Theory of Mind and Mental Time Travel

The inventory of specifically human abilities has undergone a severe revision during the last decades. Concerning cognition, there has been an upsurge of enthusiasm about animal skills. Little remains for humans to be proud of in this area. Impressive as the evidence is, often overlooked is the fact that behaviors that seem similar from their outward appearance may rely on mechanisms of different complexity. A comparable trend is present in Developmental Psychology. There, too, is a tendency to attribute complex competences to small infants in order to explain the social skills they demonstrate. Simpler mechanisms may apply here as well. A phylogenetic analysis of how cognition and motivation evolved will help to provide parsimonious explanations and increase our understanding of how more complex capacities emerged from simpler ones.

A thorough analysis of the evidence in question suggests a differentiation between two evolutionary steps of human cognition. The first step led to the ability to represent reality on an imaginary basis, in addition to perceptive representation. Evidence indicates that this capacity first manifests itself on the level of the great apes. Imagery allows for symbolic representation and for mental simulation in problem solving. It is also prerequisite for a rudimentary self-representation. The cognitive mechanisms allowing to identify oneself with one's own mirror-image appear to pave the way for empathic identification with others as well. Again, it is at the ape level that animals begin to vicariously experience others' intentions and to understand the subjective state of conspecifics. The second step, responsible for the transition to human-specific cognition, is characterized by time representation and the ability to reflect upon mental states ("theory of mind"). Both abilities enable humans to go on a "mental time travel", that is, to represent oneself at every possible instant in the past and in the future and to imagine the desires and motives at each of those instants independently of one's present motivational state ("Bischof-Köhler-hypothesis"). Mental time travel has fundamental implications for the organization of action, most importantly, for planning of the future and recapitulation of the past.

Both evolutionary steps can also be taken as developmental transition markers in ontogeny. First, the onset of imagery emerges in the middle of the second year when toddlers become capable of mental problem solving. Simultaneously, toddlers start learning a language, understand the symbolic character of representations, recognize themselves in a mirror, and change their sharing of other's emotions from mere contagion to true empathizing. We could show in experiments with 126 children that only children who recognized themselves demonstrated emotional concern when confronted with a person in need by offering consolation. Children who still took their mirror image for a playmate stayed indifferent in this situation. The second transition begins in the fourth year with the onset of a theory of mind. In our investigations on 170 three- to five-year-olds, theory of mind correlated highly with the development of time representation. Also demonstrated were the consequences of these two abilities on the organization and planning of actions. As soon as children were competent in both abilities, they could go on "time travel". They were able to delay gratification, to arrange conflicting desires in a temporal order, and to plan for future needs.