Sensory information from the environment is ultimately processed at the level of synapses, the connection between neurons that form the most fundamental information-processing units in the nervous system. In recent years, human genetic studies have increasingly highlighted that many of the mutations implicated in cognitive disorders converge upon genes associated with the synapse. Our recent work has focused on the vertebrate postsynaptic density, containing cell adhesion proteins, neurotransmitter receptors and scaffolds that are integral for synapse function and plasticity. Using mice with mutations in key postsynaptic genes, we have begun to dissect the functional role of distinct postsynaptic proteins in complex cognition using the recently developed touchscreen methodology, an innovative tool for bridging the gap between mouse and human cognitive testing. Our approach has begun to elucidate the synaptic molecular codes essential for regulating distinct behaviours and paves the way towards uncovering the genetic basis of cognition.