"As with the carrion crow study, when these crows were presented with playback of a more familiar acoustic style—in this case a Japanese speaker—they didn’t show a strong reaction. Play them what was likely a completely unfamiliar language—Dutch—and the crows were rapt. Or at least they acted more vigilant and positioned themselves closer to the speaker. In other words, large-billed crows were able to discriminate between human languages without any prior training!"
I would be interested to hear the respective recordings - is it possible that something else in the speaker's voice (tone/manner/volume) that they were responding to?
"We used twenty Dutch and twenty Japanese sentences as stimuli. They were all declarative, adult-directed, approximately 2.5 seconds long, and spoken by four
female native speakers. After the habituation to the aviary on three consecutive days, the crows were tested for their responses to the Dutch and Japanese stimuli
in a total of eight trials which were distributed over four days (i.e., two trials per day). Four crows received Dutch stimuli for the first four trials and Japanese stimuli for the last four trials, while the other three crows were assigned the opposite language order. Before the start of each trial, the crows were given 3–5
min for familiarization to the surroundings. Each trial consisted of four blocks of stimulus presentation with inter-block intervals of a 1–2-min silent period. Within
each block, a set of ten sentences spoken by two different speakers was continuously presented twice in a random order. A 30 min silent period was inserted between the trials each day. The trial schedule including stimulus presentation was controlled by the programme PsychoPy 3 (Peirce, 2007). The sound level was set at a range between 70 and 80 dB across the perches. According to the different behavioural responses to 1,000 Hz and 1,600 Hz tone......"
For reference, this testing process is similar to a standard one used with human infants. This paper isn't one cited by the crow paper, it's just one I'm familiar with that uses a similar process; it may be connected to the crow paper through a citation chain, as some of their cites also deal with human infants.
I would be interested to hear the respective recordings - is it possible that something else in the speaker's voice (tone/manner/volume) that they were responding to?
Edit: Ok so i went looking in the original paper which describes the method and it looks quite thought out - though i would still love to hear the recording or see the video footage. (https://brussels.evolang.org/proceedings/papers/EvoLang13_pa...)
"We used twenty Dutch and twenty Japanese sentences as stimuli. They were all declarative, adult-directed, approximately 2.5 seconds long, and spoken by four female native speakers. After the habituation to the aviary on three consecutive days, the crows were tested for their responses to the Dutch and Japanese stimuli in a total of eight trials which were distributed over four days (i.e., two trials per day). Four crows received Dutch stimuli for the first four trials and Japanese stimuli for the last four trials, while the other three crows were assigned the opposite language order. Before the start of each trial, the crows were given 3–5 min for familiarization to the surroundings. Each trial consisted of four blocks of stimulus presentation with inter-block intervals of a 1–2-min silent period. Within each block, a set of ten sentences spoken by two different speakers was continuously presented twice in a random order. A 30 min silent period was inserted between the trials each day. The trial schedule including stimulus presentation was controlled by the programme PsychoPy 3 (Peirce, 2007). The sound level was set at a range between 70 and 80 dB across the perches. According to the different behavioural responses to 1,000 Hz and 1,600 Hz tone......"