Recent research indicates a direct relationship between low-level color features and visual attention under natural conditions. However, the design of these studies allows only correlational observations and no inference about mechanisms. Here we go a step further to examine the nature of the influence of color features on overt attention in an environment in which trichromatic color vision is advantageous. We recorded eye-movements of color-normal and deuteranope human participants freely viewing original and modified rainforest images. Eliminating red–green color information dramatically alters fixation behavior in color-normal participants. Changes in feature correlations and variability over subjects and conditions provide evidence for a causal effect of red–green color-contrast. The effects of blue–yellow contrast are much smaller. However, globally rotating hue in color space in these images reveals a mechanism analyzing color-contrast invariant of a specific axis in color space. Surprisingly, in deuteranope participants we find significantly elevated red–green contrast at fixation points, comparable to color-normal participants. Temporal analysis indicates that this is due to compensatory mechanisms acting on a slower time scale. Taken together, our results suggest that under natural conditions red–green color information contributes to overt attention at a low-level (bottom-up). Nevertheless, the results of the image modifications and deuteranope participants indicate that evaluation of color information is done in a hue-invariant fashion.

Problem solving research has encountered an impasse. Since the seminal work of Newell und Simon (1972) researchers do not seem to have made much theoretical progress (Batchelder and Alexander, 2012;Ohlsson, 2012). In this paper we argue that one factor that is holding back the field is the widespread rejection of introspection among cognitive scientists. We review evidence that introspection improves problem solving performance, sometimes dramatically. Several studies suggest that self-observation, self-monitoring, and self-reflection play a key role in developing problem solving strategies. We argue that studying these introspective processes will require researchers to systematically ask subjects to introspect. However, we document that cognitive science textbooks dismiss introspection and as a consequence introspective methods are not used in problem solving research, even when it would be appropriate. We conclude that research on problem solving would benefit from embracing introspection rather than dismissing it. In contemporary cognitive science introspection is widely regarded as a mysterious and problematic method for uncovering the operations of the mind. Most researchers will typically avoid the conceptual and methodological minefield of introspection. Johnson-Laird (2008, p. 17), in the context of reasoning, expresses an attitude towards introspection that many cognitive scientists share: "To reason is to carry out a mental process. Introspection doesn't reveal to us how that process works. (If it did, then psychologists would have understood how it worked long ago.) Hence the process is unconscious. " There are good reasons to be skeptical about the usefulness of introspection as a method in many areas of perception and cognition. Many processes are unconscious and hence, by definition, unaccessible for introspection. From this, however, it does not follow that introspection has no role to play in psychological research or that introspection is not an interesting process worthy of study in itself.In the context of problem solving it is important to stress that introspection is, at least sometimes, an essential part of problem solving processes. When dealing with new or hard problems that cannot be solved by standard methods, good problem solvers introspect while they engage with their task: they examine their strategies and representations, they evaluate their progress, and they realize that they are stuck or that they have had an insight. Understanding often seems to depend on some form of conscious and deliberate reflection on one's own thoughts. These are salient phenomena that we should not ignore. In the literature, the dubious term introspection is often avoided and is replaced with notions such as self-observation, self-monitoring, self-reflection, or metacognition, but also these terms remain mysterious (Brown, 1987).We, thus, believe that research on problem solving, at some point, will have to face squarely the conceptual muddle surrounding introspection, metacognition, and consciousness.Pr...

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