Lab Report on Facial Recognition

Introduction

The process of facial memory is crucial in real-life circumstances that it is involved in judiciary and laws. Despite the sophisticated mechanism of memory, inaccuracies can still be resulted by factors such as familiarity, attention, emotion, encoding and retrieval steps. In eyewitness identification task of criminals, facial memory is applied and taken as evidence of accusations. Therefore, the process and biases of facial memory should be studied to lower risks of unjust allegations

Brown, Deffenbacher and Sturgill (1977) invited psychology students in their study that they were presented with 12 mugshot pairs of criminals encountered who delivered test materials and innocents in the mugshot phase. It was followed by the lineup phase that participants were shown with 4 criminals appearing lively and asked to identify whether they had delivered the materials and if so described the materials, appeared in the mugshots and indicated the confidence in their judgements.

The researchers found out the “mugshot-only” group had a higher significant level of falsely indication than the “lineup-only” group, suggesting memory confusions with previous encounters existed in the mugshot phase. Moreover, there were significant indictment proportions except for criminal without mugshot, mugshot-only condition and lineup-only condition, implying higher accuracy with mugshots previously seen. A correlation between confidence when correct and incorrect; and the responses of description of test materials at the chance level were found.

Hinz and Pezdek (2001) investigated the effect of intervening lineups to the identification accuracy with a repeated distractor face (RDF). In the presentation phase, participants were shown the target face. In the intervening lineup phase, they were presented with a target-absent lineup containing the RDF. In the test lineup phase, 3 different combinations of foil faces, target faces and the RDF, were given to the participants. They were then asked to identify the target face.

The experimenters found out a significantly higher hit rate of the target face when the RDF was absent, higher false alarm rate of RDF as the target face when the target face was absent and lower hit rate of the target face in the presence of both the RDF and the target face, suggesting participants made source confusing errors about the RDF and the target face that they identified the target face based on familiarity.

The hypothesis of the current study is the repeated exposure of same foil faces would result in a higher incorrect identification rate in face recognition task than new exposure of different foil faces. It is based on the study of Brown, Deffenbacher and Sturgill (1977) and Hinz and Pezdek (2001) that repeated presentation of foil faces decreased the identification accuracy of the target face and lowered the performance of the face recognition task.

Method

Participants

Participants consisted of 87 undergraduate university students recruited from the PSYC2007 course of HKU in the current experiment and participation was compulsory for the coursework component of the course. The gender (Male = 19 and Female = 68) had a larger distribution on females while the descriptive statistics of age from 18-28 of the sample were summarised (Mean = 20. 31, Median = 20, Mode = 20 and SD = 1. 497).

Apparatus and materials

The visual stimuli used were photographs of 10 black and white “Most Wanted” man faces, 10 black and white “Foil” man faces and another new set of 10 black and white “Foil” man faces. In the study phase of 10 “Most Wanted” face presentation, the photographs were shown simultaneously and there were no time limits. In each recognition phase of the 2-day trials, the photographs were presented separately which was different from the study phase.

The equipment used were any accessible electronic devices of the participants in any venues. The “Facial Recognition” test from the experiment section in the American Psychology Association (APA) Online Psychology Laboratory (OPL) website was adopted to present the stimuli. Participants would be required to enter their Class ID to save data, launch and engage in the experiment. Collection of responses was then collected by their Profile ID and Experiment Results ID to gather data.

Procedure

The independent variables to be manipulated in the current study were sorts of “foil” man faces presented in day 2 of the experiment. Participants were separately assigned to experience different independent variables, which refers to part of them being exposed to the same repeated “Foil” faces while another part of them being exposed to the different new “Foil” faces in day 2 comparing with day 1.

Two groups with various experimental conditions were included in the design of the study. In day 2, the control group was introduced to the new set of 10 “Foil” faces different from those in day 1 and 10 “Most Wanted” faces. On the other hand, the experimental false memory group was shown the same set of 10 “Foil” faces in day 1 and 10 “Most Wanted” faces.

There were 39 participants in the control group and 48 participants in the experimental false memory group. Both groups had both genders of males and females, as well as different ages. The assignation of the participants to either the control or the experimental false memory group was out of random selection.

Common factors existed to the participants in each group. In the learning block of the experiment, 10 “Most Wanted” faces were shown without time limits and simultaneously to both groups. In the day 1 testing, two groups were given the same 10 “Most Wanted” and 10 “Foil” faces. Moreover, the instructions and the computerised task including colours and sizes of photographs as well as yes/no response also remained identical. Although participants experienced part of the design commonly, there were yet differences. In the day 2 testing, participants in the two groups were provided various independent variables accordingly. The control group viewed the different set of “Foil” faces while the experimental false memory group viewed the same set of “Foil” faces from those presented in the day 1 testing alongside with 10 “Most Wanted” faces.

The dependent variable measured in the study was the difference of the d-prime results comparing day 1 and day 2 testing. Hits and Misses regarding the correct and false identification of the “Most Wanted” faces respectively as well as false alarm and correct rejection of the “Foil” faces were measured in both day 1 and day 2 of the experiment independently. The difference of these results refers to the difference of the d-prime results.

D’ is the d-prime which calculates the distance between the signals referring to stimuli and the noise referring to no stimuli in terms of standard deviation units. In the yes/no task of the current study, d’ between the “Most Wanted” faces and “Foil” faces was measured. D’ is used because Stanislaw & Todorov (1999) addressed it is uninfluenced by the response bias and the sensitivity could be clearly measured under assumptions.

Results

The data was analysed by the independent-sample t-test under the RStudio to determine whether there was a statistically significant difference between the two groups in terms of the difference of d-prime results from day 1 to day 2 of the experiment. Descriptive statistics as well as inferential statistics were adopted to interpret the conclusions from the data analysis. (

The descriptive statistics showed that the day 1 d-prime results (M = 2. 84, SD = 1. 31) and the day 2 d-prime results (M = 1. 88, SD = 1. 24). Meanwhile, the inferential statistics demonstrated a statistically significant difference (t[85] = 4. 50, p

Discussion

The results implied there was a larger significant decrease of the difference of d-prime results of the experimental group (same set of “Foil” faces) compared to the control group (new set of “Foil” faces) across day 1 to 2. Findings may be resulted from the repeated exposure to the same “Foil” faces for the participants in the experimental group instead of the control group, leading to their incorrect recognition as the “Most Wanted” faces.

The aforementioned results support the hypothesis of the current study that higher false identification rate of people would be caused from the repeated exposure of the same foil faces compared to the new exposure of the different foil faces in a face recognition task. (

The present study had coherent findings with Brown, Deffenbacher and Sturgill (1977) and Hinz and Pezdek (2001) in which the repeated presentation of faces would detrimentally influence people’s identification of the target faces, resulted from the source monitoring errors when people identify based on the familiarity of the previously encountered faces. Nonetheless, the current findings were not based on a lineup phase and details of the encounter of faces were not required.

Possible direction for future research on this topic would be investigating the effect of the identification of faces in a larger age range since the current study only focused on relatively young ages of students. Furthermore, the time range of the experiment could be extended longer to weeks or months to demonstrate if a same result still exist. Better insights are provided to the real-life circumstances since the criminal identification task requires the aforementioned factors.