A Comprehension- or a Production-Based Monitor? Response to Roelofs (2020)

Abstract

Roelofs (2020) has put forth a rebuttal of the criticisms raised against comprehension-based monitoring and has also raised a number of objections against production-based monitors. In this response, I clarify that the model defended by Roelofs is not a comprehension-based monitor, but belongs to a class of monitoring models which I refer to as production-perception models. I review comprehension-based and production-perception models, highlight the strength of each, and point out the differences between them. I then discuss the limitations of both for monitoring production at higher levels, which has been the motivation for production-based monitors. Next, I address the specific criticisms raised by Roelofs (2020) in light of the current evidence. I end by presenting several lines of arguments that preclude a single monitoring mechanism as meeting all the demands of monitoring in a task as complex as communication. A more fruitful avenue is perhaps to focus on what theories are compatible with the nature of representations at specific levels of the production system and with specific aims of monitoring in language production.

Keywords: Speech monitoring; conflict; forward models; perceptual loop.

Figure 1

Schematic of the DIVA model (adapted from Guenther, 2016). The inset shows the calculations within the auditory feedback controller. A_T = Auditory Target; M_T = Motor Target; S_T = Somatosensory Target; Ṁ_A and Ṁ_S = corrective movement commands from auditory and sensory routes, respectively; Ṁ_FF = feedforward movement command; Ṁ = overall movement command. M = motor position command; α_A = gain factor.

Figure 2

Schematic of the HSFC model (adapted from Hickok, 2012). The internal monitoring loop operates via connections between motor programs and perceptual targets (A_T and S_T) mediated by the coordinate transform system. Note the direction of the connections in bold: connections from perceptual to motor representations are excitatory (filled circles), while the connections from motor to perceptual representations are inhibitory (empty circles).

Figure 3

The N2 in language production (Cz is shown). a) Production of the target (e.g., “cat”) in the presence of an unrelated competitor (e.g., “pen”) vs. in the presence of a semantically related competitor (e.g., “dog”). b) Production of the target from the target picture vs. from the picture of a different item. In both cases, the black line represents the condition that led to behavioral interference, but this interference cannot be predicted from the direction of change to the N2.