both while they are in the T-group, and in other reflective and skill building activities. Crosby was first a T-group participant in 1953, and was mentored by Lewin associates Ken Benne, Leland Bradford and Ronald Lippitt. Crosby, worked closely with Mr. Wallen from 1968 to 1975, co-leading several National Training Laboratories T-groups during that time. When Crosby founded the Leadership Institute of Seattle (LIOS) Applied Behavioral Science Graduate Program he made T-groups a core requirement of the curriculum, and he did the same when founding and leading the ALCOA Corporate leadership program from 1990 to 2005. Throughout Crosby's Organization Development career he has used T-groups in numerous business culture change and performance improvement initiatives, most famously during the PECO Nuclear turnaround following the shutdown of Peach Bottom Atomic Power Station for human performance issues by the Nuclear Regulatory Commission in 1987. Crosby and his associates still lead T-groups in public workshops and in businesses. Another recent version of the T-groups is the Appreciative Inquiry Human Interaction Laboratory, which focuses on strengths-based learning processes. It is a variation of the NTL T-groups, since it shares the values and experiential learning model with the classic T-groups. A commercialized strand of the encounter group movement developed into large-group awareness training. Other variations popular in the late 1960s and early 1970s included the nude encounter group, where participants are naked, and the marathon encounter group, where participants carry on for 24 hours or longer without sleep. "Encounter groups, in contrast to T-groups, are far less concerned with group dynamics. Instead, they focus on the individual, on getting each group participant to talk about and express his feelings as deeply and spontaneously as possible." Controversial aspects This type of training is controversial as the behaviors it encourages are often self-disclosure and openness, which many people believe some organizations ultimately punish. The feedback used in this type of training can be highly personal, hence it must be given by highly trained observers (trainers).. In the NTL-tradition, the T-group is always embedded in a Human Interaction Laboratory, with reflection time and theory sessions. In these sessions, the participants have the opportunity to make sense of what's happening in the T-group. Encounter groups are also controversial because of scientific claims that they can cause serious and lasting psychological damage. One 1971 study found that 9% of normal college students participating in an encounter group developed psychological problems lasting