## 1 Introduction
Thus, in such a situation, monitoring the cognitive load imposed on the interviewer by measuring pupillary responses may be reduced. For example, if an emotional response already triggers pupil dilation, there would maybe be less room for a pupil response to the higher demands. Thus, it might be difficult to identify questions or phases of the interview where difficulty increases and where questions possibly have to be rephrased. Can load be assessed through pupillary responses in all such cases? It should be noted that emotional effects can impact pupil sizes by effects that do not correspond to a cognitive-load effect itself. It is true that, for example, some emotional processing such as an observer's anxiety may draw on her or his limited capacity and, thus, impose a cognitive load itself [42]. In such cases, emotional and load effects converge to increase load, and there is no need to tell the two apart and to derive a pure measure of load. However, other emotional content besides one's own felt stress or anxiety can also elicit pupillary changes, but these are load-independent effects. In these cases, to make use of a pupil-based load measure, it is important to tell apart which pupil-size changes are true reflections of cognitive load and which are due to emotions. For example, it would be important to know if the emotion-specific but load-independent pupillary effect limits the sensitivity of the pupil's response to an additional load effect. It is exactly such a situation, where emotion and load lead to independent effects on pupil size, that we studied in the present research. We did this with a clinical interview in which patients--in fact, a confederate of the experimenter--voiced more neutral or more negative content. Here, the more negative content is independent of the cognitive load per se, and, thus, has the chance to compromise our cognitive-load measure by load-independent means. As explained, clinical interviews are common practice and an important tool in diagnosis, methods to understand and improve their application are needed [43; 44]. Therefore,the present study investigated exactly the question of whether varying processing demands can be successfully and unobtrusively tracked by measurements of pupil dilation under conditions of varying emotional content of the answers of the interviewee. To this end, the current study used four different groups varying with respect to the processing demands or cognitive loads on the one hand, and independently of the load with respect to the emotional content of the answers, on the other hand. All participants acted as interviewers conducting an interview with a confederate of the researchers that gave prepared verbal answers and displayed generic mimics and gestures. Participants in two of the groups had to monitor the verbal content of the answers of the interviewee only, both for current classification of the responses in the course of the interview (by button presses) and for later recall (in a memory test). These were the low-load or low-demand (L) conditions. Participants in the other two groups had to monitor both the verbal and nonverbal content of the interviewee, again for current classification of the responses during the interview and for later recall. These were the high-load or high-demand (H) conditions. In each of the two load conditions, one group of participants heard more neutral, less emotional answers (NEU), while the other group heard less neutral, more negative (NEG), and, thus, more emotional answers. Thus, there were four groups (NEUL, NEUH, NEGL, and NEGH) altogether. To track the processing demands, we measured the pupillary responses of the interviewers with an eye-tracker and analyzed the data conventionally, and also used an algorithm that automatically subtracts light-elicited pupillary responses [19]. This algorithmic measure of cognitive load could be used online, with little temporal delay between recording and resulting identification of cognitive load experienced.