## 3 The NAPS and NAPS BE Affective Picture Databases  
Affective multimedia databases are standardized digital repositories that store auditory, linguistic, and visual materials for emotion research [5]. Currently, there are many databases indexing affective information in multimedia [4; 5], but to our knowledge, the Nencki Affective Picture System (NAPS) is currently the largest database of visual stimuli with general semantic content and with a comprehensive set of accompanying normative ratings and physical parameters of pictures (e.g., luminance, contrast) [22; 39]. The NAPS picture system is the result of a multi-year research effort conducted by the Polish Nencki Institute of Experimental Biology [22]. This database was constructed in response to limitations of existing databases, such as a limited number of stimuli in specific categories or poor picture quality of visual stimuli. The NAPS can be used in various affective research areas. The original database comprises 1356 realistic, high-quality photographs divided into five disjoint categories: people, faces, animals, objects, and landscapes. The photos were chosen to elicit a specific emotional response in the general population, i.e., not all photos are content neutral. One of the main features of the NAPS picture system as a whole, i.e., with its extensions, compared to other emotion elicitation repositories, is that it combines a relatively large number of pictures with normative ratings elicited per both dimensional and categorical (discrete) emotion theories [22], in addition to having additional multi-word semantic descriptions organized in a variety of different topics. More recently, three extensions of NAPS have been developed. The first is NAPS Basic Emotions (NAPS BE), which includes normative ratings based on the discrete model of emotions and additional dimensional ratings for a subset of 510 images from the original NAPS [9]. These additional ratings were obtained using a different psychometric methodology than that NAPS [9]. It is important to emphasize that NAPS BE does not contain additional images but only discrete and additional dimensional emotion annotations to the original 1356 pictures in NAPS. Examples of 6 pictures (Animals_073_h, Animals_177_h, Faces_116_h, Faces_192_h, Landscapes_025_h, Landscapes_121_h) with dimensional emotion ratings from NAPS are shown in Figure 3. Mean values and standard deviations of discrete emotions (_happiness_M, sadness_M, fear_M, surprise_M, anger_M, disgust_M, happiness_SD, sadness_SD, fear_SD, surprise_SD, anger_SD, disgust_SD_) from NAPS BE for these 6 pictures are shown in the chart in Figure 4. For further illustration of the relationship between dimensional and discrete models in affective images, see [40]. The dimensional picture ratings of NAPS were collected using Likert-scale questionnaires, while participants in the creation of NAPS BE provided their subjective ratings using a standardized Self-Assessment Manikin (SAM) graphic scale [41; 42]. The SAM is a non-verbal pictorial assessment technique that directly measures the pleasure, arousal, and dominance associated with a person's affective reaction to a wide variety of stimuli [41; 42]. It has been shown that SAM provides consistent and culturally independent cues to emotional responses [41; 42]. The SAM can be used in a variety of settings with different populations, adults, and children. Because of its brevity, it can be used to rapidly assess emotional responses to a wide range of emotion elicitation methods [41; 42]. To acquire NAPS and NAPS BE picture ratings, several hundred participants from several countries representing the general population provided input in a controlled environment. Figure 4: Mean and standard deviations values (_happiness_M_, _sadness_M_, _fear_M_, _surprise_M_, _anger_M_, _disgust_M_, _happiness_SD_, _sadness_SD_, _fear_SD_, _surprise_SD_, _anger_SD_, _disgust_SD_) from NAPS BE database representing discrete emotions of 6 pictures used in the experiment.