Combined in one short NewScientist piece:
To test whether behaviour can be truly random, Björn Brembs, a neurobiologist at the Free University of Berlin in Germany, put fruit flies into a sensory deprivation chamber: a drum with a white interior, that offers the flies no visual cues to orient themselves.
Brembs and colleagues analysed the resulting flight records using increasingly sophisticated models of random behaviour. Were the flies' decisions random, like the result of a coin flip? No. Did they fit a coin-flip model in which the probability of "heads" varied randomly? Again, no.
Nor could they be explained by a series of random inputs, or a series of random inputs combined in non-random ways.
Instead, the researchers found that the flies' behaviour bears the hallmark of chaos – a non-random process that is nevertheless unpredictable, like the weather. No one has yet been able to adequately explain how chaos arises.
Well, color me ignorant. Thanks to study author Björn Brembs for showing up and pointing out a link to the (different) study from the video I passed on above. That's what I get for posting without fact-checking.