Procedure

At the beginning of each semester, a list of potential research participants scoring above 15 and between 1 and 6 on the BDI at a mass testing session was created. Potential research participants were contacted by phone and were told that they could, if they wished, participate in an experiment involving the perception of words. They were told that they would receive five points of credit towards their introductory psychology course for their participation. If they agreed to participate, an appointment was set up. Research participants were recontacted the night before the experiment.

When research participants arrived for the experiment they were brought into the room where the testing was to be done. A bare room containing only two chairs, a desk, and a computer was used. After obtaining informed consent, directions were shown to the research participant on the computer regarding two computer-generated tasks: a lexical decision task, and a valence identification task. The research participant was then shown the directions again for the first task which he or she would be completing. The research participant was given a practice session consisting of four trials. The practice session was repeated until the research participant clearly understood the task, and had performed correctly on all of the practice trials. The research participant was queried regarding any questions he or she might have regarding the task. The research participant then completed the first task. After completing the first task, the research participant was asked to write all the words he or she remembered from the task, on a blank piece of paper. Next, the identical procedure was completed for the second task. In each of the two tasks, each word in a given word set was presented at each of three Stimulus Durations (SDs) including 50ms, 100ms, and 150ms.⁷ The order in which the tasks were completed, the order in which buttons for responses on the keyboard were labeled, which word list was used with which task, the order of words within each task, and the order in which a given word was shown in a given SD was counterbalanced by computer.

The lexical decision task was conducted in the following manner. The research participant was asked to place his or her right palm below the keyboard with the index finger extended poised above the space bar, equidistant from the ``N'' and ``M'' keys. A row of X's was present on the screen at the beginning of the task. After 2000ms, the X's in the middle of the string was replaced by letters spelling a word or nonword. After the SD, the word was masked by a row of X's again. The question "Is it a word?" appeared on the screen. The research participant pushed a button for "Yes" or "No", which was placed over the ``N'' and ``M'' keys on the keyboard in a randomized order. This procedure was repeated for each word and nonword, at each SD. The research participant's reaction time and response was recorded on the computer for each stimulus. This task took approximately 15 minutes for most research participants.

The valence identification task was conducted in the following manner. The research participant was asked to place his or her right palm below the keyboard with the index finger extended poised above the space bar, equidistant from the ``Z'' and ``C'' keys. A row of X's was present on the screen at the beginning of the task. After 2000ms, the X's in the middle of the string was replaced by a word. After the SD, the word was masked by a row of X's again. The question "What's the Valence?" appeared on the screen. The research participant pushed a button labeled ``+'', ``-'', or ``N'' for ``Positive'', ``Negative'', or ``Neutral'', respectively, which was placed over the ``z'', ``x'', and ``c'' keys in a randomized order. This procedure was repeated for each word, at each SD. This task took approximately 15 minutes for most research participants.

After the research participant had completed both tasks, the measures used to assess the research participant's mood and related variables were administered. The BDI and GBI were administered on a computer. The SFSC and MAACL were completed with pencil and paper. Once these tasks were completed, research participants run during the first semester in which the experiment was conducted received the SCID interview for previous manic and depressive episodes. Research participants run during the second semester received the SCID interviews for previous manic and depressive episodes and, if time permitted, the SCID interviews for current manic and depressive episodes. Research participants run during the third semester during which the experiment was conducted received a computer administered task in which they were asked to rate the affective intensity of each word they had seen, for them, on a scale from 1 to 7 where 1 was ``very negative'', 4 was ``neutral, not emotional at all'', and 7 was ``very positive''. When the research participant had completed all parts of the experiment, he or she was verbally debriefed and was given a written debriefing and a list of counseling services in the San Diego Area. The student's Psychology 101 teacher was recorded with his or her name such that he or she could receive course credit for having participated in the experiment. Procedural differences between semesters reflect the ongoing development of the theory motivating the experiment and the desire to test multiple hypotheses regarding the theory behind the experiment which, if tested simultaneously, would make the experiment extremely long. Because all procedural variations happened during the last part of the experiment, none of the other data which were collected should be compromised as a result of semester-dependent procedural differences.