Incidental bidirectional naming (Inc-BiN) has been defined as a verbal developmental cusp whereby children demonstrate learning the names of things as listener and speaker as a function of observation alone. Stimulus characteristics have been found to affect performance in tests for Inc-BiN. To further explore this effect, Experiment 1 compared untaught listener and speaker responses for novel familiar-type versus novel nonfamiliar-type stimuli with 20 first-grade students following naming experiences in which the participants observed each visual stimulus five times while hearing its name. Participants performed significantly better with familiar-type than with nonfamiliar-type stimuli. Experiment 2 examined the effects of a repeated-probe intervention to induce Inc-BiN with nonfamiliar-type stimuli. Participants were six first-grade students who demonstrated incidental unidirectional naming (i.e., acquired names as listener from exposure alone). Implementation of the intervention was staggered across dyads of participants in a multiple-probe, simultaneous-treatments design. One participant in each dyad received the intervention with nonfamiliar-type stimuli only and the other with both nonfamiliar-and familiar-type stimuli. Pre-and postintervention Inc-BiN probes with stimuli not included in the intervention suggested both conditions were effective in establishing Inc-BiN for nonfamiliar-type stimuli. These findings have implications for understanding the mechanisms underlying Inc-BiN.