Before the experimental session, the participants were given details about the contents of the images and familiarized themselves with the dimensions through the use of example stimuli. In addition, participants were informed that if they felt any discomfort during the session, they should report it immediately in order to stop the experiment.
Each participant was presented with 362 images chosen pseudorandomly from all of the categories, with the constraint that no more than three stimuli of one category were presented in succession. In all, 12 different sets of stimuli were prepared on the basis of this rule. On average, 55 ratings were collected for each picture. The sessions started with an instructional screen and 12 practice trials, with a longer time limit for the first seven of these trials. In the main experiment, each picture was presented in full-screen view for 3 s. After the first presentation of each stimulus, rating scales were displayed on a new screen to the right, and a smaller version of the image was presented on the left side of the screen. The small picture and rating scales remained available to the participant until she or he had completed all three ratings. The participants had 3 s to complete ratings on each dimension, amounting to 9 s in total. After the participant had completed all ratings, the offset picture and scale disappeared and were immediately replaced by the next picture in the series.
Three continuous bipolar semantic sliding scales were shown, each ranging from 1 to 9. Participants indicated their ratings by moving a bar over a horizontal scale using a standard computer mouse. On the valence scale, participants were asked to complete the sentence, “You are judging this image as . . .” (from 1 = very negative to 9 = very positive, with 5 = neutral). Next, participants judged motivational direction by completing the sentence, “My reaction to this image is . . .” (from 1 = to avoid to 9 = to approach, with 5 = neutral). Finally, participants judged the degree of arousal elicited by pictures with the introductory sentence, “Confronted with this image, you are feeling: …” (from 1 = relaxed to 9 = aroused, with 5 = neutral/ambivalent).
We decided to use semantic bipolar scales in the present study because it has been show that the SAM arousal scale may lead to misinterpretations (Riberio, Pompéia, & Bueno, 2005 (link)). In the original technical manual of IAPS and SAM (Lang et al., 1999 ), the description of one of the extremes of the arousal scale uses the terms relaxed, calm, sluggish, and unaroused. However, the affective space obtained from stimuli in American (Lang et al., 1999 ) and Spanish (Moltó at el., 1999 ; Vila et al., 2001 ) populations showed that the standardized rating is “boomerang-shaped,” with one extreme of the arousal scale being referred to as no reaction. As a result, this extreme anchor of the scale was used only for neutral photographs, whereas the opposite extreme was used to describe both pleasant and unpleasant pictures (arousing, value = 9). On the other hand, Brazilians (Ribeiro et al., 2005 (link)) and Germans (Grühn & Scheibe, 2008 (link)) interpreted the SAM arousal scale differently, and attributed less arousal to pleasant photographs and more arousal to neutral and negative ones. Pleasant images of landscapes, flowers, and babies were rated as being relaxing and calming. This led to a more linear distribution of scores in the affective space.
The present experiment lasted approximately 1 h. An obligatory 10-min break was taken after half of the stimuli had been presented, during which participants were asked to leave the experimental room. The study was conducted on standard PC computers using 24-in. LCD monitors. The core software for stimulus presentation and data acquisition was created using Presentation software (Version 14.6,www.neurobs.com ). All responses were analyzed further using the statistical package SPSS (2009 ).
Each participant was presented with 362 images chosen pseudorandomly from all of the categories, with the constraint that no more than three stimuli of one category were presented in succession. In all, 12 different sets of stimuli were prepared on the basis of this rule. On average, 55 ratings were collected for each picture. The sessions started with an instructional screen and 12 practice trials, with a longer time limit for the first seven of these trials. In the main experiment, each picture was presented in full-screen view for 3 s. After the first presentation of each stimulus, rating scales were displayed on a new screen to the right, and a smaller version of the image was presented on the left side of the screen. The small picture and rating scales remained available to the participant until she or he had completed all three ratings. The participants had 3 s to complete ratings on each dimension, amounting to 9 s in total. After the participant had completed all ratings, the offset picture and scale disappeared and were immediately replaced by the next picture in the series.
Three continuous bipolar semantic sliding scales were shown, each ranging from 1 to 9. Participants indicated their ratings by moving a bar over a horizontal scale using a standard computer mouse. On the valence scale, participants were asked to complete the sentence, “You are judging this image as . . .” (from 1 = very negative to 9 = very positive, with 5 = neutral). Next, participants judged motivational direction by completing the sentence, “My reaction to this image is . . .” (from 1 = to avoid to 9 = to approach, with 5 = neutral). Finally, participants judged the degree of arousal elicited by pictures with the introductory sentence, “Confronted with this image, you are feeling: …” (from 1 = relaxed to 9 = aroused, with 5 = neutral/ambivalent).
We decided to use semantic bipolar scales in the present study because it has been show that the SAM arousal scale may lead to misinterpretations (Riberio, Pompéia, & Bueno, 2005 (link)). In the original technical manual of IAPS and SAM (Lang et al., 1999 ), the description of one of the extremes of the arousal scale uses the terms relaxed, calm, sluggish, and unaroused. However, the affective space obtained from stimuli in American (Lang et al., 1999 ) and Spanish (Moltó at el., 1999 ; Vila et al., 2001 ) populations showed that the standardized rating is “boomerang-shaped,” with one extreme of the arousal scale being referred to as no reaction. As a result, this extreme anchor of the scale was used only for neutral photographs, whereas the opposite extreme was used to describe both pleasant and unpleasant pictures (arousing, value = 9). On the other hand, Brazilians (Ribeiro et al., 2005 (link)) and Germans (Grühn & Scheibe, 2008 (link)) interpreted the SAM arousal scale differently, and attributed less arousal to pleasant photographs and more arousal to neutral and negative ones. Pleasant images of landscapes, flowers, and babies were rated as being relaxing and calming. This led to a more linear distribution of scores in the affective space.
The present experiment lasted approximately 1 h. An obligatory 10-min break was taken after half of the stimuli had been presented, during which participants were asked to leave the experimental room. The study was conducted on standard PC computers using 24-in. LCD monitors. The core software for stimulus presentation and data acquisition was created using Presentation software (Version 14.6,
