Abstract
Temporally unpredictable stimuli influence murine and human behaviour, as previously demonstrated for sequences of simple sounds with regular or irregular onset. It is unknown whether this influence is mediated by an evaluation of the unpredictable sound sequences themselves, or by an interaction with task context. Here, we find that humans evaluate unrelated neutral pictures as more negative when these are presented together with a temporally unpredictable sound sequence, compared to a predictable sequence. The same is observed for evaluation of neutral, angry and fearful face photographs. Control experiments suggest this effect is specific to interspersed presentation of negative and neutral visual stimuli. Unpredictable sounds presented on their own were evaluated as more activating, but not more aversive, and were preferred over predictable sounds. When presented alone, these sound sequences also did not elicit tonic autonomic arousal or negative mood change. We discuss how these findings might account for previous data on the effects of unpredictable sounds, in humans and rodents.
Highlights
Forecasting the state of the world is fundamental for all organisms
We found that sound sequence had no impact on ratings, reaction times (RT), tonic sympathetic arousal quantified as spontaneous fluctuations (SF), or phasic stimulus-associated skin conductance responses (SCR)
We demonstrate that evaluation of neutral IAPS pictures and of neutral, angry and fearful face photographs is biased towards a higher percentage of negative ratings while participants are exposed to the unpredictable sound sequence
Summary
Forecasting the state of the world is fundamental for all organisms. Because environments differ in the degree to which events are predictable, humans and other animals can maximise predictability by, for example, moving from one environment to another. A large literature shows that organisms actively prefer predictable over unpredictable salient events such as punishments and rewards [1, 2]. Such observations fit a class of theories which invoke reduction of uncertainty [3] as a prime motivating force in a wide class of behaviours [4, 5]. It has been argued that a preference for predictable salient events does not reflect a propensity to reduce uncertainty, but instead a propensity to maximise periods of safety.
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