Cognitive dysfunctions in patients suffering from schizophrenia (SZ) are also found in their unaffected parents though to a lesser degree. According to several researchers, short-term memory (STM) deficits are a potential marker of vulnerability to SZ. However, the cognitive processes underlying the observed STM deficits remain underspecified in SZ (Lee & Park, 2005). In the present study, our goal was to pinpoint those processes at play in the manifestation of STM deficits by using the paradigm of the sandwich effect (e.g., Hitch, 1975) to manipulate information load (5 vs. 7 to-be-remembered items) and distraction (control vs. sandwich) in the verbal domain. Our study comprises four groups: patients with SZ (n = 25), their unaffected parents (n = 25), and their respective healthy controls. The pattern of results indicates a generalized dysfunction of STM in patients with SZ characterized by saturation and an increased susceptibility to distraction. The impact of saturation and distraction was also observed in unaffected parents of patients with SZ to a lesser degree. The methodological strategy adopted here allowed us to show that the dysfunction of STM is genuine, can be aggravated by deficits in selective attention, and is a good candidate for further research on genetic epidemiology.