TIME WINDOW AND UNIT CAPACITY - DUAL CONSTRAINTS ON THE ACQUISITION OF SERIAL INFORMATION IN SONGBIRDS

Hand raised nightingales (Luscinia megarhynchos) perform imitations of song-types that were serial neighbours in a string of master song-typ es sequentially associated as "packages" of limited size. This study e xamines whether such "chunking" of auditorily perceived serial informa tion can be influenced by the presentation rate of stimuli. Subjects ( n = 8 males) were exposed to 3 different tutoring regimes, designed to offer either a "normal", or a "dense", or a "spaced" distribution of information (measure: number of songs per unit time): The duration of silent intervals separating subsequent songs in a string of master son g-types was 4 s ("normal"), 1 s ("dense") or 10 s ("spaced"). The anal ysis of packages of acquired song-types revealed the following results : 1. Packages developed from the "dense" programmes were not larger in size (number of song-types, X +/- SD: 3.9 +/- 1.2) than those develop ed from the "normal", programmes (X +/- SD: 4.5 +/- 1.6). This suggest s capacity constraints on data processing to account for package forma tion. 2. Packages developed from the "spaced" programmes, on the other hand, were significantly smaller (number of song-types, X +/- SD: 2.5 +/- 0.7), suggesting that the parsing is controlled by time factors. 3. This was supported by analyzing the duration of master string segme nts from which packages had been developed: The duration was not diffe rent for both the "normal" programmes (X +/- SD: 32.1 +/- 11.9; Max: 5 6.4 s), and the "spaced" programmes (X +/- SD: 32.8 +/- 9.6; Max: 54.1 s). The results confirm an earlier hypothesis predicting that the for mation of song-type packages is mediated by a process which parses str ings of auditorily perceived information upon exposure to serial stimu li. In addition, the results suggest that the parsing of a song-type s tring is controlled by two components: a unit (or information) based c apacity buffer (evidence: constraints during "dense"), and a time wind ow based gating mechanism (evidence: constraints during "spaced").