Does agreement or disagreement alone strongly influence people’s thoughts and emotions, or does cognitive and affective reaction relate more to shifts in agreement and disagreement? The present study investigated how attitudes and emotions respond to the evolution of different patterns of agreement and disagreement in an interaction. Combining conventional methods with novel dynamic systems techniques, we found that people’s attitudes and emotional valence undergo significant change and become less stable when disagreement replaces agreement in an interaction. However, the same reaction does not occur when agreement replaces disagreement. Findings also reveal that the attitudes and emotions do not respond to disagreement alone, but react to the interaction transitioning from an exchange based on agreement to one defined by disagreement. These results provide insight into how attitudes and emotions evolve as social interactions undergo change and confirm key ideas from dynamic systems theories about social interaction.