Adults with serious mental illnesses (such as schizophrenia and schizoaffective disorders) often experience a range of cognitive difficulties (such as memory, problem solving difficulties) that affect their ability to lead meaningful life roles. Cognitive remediation is an intervention to address cognitive difficulties in this group of mental health service users. Its implementation in less well-resourced community-based settings is less well-studied. Therefore, the aims of the study are: * To investigate the effects of cognitive remediation on various cognitive skills (such as attention, memory, problem-solving, facial expression recognition, taking others' perspectives etc), for participants with schizophrenia or schizoaffective disorders in community mental health settings. * To investigate if factors such as participants' motivation for engagement and social interaction can affect changes in cognitive skills and functional ability. Participants in the treatment group will attend computer-based cognitive exercises to improve their cognitive skills. They will also participate in group sessions facilitated by therapists to learn how to utilize strategies learned from the computer sessions in their daily lives. Participants in the control group will attend the usual rehabilitation activities in their respective community-based psychiatric rehabilitation centers. This research study will compare the differences in their cognitive performance, functional ability and recovery immediately after the intervention and 8 weeks later.