In Experiment 1, 3 budgerigars (Melopsittacus undulatus) were trained with food reinforcement to make low-or high-frequency calls in response to different color stimuli, Cl and C2 (a color-naming task), using a gradual response-differentiation procedure and an automatic call-recognition system. Thus, a call within a certain frequency band was reinforced in the presence of Cl ("Cl call"), and a call within a different band was reinforced in the presence of C2 ("C2 call"). In Experiment 2, all 3 budgerigars were trained in a form-to-color matching-to-sample task, alternating trial by trial with either the color-naming task (2 birds) or an identity color matching-to-sample task (1 bird). Sample stimuli for the new matching-to-sample task were forms (Fl or F2) and comparisons were the same two colors (Cl and C2). Given Sample Fl or F2, birds had to make a call to produce Comparison Pair Cl and C2. With Fl as the sample, a peck on Cl was reinforced; with F2 as the sample, a peck on C2 was reinforced. Although no particular call was specified in the presence of Fl and F2, 2 birds made the Cl call in the presence of Fl and the C2 call in the presence of F2. In Experiment 3, the bird that failed to match form and color calls in Experiment 2 and another bird were first trained in a color-to-form matching-to-sample task: C1 to F3 and C2 to F4. In this task, to produce the comparison pair of forms, a high call (or low for the other bird) was required in the presence of Cl, and a low call (or high) was required in the presence of C2. Both birds were then trained with an identity matching-to-sample task in which sample and comparison stimuli were the same two forms, F3 and F4. Trials on the identity task alternated with the color-to-form trials. Although no particular call was required in the presence of Samples F3 and F4, both birds came to make the C1 call in the presence of F3 and the C2 call in the presence of F4. Our technique promises to be useful for the study of emergent vocal relations in budgerigars and other animals.

Call production in budgerigars was studied using operant conditioning. In several experiments, budgerigars were reinforced with food for producing calls that were above or below a criterion level of intensity. This differential reinforcement procedure was successful in controlling vocal intensity in both directions showing that the intensity with which budgerigars produce vocalizations is under voluntary control. In additional experiments, call intensity maintained by food reinforcement was measured both in the quiet and in the presence of various levels of broadband noise. Call intensity in budgerigars increased significantly in noise, paralleling the well-known Lombard effect in humans which is the reflexive increase in speech intensity during communication in noise. Call intensity was measured in broadband noise and in a notched noise (no energy between 1.5 and 4.5 kHz) with the same overall level. Results show that noise in the spectral region of contact calls is most effective in causing an increase in vocal intensity. In aggregate, these experiments show that budgerigars have voluntary control over the intensive aspect of their vocalizations, that they normally monitor their vocal output though external auditory feedback, and, like humans, they exhibit the Lombard effect.

The calls of some bird species may be modified by reward and punishment. However, the operant control of vocal topographies (i.e., the effect of reward or punishment on the physical dimensions of a vocal response) in such species has not been extensively explored. Using a computer-based, real-time system for rewarding vocalizations with food, the authors placed 3 budgerigars under a frequency-dependent reward schedule. During a session, the budgerigars received food for each vocalization that differed from the last N rewarded vocalizations. It was found that each of the budgerigars adapted their vocalizations to this procedure. When the value of Nwas 1 or 2, the birds "solved" the frequency-dependent schedule by developing N + 1 call types and used a simple "win stay, lose switch" sequencing strategy. At N = 3, 1 of the birds again produced N + 1 (i.e., 4) call types, and another solved the criterion by markedly increasing call variability. New calls developed from the elements of old call types and using multidimensional scaling techniques, the authors traced the evolution of each new call type from the previous experimental call repertoire.

Postmitotic hair-cell regeneration in the inner ear of birds provides an opportunity to study the effect of renewed auditory input on auditory perception, vocal production, and vocal learning in a vertebrate. We used behavioral conditioning to test both perception and vocal production in a small Australian parrot, the budgerigar. Results show that both auditory perception and vocal production are disrupted when hair cells are damaged or lost but that these behaviors return to near normal over time. Precision in vocal production completely recovers well before recovery of full auditory function. These results may have particular relevance for understanding the relation between hearing loss and human speech production especially where there is consideration of an auditory prosthetic device. The present results show, at least for a bird, that even limited recovery of auditory input soon after deafening can support full recovery of vocal precision.The avian inner ear provides a useful model for the study of hair-cell regeneration and recovery in the vertebrate ear, but the ultimate value of this regenerative capacity depends on whether it results in functional recovery of auditory and vocal behavior (1-3). In response to either acoustic trauma or insult from ototoxic drugs, both young and adult birds show a temporary period of hair-cell loss and regeneration, usually culminating in considerable anatomical, physiological, and behavioral recovery within several weeks (4-12). Behavioral recovery, as typically defined, refers only to a return of absolute auditory sensitivity to near pretrauma levels (13-16). Much less is known about the recovery of more complex auditory behavior, and nothing is known about the effect of hearing loss and recovery on the production or recognition of learned vocalizations. Though evolutionarily distant from humans, birds provide the only animal model for studying hearing restoration by renewed sensory-cell input and for examining the effect of such recovery on learned vocalizations. The question is whether a ''new'' auditory periphery results in sufficient functional recovery that a bird can again perceive, learn, and produce complex acoustic communication signals. The nature of this recovery bears on fundamental issues in auditory plasticity and sensorimotor interfaces. Moreover, the ability to track the time course of such recovery in a vertebrate auditory system may have particular significance for the effective use of auditory prosthetic devices, such as cochlear implants, for the severely hearing impaired (17).Budgerigars (domesticated parakeets), learn new vocalizations throughout life, especially in response to changes in their social milieu (18)(19)(20). Further, our work, as well as the work of others, has shown that these birds experience hair-cell loss and threshold shift after administration of the ototoxic drug kanamycin followed, within several days or weeks, by hair-cell regeneration and a gradual recovery to within 20 dB of normal auditory sensitivity (21,22). In th...

Animal species are expected to evolve specialised cognitive abilities to solve the tasks that are critical for their fitness. The literature contains several examples of specialised cognitive abilities, but few regard fish. The guppy, Poecilia reticulata, is a freshwater fish in which females choose their mates based on colouration, and orange‐coloured fruits are important diet enrichments for both sexes. For these reasons, we expect that this species has evolved enhanced learning abilities in colour discrimination compared to other types of discrimination. The comparison between studies in which guppies were tested for colour discrimination and studies in which guppies were tested for shape discrimination seems to support this hypothesis, but direct testing is still lacking. We experimentally compared the learning performance of guppies trained in a red–yellow colour discrimination learning task and that of guppies trained in a shape discrimination learning task using the same, automated conditioning procedure. Guppies trained in the colour discrimination showed greater learning performance, which provides support to the hypothesis that guppies possess enhanced colour discrimination abilities. Moreover, we found that male guppies performed better than females in both shape and colour discrimination learning.

An automated device and a procedure for the operant conditioning individual zebrafish were developed. The key feature of this procedure was the construction of a simple, inexpensive feeder that can deliver extremely small amounts of food, thus preventing rapid satiation. This allows the experimenter to run multiple trails in a single test session and multiple sessions in one day. In addition, small response keys made from acryl rods and fiber sensors were developed that were sufficiently sensitive to detect fish contact. To illustrate the efficiency and utility of the device for traditional learning paradigms, we trained zebrafish in a fixed ratio schedule where subjects were reinforced with food after 10 responses. Zebrafish reliably responded on the response key for sessions that lasted as long 80-reinforcements. They also showed the traditional "break and run" response pattern that has been found in many species. These results show that this system will be valuable for behavioral studies with zebrafish, especially for experiments that need many repeated trials using food reinforcer in a session. The present system can be used for sensory and learning investigations, as well applications in behavioral pharmacology, behavioral genetics, and toxicology where the zebrafish is becoming the vertebrate model of choice.

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