The results of Kidd et al. (2012) confirmed the hypothesis that infants are more likely to terminate their looking to events that are either overly simple or overly complex, given the sequence of

events leading up to that terminating event, and less likely to terminate their looking to events of intermediate complexity. This generates Napabucasin clinical trial a U-shaped function of the likelihood of ending a trial as a function of the information content of the events in the sequence (see Figure 1). Crucially, the U-shaped function was not the result of a variety of other variables that could have plausibly led to this outcome. A special form of regression (survival analysis) accounted for factors such as the number of repeated events (e.g., AAA versus ABC), number of unseen events (e.g., ABA without C), the first instance of an event (e.g., C after ABA), and the overall

tendency to look less to events as the sequence continued. Thus, the tendency to maintain fixation to events of intermediate complexity—which Kidd et al. called the Goldilocks effect—appears to be based on an implicit sense that some patterns of information are more or less informative than others and therefore worthy of further sustained attention. A number of follow-up experiments confirmed the general nature of the Goldilocks effect. The sequences of events did not have to consist of three possible objects in the display, but could consist of a single object whose presence versus absence created variations in selleck surprisal. The events did not have to be visual,

but could be sequences of auditory stimuli (Kidd, Piantadosi, & Aslin, 2014). And crucially, the U-shaped function, which was based on group data, was not an artifact of averaging some infants who had decreasing probabilities of terminating a trial as complexity increased with some infants who showed the opposite pattern. A more detailed analysis of each infant’s data confirmed that 39 of 41 infants showed U-shaped functions, thereby verifying PAK6 the ubiquity and robustness of this active process of allocating attention to sequential events (Piantadosi, Kidd, & Aslin, 2013). In ongoing work, these same visual events were presented to macaque monkeys in a nonreinforced visual attention task, and a similar U-shaped function was obtained (C. Kidd, T. Blanchard, R. N. Aslin, & B. Y. Hayden, unpublished data). Thus, it appears that the general principles by which naïve learners allocate their attention are not unique to human infants or to paradigms used with human infants. It is important to be clear about how this work on the Goldilocks effect relates to prior work showing U-shaped functions and to point out several unanswered questions that must be addressed in the future.