Octave equivalence occurs when notes separated by an octave (a doubling in frequency) are judged as being perceptually similar. Considerable evidence points to the importance of the octave in music and speech. Yet, experimental demonstration of octave equivalence has been problematic. Using go/no-go operant discrimination and generalization, we studied octave equivalence in humans. In Experiment 1, we found that a procedure that failed to show octave equivalence in European starlings also failed in humans. In Experiment 2, we modified the procedure to control for the effects of pitch height perception by training participants in Octave 4 and testing in Octave 5. We found that the pattern of responding developed by discrimination training in Octave 4 generalized to Octave 5. We replicated and extended our findings in Experiment 3 by adding a transfer phase: Participants were trained with either the same or a reversed pattern of rewards in Octave 5. Participants transferred easily to the same pattern of reward in Octave 5 but struggled to learn the reversed pattern. We provided minimal instruction, presented no ordered sequences of notes, and used only sine-wave tones, but participants nonetheless constructed pitch chroma information from randomly ordered sequences of notes. Training in music weakly hindered octave generalization but moderately facilitated both positive and negative transfer.

Black-capped Chickadee (Parus atricapillus) song consists of two notes, termed fee and bee. Frequency measures at three key points (at the start and end offee, and at the start of bee) were obtained from the songs of a large sample of chickadees (n = 15 1) in the wild. In this sample, 19 birds produced songs shifted downward in frequency as well as their normal songs. Analysis of normal song revealed that fee declines in frequency in a glissando of nearly pure tone, then continues at greatly reduced amplitude at the start of bee; whereas bee, also a nearly pure tone, is always lower in frequency than either the start or end offee. The absolute pitches (frequencies) of these measures vary substantially among birds, but much less within individuals. In contrast, pitch intervals (ratios of higher to lower frequencies) for frequency changes among the three measures are highly invariant among birds. Moreover, chickadees with normal and frequency-shifted songs maintain virtually the same pitch intervals in both. This analysis suggests that the absolute and relative pitch constancies in chickadee song production may provide information for individual and species recognition, respectively.

Interspersed reinforcement and extinction during discrimination learning generate a U-shaped gradient of inhibition about the stimulus correlated with extinction. The present work showed that extinction is not a necessary determinant of inhibitory stimulus control. In Exp. I, a reduction in the rate of reinforcement, through a shift from a multiple variable-interval 1-min variable-interval 1-min schedule to a multiple variable-interval 1-min variable-interval 5-min schedule, resulted in a post-discrimination line orientation gradient of inhibition about the stimulus correlated with the variable-interval 5-min schedule. In Exp. II, the rates of reinforcement, correlated with a pair of stimuli, were held constant during a shift from a multiple variable-interval 1-min variable-interval 1-min schedule to a multiple variable-interval 1-min differential-reinforcement-of-low-rate schedule. Inhibitory stimulus control about the stimulus correlated with the differential reinforcement of low rate was obtained. In both experiments, a reduction in the rate of responding during one stimulus and behavioral contrast during the other stimulus preceded the observation of inhibitory stimulus control.

Rats were trained to turn a wheel to avoid unsignaled shock. They then had Pavlovian conditioning in which a tone signaled shock (CS+ group) or time free shock (CS-group). During a "test" session presentation of the tone increased the mean rate of responding of the CS+ group and reduced the mean rate of responding of the CS-group. In a second experiment, the tone was first contingent on an increase, then, later a decrease, in the avoidance response rate. The distribution of avoidance responses of the CS-group was successfully modified by both reinforcement contingencies. The results demonstrated that CS-, a conditioned stimulus for safe periods, established independently of any avoidance situation, can reinforce ongoing avoidance behavior. Rescorla and LoLordo (1965) have examined the discriminative properties of Pavlovian conditioned stimuli superimposed on unsignaled avoidance (Sidman, 1953) extinction. In their experiments, dogs were trained in a Sidman shuttleavoidance task, then subjected to Pavlovian conditioning in which one tone, CS+, signaled shock, while another tone, CS-, signaled shock-free or safe periods. Both CS+ and CS-were later presented during Sidman avoidance. Responding increased over the base line during CS+, and declined below the base line during CS-. In ordinary terms, CS+ elicited fear and CS-elicited relaxation.The present experiments examined the discriminative and reinforcement functions of inhibitory, or safe, signals established during independent Pavlovian conditioning sessions. According to theories of avoidance behavior advanced by Soltysik (1963) and by Weisman, Denny, and Zerbolio (1967), CS-should not only elicit conditioned inhibition or relaxation, but also when made contingent upon an instrumental response, CS-should function as a positive conditioned reinforcer for instrumental behavior in much

The acoustic frequency ranges in birdsongs and human speech can provide important pitch cues for recognition. Zebra finches and humans were trained to sort contiguous frequencies into 3 or 8 ranges, based on associations between the ranges and reward. The 3-range task was conducted separately in 3 spectral regions. Zebra finches discriminated 3 ranges in the medium and high spectral regions faster than in the low region and discriminated 8 ranges with precision. Humans discriminated 3 ranges in all 3 spectral regions to the same modest standard and acquired only a crude discrimination of the lowest and highest of 8 ranges. The results indicate that songbirds have a special sensitivity to the pitches in conspecific songs and, relative to humans, have a remarkable general ability to sort pitches into ranges.