Question 4 Read the description of a study in the file Study_Info.p.pdf
- 1. Question 4: Read the description of a study in the file "Study_Info.pdf" and answer the following questions (5 Points): - How many trials did the experiment consist of? - Explain how these trials were designed and list all the factors and how many levels each factor had. Note that this question is about the design of the stimulus material, not about the analysis. Study Information Introduction It is hypothesised that when we observe the actions of other people, we simulate them internally that is we create a mental model of the action. It has been shown that motor-related areas of the brain not only subserve the production of movements, but also the observation of actions. Research has provided evidence that people with extensive motor expertise for rotational movements (such as gymnasts) are better able to mentally rotate body postures than comparable controls, and this advantage should be limited to tasks that induce an alignment of the participant's own reference frame with the observed human body. This idea is summarised in the concept of perceptual resonance which suggests that action production primes perception in a way that makes observers selectively sensitive to actions that are related or similar to their own action repertoire. In an experiment, researchers examined whether motor expertise can benefit perceptual processes during higher cognitive tasks such as mental rotation. Mental rotation is defined as the ability to mentally manipulate spatial information, typically tested by asking participants to judge whether two images of asymmetric objects depict the same or different objects, regardiess of any differences in orientation. The mental rotation paradigm is highly relevant not only to motor expertise but to all cognitive processes that require different spatial transformations and accompanying internal representations The hypothesis was that motor experience affects the performance selectively in the mental rotation of human figure when the rotation refers to left-right judgments, whereas an effect of motor expertise should be absent in a same-different task. Experiment The researchers conducted a comparison of response times (RTs) and response errors (REs) between expert participants with motor expertise and non- experts in rotational movements around various body axes in space. They used a mental rotation task where images of human bodies were rotated in the picture plane (MPHB). The experimental procedure was similar to that employed by Johnson (1987), Where participants were presented with two images of a female person simultaneously, with one of the person's arms extended to either the left or right side. The lower image was displayed in different orientations, and participants had to determine whether the two images were the same or different (mirrored) by making a judgment. Participants also completed a mental rotation task with images of objects (MRO), which used the same design as the MRHB. Apparatus The experimental stimuli were displayed on a 15.4" LCD colour screen of a Lenovo notebook. To respond to the stimuli, participants used their index fingers to press either the left or the right arrow, which were color- coded and labelled with small signs indicating "same" and "different". The mapping of the
- 2. buttons to left or right key presses was counterbalanced across groups and participants. The test and reference stimuli were presented on a black screen and were 7.5cm in diameter. Stimulus Material The stimulus material consisted of pairs of images presented simultaneously on the screen, one above the other. The pairs were either identical or mirror image reversals. In each pair, the upper image was always upright (0), while the orientation of the lower image was randomly rotated in the picture 1 plane (clockwise 0,45,90,135,180,225,270, and 315 ). Two types of stimull were used: in the MAHB, images of a female person with the left or right arm extended were presented (see Fig. 1.A). presented at similar angular disparities (i.e, five different angles rotated in the picture plane: 0, 45, 90,135, and 180. The images of the female person were real photos taken in front of a bright. homogenous background using a digital camera, and were edited with lmagel. The character " R " was presented in Calibri font and appeared either normally or as its mirrored version. Fig. 1. Examples of stimuli used in the experiment with same-different judgment. Procedure and task Participants were individually tested in a separate room at either the university or gymnasium, which was darkened during sessions to prevent screen reflections. Standardiaed task instructions were provided for participants to read on their own. Participants sat approximately 50cm away from the computer screen and were instructed to quickly and accurately desermine whether the two images presented simultaneously were the same (copies with different rotation angles) or ditferent (mirrorreversed images) using color-coded buttons labelled with signs for "same" and "different" responses. Before starting the experiment, participants completed a short training session with 32 test trials. The order of the test, trials within experimental blocks was randomized, and the order of the two experimental blocks (MRO vs. MRHB) and judgments about same and different pictures were counterbalanced. The experiment consisted of 320 test trials, divided into two blocks. One block presented the images of the asymmetrical character " R and the other block the images of the female person in front view. Each combination of eight angular orientations of the lower image 10,45,90,135,150, 225", 270*,315"), stimulus pairs (same or different), and two images (ociginal, mirrored) was presented once in the training sessions and five times in each experimental test block. Half of the trials showed the same (i.e. identical images), and the other half different images (i.e. mirrored images). A short break between blocks allowed participants to rest, and they decided when to continue with the second block. Each trial began with a blank screen, followed after 2000 ms by a white foxation cross for 500 ms, whereupon the two images (test and relerence stimulus) were presented. The images remained on the screen until a response was made. In case of incorrect responses, participants received immediate feedback, and the word "Error" appeared on the screen.
- 3. Data analysis Only RTs from correct trials were submitted to a repeated analysis of variance (ANOVA) with the within-subject factors Task (MRHB, MRO) and Angular Disparity (0,45,90,135, and 180 ) and the between-subject factor Expertise (expert participants vs. non- experts). Data from incorrect trials (5.74%) were discarded from data analysis for RTs. These error trials were computed separately in another repeated ANOVA.