In a real world search, it can be important to keep ‘an eye out’ for items of interest that are not the primary subject of the search. For instance, you might look for the exit sign on the freeway, but you should also respond to the armadillo crossing the road. In medicine, these items are known as “incidental findings,” findings of possible clinical significance that were not the main object of search. These errors (e.g., missing a broken rib while looking for pneumonia) have medical consequences for the patient and potential legal consequences for the physician. Here we report three experiments intended to develop a ‘model system’ for incidental findings – a paradigm that could be used in the lab to develop strategies to reduce incidental finding errors in the clinic. All the experiments involve ‘hybrid’ visual search for any of several targets held in memory. In this ‘mixed hybrid search task,’ observers search for any of three specific targets (e.g., this rabbit, this truck, and this spoon) and three categorical targets (e.g., masks, furniture, and plants). The hypothesis is that the specific items are like the specific goals of a real world search and the categorical targets are like the less well-defined incidental findings that might be present and that should be reported. In all these experiments, varying target prevalence, number of targets, etc., the categorical targets are missed at a much higher rate than the specific targets. This paradigm shows promise as a model of the incidental finding problem.

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The classic animation experiment by Heider and Simmel (1944) revealed that humans have a strong tendency to impose narrative even on displays showing interactions between simple geometric shapes. In their most famous animation with three simple shapes, observers almost inevitably interpreted them as rational agents with intentions, desires, and beliefs (“That nasty big triangle!”). Much work on dynamic scenes has identified basic visual properties that can make shapes seem animate. Here, we investigate the limits on the ability to use narrative to share information about animated scenes. We created 30 second Heider-style cartoons with 3–9 items. Item trajectories were generated automatically by a simple set of rules, but without a script. In Experiments 1 and 2, 10 observers wrote short narratives for each cartoon. Next, new observers were shown a cartoon and then presented with a narrative generated for that specific cartoon or one generated for a different cartoon having the same items. Observers rated the fit of the narrative to the cartoon on a scale from 1 (clearly does not fit) to 5 (clearly fits). Performance declined markedly when the number of items was larger than 3. Experiment 3 had observers determine if a short clip of a cartoon came from a longer clip. Experiment 4 had observers determine which of two narratives fit a cartoon. Finally, in Experiment 5, narratives always mentioned every item in a display. In all cases of matching narrative to cartoon, performance drops most dramatically between 3 and 4 items.

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