when later presented with a problem for which it did work (again, this problem also had a better solution). One way to explain this observation is that in actuality subjects know (consciously) that the same solution might not always work, yet since they were presented with so many instances where it did work, they still tend to test that solution before any other (and so if it works, it will be the first solution found). Neurologically, the idea of synaptic plasticity, which is an important neurochemical explanation of memory, can help to understand the Einstellung effect. Specifically, Hebbian theory (which in many regards is the neuroscience equivalent of original associationist theories) is one explanation of synaptic plasticity (Hebb, 1949). It states that when two associated neurons frequently fire together – while infrequently firing apart from one another – the strength of their association tends to become stronger (making future stimulation of one neuron even more likely to stimulate the other). Since the frontal lobe is most often attributed with the roles of planning and problem solving, if there is a neurological pathway which is fundamental to the understanding of Einstellung effect, the majority of it most likely falls within the frontal lobe. Essentially, a Hebbian explanation of Einstellung could be as follows: stimuli are presented in such a way that the subject recognizes themself as being in a situation which they have been in before. That is, the subject sees, hears, smells, etc., an environment which is akin to an environment which they have been in before. The subject then must process the stimuli which are presented in such a way that they exhibit a behavior which is appropriate for the situation (be it run, throw, eat, etc.). Because neural growth is, at least in part, due to the associations between two events/ideas, it follows that the more a given stimulus is followed by a specific response, the more likely that in the future that stimulus will invoke the same response. Regarding the Luchins’ experiment, the stimulus presented was a water-jar problem (or to be more technical, the stimulus was a piece of paper which had words and numbers on it which, when interpreted correctly, portray a water-jar problem) and the invoked response was B − A − 2C. While it is a bit of a stretch to assume that there is a direct connection between a water-jar problem and