Number of vocalizations across exposure conditions.

<p><b>(a)</b> Box plot showing the range of vocalizations produced across exposure conditions, the median (line in the box), and 95% confidence intervals. The black dots represent data points that lie outside the 10^th and 90^th percentiles. The isolate condition is shown in black, the same-sex condition is shown in gray, and the opposite sex condition is shown in white. The * represent significantly different conditions. <b>(b)</b> Box plot showing the range of vocalizations produced across exposure conditions, the median (line in the box), and 95% confidence intervals. The black dots represent data points that lie outside the 10^th and 90^th percentiles. The left half of the figure is females and the right half of the figure is males. The isolated condition is shown in black, the same-sex exposure condition is shown in gray, and the opposite-sex exposure condition is shown in white.</p

The mean proportion of USV types produced by males and females across exposure conditions.

<p>The left column is females and the right column is males. The top row is the isolated condition, the middle row is the same sex exposure condition, and the bottom row is the opposite sex exposure condition. The different colors/shadings represent the mean proportion of each of the nine different categories of ultrasonic vocalizations.</p

Spectrograms of synthetic speech syllables with high F1 frequency, "da" (upper box) and "ta" (lower box).

<p>The F1 frequency for both syllables at the onset of voicing is 750 Hz. Both stimuli are 255 ms in duration.</p

Phoneme boundaries (in ms) for the low and high F1 onset <i>da-ta</i> continua and the amount of shift in the phoneme boundary (in ms).

<p>Phoneme boundaries (in ms) for the low and high F1 onset <i>da-ta</i> continua and the amount of shift in the phoneme boundary (in ms).</p

Exposure apparatus.

<p>The exposure apparatus was a standard mouse cage lined with wood shavings, divided in half with a metal mesh divider fixed to the cage. Mice were placed in this cage for one hour prior to recordings.</p

Number of vocalizations across the sexes.

<p>Box plot showing the range of vocalizations produced by males and females, the median (line in the box), and 95% confidence intervals. The black dots represent data points that lie outside the 10^th and 90^th percentiles. Males are gray, females are black.</p

Experience with speech sounds is not necessary for cue trading by budgerigars (<i>Melopsittacus undulatus</i>)

<div><p>The influence of experience with human speech sounds on speech perception in budgerigars, vocal mimics whose speech exposure can be tightly controlled in a laboratory setting, was measured. Budgerigars were divided into groups that differed in auditory exposure and then tested on a cue-trading identification paradigm with synthetic speech. Phonetic cue trading is a perceptual phenomenon observed when changes on one cue dimension are offset by changes in another cue dimension while still maintaining the same phonetic percept. The current study examined whether budgerigars would trade the cues of voice onset time (VOT) and the first formant onset frequency when identifying syllable initial stop consonants and if this would be influenced by exposure to speech sounds. There were a total of four different exposure groups: No speech exposure (completely isolated), Passive speech exposure (regular exposure to human speech), and two Speech-trained groups. After the exposure period, all budgerigars were tested for phonetic cue trading using operant conditioning procedures. Birds were trained to peck keys in response to different synthetic speech sounds that began with “d” or “t” and varied in VOT and frequency of the first formant at voicing onset. Once training performance criteria were met, budgerigars were presented with the entire intermediate series, including ambiguous sounds. Responses on these trials were used to determine which speech cues were used, if a trading relation between VOT and the onset frequency of the first formant was present, and whether speech exposure had an influence on perception. Cue trading was found in all birds and these results were largely similar to those of a group of humans. Results indicated that prior speech experience was not a requirement for cue trading by budgerigars. The results are consistent with theories that explain phonetic cue trading in terms of a rich auditory encoding of the speech signal.</p></div

Housing type (sound attenuated vs normal vivarium) for individual birds within each exposure group.

<p>Housing type (sound attenuated vs normal vivarium) for individual birds within each exposure group.</p

Fitted identification functions showing percentage of /d/ responses for birds and humans across various VOTs.

<p>The solid lines represent the responses to the low F1 stimuli, the dashed lines represent responses to the high F1 stimuli. Error bars represent ±1 standard error of the mean.</p

Mean slopes in probit units per ms of VOT. (Numbers in parentheses are standard deviations).

<p>Mean slopes in probit units per ms of VOT. (Numbers in parentheses are standard deviations).</p