There is research to support common factors theory. One common factor is the client–therapist interaction, also known as the therapeutic alliance. A 1992 paper by Lambert showed that nearly 40 percent of the improvement in psychotherapy is from these client–therapist variables. Other researchers have further analyzed the importance of client–therapist variables in treatment. They found that improvement in the patient was due to extra-therapeutic factors, for example patients' thought processes. Data shows that patients with more positive attitudes will have a better chance of experiencing clinical improvement, regardless of the therapist's actions. Furthermore, in a meta-analysis of many studies of psychotherapy, Wampold "et al." 2002, found that 7% of the variability in treatment outcome was due to the therapeutic alliance whereas 1% of the variability was due to a specific treatment. The therapist's attitude is also a very important causal agent in positive patient change. Najavits and Strupp (1994) demonstrated that a positive, warm, caring, and genuine therapist generated statistically significant differences in patient outcome. Wampold "et al." 2002, also found that nearly 70% of the variability in treatment outcome was due to the therapist's attitude toward the efficacy of the treatment. Specific components of therapy are concluded to be relatively frivolous when compared with the more profound and directly patient affecting common factors.