical changes than others have proposed. Instead, developmental change may occur gradually as children acquire linguistic cues which map onto existing semantic representations.     

Hens use occlusion to judge depth in a two-dimensional picture

Hens (Gallus gallus domesticus) were taught to peck at a touch screen. On the screen was a grid on which a square and a circle were depicted. The square and the circle were given different positions at random for each trial, but were never overlapping. The hens were rewarded for pecking at the symbol that was higher up on the grid/screen, i.e. at the one that to a human observer was seen as being further away. Every tenth trial was a probe trial in which the animals were presented with either the circle overlapping the square or vice versa. The hens were never rewarded during the probe trials. As mentioned, the hens had learned to peck at the symbol that appeared to be further away during the nonprobe trials. During the probe trials the hens pecked at the symbol that was occluded, i.e. in the absence of any other cues they used occlusion to determine which of the two symbols was further away. The results suggest that not only can nonhuman animals use image height as a cue but that they can generalise this to situations in which occlusion is the only depth cue present.