Daniel Gilbert

Daniel is a social psychologist who is known for his research (with Timothy Wilson of the University of Virginia) on affective forecasting, with a special emphasis on cognitive biases such as the impact bias. He is the author of the international bestseller Stumbling on Happiness, which won the 2007 Royal Society Prizes for Science Books.
Link to Daniel Gilbert's TED talk on happiness

Dr Tal Ben-Shahar

Tal Ben-Shahar is an author and lecturer at Harvard University. He currently teaches the largest course at Harvard on 'Positive Psychology' and the third largest on 'The Psychology of Leadership'-with a total of over 1,400 students.
Link to Dr Tal Ben-Shahar lecture on 'The Science of Happiness'
1 hour 58 mins

Sonya Lyubomirsky

Sonja Lyubomirsky, Ph.D., is Professor of Psychology at the University of California, Riverside. She currently teaches courses in social psychology and positive psychology and serves as the Department of Psychology's graduate advisor. Her teaching and mentoring of students have been recognized with the Faculty of the Year and Faculty Mentor of the Year Awards. She is the author the book 'The How of Happiness: A Scientific Approach of getting the life you want'.

The following is the link to a TV interview.

Link to Sonya Lyubormirsky - interview on 'The How of Happiness'
Time 4'28 Mins

Stefan Sagmeister

Stefan Sagmeister is a graphic designer and typographer currently based in New York City. He has his own design firm, Sagmeister Inc. He has designed album covers for Lou Reed, the Rolling Stones, David Byrne, Aerosmith and Pat Metheny.

This is the link to his TED talk.
Link to Stefan Sagmesiter talk 'Yes, design can make you happy'
Time 17'27