temps (durée) (1) spectacle (1) recherche (1) aliment (1) delta (1) Food (1) Acquisition (1) Programs (1) Labor (1) Rates (1) Time (1) Research (1) Rats (1) Psychology (1) Process (Law) (1) Food (1) Farm produce (1) Cycles (1) Beginning (1) Opportunity (1) Research (1) Relations (1) Rates (1) Number (1) Programas (1) Estudios (1) Experimentos (1) Psicología (1) Trabajo (1) delta (1)