Figure 2.

a) Schematic of the coffee-making model from Cooper and Shallice.¹⁵ Filled circles: schema nodes. Bold labels: goal nodes. b) Activation of the schema nodes in the model from panel a, over the course of one task-completion episode. c) Schematic of the model from Botvinick and Plaut,²¹ showing only a subset of the units in each layer. Arrows indicate all-to-all connections. d) A two-dimensional representation of a series of internal representations arising in the Botvinick and Plaut model, generated using multidimensional scaling. Each point corresponds to a 50-dimensional pattern of activation across the network’s hidden units. Both traces are based on patterns arising during performance of the sugar-adding subtask (o = first action, locate-sugar; x = final action, stir). The solid trajectory shows patterns arising when the sequence was performed as part of coffee-making, the dashed trajectory when it was performed as part of another task: tea-making. The resemblance between the two trajectories reflects the fact that the sugar-adding subtask involves the same sequence of stimuli and responses, across the two contexts. The difference between trajectories reflects the fact that the model’s internal units maintain information about the overall task context, throughout the course of this subtask.