Comparing Verbal and Reaching Responses to Visually Perceived Egocentric Distances

Ability to visually perceive egocentric target distance was assessed using 2 response measures: verbal reports and reaches. These 2 response measures were made within experimental trials with the participants' eyes closed either immediately after viewing the target (Experiment 1) or after a 6- or 12-sec delay (Experiment 2). Systematic and random errors differed as a function of the response measure. The random errors for the verbal reports and the reaches were not correlated in the no-delay condition but became correlated in each of the 6- and 12-sec delay conditions. Systematic errors varied as a function of delay for the verbal reports but not for the reaches. These findings suggest that immediate verbal and action responses are not directed by a single internally represented perceived depth, as suggested by Philbeck and Loomis (1997). The findings are related to the possibility of separate neurological streams for vision (e.g., Bridgeman, 1989; Milner & Goodale, 1995; Rossetti, 1998), and our discussion contains a review that supplements Michaels's (2000) commentary on those theories. The findings are also related to the recent theories regarding task-specific devices, and a possible synthesis of task-specific devices and separate visual streams is offered.