In the TV show Alphas, Nina's alpha ability is to mentally push people to do whatever she asks of them. How come her ability doesn't work on Gary? Does it have to do with Gary's autism or alpha ability that blocks Nina's push?
Nina Theroux's Alpha ability is described on the show as Hyper-Induction.
the ability to override the willpower of another through eye contact and speech, it usually wears off after a few hours, or more or less depending on how strong the mind of the person is;
some people cannot be “pushed” at all, either because of strong minds or their brains are wired differently (e.g. Gary Bell)
Gary has multiple reasons he is likely immune to Nina's power.
Lack of Eye Contact: Nina's power requires both eye contact and the ability to understand her requests at the intellectual level. It is one of the reasons when Nina is under arrest she is blindfolded.
One of the idiosyncratic behaviors of autism (I know this personally, both myself and my son are diagnosed autistics) is a pronounced lack of eye contact. This varies widely but many autistics cannot or will not make eye contact with people they communicate with. Gary Bell is better than some, but I notice his behavior precludes regular eye contact unless he is being confrontational.
Her power also manipulates the actual brain of the target, temporarily causing changes in the subject's mental activity. These changes have been known to last for hours and can be seen under an MRI scan, one of the ways Rosen has detected Nina's influence on a subject.
Nina's power requires the receiver of the command to understand what is being requested. We have not seen her try to communicate in different languages, nor have we seen her try to push someone who cannot speak her language. In Gary's case, his communication skills are less than excellent, not for lack of ability. Gary lack of ability to grasp nuances in language may buffer the effect of her power, protecting him simply because he takes so long to understand what is being requested.
And yes, Nina has pushed people she wasn't looking into their eyes, but usually these are people whose wills are significantly weaker, she was having a psychological episode which was making her powers stronger (especially in season 2 when she goes rogue) or those people have been pushed by her before.
Strong Willed or non-neurotypical brain structures: I would not list Gary as a person who has a strong will (one of the ways to resist Nina's Alpha ability) so we will assume since Gary's autism and Alpha abilities play a role.
Overloaded Awareness: Gary's Alpha ability allows him to perceive and manipulate a range of the electromagnetic spectrum beyond the sensory ranges of human beings. He is able to detect electromagnetic phenomena along the entire range. We have seen him intercept wireless transmissions, cell tower signals, listen to the EM signature of the sun and stars. His sensitivity is so great he claims to be able to detect communication (such as it is) from plants.
Distributed Computing: His perception of so much electromagnetic phenomena (normal humans perceive less than 2% of the EM spectrum) likely takes a significant part of his brain's capability to visually represent and this may prevent outside interactions from hijacking his brain and redirecting stimuli. His brain likely processes information at multiple levels preventing her from taking control of his willpower because he simply has more brain activity than she can co-opt with her power.
More than likely it stems from his Autism. Autism affects how the brain processes information. While it is still unclear exactly the cause and mechanics behind Autism, it is essentally a break down or disruption of the signals in the brain. Nina's ability to push people works by her sending her intended result message, using her voice and eye contact as the carrier wave. In Gary's case that signal would be disrupted on it's path through his brain.
Gary's alpha ability is what probably prevents Nina from controlling him. Nina's ability probably (not definitely) manipulates the EM waves of a person's mind and since Gary can manipulate EM waves himself he is most likely immune for this reason.