AREA DE DESARROLLO URBANO ARROYO PANDO .1 DESCRIPCIÓN GENERAL

So far, what we have reported about is all kinds of music that occurred in infants’ everyday environments. This music could have been live either with a voice, like mom singing, or without a voice, like dad playing the flute. It could have been recorded music either with voices, like The Beatles singing Hey Jude on the radio, or without voices, like Tchaikovsky’s 5th _{Symphony playing on the radio. It could also have been any}

combination of these. Now, we are going to focus on only the music that was both live and vocal. This subset of music produced by a live voice represented the high-social- quality musical input infants encountered in their everyday environments. We first determined what proportion of infants’ everyday musical input was coded as both ‘live’ and ‘vocal’. For these analyses, we continued to use the tunes music corpus and the

voices music corpus, calculating the proportion of each that was coded as both ‘live’ and ‘vocal’ (“live-vocal”).

What proportion of infants’ everyday music was live-vocal?

The proportion of the cumulative duration of music that was coded as ‘live’ and ‘vocal’ ranged from .05 to .91 across infants (Median = .40, SD = .26; see Figure 3.12). Each infant encountered musical input that contained a live-vocal tune.

Figure 3.12. Each infant encountered a non-zero proportion of music with live-vocal tunes. The red line

depicts the median proportion (.40) of the cumulative duration of music that contained a live-vocal tune.

How many live-vocal tunes occurred in how many seconds of music?

Within their daily music with exactly one live-vocal tune, infants encountered from 3 to 104 unique live-vocal tunes (Median = 16, SD = 20.20; see Figure 3.13). Thus, all infants encountered some diversity of live-vocal tune types (i.e., more than one specific live-vocal tune) in the music of their days. The cumulative duration of music

with exactly one live-vocal tune varied from 77 to 2,368 seconds (Median = 623 seconds; SD = 740.94 seconds) across individual infants’ recorded days (see Figure 3.14).

Figure 3.13. All infants encountered some diversity of live-vocal tune types (i.e., more than one specific

live-vocal tune) in the music of their days.

Figure 3.14. The cumulative duration of music with exactly one live-vocal tune ranged from 77 seconds to

2,368 seconds across infants. The red line indicates the median (623 seconds). This value was not correlated with the cumulative duration recorded or the cumulative duration of coded seconds.

To what extent were some live-vocal tune types more available than others?

diversity of all tune types. We first visually examined the frequency distributions of live- vocal tune types for each infant (see Figure 3.15), noting that none of the frequency distributions of live-vocal tune types appeared to be balanced. Chi-square goodness-of-fit tests comparing each infant’s actual frequency distribution of live-vocal tune types to a balanced null distribution confirmed that none of the infants’ actual frequency

distributions of live-vocal tunes reflected balanced frequency distributions (i.e., p < .05 for each infant’s test).

Figure 3.15. Based on a visual inspection, no infant encountered a balanced distribution of live-vocal tune

types. Each plot depicts the frequency distribution of live-vocal tune types for an individual infant. The unique live-vocal tunes are on the x-axis ordered by their rank-frequency. The height of each bar represents the proportion of the cumulative duration of live-vocal music that was accounted for by each specific live- vocal tune type. The gray horizontal line shows the proportion each live-vocal type would be if the distribution were balanced (based on the number of voice types and cumulative duration of voice instances for each infant’s voice dataset). The individual plots are ordered by the difference between the rank-one proportion and the balanced-null proportion (largest to smallest, top-left to bottom-right).

Next, to quantify the degree of consistency of the live-vocal tune types, we calculated the proportion of the cumulative duration of live-vocal music that was accounted for by the rank-one live-vocal tune type (live-vocal rank-one proportion), which ranged from .09 to .92 across infants (Median = .26, SD = .16). In other words, one specific live-vocal tune accounted for about a quarter of the cumulative duration of all live-vocal music. We then compared this value to the proportion of one live-vocal tune type if each live-vocal tune occurred for an equal duration (“balanced-null

proportion”, Median = .06, SD = .08). The live-vocal rank-one consistency bias ranged from .07 to .67 across infants (Median = .17, SD = .12). We confirmed with a paired t- test that the actual proportion of the rank-one live-vocal tune was significantly greater than the proportion of one live-vocal tune type given a balanced distribution (t(34) = 10.52, p < .001; see Figure 3.16A).

Figure 3.16. Consistency bias in the live-vocal tunes infants encountered. Compared to a balanced null, (A)

the single top live-vocal tune and (B) the other top live-vocal tunes were very much more available. The red lines indicate the median values.

As we did for tunes and voices, we also examined the relationship among the rank-one proportion, balanced-null proportion, rank-one consistency bias for live-vocal tunes with respect to the cumulative number of live-vocal tune types that occurred in the music of infants’ days (see Figure 3.17). This revealed that even as the number of unique live-vocal tunes increased, the rank-one live-vocal tune still accounted for about 20% of the live-vocal music, yielding relatively higher rank-one consistency biases.

Figure 3.17. The rank-one proportion (dark teal points), the balanced-null proportion (gray line), and the

rank-one consistency bias (distance between points and the balanced-null line) were each sensitive to the cumulative number of unique live-vocal tune types that occurred in the music of infants’ recorded days.

Then, we zoomed out to examine the other live-vocal tune types that were in the top of the frequency distributions. These live-vocal tunes accounted for .48 (Median, SD = .15, range: range: .20 - .76; live-vocal other-top-ranked proportion) of the cumulative duration of live-vocal music. This means that nearly half of the cumulative duration of live-vocal music was accounted for by tune types that occurred for longer durations than would be expected given balanced null distributions. Compared to the balanced null proportion (Median = .24, SD = .08), the live-vocal other-top-ranked consistency bias

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number of unique live−vocal tunes

p ro p o rt io n

was .25 (Median, SD = .10, range: .06 - .39; see Figure 3.16B). We confirmed this difference with a paired t-test (t(32) = 14.54, p < .001). These findings provide additional evidence that infants encountered at least one live-vocal tune type for a longer duration than would be expected if they encountered each live-vocal tune type for an equal duration. In other words, the frequency distributions of live-vocal tune types exhibited a consistency bias, some specific live-vocal tunes were more available than others in infants’ everyday musical input.

How did live-vocal tune types fit in the mix of all tune types?

We next examined how live-vocal tunes occurred in the mix of all the tunes in infants’ everyday musical input (see Figure 3.18). As the first index of how live-vocal music was distributed across tune types, we calculated the proportion of all tune types that were coded as containing both live and vocal music. This value ranged from .04 to .90 (Median = .43, SD = .24). In other words, nearly half of all tune types contained live- vocal music. We also discovered that the rank-one tune type in the frequency

distributions of all tune types was live-vocal for 15 of the infants (.40). These results indicate that live-vocal tune types were not always at the top of the mix of all tune types. Only for some infants did their daily musical input exhibit a consistency bias towards one specific live-vocal tune type.

Figure 3.18. Some infants encountered live-vocal tunes in the top of their frequency distributions of all

tune types. The rank-one tune type occurred as live and vocal for 14 infants. Each plot depicts the tunes types that occurred in the music of an individual infant’s day. Each bar represents one unique tune, and the darker bars depict the unique tune that were live and vocal. The height of the bars indicates the proportion of the cumulative duration of music that was accounted for by each tune type.